The Role of Observations in the Study of Climate Variation
With the steady increase in human population, and the ever declining natural resource base, public attention has been focused on the state of global, regional and local climate related issues. These range from drought and desertification to floods and freezes, including usual seasonal inundations of river deltas and lowlands around the world. Forecasting consequences of climate change, particularly the recent CO2 doubling experiment scenarios resulting from evolving but still primitive Global Circulation Models (GCMs), has provoked major concerns among policy makers, whether they be from national or local governments, international agencies or business concerns. The recent "surprise" encounter with the seasonal ozone hole over Antarctica has stimulated concern over what we are doing to our environment that we simply do not yet understand.
Of primary concern to the science and policy making communities in recent debates and commentaries regarding these scenarios has been the efficacy and credibilities of the GCMs. There are many problems with the present generation GCMs beyond the oft cited lack of spatial resolution and limitations of the computing facilities that are available to operate GCMs. Poor representation or absence of realistic patterns of seasonality, biogeochemistry and hydrological factors in the models have proven to be of greatest concern to those trying to interpret these scenarios. While the pure physics of the models may be well represented, on some scales, those responsible for making credible consequences forecasts require information on seasonal variabilities from which pragmatic, real world forecasts can be constructed.
Treatment of the ocean, particularly the thermally dynamic upper ocean, within the present generation of GCMs should also receive considerable discussion, and a great amount more effort to have the role of the ocean defined, on all time and space scales of relevance to both weather forecasting and climate research. The relative levels of sophistication regarding gross ocean circulation models has been limited by the interests and scales of concern i.e., 5x10 degree grid sizes, until recently (Semtner and Chervin 1989, Moum et al. 1989).
Typically, atmospheric modeler's preconceptions about the relative roles of sea surface temperature, winds, and sea level gradients have dominated the mechanisms that have been posed to inter-relate the ocean and atmosphere dynamics. Such important processes as upper ocean heat dynamics, tidal mixing and frontogenesis, cloud related inhibition of both insolation and long-wave reemissions, mid water circulation dynamics, and even the remote forcing due to the hydrological cycle have been mostly ignored.
More realistic and credible regional and local scale consequences forecasts require far better local and regional model performance, with higher temporal resolution. For example, criteria for regional, seasonal seed stock selection and purchases, or even energy related decisions such as those related to proportions of heating oils that need to be produced from regional petroleum stores cannot be made with acceptable certainty from model generated future climate scenarios. All phases of agricultural, transportation, or fishery related planning require a clear understanding of the seasonal cycle.
What we know about climate, its synoptic and historical variability, is derived from studies of the consequences of these changes in time and space from ecological and geological contexts. This is because nearly all ecological processes, agricultural activities and ocean and freshwater systems are directly affected by temporal and spatial distributions of seasonal insolation, rainfall patterns, daily temperature cycles, light levels, winds, and both drying and freezing conditions. All of these have down-stream effects, depending in particular upon responses from local and regional wetlands and vegetation to the short-term climate in terrestrial contexts.
Also, what should be our concern about the other 70 percent of the earth's surface; the atmospheric moisture/latent heat cycles; or the highly populated coastal ocean habitat which is subject to extreme seasonal excursions as the terrestrial and ocean regimes interact?
The ocean is by convention treated in most GCMs as a simple thermally active surface, the importance of which is limited to primitive black body physics concepts by our ignorance of how to pose the complex feedback relations, not by our lack of understanding that such complexities exist. The facts are that the ocean's upper mixed layer has many times the heat capacity and dynamic feedbacks involving energy state changes on all time scales when compared to the atmosphere. The scales of processes are on the order of ten times more complex, with far more localized, interactive processes, e.g., biogeochemistry, photochemistry, gas and mineral and dissolved materials transport, etc., occurring than are evident from only monitoring the sea surface temperature and the atmosphere above the marine layer (c.f.. Cess et al. 1989). The marine boundary layer, which is poorly modeled in any context, is the medium for exchange of energy of many forms between these two dynamic systems.
The complexity of the upper ocean thermal dynamics and the responses of marine life in all its diversity is akin to that of the all important seasonal precipitation and water-table dynamics that controls the seasonal, annual and epochal distributions and reproductive successes of terrestrial plant life, hence all the species that depend on those processes for sustenance.
The GCMs have more often than not been sold as panaceas to the needs of decision makers, but the state of the present generation of models is that they are quite incomplete and of only partial relevance to real world problems. This will remain the situation for many years, if not decades to come. Computer technology is only a small, but not insignificant part of the general problem. The biggest obstacle to progress remains the preconceptions about the relationships between the atmosphere, the ocean, and both the transport and transformation of energy between them. This is also the kernel of the weather forecasting problem, and only begins the long sequence of logical problems needing resolved for projecting consequences of long and short-term climate variabilities.
The Task Ahead
Sorting out the anthropogenic climate change contributions from those occurring as part of naturally determined variability is not an easy task, and efforts to short circuit this process will not likely be productive. What will certainly result will be the generation of myriad intellectually stimulating potential problems, analogous to those resulting from the CO2 doubling exercises. Are these worthy steps in the progression toward fuller understanding of the real world issues? I would argue that we know so little that all these initial efforts inspire is extreme indulgence, and eventual credibility problems between the lay population and the science and engineering communities.
For example, much ado has been made about an uncertain, arbitrary end point, CO2 doubling, which already has initiated a serious science credibility problem. It is basic human nature to choose a "side" on any contentious subject, and in science this usually shapes the structure of the hypotheses that are formed. Although CO2 doubling, or even 4X CO2 scenarios have been considered, the question remains moot until someone can sort out what is due to CO2, or other Greenhouse gases, and what is natural variation, driven primarily through other, external processes.
We are hearing more and more about the "fact" that anthropogenic CO2 is already making significant contributions to climate change. What we have not been able to find are data that are unequivocal to make the point one way or another. Much of the problem is obfuscated in geopolitical bantering over who gets to study what, and who is responsible for fixing what parts of the society that is responsible, and so on, ad infinitum. The three or so major GCMs that have been employed to project the effects of CO2 doubling they have agreed on little other than the sign of "globally averaged" temperature changes that might result. The recent NOAA GFDL Q Flux model is a step in the right direction, but at present its rendition of contemporary climate is poorer than the models that do not include the interactive ocean. However, it remains puzzling how these models, each working with basically identical empirical input, could come out with such diverse answers, and still have the socio-political impact that they have had. Any other field of science would probably have lost all credibility under similar circumstances.
One consequence of the last several years GCM output has been that many well intending geoscientists and natural resource scientists have been forced to jump through various hoops that are mostly unwarranted. Because of political pressures of one sort or another, they have been made to accept, as givens, the projected climate "scenarios" that were produced by early GCMs instead of being asked to comment on the information necessary to organize the available knowledge into something credible, based on fact not on poorly specified models of even more poorly understood mechanisms.
Unfortunately, the objectivity about which science is purported to thrive is and always has been very much more responsive to political pressures than to data, as the eras of geocentricity of the universe, flat-earth, special creation and even phlogiston so well attest.
It is a recognized fact that the little more than decade long satellite data show peculiarities and anomalies of the year-to-year patterns of vegetation (chlorophylls), sea surface temperatures, and some complex (bogus) cloud distributions. This has stimulated many scientists to try to use these global scale observations as indicators of climate change. The problem is that there is no backlog of comparable measurements with which to compare these short, variable records. Local and regional in situ observations may be recorded over a long history in some locations, but many areas which would be important to know about are not well enough documented.
There are, however, some specially informative kinds of information that provide climate consequences information from the present century back through several millennia preserved in the recent through paleological records. While the theoretical debates over GCM output go on, it would be wise to study the paleo-records as best we can (at their highest resolutions), in order to define present status and trends in global climate within the longer decadal and centennial time scales. There is no substitute for these records in modern technology, nor will there be until centuries of precise, standardized observations have been made. That point is rarely discussed.
Modeling capabilities that can effectively describe the geophysical interactions in more and sufficient detail will require far more basic understanding of interactive processes than is presently available. In fact, each new stage in the development of the GCMs is probably not really so significant alone as it is in identifying hallmarks in the efforts to develop the necessary empirical understanding of processes and interactions that precedes their inclusion into these models.
It is not the purity of the models' mathematics which forms the basis for their credibility, it is the basic understanding of the important interactions and processes which these represent that are the real progress in this field.
While these stage-by-stage model increments are of interest, they are primarily the results of improvements from empirical science, leading only secondarily to the development of what will some day become useful tools. Until there is a fuller realization of the needs of climate consequences forecasters, the modeling community may remain in its rather disconnected and ethereal state. The key is to first define what problems will need what specific information, and then to build models that generate that specific information, at appropriate scales to resolve these problems. The models that are being offered today do not answer questions from which we can make policy decisions because they cannot address, specifically, local consequences with any level of credibility.
The importance of historical perspective
The basis for most forecasting and prediction is empirically derived knowledge, i.e., the experience and reexperience over time of patterns of processes and events. Statistical theories and complex probabilistic projections depend on individual sets of observations, and long time series from which to produce credible climate projections from new satellite technologies.
A useful analogy is that in which the only diagnostics in medicine should be derived from observing a patient's skin color, surface temperature, and body shape. It certainly would be difficult to find a provider of insurance in such a situation, to either the doctor or the patient, but of even greater concern when one considers how little is being invested in the corroborative monitoring of the climate and subsurface ocean relative to the costs of launching and maintaining satellite technologies. What insurance are we offering the taxpayers that we are measuring the right things? Apparently, not much.
Too often ignored are the facts that satellite sensors are affected by the very types of changes that are expected, i.e., changing seasonal and regional patterns of atmospheric moisture and cloud/albedo as well as other atmospheric components. It is also known, but not often discussed publicly that the sensors degrade erratically, and often at rates that are greater than the longer term changes that they are suppose to track. This problem alone may preclude satellite technology from ever providing the long-term perspectives necessary to provide clear answers for these very pertinent and persistent issues. In any case, until there is a truly global, in situ monitoring system developed to provide the necessary ground truth for calibrations and verifications, satellite derived climate information will continue to be composites of artifactual, algorithm mediated "proxies" of what can and needs to be measured directly rather than inferred from unstable sensor's atmospheric soundings and various irradiance measurements.
There is a cart and horse relation between understanding and levels of successful forecasting. In spite of the optimistic expectations from pure mathematicians and physicists regarding the pure physics of climate modeling, the present generations of climate models are far from being interpretable and applicable. In some cases being wrong is not critical, but the order of potential societal disruption that is proposed in order to counter some results of projected climate scenarios is so great that to be off by much of a margin is simply unacceptable. What is it then that is required to adequately project future climate, the transitional conditions, and their consequences? It is fairly clear to the science community that we need more knowledge, more information that is relevant, in order to progress toward useful understanding. The extremes to which the science funding seekers have had to go to make their point in Congress and in the White House has become an embarrassment to many or all of the scientists that have done basic climate research and that have some authoritative empirical knowledge in this field. A few, mostly vested techno-interests have been asked to go before Congress, or to design the Earth Observing System Program. Will someone get around to worrying about the paleological research and synthesis that needs done before most or all new resources are spent on expensive, unproven and all too often short-sighted technologies.
Historical data records show that there are consistencies and coherences in temperature records for some regions and within hemispheres, but not necessarily between all regions or between hemispheres for all time scales. The point is that if there is anything that the climate consequences (proxy) records have in common beyond the coherence of hinge points of transitions from one phase (climate regime) to another that are concurrent in time, it is the fact that there are discrepancies in magnitudes, if not signs of regional temperature signals and hydrology over the globe.
Recent studies by Ropelewski and Halpert (1987) of the global precipitation response patterns of only the warm, El Niño phase of the ENSO process are prime evidence of the mosaic distribution of positive, negative, and null regional responses. This poses problems for the interpretations from any sensing system that is deployed to monitor climate related changes.
For example, consider that due to funding exigencies the proposed ocean sound propagation rate measuring technologies (Munk and Forbes 1989) might be installed to monitor individual sound paths for only part of the globe; or one hemisphere, but not the other; or that monitoring tools that might be set up without an appropriate mechanism in place to monitor and describe the ocean thermal structure and eddy field conditions and their variations along the pathways that are needed for the calibration of these tools. What would the value of all the effort if this system were not carefully calibrated along its entire path length? Useful interpretation of any sensors, remote or in situ, will require firm understanding of the patterns of seasonal and longer term variations of the processes about which inferences are made. Only after the fact will these measurements become useful in the context of defining climate scale status and trends, hence credible forecasts.
Armed with historical reconstructions of past climates, it is agreed that the kinds of changes that one might expect under the greenhouse warming analogy will not be uniform over the globe. There is also a great difference between transitional conditions and "equilibrium" or arbitrary "end point" states that might be arrived at after many decades of any one-way forcing. If global warming is implicit, then the higher latitudes would ultimately warm more relative to the tropics, and a great variety of different ocean and atmospheric gradients will form that will result in a redistribution of the atmospheric and oceanic heat such that eventually both winter and summer temperatures will be greater at high latitudes. The transitional period might actually yield rather opposite conditions.
During global warming equatorial temperatures may only increase by some small increment, or not at all. If the warming were to be long-term, then tropical conditions would most likely spread to higher latitudes, as they have over earlier, even recent warm geological time periods. The real uncertainty is what would be the interim climate situation that would prevail? There will obviously be more physical variability during the transitional period than scenarios from equilibrium conditions might suggest. But, will the extremes be greater, or lesser at one or the other end of the process compared to the transitional stages? This is a far different set of basic tenets from which to begin work than that from which so many have attempted to divine future climate consequences from simplistic one-step heating models.
Without any doubt global warming will correspond with increased surface winds. The COADS wind observations show that warm periods and cool periods are directly indicative of the relative wind forcing, which vary over a range of about 2X (as will be evidenced later), from high average periods during warmest epochs, over cool periods. These processes alone force great changes in the hydrological portions of the global heat balance, and provide major feedback to the global climate situation, in the form of seasonal and longer term patterns and trends which are very well documented, if poorly understood.
In light of the varied pressures on those that have had to produce reports from the "presumptions" arising from early GCM CO2 doubling scenarios, it seems that there should have been somewhat more interest or concern about the credibilities of the CO2 scenarios themselves than in the types of perturbations such climatic conditions would impose. This is not because there is any question about the CO2 rise, but because the state of all atmospheric modeling is so primitive, as evidenced by our most sophisticated weather forecasting capabilities.
The lack of understanding of basic biogeochemistry in climate processes, the role of the ocean in climate, and even about the signs of feedbacks from hydrological or other sources precludes credibility. Even the basis for the 18Ka BP to recent climate period comparisons that have been used to "initiate" GCM efforts has been jumbled by recent paleological research in which 14C dating has proven to be off by as much as 3500 years in 20,000 years (Fairbanks 1989, Kerr 1990).
In fact, the paleoclimate record indicates many examples within recent hundreds to thousands of years of decadal scale climate changes that are of similar magnitude to those projected by GCMs in CO2 doubling experiments. The difference is that these changes were not apparently necessarily related to atmospheric gases, or other obvious forcing functions.
Nor is the fact that humans have become a threat to their own environment news. The loss of forests across Asia and parts of Africa, western Europe and North America and their displacement or substitution by agriculture and cities is a process as old as civilization. The climate has varied even more extremely on that time scale than it has over the last few centuries, and certainly more than it has over the few decades since the industrial revolution really began.
What is needed is a clear, high resolution historical perspective, of the sort which Thomas Crowley (1983) framed within the larger, longer term geological context. This document, on the other hand, is a collation of materials and information for those interested in what is known from the last one hundred fifty years' instrumental records, and from the higher resolution geological records that have been compiled. Also to be discussed is what needs to be measured or monitored in order to derive appropriately scaled climate consequences, particularly in the ocean sediments, and terrestrial aquatic systems. The advantages of these records is that they are not "proxies" of climate consequences that need to be somehow converted, they are the consequences of climate processes, local and remote, from which past climates can be inferred.
Coherence of signals
Comparison of historical records, time series of surface temperatures, wind fields and precipitation records indicate coherences that are useful. For example Diaz (Figures 1-4) has summarized both the terrestrial hemispheric and Atlantic Ocean surface temperature (SST) time series to show the differences in integrated contexts. It is well established that the trends in apparent global warming that are being debated are heavily weighted by the contribution of the southern oceans, and that the terrestrial records have not been parallel, although long-term trends are positive, as expected from a period of emergence from the Little Ice Age (since 1785 or so).
Figure 1 shows that the northern hemisphere land mass had actually been cooling from about 1940, until the recent 1967-1983 general warming period, while there has been fairly steady warming in the southern hemisphere since the record began in the mid 19th century.
Regional (ocean basin) records from the recent instrumental records period, 1947 to present, when compared to the global COADS records from the mid 1850s to present provide unique insights into the relative signal coherences and contributions from region to region, as well as portraying the phased nature of the recent processes that dominate the instrumental record period. North Atlantic sea surface temperature anomaly records are compared in Figure 2 with those of the South Atlantic for the most reliable period of the instrumental records, 1947 to 1988.
Figure 2. From the early 1950s the North Atlantic SST went through a marked decline until 1974, when it began rising back to the long-term mean. The South Atlantic has been experiencing a positive trend, although the SST only rose above small oscillations about the long-term mean since the late 1970s. The north Atlantic basin was warm relative to the southern Atlantic basin for most of the period from 1947 to 1968. For the two recent decades, however, this trend reversed and reached a maximum difference in 1972 (see Figure 3) when the south Atlantic SST was still warmer, a trend which persists.
Figure 3. Subtraction of the northern hemisphere Atlantic basin means from the southern hemisphere basin means shows that there have been very strong differences in surface heat budgets for the two Atlantic basins. Compare this and Figure 2 with Figure 4 which is the result of similarly treated, but globally averaged information.
Figure 4. The subtraction of the mean global hemispheric sea surface temperatures, as provided by the U.K. Meteorological Office, yields another insight into the interpretation problems related to comparisons of regional and global patterns. Note that the departures (anomaly) about the long-term mean do not have either the same patterns or trends during the record period, particularly from the mid 1940s to present as the Atlantic records for the instrumental period. This exemplifies the problems in defining any meaningful trends within these spatially disparate processes. Clearly a macroscope-microscope approach is needed, along with abundant care for not over-valuing one sort of signal over others.
It is fairly well agreed that surface winds will be one of the most significant environmental factors that will change in response to global climate change, no matter what the sign. Bakun (1990) identified a set of likely scenarios that will have persistent effects on coastal fog and heat budgets, and upwelling, hence coastal ecosystems and fisheries. This is as a general response to climate warming. Let us examine the coherences of recent and long-term instrumental data for various locations around the globe.
Expected coherences which are of perhaps more relatively direct climatic significance than are either sea surface or terrestrial surface temperatures are the (scalar) surface winds. Comparison of these records within and amongst regions around the globe, stratified by latitude for the eastern Pacific Ocean and the western Indian Ocean exhibit similar shifts over that period, with some latitudinal and onshore-offshore effects. Figures 5 and 6 show these patterns for the recent instrumental record period.
Figure 5 The scalar surface winds are compared for the western coastline of the Americas from about the State of Washington down the coast by 20 degree latitudinal increments to Valparaiso, Chile. The seasonal patterns are shown for the northernmost block, and only the "All seasons" summary for the southerly blocks. Note particularly the contrasts in mean wind speeds for each region. These data are primarily records from instruments and were provided by R. Pyle of the NOAA/ERL/Climate Research Division in Boulder, Colorado.
Compare the surface scalar winds above to those for the western boundary of the Indian Ocean. In Figure 6 three climate regimes are shown: from the equator to the north coast of the Arabian Sea (0-26oN); South of the equator to Madagascar (0-16oS); and from 16-32oS (to the Cape of Good Hope). Note the patterns and the long-term similarities to the records from the eastern Pacific Ocean. Such important signals persist, even though there are such fundamental differences between the Indian Ocean subregions, the eastern and western climate regimes such as are manifest in the strong seasonal, monsoonal effects that are absent from the eastern Pacific region.
Figure 6. The western coast of the Indian Ocean was divided into three ocean/climate regimes. As in Figure 5 the four seasons are portrayed for the northernmost sector, and only the All Seasons composites are shown for the other two.
Note that in contrast with the eastern Pacific Ocean the mean winds are rather milder, except for the summer monsoon period, and that although there is a minor lowering of the mean range for the central east African coastal regime, that the scale of differences is not heavily influenced by latitude as it is in the Pacific Ocean. Note also that the Pacific Ocean offshore high latitude example has both higher means and extremes than any of the other records.
Placing these short time series into larger, longer contexts, extending back from the present to the mid 18th century, provides some additional insights about the coherence of the data. There are some obvious and not so obvious methodological biases that have been incorporated in the longer time series, but the trends and cyclical patterns tend to be coherent on the global scale, regardless of the methodology issues. Another important fact that can be seen in Figure 7 is that strong surface winds and trends are well correlated with sea surface temperature patterns and trends. This is not an intuitively obvious fact, given the amount of emphasis given to the role of surface winds in upper ocean mixing. There is little evidence that surface winds of the magnitudes alluded to in these figures are even relevant to upper ocean mixing, in contrast to the diel outgoing long-wave radiation, latent heat flux, and buoyancy flux related to clear sky, low insolation periods (e.g., see for example Moum, et al. 1989).
Figure.7 COADS time series for the Panama Bight (0-10oN, 90-100oW) show that recent changes in both wind speeds and temperature are relatively mild, and that cooler SST and lower wind speeds are coherent.
The scalar wind from Figures 5 and 6 also provide comparisons of northern mid latitudes to the equatorial and southern mid latitudes, in contrast to the above record from the Panama Bight region. The latter is a bit more erratic, as one might expect from a region of major contrasting ocean current confluences which is under the direct seasonal influence of the dynamic inter-tropical convergence zone (ITCZ) and its seasonal and longer term location changes.
Now let us examine the records presented by Bakun in his study of the coastal upwelling regimes, since 1947 (Figure 8). It is clear from Bakun's (1990) discussion that he remains skeptical that the available records are "pristine" physical evidence of global warming trends, particularly given the short time periods for which the instrumental records have been collected, and the changes in technique that have ensued during the four decade period. Other issues emerge from close examination of the data set, beyond the questions about technique and possible consequences of changes in upwelling intensity due to the processes outlined so eloquently by Bakun.
Figure 8. The within-year averages of monthly estimates of along shore wind stress in five upwelling regimes (after Bakun 1990) are compared to show their relative coherences. The period from 1968-1972, outlined by the dotted box, indicates that each regime was subject of a dramatic range excursion of at least 0.2 Dynes cm-2, and about 1.2 dynes cm-2 for the California example. These are not unprecedented changes, but the rather consistent downward trends following this "set" period is in marked contrast to expectation from the context of the regional trends in ocean warming that were transpiring in each system.
While the long-term trend analyses for each of Bakun's five upwelling regimes, California; the Iberian Peninsula; Morocco; Peru summer and Peru winter each result in similar positive forcing trends for the instrumental period, it is also intriguing that commencing at around 1968-72 each regime experienced a rather rapid and dramatic excursion about the long term mean, then a step well above the mean; and then with the exception of Morocco, the wind stress for each regime trends downward, with increasing amplitude oscillations. This is in marked contrast with expectation, given that there was ocean warming over most of this period in each area, even though this occurred at different relative rates in each area.
There has been a series of indications that the upwelling intensity and the ecological changes associated with a suite of environmental changes that occurred during the 1968-1972 period were concurrent with, if not the cause of these dramatic changes. For example, Loeb and Rojas (1988) described the onset of the decline of the coastal fish populations off northern and central Chile for this period, as well as the incursion of the offshore oceanic species as the coastal upwelling declined. Entire marine populations, not only commercially exploited pelagic fishes, failed, and others blossomed within each of the study areas defined by Bakun during the last decades of these series (Sharp 1987, 1988, Sharp and Csirke 1984).
The most dramatic fishery associated changes are those of the anchovies (Engraulis spp.) and sardine (Sardinops spp.) off South America, while the patterns are not inconsistent with the blooms of Sardinops off Morocco in the late 1970s, and in the Gulf of California since the mid 1970s. Another, closely related species is the Sardina spp. complex of the Northeastern Atlantic and Mediterranean. These smaller populations expand and contract as the ocean environment shifts on local and subregional scales (Southward 1974a, 1974b, Southward et al. 1975). The eastern Atlantic has been sampled in a much more patchwork fashion, but studies such as those by Southward, as summarized in Figure 9, have been carried on for decades. These fit within a larger context, as we will see in the following discussions.
Figure 9. The graphic above was redrawn from Cushing (1986) in his review of Southward's studies. The two species whose abundances are plotted have distinctly different habitat requirements, the sardine prefers warmer ocean regimes than does Sagitta, a major planktivorous predator. The continuing efforts to monitor marine population changes had its origins in the studies of the variations in the fisheries of the North Sea (Hjort 1914) and has been ongoing for decades.
Nowhere else compared to the North Sea and adjacent ocean habitat has so much unresolved debate gone on over the relative roles of climate and ocean variation in fishery and fish population behavior changes. However, during the recent several decades the access to resources, fisheries management and related science have become so politicized that there is as yet no inclusion of climate, or even basic oceanographic status included in stock assessments or fisheries management operations in the entire region. This is slowly changing as the concern of the public for climate change policies forces the consideration of the obvious, and as particular personalities have retired out of the fisheries management regimes.
Robert Webb and colleagues at the USGS laboratory in Tucson, Arizona have amassed time series from drainage basins throughout the southwestern USA and Sonora desert regions. Highest rainfalls have been associated with two distinctively different processes. The periods when cool, "La Niña" phases of the ENSO cycle dominate the eastern tropical Pacific region, which tends to bring large low pressure systems in from the Caribbean; and those tropical cyclones originating from within the eastern Tropical Pacific which are drawn northeastward rather than following their more usual northwestward pathways during warm, "El Niño" phases of the ENSO cycle. There is clearly a centennial scale pattern of extreme events within these records.
Patterns such as those in Figure 10, below, provoke the consideration that many of the higher frequency changes within which the recent fifty years of intense instrumental observations might only be considered as half a longer cycle.
Figure 10. Webb and colleagues (Hjalmarson 1990, Webb and Betancourt 1990) have compiled records from several drainage basins, and collated the peak discharge rates by season and year so that the various components of the seasonal cycle and atmospheric states might be inferred.
The southwestern USA is a complex hydrological regime with strongly seasonal patterns of climatic forcing. The late spring shift of the Bermuda high from the offshore regime off the eastern seaboard, inland and onto the central plains, produces high humidity, and a constant source of boundary layer moisture for summer thunderstorms that range initially from the southeastern states, and later in summer to Colorado, where the Rocky Mountains act as a barrier to further western extension. In late June or early July, the terrestrial heat balance over the Sonora desert and Baja California generates a true monsoon flow of moist oceanic air from the eastern Pacific and the lower Gulf of California, which also spreads northeastward to include the southern Rocky Mountains, and much of the southwestern desert region. The dominance of these two moist air masses shifts from year to year in response to the changes in SST in the Gulf of Mexico and in the eastern Pacific Ocean, and to the upper atmospheric dynamics related to the quasi-biennial oscillation (QBO).
El Niño years tend to steer the late summer cyclones which form off the west coast of Central America due to the evolution of high heat contents in that region during warming events, northeastward, off their normal northwestern course, such that they recurve over Baja California, or across Mexico from about Acapulco, northward. These storms bring deluges and major floods to this region. During usual cool eastern Pacific SST years when the Caribbean and Gulf of Mexico are warmest, these storms form well east of the Pacific, and tend to remain within the Gulf of Mexico, or if they form off Africa, they are guided up the eastern US seaboard by the combined effects of the equatorial warm waters , the QBO and the Gulf Stream. Much of the air mass moisture originates off Africa, but where the convection cells form is related to upper ocean thermal balances on local scales.
While there remain many whose concepts of marine fish population responses to environmental change are constrained to the comings and goings of thermal regimes, as Bakun (1990) and Bakun et al. (1982) allude, it is not going to be a simple task to project the consequences of climate change on marine populations without considering many other factors. For example, Andrew Soutar and colleague Timothy Baumgartner have examined the scale counts in sediment laminae (annual varves) for both the Southern California Bight and the Gulf of California (Soutar and Isaacs 1974, Soutar and Crill 1977, Baumgartner et al. 1985, 1989). The former records are the best studied, and provide the following insights into patterns and frequencies (Figure 11) of the relative abundances of anchovies and sardines.
Figure 11. The Annual varve sediment records of the Santa Barbara Basin have been sorted and fish debris (e.g., scales, otoliths, hard parts) identified, and enumerated for contiguous segments for the recent two thousand year period. These records have been the inspiration for much speculation about the periodic ebb and flow of pelagic species, and the climatic regimes that dominated each period (e.g., Moser et al. 1987, Smith and Moser 1988).
There are others that have tried to turn these and related species abundance indications into clever transposes for the state of the local ocean (Valentine..., Dunbar 1983, Druffel 1985, Druffel et al. 1989). Clearly the records from the southern California Bight in the above figures represent definite, local oceanic opportunity regimes within a special environment, one which encompasses the interactions of at least three adjacent habitats. The countercurrent gyre within the southern California Bight tends to concentrate passive organisms, including early life history stages of pelagic species which apparently dominate the system under any regime.
From the south, prominent upwelling regimes off Baja California provide a steady source of potential colonizers. Also from the south, the subtropical convergence which can range seasonally from well below Baja California, to mid California on the long-term, which affects the southern California Bight on different time scales, during long-term epochs of equatorial warming and cooling, and on the shorter term during ENSO warm events. These epochs clearly enhance or suppress the success of Sardinops, and many other species, and thereby the sediment deposition records provides insight into the climatic regimes for each of the stages that can be discriminated.
From the north, the California Current flow and along shore wind regime dominates this and other eastern boundary current upwelling regimes, and supports the associated species, i.e., Engraulis , Sardinops, Sarda, Scomber and Merluccius spp. (Parrish et al. 1981). From the west, the oceanic habitat can dominate the coastal regimes during periods of lower along shore winds (the case off Central California for the recent several months, October 1989 to summer 1990) during which unusual sightings and strandings of oceanic species such as Risso's dolphin and leatherback turtles, and suppression of usual forage species for bird colonies in the Farallon Islands resulting in definite population stresses and lowered nesting success for these and other species. Central California coastal fish are dominated by internally fertilized, live-bearing species such as the complex of long lived Sebastes spp. These populations are subject to the whims of all of the circulation related and species incursions, and many have notoriously unstable populations. This is due to the relatively low frequency of optimal conditions off this region, due to the great fluxes of the various contiguous pelagic regimes.
It is clear from the Santa Barbara Basin scale deposition records in Figure 11 that there was a major shift in climate related dynamics from one regime to the present at about 1050 to 1100 AD. The previous epoch was much more productive for both indicator species, suggesting both warmer, wetter conditions, along with greater upwelling productivity which is consistent with records of the lake level heights in and about Southwestern North America (Hubbs 1960), and Bakun's scenarios of the consequences of general global warming on eastern boundary current systems. There is also a rather characteristic 250-350 year ebb and flow during the last thousand years, which aligns with data from high resolution tree ring, river flow and hydrological studies from the region, too (Dr. Peter Kesel, personal communication, SAIC, Las Vegas, Nevada), as well as with geological observations made by R.Y. Anderson, to be described in another section.
Decadal time series for marine biological sampling are available from regional studies, and fisheries catch/research records. These data sets are much like the recent instrumental period in meteorology and oceanography in that they are often so short that their interpretations are complicated by the statistical problems associated with too few observations, hence often the conclusions drawn are either misleading, or worse, simply false. On a somewhat short time scale, Kawasaki (1984) and several related studies have focused on the coherence between the responses of pelagic species across basins and globally. The stimulating, or perhaps the better word is compelling basis for this interest can be viewed in Figure 12.
Figure 12. Catch statistic records from three isolated Sardinops spp. fisheries around the Pacific Basin provoke consideration of the existence of a basin-wide process that stimulates the bloom and demise of local populations (amended from Kawasaki 1984).
Kondo (1980) first documented the expansion of the population of far east sardines from small population refuges around the Pacific coast of Japan, to the Sea of Japan, to locations known to have been occupied in the mid 1930s, until the declines of this population began in the early 1940s. A similar population bloom and range expansion occurred off South America in the late 1960s, and a smaller scale parallel bloom has occurred from the California sardine's Gulf of California refuge, with subsequent low level recolonization of the California Current region, to the Strait of Juan de Fuca.
The 1989-90 ocean surface warming and onshore movement of the oceanic regime off the Californias heralds the onset of conditions that will be (are) conducive to local Sardinops blooms, along with other oceanic species, and the suppression of the coastal upwelling species. The numbers of partial data sets and analogous studies that have been begun that show similar patterns of temporal changes is remarkable.
There are distinctly different patterns of species expansion and contraction that have been documented (Loeb and Rojas 1988, Southward 1974a and b, Smith and Moser 1988) and the relative synchrony is compelling. The most recent study that appears to have provided insights into the variations of Sardinops spp. blooms and collapses was reported by Dr. Robert Crawford at the recent International Symposium on Long-term Variability of Pelagic Fish Populations and Their Environment, held in Sendai, Japan, November 1989. Crawford and colleagues compared the population response patterns of temporal variability from around the Atlantic Basin, the Benguela Current and the Pacific Basin, showing that there were local or regional patterns and differences, that argues for some level of independence, which is reasonable. However, the Pacific Basin catch records certainly argue for common stimulus within the context of a general ocean/atmosphere regime in which warming periods provide Sardinops spp. with unique conditions which promotes the survival of early life stages, hence population growth and expansion. The real test of our emergent understanding during the next decades will to be accurate forecasts about which characteristic fauna will dominate at any one period in each region, and when changes will occur.
Cool periods, or seasons with negative heat flux from the upper ocean tend to damp these sardine population's survival. Extended epochs of cooler, coastal upwelling dominated situations, such as the period from the mid 1940s until 1967-68, are dominated by another array of coastal species such as the Engraulids, and many other species often of little interest to any commercial fisheries. From the changes in behavior in the environmental records that are occurring around the Pacific Basin, and apparent changing responses from the Sardinops populations, we have entered another period of general cooling of the South American and far eastern sardine habitats. However, the western coast of North America is now (1990) warming. If this trend continues, subject to the pattern of north-south oscillation of the equatorial system and associated subtropical boundaries as indicated in the southwestern and Sonora desert precipitation records, perhaps an explanation will emerge about the different magnitudes and timing of the California sardine blooms compared to those we have observed over the last decades in the other two Pacific populations.
A major contribution to the question of Global Climate Change, on the decadal scale as well as the longer centennial and millennial scales will be that monitoring the blooms, collapses and distributions changes of these species as indicators of the status and trends in the upper ocean. This is particularly likely since sardines appear to thrive at the warm edges of the subtropical boundaries. They apparently provide obvious signals for both longer and interannual ocean/climate processes. As can be seen from both the sediment and catch records, pole to pole transect studies of fish debris and other indicator species from ocean margin sediments along with this century's catch information could provide many useful insights into the ocean thermal expansion and contraction rates, frequencies and magnitudes, which will literally never be available from instrumental records. The patterns of coherence would be of great practical application, as the patterns of seasonal hydrology, and ocean dynamics will be traceable from local through regional scales, and their atmospheric analogs can be inferred, as for terrestrial systems (e.g., Enzel et al. 1989).
Fletcher has provided another view of the pattern of coherence, or more appropriately, the coherence of the patterns of change in climate as they progress from one state to another. There are two dominant, recurring climate fluctuations on the annual to centennial time scales. One is the El Niño-Southern Oscillation phenomenon (ENSO), a coupled tropical ocean and atmosphere fluctuation that is phase locked to the annual cycle and recurs at 3 or 4 year intervals, as a function of the ocean basin hydrology and upper ocean thermal dynamics. The other fluctuation exhibits a recurrence period of about 90-130 years of patterns of surface wind strengthening and weakening (Figure 13) which appears to be forced from high latitudes in winter, and more strongly from the Arctic than from the Antarctic.
The unusual 1989-90 winter phenomenon that stimulated Fletcher's thinking on this problem was the several month long period of extreme high pressures that were observed in the high latitudes, from November to mid January. It was probably the only well measured such occurrence of this century, but might have had a counterpart in the first decade of the century.
Major effects or processes that these observations compels one to consider are the sequences of events that must transpire in order for glacial and gross sea ice formation. The clues lie in the tremendous atmospheric subsidence, hence surface cooling and precipitation deposition that was observed. Consider, for example, the optional scenarios in which general global cooling would induce lower surface winds, drier lower atmospheric conditions, hence less precipitation at all latitudes. Then consider the pattern of events that might be required in order for there to be persistent deposition of precipitation, and ice mass formation, recognizing the necessity for there to be a mechanism of transport of heat away from the poles, and moisture from the tropical ocean to the higher latitudes.
Certainly the novel concept is the scale changes that would need to take place, as moisture from the ocean enters the atmosphere primarily from the tropics and only a few localized mid-latitude regions of high latent heat loss around the world. The moisture is then transported poleward via mesoscale mid-latitude atmospheric turbulence. In the northern hemisphere it is also mediated by terrestrial hydrology and seasonal transfers to the atmosphere, as the summer climate dictates. Combine these requirements with the difficulties of deposition of ice and glacier formation, and you soon recognize the need for strong seasonal cycles, particularly summer and equatorial heating, simply to provide adequate moisture to the higher latitudes, which a generally colder planetary system would not likely offer.
Figure 13. The four panels are portrayals of the globally averaged scalar wind departures about the mean wind speeds (values given on left for each panel), for the winter months, for 30 degree latitudinal bands. The other seasons have nearly identical forms for each panel, but lower wind speeds. These data were summarized and graciously provided from the COADS by R. Pyle, of the NOAA/ERL in Boulder, Colorado.
Note that the southern most record in Figure 13 has a greater scale than the others, although maxima for the northern and southern hemispheres are nearly identical. Note also that there appears to be a temporal damping of the trends from north to south, and that the recent five decades of most reliable instrumental records also has been collected during a period of nearly constant positive trend. It is also interesting to note that only since about the mid 1960s have the surface winds risen above the long-term mean, and the range of increase is well below the historical extremes, no matter what manner of biases that the earlier records may include. Consider also the levels of surface wind forcing at the various extremes of the record.
The northern hemisphere record shows that the mean wind forcing ranged from (11.4ms-1)2 /(7.4ms-1)2 - or a minimum ratio of 2X.
We know that lower surface winds mean less sea surface evaporation, hence less transport of moisture to the higher latitudes, and we also know that the strongest terrestrial warming occurred for the period from 1920 to 1940, a period of lowest wind speeds. We also know that the dialogue about global warming and greenhouse phenomena began in the late 1880s and 1890s, suggesting that the climate variability that stimulated the concepts must have been associated with the severe changes in the climate around that time, which is clearly recorded in these and other records. This provides the backdrop for a major revision of thinking regarding a probable mechanisms for natural global climate changes, including views on what might be required for ice formation, particularly related to that formed and lost that would be necessary to explain Ice Age climate dynamics.
It is a given fact that the ice formation process requires massive transport of water vapor from lower latitudes to higher latitudes, and extraction of heat from the high latitude land/water/ice surface. From this consideration alone it can be inferred that there is a requirement for increased surface winds and low latitude ocean warming during some portion of the seasonal cycle in order to transfer water vapor into the atmosphere; and that this water vapor must be carried aloft into the higher latitudes, where, along with high pressures and enormous subsidence, the heat content of the surfaces of the higher latitudes would be decreased at rates high enough to form persistent snow and ice cover. Not unlike the upwelling of eastern boundary currents, it may be easier to explain the behaviors of these systems if we do not assume that they are either On or Off, as is inherent in all available GCM scenarios, but more likely that the systems pulse at different frequencies and intensities, and either ice forms and accretes, or melts. This scenario broaches present concepts of precursor ocean and atmosphere dynamics in order to begin an Ice Age. Maintenance of ice cover, once it has formed, is somewhat less demanding, in climatic terms, but the seasonal cycles leading into, or out of an Ice Age must surely be well beyond the recent climatic experience, and perhaps even the comprehension of modern man. Included in the problem of short instrumental records is the fact that we experience processes on lifetime scales. The observations may be approximately stable for various periods, but are in constant flux on longer time scales.
The process that Fletcher has posed for controlling global climate trends is a result of dynamic forcing that is exhibited most strongly as deepening (or shallowing) of the sub-polar surface pressure troughs in both the Atlantic and the Pacific sectors and some changes in the central pressure of the subtropical highs. This can be visualized as strengthening (or weakening) of the mean winter fields of pressure and wind, reflected by southward displacement and strengthening of the major wind and SST fields over the Atlantic and Pacific. These dynamical relationships are reflected in the teleconnections extending from the Arctic far into the southern hemisphere.
Figure 13. shows that the globally averaged meridional surface winds were strongest in the 1860s, with a sudden weakening in the northern hemisphere in the 1870s, with continued weakening until the minimum was reached in the 1930s. Surface wind speeds have increased since then, especially since the 1960s, which corresponds to the recent SST warming. Compare these longer scalar wind time series to the shorter records displayed in the first sets of figures in this manuscript. The critical message here is that there is an apparent north-to-south progression of climate features from the high latitudes in the northern hemisphere, southward to and across the equator. The largest signals appear in the winter months, and the patterns of change over the term of the COADS observations, 1854 to present, scalar wind data are consistent, even if other measures, such as surface temperature and rainfall are of differing signs from one part of the globe to another, as documented by Ropelewski and Halpert (1987).
Resolving Seasonality In Climate Consequences Records
R.Y. Anderson and colleagues have shown that over very long time scales there are clear records of climate-driven seasonal process which are coherent over catchment basins, over broad regions, which can be related through different types of records, and methodologies. Their detective work has been able to provide measures of changes in seasonal climate patterns on annual and epochal bases. From many if not all of the records compiled by Anderson and his colleagues, ranging from recent to 10000 year old and even a 250,000 year annual varved record, seasonality and small departures from mean seasonality are involved in generating decadal to millennial climatic variability. Seasonal variability at all frequencies of change, not just within the Milankovitch band, appears to be the key to characterization and interpretations of climatic variability at lower than annual frequencies.
Among the important changes that need to be made in the way geoscience studies are carried out is the addition of a generic in situ climate observation system for each sort of environment. This would allow the calibration and verification of climate related biogeochemical and geological processes, and would provide the needed mechanism for translation, or linkage of climate consequence data to atmospheric and local climate processes. Much in the same sense as previously discussed in the case of the sound propagation ocean monitoring technique. Without a firm and clear picture of the environmental variations, it is very difficult to extrapolate from highly filtered, sequential data.
A major question that was posed was whether there were similar high resolution capabilities from climate consequences records from the marine environment, and whether or not these could be related to other types of terrestrial information? This required that new techniques be developed, with accompanying understanding of what climate variables were being measured. These were then compared across sources and over broader regions.
Boyle and Keigwin (1987) examined sediment cores from various regions around the North Atlantic Ocean and from isotopic ratio studies of the various carbonate shelled, bottom dwelling foraminifera. They were able to identify several near square wave shifts in formation of warm or cool Atlantic deep water. These studies indicate that there were several periods when there were reversals of the formation of nutrient rich or nutrient poor bottom waters, indicating reversals in the sea surface temperatures in the high latitude North Atlantic during and after the last glacial period. They were also able to infer changes in circulation patterns at intermediate ocean depths during warmer, interglacial periods. It is clear that these sorts of studies will be invaluable to a complete understanding of climate change over the longer time scales. However, these types of studies may only be of marginal relative value to understanding the next century's experiences.
Insights into the potentials for expanding the logic and methods for developing higher resolution climate-system linkage concepts are being developed in several sites, and the most recent successes have been encouraging. Figure 14 shows an example from Galapagos corals illustrates the degree of association that is resolved by closely spaced (3-month) temporal observations and short interval continuous monitoring. The trace-metal ratio time series records reproduce, approximately, an anomaly in sea surface temperature measured at an adjacent island, about 100 km away from the coral collection site. Notice that both the annual cycle and a pattern of interannual variability are resolved in the 15-year record.
Figure 14. Changes in cadmium/calcium in relation to changes in sea surface temperature anomaly, as recorded in Galapagos corals (from Shen et al. 1987 and in review).
Broecker's Great Ocean Conveyor (1987a) (Revised Update in 1999) broke the ice, so to speak, changing basic concepts of climate change. His interpretations of isotopic data and sediment species compositions for the North Atlantic data provide evidence that climate change is often abrupt, and further, he observes that ice core records indicate that climate varies frequently and much more dramatically than indicated by deep ocean sediment cores. This, of course, follows from the greater heat capacity of the oceans relative to the atmosphere, and Broecker (1987b) develops his global overview from a North Atlantic perspective related to the transport of heat at both the air-surface interface and the "conveyer belt" of dense deep water that forms when winds are particularly intense over the high latitude North Atlantic. Fletcher's high-to-low-latitude forcing concepts are analogous.
Figure 15. Relationship between cadmium/calcium in Galapagos corals, oxygen isotope ratio in Quelccaya ice core, and northern hemisphere temperature (from Shen et al. 1987, and in review).
At mid to high latitudes studies of tree rings and various lacustrine environments (Dean et al. 1987) have been the bases for most of the progress in recent decades' in high resolution paleoclimatology as well as in our understanding of temporal and spatial coherence of annual and epochal climatic processes. These studies along with hydrological information, on many time scales, from instrumental to inferential sources, provide methods for interpreting seasonal patterns and their variations by region, as well as the major events within epochs, and their likely atmospheric precursors (e.g. Enzel et al. 1989).
Marginal marine environments with high sediment accumulation rates and tendencies toward anoxia promote varve formation, as the dysaerobic conditions tend to restrict the depth of bioturbation to a few centimeters, and may preserve temporal resolution in the range of decades to centuries. For example, sedimentation rates along the upper continental shelf California are in excess of 30 cm/1000 years. Today this region is one of high wind stress, Ekman transport, upwelling, and high primary production. Episodes of higher productivity in the late Pleistocene increased biological oxygen demand which decreased the concentration of dissolved oxygen in the oxygen minimum zone. Sediments that accumulated under these dysaerobic conditions consist of decimeter scale zones of varved sediments, interrupted by decimeter scale zones of bioturbation.
These epochs of varves and bioturbation are believed to be the result of strong, quasi-cyclic changes in dissolved oxygen concentration that are in turn linked to episodic surface wind changes, hence changes in coastal productivity, via increased wind stress and upwelling. Coastal sites with known varved records are scattered about the world ocean eastern boundary currents: Walvis Bay, South Africa; south and central California and the Gulf of California; Peru; Chile; Central California, and, as well, the Cariaco Trench off Venezuela's north coast. There are also known and suspected sites within estuaries scattered around the world from Alaska to Norway, and within the fjords of Chile and known sites near the Palmer Peninsula in Antarctica. The idea that these could be studied, and the high resolution seasonal patterns compared across a single North-South Global transect was the basis of the "Climate Barometer" concept that Sharp and Anderson proposed in 1990.
The methodologies developed for varved sediments have wider application. Suitable coral sites are widely distributed and a survey of lacustrine sites (Anderson et al., 1985) has identified many varved or laminated lake sediments in which interpretations could be improved by linkage to climatic variables. However, most of the world ocean margins remain under sampled, and what needs developed is a coordinated global program. The prototype for a system of marine and lacustrine observations has been developed, and is in place in Monterey Bay. Both the first retrieval of sediment traps and environmental information after an eight months and the one year sampling cycles have proved successful.
Patterns of variation
In the central California region, the Holocene sediments (the recent 10,000 years) are intermittently varved and are strongly bioturbated, suggesting that there was a different climatic regime and a greater millennial variability in the ocean atmosphere system off central California during the late Pleistocene. Similar materials from the southern California Bight anoxic basins are continuously varved over this latter period. The period of the oscillations cannot yet be accurately determined, because the records are incomplete, but one average climatic period appears to be near 2000 to 3000 years, with evidence for some longer cycles, and several shorter ones.
Even ventilated basins with accumulation rates of ~10cm/1000 years, such as the Sulu Sea, a deep-marine, shallow silled basin located in the humid tropical region of the western Pacific, preserve millennial scale variability. For example, Linsley (1989) found very strong stable oxygen isotope and species census signals from assays and counts of planktonic foraminifera in core samples that showed that the Sulu Sea temperatures were well below usual tropical temperatures. Evidence of the Younger - Dryas climatic cooling event between 10,000 and 12,000 years ago was found, and in fact there were clearly recorded millennial scale patterns of cooling and warming in this region.
Detailed calcium carbonate analyses for the last 40,000 years reveal strong millennial cycles in carbonate accumulation from 30,000 years B.P. to the present. Spectral analysis defined the period of the cycles during the last glacial maximum at 5,000 years, with a shift to a 3000 year period in the Holocene. Further study and high resolution dating techniques are needed to determine if these fluctuations represent the same sort of climate forcing from which the central California sediment patterns were derived. Clearly, there are immense opportunities to develop information from which to evolve the necessary understanding of climate dynamics within a higher resolution global climate context with these types of environmental research tools. The problem is to initiate these rather more demanding research efforts, rather than to remain locked in on the longer time scales and the somewhat more fuzzy spatial scales that more remote time studies provide.
Dealing with "noisy" signals
For decades we have heard that there is too much "noise" in climate-proxy data, that it is difficult to resolve the climate signals. What needs to be reconsidered are the relative importances and relations of the frequencies and magnitudes of extreme climatic events on time scales ranging from synoptic to geologic, within contexts of long term climate patterns and global trends. One of the properties of geologic processes is that they act as low pass filters of the climatic signals, removing information and recording only a smoothed proxy of climate change.
Annual cycles and longer scale processes are clearly important in climate studies, but it is often difficult to discriminate between the shorter term consequences and those of most of the longer time scale processes except through changing manifestations of the frequencies and intensities of extreme climate events, droughts, floods, freezes and thaws. Whatever the process, it is important to develop fuller understanding of the range and scope of climate consequence information during periods of relative climate stability, and compare these to patterns that occur during transitional phases from one climate regime to another. For the period since 1945 or so, the climate varied from a relatively stable state to one of relatively strong trends, and a reversal has begun since the peak of the 1982-83 warming event. All of this has taken place within the context of a general positive trend, as Bakun's (1990) report on coastal ocean surface winds indicates.
Unfortunately, much of the historical, instrumental climate record has been collected as we emerged from the Little Ice Age, which ended in the late 1700s. The continuous warming of the earth, the atmosphere and the oceans since then has been sporadic, somewhat disjointed, although clearly part of bigger, unified global processes.
This lesson alone should provoke the scientific community to retain humility and recognize that there are simply not sufficient measurements or understanding to provide the bases for long term climate forecasts. The necessary "context" needs to be assigned from studies of longer records and consequences (so-called proxies) of climate variability, not by defining the base period as the most recent stable period with the assumption that this variation is wrapped about a long-term mean that is somehow stabilizable and dependable, that is if one could somehow immediately turn off and even reverse the greenhouse emissions.
Our concerns should be two-fold. First, to get studies and interpretations done that will provide information on the natural patterns of climate variability, that resolve seasonal processes, and then work out a reasonably effective and efficient means to link our observing systems in such a fashion as to insure that they are functionally intercalibrated, and that they can be employed to understand, hence forecast annual seasonal processes, including seasonal events, in the manner of the approach employed by William Gray and colleagues, of Colorado State University, for their annual hurricane forecasts. Then, if we are successful, we will have come full circle from empirical observation, through synthesis, to understanding.
Consequences of climate variability are often ephemeral, and it is important to classify the various types of consequences in relation to the perturbation in terms of immediate impact, persistence, and elasticity of the system in which the event or events have taken meaning. These types of classifications can be very useful, in defining the relevance of efforts to ameliorate, or not, in long or short term. While there are many whose immediate concerns about climate change are broad, there is a body of the science community that has focused on sea level change as a major threat. This topic is also not without its controversial issues (Pirazzoli 1989), and warrants little attention here, other as another example where even with global measurements, the secular trends are very fuzzy, and even contradictory.
A series of very different types of ecological responses to local and regional climate driven processes have been documented and outlined in many other publications, particularly within the last decade (e.g. Sharp and Csirke 1984, Csirke and Sharp 1984, Wyatt and Larrañeta 1988, Payne et al. 1987). The local and regional conferences resulting from the 1982-83 warm event stimulated literally dozens of compilations and descriptions of consequences from the devastating flooding from the 1982-83 El Niño in Ecuador and Peru which removed entire human colonies from river bottoms around northern South America, to the localized blooms of scallops in several bays along the southern Peruvian and northern coasts of Chile (Arntz 1984, Avaria 1985, IFOP 1985, Illanes 1985 ).
Beyond the terrestrial consequences, reviewed by Glantz et al. (1987) the displacement of aquatic populations were reported globally. However, many of the local changes were very short lived, often lasting for as little as eighteen months, or as long as it might take for the replacement populations of, for example, mussels, to be once again displaced and alga to recolonize. Year to year variations in growth, reproduction and behavior of these aquatic populations are integrations of their habitat variations, and as such provide a useful monitoring opportunity for climate studies.
The 1983-84 expanses of burned off areas in northern Australia are an echo of previous events associated with the ending of major ENSO warming periods earlier in this century, and before. The fact that the Amazon basin has been burned and replaced by pampas many times in history is not trivial, given that we are going to have to cope with such an inevitability. The scenario in which the subsequent recuperation and recolonization of highly disrupted terrestrial environments by wildlife and plants might take several decades to millennia has had little impact in spite of those portending doom and gloom from CO2 warming. Also, the fact that this type of cataclysmic displacement is common in aquatic environments should not be forgotten.
Perhaps there is too much concern for maintaining status quo, and too little understanding that this is not only unlikely, but not possible, particularly given the pressures of an ever expanding and ever more perturbing humanity. What is relevant is that scientists should do more to inform.
While we can applaud efforts to maintain pristine environments, we can also see that this is another artifact of our misconceptions about the "balance" of nature. The most obvious thing about nature is that it thrives on imbalance, and in fact that natural systems are most productive when given a good "kick", ranging from diel water column mixing, to lunar tidal cycles, in the oceans, to seasonal cycles of rainfall and insolation across terrestrial landscapes, on to more dramatic seasonal events such as flooding and related nutrient transport processes. There is a very important similarity between terrestrial hydrology patterns and their effects on nutrification and turnover of plants and therefore the entire food web of terrestrial systems, and the dynamics of the upper ocean and its effects on aquatic ecosystems.
The types of perturbations that are least common are often most destructive in the short term, but they can portend much longer epochs of increased production, for example, due to refertilization and mineralization of leached environments. We are still reaping the rewards of the last Ice Age in the form of ground water and fertile mid continental plains. Even the most catastrophic volcanic events provide opportunities which are quickly taken advantage of by vagrant species with adaptations to such initially harsh environments. The downstream effects of great environmental upheavals are generally increased primary production, and increased turnover rates.
It is more difficult to define the positive benefits in human contexts from earthquakes and volcanic activities, or to long, wet or harsh winters or dry hot periods, but these should not be measured solely in terms of immediate costs to society. It is also important that we should understand that although we might be able to plan ahead for the next fifty year's sea level rise, or tectonic displacements that the planning to either "resist or retreat", in the words of Dennis King, should include a long term analysis of the benefits of letting nature take its course, and investing in the future by careful analyses that account for normal depreciation and projected replacement costs of the various threatened facilities.
It is certain that sea level has been rising continuously for millennia, although rather slowly during this century (Pirazzoli 1989), and that it will continue to do so. There are also major regions of the world where the earth's surface is being subducted in plate tectonic processes, and others where removals of natural gas and petroleum have induced submergence of coastal areas. This problem has in many cases been viewed as an engineering problem. However, it is not certain that building major barriers and dikes provides anything positive in either the near or long term to those waterways and wetland systems around which the recent centuries' water based transport for trade and commerce has developed, and recently, has begun to decline. It also should not be forgotten that the reasons that the transport industry was initially coerced into investments in these transient and often inhospitable environments was because of the needs of railroads and waterways to meet shipping lines at points that provided safe, navigable harbors and access to regional industrial centers. However, minimizing loss of wetlands due to coastal development is a socially responsible behavior.
Initially, rail-head and port loading sites were often chosen in low value, marginal regions because they would be away from towns and families, and so as to minimize the impacts that accompany the convergence of industrial transportation and, as well, so that industrial noise and refuse would not pose issues to home owners and town folk. These sites are now taking on different functions is part of the evolution that will continue in the wake of new industrial opportunities and technologies.
Although we should not be loath to see another age of "tall ships", it is not a likely scenario given the evolution of shipping technologies, particularly now that water transport has taken on new tasks, which include rapid transport of perishables, which is by its nature very energy demanding. With the growing dependence upon air transport and the rapid transport capabilities that grew in relation to super highway systems, many countries have joined in the market place. With very different labor costs and natural resource distributions, many lifestyles are changing, again, as most of the world industrial centers that were dominant at the turn of the century have slowed their pace and been transformed into commerce and banking centers, with the associated change from blue collar to white collar residents. These changes are a statement about the global society, and its changing status and expectations.
With the above changes in emphases in commerce has evolved ever more demand for a global climate monitoring network and weather forecasting capability. The fact that the global weather monitoring system exists at all is due to the rapid changes that were observed in the last two decades of the last century. With shipping and transport industry growth has evolved the global weather information system, the World Meteorological Organization's Global Telecommunication System being one of the few truly global and mutually beneficial functional information networks.
Clearly, what has been missing from this great enterprise has been the development of an analogous system of ocean monitoring interests and tools. Now that the global climate forecast and monitoring issues are surfacing, in the face of various observations and speculations, it is imperative that the role of the ocean in these processes be brought into context. Appropriate expansion of the global environmental monitoring system should include means to monitor at least the upper 500 meters of the ocean. Obviously, the associated costs are not trivial, but the overall benefits would range well beyond climate forecasts. There would then be some hope for the development of the understanding needed to cope with many real world problems, within a truly global system context, rather than disconnected and societally ill-defined ones that provide only modelers with ingest data. Projections and extrapolations are inadequate tools for the problems being faced, given the well recognized uneven geographic and demographic impacts of climate change. Lest we forget, daily events are most relevant.
Consequences of climate variability can and will in most cases continue to extend well into society, present and future. How we deal with the lessons from history will certainly shape the pathway toward a resolution of the climate forecast problem, after building sufficient understanding for credible predictions. As time passes it is important that we recall the lessons of history, as was well stated by Santana in his oft quoted admonition.
Likewise, those sciences which are based on historical perspectives rather than on mathematical conventions need to be better integrated into our systems of defining what climate change is about, particularly its societal implications. Naturalists, geologists and climatologists have had little voice until recently in the debates regarding the values and roles of various measures of climate change. Very few or no purely physical scientists would likely agree, but the most readily observed global phenomena that provide evidence for climatic changes on all scales are biological responses by local plants and organisms that have adopted their annual life history strategies in response to local and regional seasonal patterns and their variabilities over generations. Unseasonal weather, or a geophysical event can extinguish centuries of adaptation to even the severest of climate change.
This knowledge has provided a basis for entire fields of scientific and empirical research over the last century. This includes the shaping of growth and transport related characteristics of agricultural products through selection of special physiological tolerances amongst cultivars, domestic animals, and aquacultured species. More recently, molecular genetics and highly specific genetic engineering technologies have replaced the longer term empirical field selection programs, but they are still dependent upon clear, objective identifications of each very particular characteristic that one would transfer from one genome to another. This can only be done through careful observation of the responses of individuals to controlled patterns of environmental changes, in nature or in the laboratory.
The examples which best provide the insights into the problems in marine resources contexts are those surrounding the debates over what constitutes sufficient versus necessary information for monitoring and managing fisheries resources, within a context of continuously varying climate. The debates stem from the early period of recognition that man can have adverse impacts on the ocean and its inhabitants, and the understanding that fish and other marine life are very responsive to local and regional ocean condition changes. Sette (1943) initiated a sequence of approaches that evolved into the California Cooperative Fisheries Investigations (CalCOFI), a unique ocean ecosystem research and monitoring scheme which evolved and operated intensely for several decades (Sette 1960). CalCOFI has nearly collapsed in recent years in the ever increasing scramble for funds for monitoring the oceans from space, and fisheries from catch statistics (Isaacs 1976). Of course, it turns out that the program was entirely inadequate for fisheries management purposes, as conceived, except for monitoring processes and their consequences that occur on the annual to decadal and longer scales.
Employing the long, high quality data sets from the California Fisheries, Parrish and MacCall (1978) provided the prototype environmental investigation and developed a forecast model for the Chub mackerel, (Scomber japonicus) in the California Current region. The forecasting paradigm that emerged from their study failed in recent years, for many reasons, but primarily due to broad, system changes which were concurrent with changes throughout the global ocean.
The recent decade's efforts to stimulate research into pelagic fish recruitment issues was partially stimulated by observations such as those described by Owen (1981, 1989) on the relations between micropatch structure and species composition within eastern boundary currents, and Reuben Lasker's stratification hypothesis relating survival of the early feeding stages of pelagic species to the presence or absence of food patches of sufficient densities to sustain them, as outlined in Sharp (1981) and developed further to include predation and other issues by Bakun et al. (1982). It was obvious that several approaches could be taken, which, by the nature of funding climates in the 1980s, did not include intense observational field studies and environmental monitoring on high resolution scales in the USA.
The decision to take the comparative approach to the problem by studying diverse eastern boundary and potential analog systems was taken by Parrish et al. (1981 and 1984) Bakun and Parrish (1990 and in press). They succeeded in developing sufficient insight into the behaviors of an array of species that they have been able to define the conditions that apparently are required for the successful growth and reproduction of engraulid fishes in many current systems. They discovered that each species faced a different physical regime in which the processes leading to their requisite habitat conditions for reproductive success were unique. In spite of this great physical and consequential ecological diversity, the structures and necessary ambient conditions were propagated, exploited, and successive year classes emerged. It was also obvious from this and similar work being done around the globe that we were looking at identifying rare, specific processes and features. Unfortunately, full, high resolution monitoring of these ecosystems would be expensive, if possible at all, hence socially inappropriate. Yet there are some types of forecasting which appear to be feasible, given that the kind of monitoring necessary for society in the global change problem are implemented, and that fisheries monitoring can contribute to greater or lesser extent in the determination of regional climate status and trends.
The examples of failed recruitment forecasting paradigms in fisheries is a study in short term climate changes, and the conclusion that is emerging is that until there is a step back, away from the immediate need for year to year management methods, there cannot be any reasonable and reliable forecasting, simply because the ocean is a complex mosaic of opportunities, which are only rarely repeated, hence statistical approaches cannot be relied upon. Nothing is quite so sobering to those that believe in their mathematical population models as an era or event that precludes the biology that the paradigms predict from taking place.
The recent droughts in the northwestern USA simply preclude salmon from getting up stream to their spawning grounds. This is a conditional process that is clearly beyond those populations' inherent stabilizing mechanisms. The persistence or frequencies of such events shape the zoogeography and plant distribution of the entire globe, on a seasonal basis. The lethal events can be spread over decades, as in climate change, or over days, as in severe aseasonal freezes or deluges. On the other hand, the number of potential larval survival windows for a number of aquatic species may actually increase under system wide perturbations of this sort, and lower predation from the salmon that do not arrive on the high seas or coastal nursery grounds may actually be the source of another valued resource's sporadic success story.
Given the array of climate variabilities and manifestations that are described in this brief document, it should not be surprising to anyone that we have been so unsuccessful in managing natural resources by employing primarily conventional equilibrium models, and such short data/observational records. An event such as the 1982-83 ENSO warming captured the entire global population's attention, simply because consequences of one sort or another reverberated throughout all society. The ultimate challenge will be to rebuild our earth observing capability, particularly the in situ monitoring capability, so that records of the coastal ocean dynamics, terrestrial hydrology and other important processes can be brought into focus in useful manners.
Without some clear understanding of the true trajectories of pending climate changes, the proposition that ecological, and related societal responses can be forecast is just another game of chance, without much to gain, whether right or wrong, but with much to lose if there is nothing done to improve our understanding. It is a case of declining human status, within a much stressed environment. Null hypotheses do not include status quo, in any sense, providing ample reason for better monitoring, more historical perspective, and great effort to coordinate the knowledge as it accrues, into a global perspective, and to apprise the public of their options.
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