Observations speculations and suggestions

Dr. Timothy Barnett of Scripps Institution of Oceanography (California) found that the recent decades' strong correlations between SST in the eastern Pacific Ocean and solar activity appeared to fall apart for earlier records from about the mid-1920s (Fig. 16.5). R.Y. Anderson (1990) posits that solar activity modulates ENSO frequency. The sunspot numbers (Fig. 16.6) are related with solar energy emissions, hence following the empirical engineering principle where oscillating systems are apparently modulated by solar input. In this case ENSO (warm) events occur less frequently, separated by extended tropical ocean cooling periods. If Anderson's interpretations are correct, Barnett's findings might even be expected, given that the annual sunspot numbers shot upward from about the 1920 period from a nearly constant, relatively lower value for the 1880-1920 period.

Long- and short-term trends, as well as forcing functions, complicate the issues surrounding recent emphases on anthropogenic changes. This, however, should not dull one's interests in separating out the latter from amongst the strong natural changes that are not only unmanageable, but also are of great magnitude. Since the upper ocean heat content is at least an order of magnitude greater than that of the atmosphere, the upper ocean mixing, and related heat transfers and transformations, have surely been underestimated by atmospheric modelers among the more critical climate mediating processes related to the earth's nonatmospheric energy contents and transfers on all time scales.

Similarly, fisheries variability has been documented in nearly every region of the world to vary on similar time scales, and in many cases can be shown to be changing in phase with climate signals, no matter what their source. Soutar and Isaacs (1969)

EASTERN PACIFIC SST MODULATION vs SUNSPOT NUMBER

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Fig. 16.5 The sunspot frequency (gray pattern) for the period from the 1880s to the late 1980s appears to be very well correlated with sea surface temperature (oscillating positive-negative anomaly record) in the eastern Pacific Ocean during the period from the mid-1980s back to about the mid-1920s. Prior to that period the records are far less convincing (personal communication, Dr. T. Barnett, Scripps Institution of Oceanography).

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Fig. 16.5 The sunspot frequency (gray pattern) for the period from the 1880s to the late 1980s appears to be very well correlated with sea surface temperature (oscillating positive-negative anomaly record) in the eastern Pacific Ocean during the period from the mid-1980s back to about the mid-1920s. Prior to that period the records are far less convincing (personal communication, Dr. T. Barnett, Scripps Institution of Oceanography).

documented 2,000 years of ecological changes of similar magnitude in the sediment records from the Santa Barbara Basin off southern California; similar studies are in progress around the world. Natural population states are demonstrably unstable, and they are not always high in the absence of fishing. More frequently they are low, with occasional periods of expansion, inevitably followed by natural or human-induced collapse.

How to adapt to these processes and minimize human effects demands that attention be paid to the entire global ecosystem, to its major source of energy, and to the interactions from the high stratosphere, through the marine layer and into the sea, if we are ever to understand and adapt appropriately. Meanwhile, North American fisheries science continues its struggle over "who was right" and whether it is the Ricker or Beverton and Holt growth model which applies in individual species assessments. In truth, these models are inappropriate to address the problem of trying to understand responses of entire regional ecosystems to climate-

1650 1750 1850 1950

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Fig. 16.6 Combining the estimates of El Niño frequency (dashed line) and sunspot numbers (relative numbers portrayed by continuous line), R.Y. Anderson (1990) showed that the records for the last 300 or so years are strongly negatively correlated, from which he concludes that solar energy may modulate ENSO frequencies.

driven ocean variabilities, with man pecking away at the biomass along with an array of other competitors.

After the collapses of the California sardine fishery in the early 1950s and the Peruvian anchoveta fishery in the late 1960s and early 1970s, it is clear that recovery from such conditions, if at all possible, will require some combination of complete fishery closure and a long waiting period for the next round of climatic changes that favor a period of natural population growth. Many fishery scientists now believe that single-species fisheries management and associated assessments that ignore climate variation are outmoded (Bax, 1991; Caddy & Sharp, 1986). Some within the marine ecological community have trouble dealing with the fact that climate is the dominant force in long- and short-term fishery resource production in both oceanic and limnological contexts. Others, however, have accepted the relative importance of climate impacts on these ecological changes. We remain relatively ignorant of specific mechanisms that dominate local ecosystems at any place or point in time, beyond the basic seasonal production patterns and their perturbations. The last decade's collapse of support for ocean monitoring and shipboard research has hindered understanding.

Where adequate population- and climate-related data have been collected, the models, and their sustaining theories, have too often oc <

Sunspot Number

1650 1750 1850 1950

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Fig. 16.6 Combining the estimates of El Niño frequency (dashed line) and sunspot numbers (relative numbers portrayed by continuous line), R.Y. Anderson (1990) showed that the records for the last 300 or so years are strongly negatively correlated, from which he concludes that solar energy may modulate ENSO frequencies.

Sunspot Number been shown to deviate significantly from reality. This is the reason why many of us are perhaps more reluctant to accept pure model output as fact. However, science is not purely objective; much of the scientific controversy is not over fundamental principles of faith, or mythos, in spite of facts (see, for example, Roberts, 1989).

With regard to the impacts of climate variability and change, many records of various types show that the ocean, even within a basin at similar latitudes and in the same region, responds quite differently to the same forcing mechanisms such as ENSO events. Given that seasonal variability in some regions is greater than the annualized global averages projected from most (if not all) general circulation models (GCMs), there are precedents for estimating ecological responses. Yet, the formats of the climate-ocean scenarios produced by the present generations of GCMs are to date inappropriate for projecting with any degree of confidence the consequences of these scenarios.

The transitional nature of the ocean and the atmosphere is well embedded in the response mechanisms of all terrestrial and marine ecosystems; the paleoclimate records document this. What appears to be missing from the logic of the general circulation models is the importance of seasonality, regionality, and specified linkages to ecological systems that would permit reliable regional scenarios and their consequences to be developed.

For example, monsoon rains and floods account for sporadic occurrences of thousands of human deaths each year in many areas, particularly around the northern Indian Ocean. Changes in the frequencies, intensities, durations, and locations of these events will be of greater societal concern than "statistically smoothed" statements about global-averaged surface temperatures and soil moisture coefficients. Clearly, it is time to revise the approach being taken in order to reflect the most pressing requirements for defining impacts on society.

If global heating phenomena take place from the equatorial region, then we have some degree of experience and untold opportunities to obtain valuable insights from sediments and other proxy records with seasonal, and annual-to-centennial resolutions of these types of processes. If arguments can be proposed for another mode of change different from those that have been documented to have occurred in the recent glacial and inter-glacial periods, then it is important to get those mechanisms described as soon as possible. This requires carefully reasoned definitions of transitional processes, and their array of interactions.

It is clear that marine and terrestrial populations respond on short seasonal scales to all levels of perturbations. Biological indicators have been described that define nearly the entire spectrum of climatic regions, terrestrial as well as aquatic. Zoogeography is the basis for much of our current understanding of both near-term and paleoclimatic variability.

In the marine environment there are many clear-cut indicator species. Although our knowledge is greatest from harvested species, one does not have to depend only on commercially harvested species as status and trend indicators. This is so because some clearly identifiable species are already useful indicators of ocean boundary and vertical thermal partitioning processes (cf., Loeb & Rojas, 1987). For example, tuna fisheries around the world appear to benefit from increased recruitment in years following El Niño events (Suzuki, 1989). If this is because of the general warming of the upper ocean, and associated biophysical processes, then one might have to conclude that the ocean's higher trophic level production is in general actually enhanced during strong transitory heating periods.

In developing climate change (and consequences) scenarios, competing hypotheses need to be examined. For example, it could be that the apparent lack of new primary production during warm periods, shown from long-term studies, might actually be confounded because that new production may perhaps be quickly sequestered in the higher trophic levels (during the early life history stages when more direct advantage can be taken of local production blooms).

That so many species, both predators and prey, seem to "bloom" during the warming trends (e.g., sardines, Pacific halibut, tunas, etc.) belies the argument that warm periods are not favorable for biological productivity in the ocean. These species have extensive energetic demands, relative to their counterparts, and there is obviously some substantive mechanism that provides for blooms, colonizations, and broad spatial distributions of these populations on local to basin-wide scales. Cooling periods are tracked by other species such as those associated with coastal upwelling systems, that is, anchovies, or those in open ocean systems, such as the Todarodes squid.

This suggests that the warming of the upper ocean forces the interaction of water masses, both vertically and horizontally, and that the species that can forage over the broader opportunity fields have an advantage over those limited to, for example, coastal up-welling environments (e.g., anchovies). The opposite conditions benefit other species, as evidenced by the natural oscillations in dominance between these groups, for example, between sardine and anchovy or between tuna and squid.

Another group of species that would respond in synchrony with various scales of climate variations are those that depend upon freshwater flows in estuaries, such as shrimp (Garcia & LeReste, 1981), anadromous (Pearcy, 1984), and obviously also catadro-mous species. The Indian Ocean resource base is a mosaic of such estuarine and coastal species. As such, any seasonal changes in the hydrological cycle will affect each region to a greater or lesser extent (Pauly & Navaluna, 1984).

While there are many regions where tropical tunas appear to behave primarily as oceanic predators, the entire northern Indian Ocean coastal area is inhabited by T. tonggol, the long-tail tuna, which thrives on shrimp and many other estuarine species. In fact, the northern coast of Somalia is home to a tuna fishery which harvests long-tail, yellowfin, and many other scombroids, within the nearshore (shelf) environment. From this one would infer that any changes that affect nearshore productivity would certainly affect these opportunistic predator species. Long-term monitoring of such areas is necessary, if one is to expect to project, as well as to compensate for, marine resource responses to climate-induced environmental change.

Open ocean tuna fisheries, on the other hand, are likely to become even more versatile. If the seasonal monsoonal gradients should shift, invoking greater surface winds, or greater current strengths than presently exist, there would be large areas of the western Indian Ocean that would become unfishable for purely geophysical reasons. The Somali Current provides an example; there are periods of the year (e.g., June and July) during which strong surface and subsurface currents produce shear forces which make it difficult, if not impossible, to deploy purse seine gear. However, the traditional dhows, dhonis, and outriggers that ply these coastal regions have evolved such that they employ breakaway stays and rigging in order to minimize the adverse effects of extreme weather. They will likely persist, as have their crews' cultures, for millennia.

Without a doubt, the long-term trends with regard to climate change will affect local coastal environments and island communities within the Indian Ocean, yet each one is likely to respond in different ways to such changes in their regional environmental settings.

The Seychellois will have the advantage of the interests of the European Community, as "investors" in the western Indian Ocean fishery system, but it is not likely that the Maldivian culture will have become so changed over the next decades as to alter their traditional survival strategies. The Maldives' extended geographic position within the ocean ecosystem is such that they will be able to take advantage of nearly any latitudinal shifts in availability of their prey, and the geomorphology of their situation provides the unique focus for aggregations of tunas, and other species that will provide some level of needed support. However, a sea level rise may simply erase the Maldives from the surface of the ocean.

I have not emphasized, except for Thailand, the position of eastern Indian Ocean tuna in this chapter. However, it should be noted that, except for the southern bluefin tuna, there are few developed fisheries in the region, although there is a growing Indonesian-based fishery. Much of this fishery's growth will depend on the development of local technical expertise, and the evolution of collection and marketing systems. There is an opportunity within this region to harvest far more tuna, particularly skipjack and small yellowfin, than is presently taken.

Among other opportunities yet to be developed are subtropical fisheries for albacore tuna, particularly off southern Madagascar and the coast of South Africa. While these do not provide comparably dense schools, nor aggregate well enough for large fishing vessels to operate economically, smaller crafts with smaller crews, along with relevant operational oceanographic support via satellite, could provide a basis for significant catches in the future. It may be decades, however, before such a fishery evolves, given the harsh lifestyle that such a fishery would impose.

Climate change scenarios emanating from research institutions in industrialized countries in the Northern Hemisphere will not necessarily impress Indian Ocean fishermen who are already coping with some of the most dynamic systems in the world; these fishermen have come to expect change. One must wonder, however, about the stability of the infrastructure that has quickly developed in the region, and the possible effects of changes in climate and ocean on these fragile Indian Ocean ecological settings.

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