be associated with a decrease in the temperature gradient 

 between the equator and the poles and, as a consequence, with 

 a decrease in the intensity of winds and oceanic currents 

 (Mitchell, 1988). This in turn could lead to a shrinkage of 

 oceanic upwelling areas and weakened upwelling. 



In addition to its effect on the circulation of World Ocean 

 waters, warming in the Arctic and Antarctic region would have 

 a marked impact on the state of the Earth' s cryosphere (glaciers, 

 shelf and marine ice). Such changes would in turn affect the 

 functioning of the climatic system. 



First, the ice that covers 1 1 % of the World Ocean's surface 

 area to a large extent determines heat transfer between ocean 

 water masses and the energy balance at the ocean-atmosphere 

 interface. These factors influence the intensity of oceanic 

 convection, which in turn establishes the time scale of processes 

 that extend to great depths (e.g., CO, circulation). In addition, 

 exposed ocean waters absorb considerably more solar radiation 

 than do ice-covered waters (Walsh, 1983). Hence, changes in 

 the extent of ocean ice cover would inevitably affect atmospheric 

 circulation and temperature. 



Second, even minor changes in the Earth's cryosphere 

 would lead to a significant change in global sea level as 

 compared with current values. 



The rise in air temperature expected to occur in the Arctic 

 would have considerable consequences for the extent of marine 

 ice cover. Thus, sunmiers could bring about the complete 

 melting of the ice cover around Svalbard, along the north coast 

 of Siberia, and along the Arctic coast of Canada. Nevertheless, 

 in our view the global warming predicted by the middle of the 

 2 1st century will not lead to a majordiminutionof the ice mass 

 of the Antarctic and Greenland ice shields. Indeed, recent 

 studies in the Northern Hemisphere have shown that the extent 

 of ice cover over the past decade has increased despite a small 

 rise in mean annual temperature (Bryan et uL, 1988). On the 

 otherhand, the warming by 4° to 5°C that is expected (Mitchell, 

 1988) may lead to an acceleration of the flow of continental ice 

 sliding into the ocean and, therefore, to some decrease in ice- 

 cover thickness in the western Antarctic (Bud'ko & Izrael, 

 1987). 



It may be noted in summary that global warming would 

 very likely entail displacement of surface isotherms toward the 

 poles, changes in the functioning of upwelling areas, and some 

 shrinkage of ice cover in the Arctic. Melting of sea ice in the 

 Arctic may produce a freshening of waters in the northern 

 Atlantic with consequential changes in the formation of ocean- 

 bottom waters. This process may affect heat flow in a northerly 

 direction, which might ultimately result in a shift in global 

 oceanic circulation (Bi7an el <;/., 1988). 



Changes in the Carbon Cycle 



The doubling of the carbon dioxide content of the 

 atmosphere predicted for the year 2050 may well disrupt the 

 global carbon cycle and therefore involve severe consequences 

 for the formation of the Earth's climate. Assessment of these 

 consequences requires profound insight into the cause-and- 

 effect relationships that constrained the natural variability of 

 CO. content in past geologic ages. 



It should be noted that the elevated solubility of carbonates 

 occasioned by the increased salinity of seawater resulting from 



increased CO, levels produces increased alkalinity and therefore 

 augments the ocean's CO,-hoIding capacity (Boyle, 1988). 

 Furthermore, CO, absorption in upwelling areas occurs largely 

 through the photosynthctic activity of phytoplankton, whereas 

 in the higher latitudes considerable amounts of atmospheric 

 CO, are extracted by oceanic masses in the process of deep- 

 water formation, particularly in places where the deep waters 

 in question rise to the surface (Roots, 1989). In addition, 

 increased carbonate solubility (as a consequence of the 

 acidulation of the surface layer by increased amounts of 

 dissolved CO,) can raise the alkalinity of seawater and hence 

 enhance the ocean's ability to absorb CO, (Boyle, 1988). 

 Possible increases in the amount of organic matter deposited in 

 bottom sediments due to augmented entry into the marine 

 environment of biogenic elements due to sea level rise can also 

 be regarded as a probable mechanism of removal of human- 

 generated CO, from the atmosphere (Siegenthaler, 1989). 



It is therefore evident that rises in the carbon dioxide 

 content of the atmosphere may result in a disruption of the 

 global carbon cycle. The scale and thrust of possible changes 

 would be determined largely by the particularities of upwelling 

 ecosystem functioning under global warming conditions. 



Changes in Biogenic Elements 



Increased releases into the atmosphere of gases and aerosols 

 containing nitrogen, phosphorus, and sulfur compounds as a 

 result of human activities in highly industrialized countries 

 such as those of the North Atlantic seaboard are increasing the 

 amount of these substances entering the ocean (Oppenheimer, 

 1989). This process is particularly significant in the case of 

 nitrogen and sulfur, whose entry into the photic zone of the 

 ocean through the atmosphere may be compared with its 

 delivery by diffusion convection (Duce, 1986). Rises of 

 nitrogen and sulfur levels of regional scale, especially in 

 impacted ocean areas, may be accompanied by rises in the 

 bioproductivity of the affected ecosystems. Such phenomena 

 have already been reported for the coastal marine areas of the 

 North Sea (Lancelot et al., 1987). 



Sea level rises accompanied by flooding and soil erosion 

 would result in considerably augmented influx of N, P, and S 

 into coastal areas, which might well produce intensified 

 eutrophication processes in the ecosystems thus impacted. 

 One consequence of this may be an acceleration of the 

 biogeochemical cycles of all biogenic elements (Oppenheimer, 

 1 989). This would depend on regional circumstances, however. 

 In the Beaufort Sea, for example, the erosion-susceptible peat 

 might become an important source of organic carbon for the 

 food chain in adjacent coastal waters. On the other hand, most 

 continental high-latitude regions can expect increased 

 precipitation, which would tend to increase biogenic-element 

 input into the nearby ocean. 



Changes in Polliiltnit Cycles 



Being associated with the intensification of microbial 

 degradation processes, the rise in marine surface-water 

 temperature currently predicted for the higher latitudes could 

 result in the accelerated hiodegradation of globally occurring 

 pollutants (chlorinated and petrolic hydrocarbons, phenols, 

 etc.), which would, in turn, promote the decomposition of such 



