OBSERVATIONS AND PREDICTIONS OF ARCTIC CLIMATIC-CHANGE - POTENTIAL EFFECTS ON MARINE MAMMALS

Recent analyses have revealed trends over the past 20-30 years of decr easing sea ice extent in the Arctic Ocean coincident with warming tren ds. Such trends may be indicative of the polar amplification of warnin g predicted for the next several decades in response to increasing atm ospheric CO,, We have summarized these predictions and nonuniform patt erns of arctic climate change in order to address their potential effe cts on marine mammals. Since recent trends in sea ice extent are nonun iform, the direct and indirect effects on marine mammals are expected to vary geographically. Changes in the extent and concentration of sea ice may alter the seasonal distributions, geographic ranges, patterns of mi,migration, nutritional status, reproductive success, and ultima tely the abundance and stock structure of some species. Ice-associated seals, which rely on suitable ice substrate for resting, pupping, and molting, may be especially vulnerable to such changes. As recent decr eases in ice coverage have been more extensive in the Siberian Arctic (60 degrees E-180 degrees E) than in the Beaufort Sea and western sect ors, we speculate that marine mammal populations in the Siberian Arcti c may be among the first to experience climate-induced geographic shif ts or altered reproductive capacity due to persistent changes in ice e xtent. Alteration in the extent and productivity of ice-edge systems m ay affect the density and distribution of important ice-associated pre y elf marine mammals, such as arctic cod Boreogadus saida and sympagic ,aic (''with ice'') amphipods. Present climate models, however, are in sufficient to predict regional ice dynamics, winds, mesoscale features , and mechanisms of nutrient resupply, which must be known to predict productivity and trophic response. Therefore, it is critical that meso scale process-oriented studies identify the biophysical coupling requi red to maintain suitable prey availability and ice-associated habitat fur marine mammals on regional arctic scales, Only an integrated ecosy stems approach can address the complexity of factors determining produ ctivity and cascading trophic dynamics in a warmer Arctic. This approa ch, integrated with monitoring of key indicator species (e.g., bowhead whale, ringed seal, and beluga). should be a high priority.