92-30570I 17With past ONR support from Grant N00014-87-J-1218, we had successfully coupled simple biological models of phytoplankton production (light and nutrient regulation of one size fraction) to time-dependent, 3-dimensional physical models of basin circulation at 25-30 km resolution in the Gulf of Mexico . While these coupled models mimicked seasonal cycles of phytoplankton abundance in basin waters, as estimated by changes in chlorophyll stocks, they failed to replicate fluctuations of biological populations within more complex slope and shelf regions.Accordingly, a more diverse biological model of particle decay within the aphotic zone (3 size classes of phytoplankton, macroaggregates, and zooplankton fecal pellets) was coupled to a static, 2-dimensional model of slope circulation at 0.5 km resolution in the Middle Atlantic Bight (Walsh et al., 1991). By specifying the influx of these particles, both at the shelf-break and from the overlying slope euphotic zone, with variable sinking velocities, the second set of coupled models reproduced seasonal time series of organic carbon caught by moored sediment traps on the slope and rise.A total of 8 publications were derived from this ONR grant: yr-1 , gases, C0 2 , N 2 0, CH4, and freons, to the tenfold that of other high Arctic shelves, atmosphere, is attributed to altered ice/ and may supply 50% of the carbon snow albedo at sea level, i.e., melting of respiration demands within the halocline sea ice.A 5% decline of sea ice extent of the deep Canadian and Eurasian basins in the Arctic and Antarctic from 1979 to via brine-mediated runoff. Continued 1987 may have resulted in increased light melting of ice in the Arctic could availability within previously ice-covered increase by an order of magnitude the polar regions.If such a short-term trend present CO 2 sink of 1-0.i x 109 t C yr'. were to continue, it might lead to a negative biogeochemical feedback, i.e., enhanced extraction of atmospheric CO 2 INTRODUCTION during marine photosynthesis.As a consequence of deep vertical mixing in the The global temperature of surface air Antarctic Ocean, however, primary producincreaseu by 0.4*-0.5*C from 1880 to 1980, tion during the austral summer may have while temperatures of Arctic regions actually declined in response to a reduc-(%64*-90N) instead rose by as much as tion in extent of meltwater regions, where 1.2*-1.5 0 C over this period [Hansen et stratified water columns allow carbon al., 1983]. After 1980, six of the fixation tenfold that of open water.In warmest years in the past century have contrast, within shallow adjacent seas of subsequently been observed , 1981, the Arctic Ocean, where shelf regions are 1983, reflecting tenfold larger than those of the possible early signs of a "greenhouse" warming of the Earth [Hansen and Lebedeff, Copyright 1989Copyright 1988. Initial one-dimensional [Hansen et by the American Geophysical Union. al., 19811 and then three-dimensional climate models of varying sophisticationPaper number 90GB00583. [Mitchell,...