HR: 1340h
AN: A53B-0874    [Abstracts]
TI: Bering Sea Observations Indicate Persistent Warming and Species Impacts
AU: * Overland, J E
EM: james.e.overland@noaa.gov
AF: NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AU: Stabeno, P J
EM: phyllis.stabeno@noaa.gov
AF: NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AB: Observations over the previous four years show persistent warm and ice-free conditions from late winter through summer, despite large variability in climate indices such as the Arctic Oscillation(AO) and the Pacific Decadal Oscillation(PDO). If such conditions continue, it will have a major effect on the ecosystem, as Arctic species seek colder waters and sub-Arctic species become dominant. Such a change is ecologically and socially important as the Bering Sea provides 47 percent of the U.S. fishery production by weight and is home to major populations of sea birds and marine mammals. On the southeast Bering Sea shelf (57 deg N) the warmest vertically-averaged ocean temperatures of the decade occurred in 2001-2003(6 deg summer mean temperature relative to 4 deg summer mean temperature in 1995-1997), and sea ice is now nearly non-existent. These conditions follow a major transformation, or regime shift, of the Bering Sea around 1976/77, which changed from a predominantly cold Arctic climate to a warmer subarctic maritime climate as part of the PDO, accompanied by a major reorganization of the marine ecosystem. Over the last decade annual fisheries surveys indicate a continued decline in the addition of young fish and shellfish to cold water stocks, such as Greenland turbot and snow crab. However, Walleye Pollock, which prefers warmer waters, is characterized by a large, rather stable, population. Pacific Walrus is another species showing northward movement due to lack of sea ice and warmer temperatures. Weather data beginning in the 1910s and proxy data(e.g. tree rings) back to 1800 suggest that, except for a period in the 1930s, the Bering Sea was generally cool before 1977, with sufficient time for slow growing, long-lived, cold-adapted species to adjust. Thus the last decades, and particularly the previous few years, are a transition period for the Bering Sea ecosystem to warmer conditions. We hypothesize that the overall climate change occurring in the Arctic is making the Bering Sea less sensitive to the intrinsic climate variability of the North Pacific. Bering Sea indicators, such as sea ice cover and change in the types of fish, should be watched closely for the next five years to confirm or reject the hypothesis of the northward movement of a cold water curtain, replacing Arctic with sub-Arctic species.
DE: 9315 Arctic region
DE: 4815 Ecosystems, structure and dynamics
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 1610 Atmosphere (0315, 0325)
DE: 0315 Biosphere/atmosphere interactions
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting