HR: 0800h
AN: OS51A-1285    [Abstracts]
TI: Changes in World Ocean Nitrate Availability Through the 20th Century.
AU: * Kamykowski, D
EM: dan_kamykowski@ncsu.edu
AF: Department of Marine, Earth and Atmospheric Sciences North Carolina State University, 1125 Jordan Hall, Raleigh, NC 27695-8208 United States
AB: Conceptual models linking climate change with fluctuations in fish population abundances are based on how cyclic patterns in air-sea interactions and ocean circulation influence pelagic food web dynamics. The effect of changing mixed layer dynamics on phytoplankton light and nutrient exposure is a prominent focal point in the overall mechanism. The Extended Reconstruction (ER) of Sea Surface Temperature (SST) version one (ERSST.v1) and version two (ERSST.v2) monthly time series from 1854-2003 interpreted with the aid of a historically based Nitrate Depletion Temperature (NDT) matrix provides a tool for examining temporal and spatial patterns in nitrate availability. After a temporal analysis of NDT at four time series stations demonstrated temporal stability, [SST-NDT] was calculated for April and October for the whole ERSST data set to provide indices sensitive either to changing surface nitrate concentration (negative values of [SST-NDT]) or to changing subsurface nitrate stratification (positive values of [SST-NDT]). The records from both months showed that nitrate availability generally decreased throughout the 20th century in association with global warming. In the northern (southern) hemisphere, the greatest losses in nitrate availability occurred in two warming events in the time periods 1909-1937 (1926-1937) and 1977-present (1950-1990). Different areas of the world ocean were affected in each warming event. Prominent exceptions in ERSST.v1 where 20th century nitrate availability actually increased at least in one season were in western parts of the South Indian, the North Pacific, the equatorial Pacific, the South Pacific, the North Atlantic, and the South Atlantic and in eastern parts of the South Pacific and South Atlantic. ERSST.v2 also showed increased 20th century nitrate availability in the eastern subarctic Pacific. The resulting nitrate availability trends in the present analysis agree with reports on regional changes in plant nutrient availability, on increased occurrences of Harmful Algal Blooms, and on changes in marine fisheries and raise issues concerning the resilience of historical pelagic community oscillations in the face of a continuing warming trend and decreasing overall nitrate availability that has spanned the 20th century.
DE: 4815 Ecosystems, structure and dynamics
DE: 4845 Nutrients and nutrient cycling
DE: 4215 Climate and interannual variability (3309)
DE: 1699 General or miscellaneous
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting