Temporal and spatial variability in primary production west of the Antarctic Peninsula (64° - 68° S).

VERNET, M.; KOZLOWSKI, W.; SINES, K.; SMITH, R.C.; DIERSSEN, H.; STAMMERJOHN, S.; BAKER, K.; MARTINSON, D.; IANNUZZI, R.; GARIBOTTI, I.A.; CURCHITSER, E.

Seattle, USA

Congreso; Long-Term Ecological Research Network All Scientists Meeting; 2003

Primary production in the Western Antarctic Peninsula (64° S to 68° S ) in the decade of the 1990’s presents variability at several time and space scales. Inshore production during the growth season usually includes from 2 to 4 pulses per year, lasting 1-3 weeks each. Years of high production have pronounced pulses (1995-1996) while years of low overall production have diminished pulses and present a more constant rate of production. Average daily production can vary by a factor of 5, with maximum average production in 1995-1996 (1719 mgC m-2 d-1) and minimum in 1998-1999 (363 mgC m-2 d-1). Integrated over the growth season (15 October to 15 March), primary production estimates varied from 378 gC m-2 to 55 gC m-2, respectively. Similarly, average daily production rates over the continental shelf during January varied by a factor of 5, with maximum rates in 1996 and minimum in 1999 (1213 to 247 mgC m-2 d-1, respectively). Spatially, the main variability is along an offshore-onshore gradient that is always present but it is more pronounced during years of higher regional average production. In addition, the onshore-offshore gradient can more pronounced in the Northern part of the study area (64 S), off Palmer Station, as occurred in 1995-1996, resulting in a North-South gradient with lower values towards the South (68° S), off Marguerite Bay. This distribution was reversed in 2001-2002 when the onshore-offshore gradient was more pronounced in the South. The onshore-offshore gradient can be explained by ice edge dynamics that develop perpendicular to the shore during late spring and summer. Comparison of annual mean productivity with estimates from satellite indicate that the interannual variability in primary production is captured only by regional studies while estimates of Southern Ocean productivity are based only on mean annual estimates.