Biophysical variability in the Kuroshio Extension from Altimeter and SeaWiFS

Abstract

Ten years (1998-2007) of Sea Level Anomaly (SLA) from multiple satellite altimeters and chlorophyll-a concentration from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) were used to investigate the eddy structure and associated biophysical processes in the Kuroshio Extension (KE) region near 35o N. Seasonal SeaWiFS chlorophyll-a concentrations cycles and annual changes of altimeter SLA are derived for the subtropical North Pacific near 35°N and along the KE axis. Spatial structure of SeaWiFS is determined as the deviations from a local seasonal cycle and examined in relation to altimeter eddy structure. In the KE region, SeaWiFS structure is evident during the spring bloom period with a scale around 460 km. Eddy propagation speeds and scales are examined. Cold-core (cyclonic) rings correspond to areas of high SeaWiFS chlorophyll-a. Warm-core (anticyclonic) rings relate to areas of low chlorophyll-a concentration. SeaWiFS chlorophyll-a anomalies and Altimeter SLA structure have an overall negative correlation coefficient of r=−0.36. Swirl currents between eddies redistribute surface chlorophyll concentrations and can spatially bias maximum and minimum concentration levels off eddy center.