Nutrient Pumping/Advection by Propagating Rossby Waves in the Kuroshio Extension
NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OCEANOGRAPHY
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Ten years 1998-2007 of sea-level anomalies SLA from multiple satellite altimeters and chlorophyll-a concentration from the Sea-viewing Wide Field-of-view Sensor SeaWiFS were used to detect eddy pumpingadvection of nutrients by the action of propagating Rossby waves in the Kuroshio Extension KE region near 35 deg N after the seasonal SeaWiFS chlorophyll-a Chl-a concentrations cycles and annual changes of altimeter SLA were eliminated. Spatial structure of Chl-a anomalies to the seasonal cycle is examined in relation to altimeter eddy structure. Eddy propagation speeds and scales by the Rossby waves are also identified. Chl-a structure is evident during the spring bloom period with a scale around 460 km. Cold-core cyclonic rings correspond to areas of high Chl-a concentrations. Warm-core anticyclonic rings relate to areas of low Chl-a concentration. Chl-a anomalies and SLA have an overall modest negative correlation coefficient of r -0.45, which may imply the co-existence of both eddy pumping and eddy advection mechanisms in the KE region. Swirl currents between eddies redistribute surface chlorophyll concentrations and can spatially bias maximum and minimum concentration levels off eddy center. The correlation coefficient has seasonal fluctuations. In the western KE region, it varies from high negative correlation r -0.70 in April and September eddy pumping dominant to low negative correlation r -0.33 in February and March eddy advection dominant. In the eastern KE region, it varies from high negative correlation r -0.67 in February to low negative correlation r -0.42 in December. It is noted that the characteristic wavelengths of the SLA and Chl-a features and the seasonality of the correlation between these two variables have not been previously documented.
- Physical and Dynamic Oceanography