Eddy‐induced sea surface temperature gradients in Eastern Boundary Current Systems

Abstract

Many processes are known to influence the distribution of sea surface temperature (SST) fronts in Eastern Boundary Current Systems (EBCS), including wind forcing, mesoscale activity, flow instabilities, and flow‐topography interactions. Here we used satellite observations to quantify the relative importance of one of these processes, mesoscale eddy activity, on the distribution of SST gradients in EBCS. Eddies are characterized by large SST and SST gradient anomalies in all EBCS. At the end of the upwelling season, eddy‐induced SST gradients are dominant components of full SST gradients offshore of 300 km from the coast, especially in regions of high eddy activity. Comparisons between eddy‐induced and full SST gradients in the California Current System indicate that the offshore migration of mesoscale eddies plays a significant role on the seasonal widening of the region of high frontal activity. SST gradients associated with anticyclonic eddies are largest within 400 km from shore, while the signature of cyclones can extend for up to 700 km from the coast.

Upwelling jet separation in the California Current System

“…Eddies and other mesoscale activity have been shown to play a critical role on physical and biological processes in the California Current System 23 , influencing the distribution of nutrients 27 , carbon 28 and SST gradients 29 . Comparing results from the different scenarios reveal substantial differences in eddy kinetic energy – a measure of the intensity of mesoscale activity – that is consistent with the distribution of mean SST gradients and mean surface currents.…”

Offshore transport of particulate organic carbon in the California Current System by mesoscale eddies

“…The CCS is one of four major EBCS, all of which share similarities in eddy activity 11,26,47 . The eddy-driven offshore transport of coastal water will presumably be important in the other EBCS as well.…”

“…To further isolate the signature associated with each eddy 47 from other mesoscale features, we extracted the POC anomaly within 2-by-2 eddy radii from the eddy center (Supplementary Fig. 2c).…”

“…2b) were used. To remove noisy, small-scale variability not related to the eddy, a 2D Gaussian function was fitted to the resulting POC anomaly field 47 . The fit is consistent with the average eddy shape that is well represented as Gaussian 1 .…”

Single super-vortex as a proxy for ocean surface flow fields

“…1), which are observed almost everywhere in satellite altimetry data of global sea surface height (Chelton et al, 2007. The total volume transport by drifting eddies is comparable in magnitude to that of the large-scale wind-driven and thermohaline circulations (Zhang et al, 2014); therefore, MEs play a crucial role in global material and heat transport and mixing of oceans. In spite of their importance, it is far from trivial to identify and characterize MEs from remote sensing data.…”