In preparation for our May expedition to characterize the variability of phytoplankton, zooplankton, and mesopelagic fish and squid in the North Atlantic, we wanted to compare the location of mesoscale eddies observed in maps of sea level anomalies with a stunning image of ocean color (phytoplankton) generated by NASA.

There are a number of interesting features that can be seen both in the altimeter data (contours) and ocean color, including cold-core (cyclonic) eddies south of the Gulf Stream and warm-core (anticyclonic) eddies north of the Gulf Stream.

This comparison of the high-resolution ocean color image (pixels are between 500m and 1km in size) with contours of the AVISO sea level product (with pixels of ~25 km) highlights just how much of the variability in marine ecosystems occurs at scales not resolved by the current generation of satellite altimeters [the submesoscale, O(1-10km)].  Our ability to observed smaller eddies and fronts will be greatly improved with the advent of swath-altmetry (SWOT, launch date around 2020-ish).  At these smaller scales, however, the assumption we use to derive currents from sea level will have to be reconsidered if we are to investigated the dynamics of physical/biological interaction at the submesoscale.