Mixed Layer Impact of Hurricane Katia Passing Over the Amazon/Orinoco Plume as Viewed in Remotely Sensed Salinity Observations
[03-Dec-2012] Carton, J., Grodsky, S.A., Nicolas, R., Lagerloef, G.S.E., Reverdin, G.P., Chapron, B., Yves, Q., Kudryavtsev, V.N., and Kao, H-Y.
Presented at the 2012 AGU Fall Meeting
Hurricane strength increases dramatically with increasing sea surface temperature (SST) and decreases in response to entrainment of cooler sub-mixed layer water into the ocean mixed layer. At its seasonal peak the Amazon/Orinoco plume covers a region of one million square kilometers in the western tropical Atlantic with more than 1m of extra freshwater, creating a near-surface barrier layer that inhibits this mixing and warms to temperatures >29C. Here new remotely sensed sea surface salinity (SSS) observations help elucidate the ocean response to hurricane Katia, which crossed the plume in early fall, 2011. Its passage left a 1.5psu high salinity wake (in its impact on density, the equivalent of a 3.5C cooling) due to mixing of the shallow barrier layer, reminiscent of features previously observed at fixed locations in the Indian Ocean and Gulf of Mexico. Destruction of this barrier layer decreased SST cooling in the plume that would otherwise have occurred, thus preserving elevated SST and evaporation.