Phytoplankton advection off the southeastern United States continental shelf

Abstract

We observed an anomalous water mass below 100 m over the continental slope just seaward of the southeastern U.S. continental shelf. The water mass was colder than expected from T-S relations and contained relatively high concentrations of phytoplankton compared to surrounding waters. Hydrographic and biological characteristics indicated that the water mass was formed from waters that upwelled into the euphotic zone on the outer shelf. Based on our analyses, we conclude that the atmosphere extracted heat from the upwelled water thereby increasing its density and causing it to cascade (advect) off the shelf. Our preliminary calculations indicate that this process could represent a significant off-shelf flux of phytoplankton carbon during winter.