|R. H. R. Stanley and D. J. McGillicuddy, Jr., |
Submesoscale Hotspots of Productivity and Respiration: Insights from High-Resolution Oxygen and Fluorescence Sections, Deep Sea Research, I, Submitted
It has been hypothesized that mesoscale and submesoscale processes can stimulate phytoplankton productivity and export production. Here, we present data from an undulating, towed Video Plankton Recorder (VPR-II) in the tropical Atlantic. The VPR-II collected profiles of oxygen, fluorescence, temperature and salinity in the upper 140 m of the water column at a spatial resolution of 1m in the vertical and <2 km in the horizontal. The data reveal remarkable "hotspots" with elevated fluorescence and decreased oxygen, both which are likely the result of intense submesoscale upwelling. Many of these hotspots in the lower half of the euphotic zone have a decrease in oxygen compared to source waters estimated from contiguous temperature and salinity surfaces. Thus, these hotspots appear to more often be areas of net respiration than areas of net production — although the inferred changes in oxygen are subject to uncertainty in the determination of the source of the upwelled waters. We characterize the distribution of these hotspots and present a conceptual model outlining their possible generation and decline. Simultaneous measurements of O2/Ar in the mixed layer from a shipboard mass spectrometer quantify rates of surface net community production. We find that the subsurface biological hotspots are often expressed as an increase in mixed layer rates of net community production.