Program

Mesoscale eddies influence upper ocean ecosystems by a variety of mechanisms, including some that stimulate productivity through nutrient supply (eddy pumping, eddy-wind interaction) and/or influencing light availability (eddy impacts on mixed layer depth), as well as those that simply redistribute biogenic material (stirring and trapping).  It has been known for some time that these mechanisms can be differentially expressed in space and time.  However, it is only recently that regional variations in the influence of mesoscale eddies on near-surface chlorophyll have been quantified on a global basis using satellite observations.  Coherent patterns of both positive and negative correlation between anomalies of sea level (SLA) and chlorophyll (CHL) reflect variations in the relative balance between these various eddy-driven processes.  Areas of positive correlation are indicative of positive CHL anomalies associated with anticyclonic eddies (positive SLA) and negative CHL anomalies with cyclonic eddies (negative SLA).  Conversely, regions of negative correlation are indicative of positive CHL anomalies associated with cyclonic eddies, and negative CHL anomalies associated with anticyclones.  Attribution of these correlations to specific mechanisms is not possible on the basis of observations alone, as each of these correlation patterns can be produced by more than one mechanism.  A global eddy-resolving coupled physical-biological model is able to simulate many of the observed patterns in SLA-CHL correlation, providing a framework in which to diagnose the contributions of the different processes of mesoscale physical-biological interaction.  Regional studies reveal multiple mechanisms operating simultaneously, and thus global patterns in the SLA-CHL correlation reflect variations in the relative importance of the various processes.