Enhanced chlorophyll along the continental shelfbreak and shelf-slope front of the Mid-Atlantic Bight and Georges Bank during the spring transition

摘要

Satellite remote sensing of ocean color defines spatial distributions of phytoplankton, microscopic algae, at a spatial scale and temporal resolution unattainable by any other method of observation. Using instruments on satellites, we can examine ocean color, temperature, and wind forcing and their variation. This research is an effort to integrate satellite and in situ observations to study processes influencing distributions of phytoplankton along the continental shelfbreak of northeastern North America.;Using observations gathered over the past 18 years, I define and study annual structure evident in ocean color satellite imagery. This structure is locally enhanced chlorophyll which develops along the continental shelfbreak during the spring transition from well mixed to stratified conditions. Continental shelfwaters of this region are among the most productive in the world. The highly productive period of the spring bloom begins relatively early at the shelfbreak due to influence of the front between continental shelf and slope waters. This work shows that, due to frontal processes, relatively high phytoplankton biomass endures longer at the shelfbreak after the spring bloom than in adjacent shelf and slope waters. Influence of the front on phytoplankton processes during the transition between spring and summer has not been well studied. This period is critical for changes in water column structure, chemical (nutrient) distributions, and phytoplankton species succession. All years of satellite ocean color observations made to date show that this period is critical for phytoplankton chlorophyll distributions at the shelfbreak.;The Gulf Stream strongly influences circulation in this region. It can directly entrain shelf water seaward, and it spawns warm-core rings which move along the continental shelfbreak and interact with shelf and slope waters. The theme of this work is the central importance of fronts and their disturbances to phytoplankton processes in this extremely complex and highly productive marine ecosystem.