New production in the Sargasso Sea: History and current status

Abstract

The Sargasso Sea has been, and continues to be, the focus for research on new production in the open ocean. The history of the concept and the evolution of understanding of the mechanisms is reviewed from its inception in the early 1960s through a controversial period in the 1980s to the current status of a plethora of sources of new nitrogen. Rather than viewing all processes supplying new nutrients as uniformly distributed over the Sargasso Sea, it is now clear that new production in the northern or subtropical area is primarily sustained by nitrogen injection via mesoscale eddies and winter convection. In the tropical area, where permanent stratification precludes deep winter mixing and eddy kinetic energy is low, nitrogen fixation is potentially the dominant source along with diapycnal mixing and atmospheric deposition. The timescale of new production measurements has lengthened to an annual basis using time series measurements and satellite imagery but, in the context of climate change, should be lengthened further to greater than decadal scales.