Premium
Pulsed, cross‐shelf export of terrigenous dissolved organic carbon to the Gulf of Mexico
Author(s) -
Fichot Cédric G.,
Lohrenz Steven E.,
Benner Ronald
Publication year - 2014
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2013jc009424
Subject(s) - terrigenous sediment , continental shelf , oceanography , colored dissolved organic matter , biogeochemical cycle , dissolved organic carbon , total organic carbon , discharge , environmental science , geology , carbon cycle , environmental chemistry , sediment , drainage basin , phytoplankton , ecosystem , geomorphology , nutrient , chemistry , ecology , cartography , organic chemistry , geography , biology
Abstract The export of terrigenous dissolved organic carbon (tDOC) and other river‐borne material across the continental shelf boundary has important ramifications for biological productivity and the cycling of continentally derived bioelements in the ocean. Recent studies revealed the 275–295 nm spectral slope coefficient of chromophoric dissolved organic matter (CDOM), S 275–295 , is a reliable tracer for terrigenous dissolved organic carbon (tDOC) in river‐influenced ocean margins. Here an empirical algorithm for the accurate retrieval of S 275–295 from ocean color was developed and validated using in situ optical properties collected seasonally in the northern Gulf of Mexico. This study also demonstrated S 275–295 is a robust proxy for tDOC concentration in this environment, thereby providing a means to derive surface tDOC concentrations on synoptic scales and in quasi‐real time using remote sensing. The resulting tDOC‐algorithm was implemented using Aqua ‐MODIS in a retrospective analysis of surface tDOC concentrations over the northern Gulf of Mexico between July 2002 and June 2013. Large pulses of tDOC were observed in continental‐slope surface waters off the Mississippi River delta, indicating cross‐shelf export of tDOC was sporadic and exhibited considerable interannual variability. Favorable winds following an anomalously high discharge from the Mississippi‐Atchafalaya river system always coincided with a major export event, and in general, cross‐shelf export was enhanced during years of anomalously high discharge. The tDOC‐algorithm will find applicability in the assessment of future climate‐ and human‐induced changes in tDOC export, in biogeochemical models of the continental shelf, and in the validation of high‐resolution coastal models of buoyancy‐driven shelf circulation.