Tracer-based assessment of the origin and biogeochemical transformation of a cyclonic eddy in the Sargasso Sea
Li, Qian P.
Hansell, Dennis A.
McGillicuddy, Dennis J.
Bates, Nicholas R.
Johnson, Rodney J.
MetadataShow full item record
Mechanisms of nutrient supply in oligotrophic ocean systems remain inadequately understood and quantified. In the North Atlantic Subtropical Gyre, for example, the observed rates of new production are apparently not balanced by nutrient supply via vertical mixing. Mesoscale eddies have been hypothesized as a mechanism for vertical nutrient pumping into the euphotic zone, but the full range and magnitude of biogeochemical impacts by eddies remain uncertain. We evaluated a cyclonic eddy located near Bermuda for its effect on water column biogeochemistry. In the density range σ θ 26.1 to 26.7, an eddy core with anomalous salinity, temperature, and biogeochemical properties was observed, suggesting that the eddy was not formed with local water (i.e., not formed of the waters surrounding the eddy at the time of observations), hence complicating efforts to quantify biogeochemical processes in the eddy. We combined conservative hydrographic tracers (density versus potential temperature and salinity) and quasi-conservative biogeochemical tracers (density versus NO, PO, and total organic carbon) to propose the origin of the eddy core water to have been several hundred kilometers to the southeast of the eddy location at sampling. By comparing the observed eddy core's biogeochemical properties with those near the proposed origin, we estimate the net changes in biogeochemical properties that occurred. A conservative estimate of export was 0.5 ± 0.34 mol N m−2 via sinking particles, with export occurring prior to our period of direct observation. Our results suggest that biogeochemical signals induced by mesoscale eddies could survive to be transported over long distances, thus providing a mechanism for lateral fluxes of nutrients and AOU (apparent oxygen utilization). Given that the proposed source area of this eddy is relatively broad, and the eddy-mixing history before our sampling is unknown, uncertainty remains in our assessment of the true biogeochemical impact of mesoscale eddies in the gyre.
Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): C10006, doi:10.1029/2008JC004840.
Suggested CitationArticle: Li, Qian P., Hansell, Dennis A., McGillicuddy, Dennis J., Bates, Nicholas R., Johnson, Rodney J., "Tracer-based assessment of the origin and biogeochemical transformation of a cyclonic eddy in the Sargasso Sea", Journal of Geophysical Research 113 (2008): C10006, DOI:10.1029/2008JC004840, https://hdl.handle.net/1912/3626
Showing items related by title, author, creator and subject.
McGillicuddy, Dennis J. (2015-03-31)Mesoscale phenomena are ubiquitous and highly energetic features of ocean circulation. Their influence on biological and biogeochemical processes varies widely, stemming from not only advective transport but also through ...
Mesoscale physical–biological–biogeochemical linkages in the open ocean : an introduction to the results of the E-Flux and EDDIES programs Benitez-Nelson, Claudia R.; McGillicuddy, Dennis J. (2008-01-24)Mesoscale currents, fronts, and eddies are ubiquitous and energetic features of ocean circulation. These phenomena, sometimes referred to as the “internal weather of the sea,” accommodate a diverse set of physical, chemical, ...
Assessment of skill and portability in regional marine biogeochemical models : role of multiple planktonic groups Friedrichs, Marjorie A. M.; Dusenberry, Jeffrey A.; Anderson, Laurence A.; Armstrong, Robert A.; Chai, Fei; Christian, James R.; Doney, Scott C.; Dunne, John P.; Fujii, Masahiko; Hood, Raleigh R.; McGillicuddy, Dennis J.; Moore, J. Keith; Schartau, Markus; Spitz, Yvette H.; Wiggert, Jerry D. (American Geophysical Union, 2007-08-02)Application of biogeochemical models to the study of marine ecosystems is pervasive, yet objective quantification of these models' performance is rare. Here, 12 lower trophic level models of varying complexity are objectively ...