The formation of a subsurface anticyclonic eddy in the Peru-Chile Undercurrent and its impact on the near-coastal salinity, oxygen and nutrient distributions.

Thomsen, Sören , Kanzow, Torsten, Krahmann, Gerd , Greatbatch, Richard John , Dengler, Marcus and Lavik, Gaute (2016) The formation of a subsurface anticyclonic eddy in the Peru-Chile Undercurrent and its impact on the near-coastal salinity, oxygen and nutrient distributions. Open Access Journal of Geophysical Research - Oceans, 121 (1). pp. 476-501. DOI 10.1002/2015JC010878.

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Abstract

The formation of a subsurface anticyclonic eddy in the Peru-Chile Undercurrent (PCUC) in January and February 2013 is investigated using a multi-platform four-dimensional observational approach. Research vessel, multiple glider and mooring-based measurements were conducted in the Peruvian upwelling regime near 12°30'S. The dataset consists of > 10000 glider profiles and repeated vessel-based hydrography and velocity transects. It allows a detailed description of the eddy formation and its impact on the near-coastal salinity, oxygen and nutrient distributions. In early January, a strong PCUC with maximum poleward velocities of ∼ 0.25 m/s at 100 to 200 m depth was observed. Starting on January 20 a subsurface anticyclonic eddy developed in the PCUC downstream of a topographic bend, suggesting flow separation as the eddy formation mechanism. The eddy core waters exhibited oxygen concentrations < 1μmol/kg, an elevated nitrogen-deficit of ∼ 17μmol/l and potential vorticity close to zero, which seemed to originate from the bottom boundary layer of the continental slope. The eddy-induced across-shelf velocities resulted in an elevated exchange of water masses between the upper continental slope and the open ocean. Small scale salinity and oxygen structures were formed by along-isopycnal stirring and indications of eddy-driven oxygen ventilation of the upper oxygen minimum zone were observed. It is concluded that mesoscale stirring of solutes and the offshore transport of eddy core properties could provide an important coastal open-ocean exchange mechanism with potentially large implications for nutrient budgets and biogeochemical cycling in the oxygen minimum zone off Peru.

Document Type: Article
Additional Information: WOS:000371432200028
Keywords: Mesoscale eddies; Subsurface anticyclonic eddy formation; Peruvian upwelling regime; Peru-Chile Undercurrent; Oxygen minimum zones; Biogeochemistry
Research affiliation: OceanRep > SFB 754
OceanRep > SFB 754 > B9
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/2015JC010878
ISSN: 0148-0227
Projects: SFB754
Expeditions/Models/Experiments:
Date Deposited: 18 Dec 2015 11:20
Last Modified: 01 Feb 2019 15:07
URI: http://oceanrep.geomar.de/id/eprint/30676

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