Eddies and an extreme water mass anomaly observed in the eastern south Pacific at the Stratus mooring.

Stramma, Lothar , Weller, Robert A., Czeschel, Rena and Bigorre, Sebastien (2014) Eddies and an extreme water mass anomaly observed in the eastern south Pacific at the Stratus mooring. Open Access Journal of Geophysical Research: Oceans, 119 (2). pp. 1068-1083. DOI 10.1002/2013JC009470.

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Abstract

In the tropical eastern South Pacific the Stratus Ocean Reference Station (ORS) (∼20°S, 85.5°W) is located in the transition zone between the oxygen minimum zone (OMZ) and the well-oxygenated subtropical gyre. In February/March 2012, extremely anomalous water mass properties were observed in the thermocline at the Stratus ORS. The available eddy oxygen anomaly was −10.5 × 1016 µmol. This anomalous water was contained in an anticyclonic mode-water eddy crossing the mooring site. This eddy was absorbed at that time by an anticyclonic feature located south of the Stratus mooring. This was the largest water property anomaly observed at the mooring during the 13.5 month deployment period. The sea surface height anomaly (SSHA) of the strong mode-water eddy in February/March 2012 was weak, and while the lowest and highest SSHA were related to weak eddies, SSHA is found not to be sufficient to specify the eddy strength for subsurface-intensified eddies. Still, the anticyclonic eddy, and its related water mass characteristics, could be tracked backward in time in SSHA satellite data to a formation region in April 2011 off the Chilean coast. The resulting mean westward propagation velocity was 5.5 cm s−1. This extremely long-lived eddy carried the water characteristics from the near-coastal Chilean water to the open ocean. The water mass stayed isolated during the 11 month travel time due to high rotational speed of about 20 cm s−1 leading to almost zero oxygen in the subsurface layer of the anticyclonic mode-water eddy with indications of high primary production just below the mixed layer.

Document Type: Article
Additional Information: WOS:000336261200027
Keywords: anticyclonic eddy; deoxygenation; Stratus mooring; oxygen anomaly; mesoscale eddies, mode water eddy, isolated water mass, eastern tropical Pacific
Research affiliation: OceanRep > SFB 754 > A5
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
OceanRep > SFB 754
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/2013JC009470
ISSN: 2169-9275
Projects: SFB754
Date Deposited: 25 Mar 2014 13:43
Last Modified: 26 Feb 2018 11:59
URI: http://oceanrep.geomar.de/id/eprint/24019

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