Circulation, eddies, oxygen and nutrient changes in the eastern tropical South Pacific Ocean.

Czeschel, Rena, Stramma, Lothar , Weller, R. A. and Fischer, Tim (2015) Circulation, eddies, oxygen and nutrient changes in the eastern tropical South Pacific Ocean. Open Access Ocean Science, 11 (3). pp. 455-470. DOI 10.5194/os-11-455-2015.

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Abstract

A large, subsurface oxygen deficiency zone is located in the eastern tropical South Pacific Ocean (ETSP). The large-scale circulation in the eastern equatorial Pacific and off Peru in November/December 2012 shows the influence of the equatorial current system, the eastern boundary currents, and the northern reaches of the subtropical gyre. In November 2012 the Equatorial Undercurrent is centered at 250 m depth, deeper than in earlier observations. In December 2012 the equatorial water is transported southeastward near the shelf in the Peru-Chile Undercurrent with a mean transport of 1.6 Sv. In the oxygen minimum zone (OMZ) the flow is overlaid with strong eddy activity on the poleward side of the OMZ. Floats with parking depth at 400 m show fast westward flow in the mid-depth equatorial channel and sluggish flow in the OMZ. Floats with oxygen sensors clearly show the passage of eddies with oxygen anomalies. The long-term float observations in the upper ocean lead to a net community production estimate at about 18° S of up to 16.7 mmol C m−3 yr1 extrapolated to an annual rate and 7.7 mmol C m−3 yr−1 for the time period below the mixed layer. Oxygen differences between repeated ship sections are influenced by the Interdecadal Pacific Oscillation, by the phase of El Niño, by seasonal changes, and by eddies and hence have to be interpreted with care. At and south of the equator the decrease in oxygen in the upper ocean since 1976 is related to an increase in nitrate, phosphate, and in part in silicate.

Document Type: Article
Additional Information: WOS:000356676300009
Keywords: NEAR-COASTAL CIRCULATION; HUMBOLDT CURRENT SYSTEM; EQUATORIAL PACIFIC; MESOSCALE EDDIES; PERU; PHYTOPLANKTON; PRODUCTIVITY; VARIABILITY; IMPACT
Research affiliation: OceanRep > SFB 754 > B4
OceanRep > SFB 754
OceanRep > SFB 754 > A5
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/os-11-455-2015
ISSN: 1812-0784
Projects: SOPRAN, SFB754
Date Deposited: 04 Dec 2014 12:29
Last Modified: 19 Dec 2017 12:47
URI: http://oceanrep.geomar.de/id/eprint/26213

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