Imprint of Southern Ocean eddies on chlorophyll.

Frenger, Ivy , Münnich, Matthias and Gruber, Nicolas (2018) Imprint of Southern Ocean eddies on chlorophyll. Open Access Biogeosciences (BG), 15 . pp. 4781-4798. DOI 10.5194/bg-15-4781-2018.

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Abstract

Although mesoscale ocean eddies are ubiquitous in the Southern Ocean, their average regional and seasonal association with phytoplankton has not been quantified systematically yet. To this end, we identify over 100000 mesoscale eddies with diameters of 50km and more in the Southern Ocean and determine the associated phytoplankton biomass anomalies using satellite-based chlorophyll-a (Chl) as a proxy. The mean Chl anomalies, δChl, associated with these eddies, comprising the upper echelon of the oceanic mesoscale, exceed ±10% over wide regions. The structure of these anomalies is largely zonal, with cyclonic, thermocline lifted, eddies having positive anomalies in the subtropical waters north of the Antarctic Circumpolar Current (ACC) and negative anomalies along its main flow path. The pattern is similar, but reversed for anticyclonic, thermocline deepened eddies. The seasonality of δChl is weak in subtropical waters, but pronounced along the ACC, featuring a seasonal sign switch. The spatial structure and seasonality of the mesoscale δChl can be explained largely by lateral advection, especially local eddy-stirring. A prominent exception is the ACC region in winter, where δChl is consistent with a modulation of phytoplankton light exposure caused by an eddy-induced modification of the mixed layer depth. The clear impact of mesoscale eddies on phytoplankton may implicate a downstream effect on Southern Ocean biogeochemical properties, such as mode water nutrient contents.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/218812
Additional Information: Data availability. The identified eddies we use in this study including their Chl characteristics are publicly available (http://dx.doi.org/10.3929/ethzb- 000238826). Other presented data are available from the corresponding author upon request.
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-15-4781-2018
ISSN: 1726-4170
Related URLs:
Projects: MyOcean, GlobColour
Date Deposited: 20 Feb 2018 13:50
Last Modified: 01 Feb 2019 15:07
URI: http://oceanrep.geomar.de/id/eprint/41936

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