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Southern Ocean wind-driven entrainment enhances satellite chlorophyll-a through the summer

TitleSouthern Ocean wind-driven entrainment enhances satellite chlorophyll-a through the summer
Publication TypeJournal Article
Year of Publication2015
AuthorsCarranza M.M, Gille ST
JournalJournal of Geophysical Research-Oceans
Date Published2015/01
Type of ArticleReview
ISBN Number2169-9275
Accession NumberWOS:000349890000019
Keywordsannular mode; antarctic circumpolar current; atmospheric forcing; Ekman pumping; hemisphere; interannual variability; Iron; langmuir circulation; mixed-layer depth; mixed-layer depth dynamics; nutrient transport; phytoplankton blooms; sea-surface temperature; Southern Ocean; spring; summer phytoplankton blooms; wind-driven entrainment

Despite being the largest High Nitrate Low Chlorophyll (HNLC) region, the Southern Ocean sustains phytoplankton blooms through the summer, when presumably there is sufficient light, but nutrients in the euphotic zone have been depleted. Physical processes that can potentially supply nutrients from subsurface waters to the euphotic zone, and promote phytoplankton growth in the summer, have not been fully explored at the large scale. By means of a correlation analysis, this study combines high-resolution satellite observations of ocean color, winds and sea surface temperature, surface heat fluxes from reanalysis and Argo mixed-layer depth (MLD) estimates to explore the role of the atmospheric forcing (i.e., winds and surface heat fluxes) on upper ocean processes that may help sustain high satellite chlorophyll-a (Chl-a) through the summer. Two physical processes that can supply nutrients to the euphotic zone are: MLD deepening, caused by wind-mixing and/or surface cooling, and Ekman pumping driven by the wind stress curl. We find that high winds correlate with high Chl-a over broad open ocean areas, suggesting that transient MLD deepening through wind-mixing (i.e., wind-driven entrainment) helps sustain high Chl-a. Wind-driven entrainment plays a dominant role on time scales associated with atmospheric synoptic storms (i.e., <10 days) and has a larger influence on surface Chl-a than storm scale local Ekman pumping. Based on our analysis of statistically significant correlation patterns, we identify regions in the Southern Ocean where wind-induced entrainment may play a role in sustaining summer phytoplankton blooms.

Short TitleJ Geophys Res-Oceans
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