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An advective mechanism for deep chlorophyll maxima formation in southern Drake Passage

TitleAn advective mechanism for deep chlorophyll maxima formation in southern Drake Passage
Publication TypeJournal Article
Year of Publication2016
AuthorsErickson Z.K, Thompson A.F, Cassar N., Sprintall J, Mazloff MR
JournalGeophysical Research Letters
Date Published2016/10
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000388293800017
Keywordsantarctic circumpolar current; biooptical properties; biophysical interactions; coastal transition zone; deep chlorophyll maximum; dissolved iron; eddy transport; light; mixed-layer; northern california; ocean color; phytoplankton; waters

We observe surface and subsurface fluorescence-derived chlorophyll maxima in southern Drake Passage during austral summer. Backscatter measurements indicate that the deep chlorophyll maxima (DCMs) are also deep biomass maxima, and euphotic depth estimates show that they lie below the euphotic layer. Subsurface, offshore and near-surface, onshore features lie along the same isopycnal, suggesting advective generation of DCMs. Temperature measurements indicate a warming of surface waters throughout austral summer, capping the winter water (WW) layer and increasing off-shelf stratification in this isopycnal layer. The outcrop position of the WW isopycnal layer shifts onshore, into a surface phytoplankton bloom. A lateral potential vorticity (PV) gradient develops, such that a down-gradient PV flux is consistent with offshore, along-isopycnal tracer transport. Model results are consistent with this mechanism. Subduction of chlorophyll and biomass along isopycnals represents a biological term not observed by surface satellite measurements which may contribute significantly to the strength of the biological pump in this region.

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