| Summary: | 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. © 2016 American Geophysical Union. Received 3 AUG 2016; Accepted 28 SEP 2016; Accepted article online 3 OCT 2016; Published online 18 OCT 2016. The authors thank the captains and crews of the ARSV Laurence M. Gould and the RSS Shackleton for their assistance in the deployment and recovery of the gliders during this project. Z.K.E. and A.F.T. gratefully acknowledge funding from the David and Lucille Packard Foundation. The authors are supported by National Science Foundation (NSF) grants OPP-1246460 (Z.K.E. and A.F.T.), OPP-1246160 (J.S.), OCE-1234473 (M.R.M.), and PLR-1425989 (M.R.M.). Seaglider measurements were processed using the UEA Seaglider Toolbox (https://bitbucket.org/bastienqueste/uea-seaglider-toolbox) kindly provided by Bastien Y. Queste. Satellite data were provided by NASA Goddard Space Flight Center at http://oceancolor.gsfc.nasa.gov/. The model was run using the Extreme ...
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