Summer ice melt influence on net community production along the Western Antarctic Peninsula

Rachel Eveleth1, Nicolas Cassar2, Robert M Sherrell3, Michael Paul Meredith4, Hugh W Ducklow5, Yajuan Lin6 and Zuchuan Li6, (1)Duke University, Earth and Ocean Sciences, Nicholas School of the Environment, Durham, NC, United States, (2)IUEM Institut Universitaire Européen de la Mer, LEMAR, Plouzané, France, (3)Rutgers University, Marine and Coastal Sciences and Earth and Planetary Sciences, New Brunswick, NJ, United States, (4)NERC British Antarctic Survey, Cambridge, United Kingdom, (5)Lamont -Doherty Earth Observatory, Division of Biology and Paleo Environment, Palisades, NY, United States, (6)Duke University, Durham, NC, United States
Abstract:
The Western Antarctic Peninsula (WAP) is a highly productive shelf sea that is undergoing rapid change, with consequences for productivity and total ecosystem carbon cycling. In an effort to unpack this complex system and work towards an understanding of future climate-carbon feedbacks, this work documents variability in net community production (NCP) in the WAP and investigates the physical underpinnings of these signals with special attention on meltwater influences as they relate to Fe and light availability.

Continuous underway O2/Ar estimates of NCP in austral summer 2012, 2013 and 2014 at sub-kilometer horizontal spatial resolution within the Palmer-Long Term Ecological Research (LTER) grid region of the WAP reveal substantial spatial and interannual variability. The LTER grid region of the WAP was a net carbon sink during the study (mean NCPO2Ar 54.4 ± 48.5 mmol O2 m-2 d-1 in 2012, 44.6 ± 40.5 mmol O2 m-2 d-1 in 2013 and 85.6 ± 75.9 mmol O2 m-2 d-1 in 2014) with particularly high export production in the coastal region and at hotspots associated with submarine canyons. Based on a strong correlation (slope 0.37, r2=0.82) between residence time integrated NCPO2Ar and NCPDIC derived from seasonal DIC drawdown, we validate the steady-state assumption for the O2/Ar method in this region and find the observed NCPO2Ar spatial and interannual variability to be consistent with the December-January NCPDIC magnitude.

Dissolved and particulate Fe concentrations indicate that Fe-limitation is widespread in the offshore region of the northern shelf, farthest from apparent coastal Fe sources (potentially glacial meltwater). In the near coastal zone, Fe stress is low so high and variable NCP in coastal waters is more related to meltwater enhanced mixed layer stratification as it controls both light availability and timing. A bit further from the coast but still on the shelf we see local indications of both Fe and light limitation. Light limitation is evident along the WAP when mixed layer depths are deeper than ~40 m.

Back to: Western Antarctic Seas: From Trace Metals to Trophic Levels II Posters