Ice melt influence on summertime net community production along the Western Antarctic Peninsula
© 2016 Elsevier Ltd The Western Antarctic Peninsula (WAP) is a highly productive marine environment that is undergoing rapid change, with consequences for productivity and total ecosystem carbon cycling. We present continuous underway O 2 /Ar estimates of net community production (NCP O2Ar ) in austral summer 2012, 2013 and 2014 at sub-kilometer horizontal resolution within the Palmer Long-Term Ecological Research (Pal-LTER) grid region of the WAP. Substantial spatial variability is observed with NCP O2Ar ranging from 0 to 790 mmol O 2 m −2 d −1 and considerable interannual variability with mean values in the grid region of 54.4±48.5, 44.6±40.5, and 85.6±75.9 mmol O 2 m −2 d −1 in 2012, 2013 and 2014 respectively. Based on a strong correlation (r 2 =0.83) between residence time integrated NCP O2Ar and NCP DIC derived from seasonal DIC drawdown, we find the observed NCP O2Ar spatial and interannual variability to be consistent with the December–January NCP DIC magnitude. Seeking to explain the mechanistic drivers of NCP in the WAP, we observe a linear relationship between NCP O2Ar and meteoric water content derived from δ 18 O and salinity. This correlation may be due to Fe supply from glacial melt and/or strengthening of stratification and relief of light limitation. Elevated surface Fe availability, as indicated by F v /F m and measurements of surface water dissolved Fe and Mn (a rough proxy for recent potential Fe availability), and shallower, more stable mixed layers are present where meteoric water and/or sea ice melt is high near the coast. Light limitation is evident in the WAP when mixed layer depths are greater than ~40 m. Additionally we document hotspots of NCP associated with submarine canyons along the WAP. While it is difficult to predict how the physical-biological system might evolve under changing climatic conditions, it is evident that NCP, and potentially carbon flux out of the mixed layer, along the WAP will be sensitive to shifts in meltwater input and timing.
Eveleth, R; Cassar, N; Sherrell, RM; Ducklow, H; Meredith, MP; Venables, HJ; Lin, Y; Li, Z
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