Late autumn to spring changes in the inorganic and organic carbon dissolved in the water column at Scholaert Channel, West Antarctica

Abstract

AbstractThe temporal changes in dissolved inorganic (DIC) and organic carbon concentrations (DOC) were monitored from late autumn to spring 2006 in the Scholaert Channel, West Antarctic Peninsula. Surface DIC spanned a small range (2163.3 to 2194.5 μmol kg-1), increasing from late autumn to winter and then decreasing in spring. An excess of DOC (7.0–63.6 μmol l-1), against a deepwater background concentration of 44 μmol l-1, existed in the surface mixed layer throughout the sampling period. Mass-balance budgeting indicates that the DIC dynamics were primarily governed by remineralization in winter and by primary production in spring despite very low biomass of both autotrophic and heterotrophic organisms. The net community production (7.3 mmol C m-2 d-1) in spring was mainly partitioned to DOC accumulation (3.6 mmol m-2 d-1) and downward export of particulate organic carbon (POC) (2.9 mmol m-2 d-1) rather than POC accretion (0.8 mmol m-2 d-1) in the surface mixed layer. The study area acted as a source of CO2 to the atmosphere in winter (∼0.8 mmol m-2 d-1) and a sink in spring (2.3–5.3 mmol m-2 d-1), and hence was not a one-way CO2 sink as had been previously hypothesized for marginal sea ice zones.