Seasonal variability of the inorganic carbon system in the Amundsen Gulf region of the southeastern Beaufort Sea

Abstract

During a year‐round occupation of Amundsen Gulf in the Canadian Arctic Archipelago dissolved inorganic and organic carbon (DIC, DOC), total alkalinity (TA), partial pressure of CO2 (pCO2) and related parameters were measured over a full annual cycle. A two‐box model was used to identify and assess physical, biological, and chemical processes responsible for the seasonal variability of DIC, DOC, TA, and pCO2. Surface waters were undersaturated with respect to atmospheric CO2 throughout the year and constituted a net sink of 1.2 mol C m−2 yr−1, with ice coverage and ice formation limiting the CO2 uptake during winter. CO2 uptake was largely driven by under ice and open‐water biological activity, with high subsequent export of organic matter to the deeper water column. Annual net community production (NCP) was 2.1 mol C m−2 yr−1. Approximately one‐half of the overall NCP during the productive season (4.1 mol C m−2 from Apr through Aug) was generated by under‐ice algae and amounted to 1.9 mol C m−2 over this period. The surface layer was autotrophic, while the overall heterotrophy of the system was fueled by either sedimentary or lateral inputs of organic matter.