Spatial and temporal variability of seawater pCO2 within the Canadian Arctic Archipelago and Baffin Bay during the summer and autumn 2011

The partial pressure of CO2 in surface water (pCO(2)(sw)) measured within the Canadian Arctic Archipelago (CAA) and Baffin Bay was highly variable with values ranging from strongly undersaturated (118 mu atm) to slightly supersaturated (419 mu atm) with respect to the atmospheric levels (similar to 386 mu atm) during summer and autumn 2011. During summer, melting sea ice contributed to cold and fresh surface water and enhanced the ice-edge bloom, resulting in strong pCO(2)(sw) undersaturation. Coronation Gulf was the only area with supersaturated pCO(2)(sw), likely due to warm CO2-enriched freshwater input from the Coppermine River. During autumn, the entire CAA (including Coronation Gulf) was undersaturated, despite generally increasing pCO(2)(sw). Coronation Gulf was the one place where pCO(2)(sw) decreased, likely due to seasonal reduction in discharge from the Coppermine River and the decreasing sea surface temperature. The seasonal summer-to-autumn increase in pCO(2)(sw) across the archipelago is attributed in part to the continuous uptake of atmospheric CO2 through both summer and autumn and to the seasonal deepening of the surface mixed layer, bringing CO2-rich waters to the surface. These observations demonstrate how freshwater from sea ice melt and rivers affect pCO(2)(sw) differently. The general pCO(2)(sw) undersaturation during summer-autumn 2011 throughout the CAA and Baffin Bay give an estimated net oceanic sink for atmospheric CO2 over the study period of 11.4 mmol CO2 m(-2) d(-1), assuming no sea-air CO2 flux exchange across the sea-ice covered areas.