DI14C, DO14C, and PO14C in the Canada Basin: Carbon Transfer Processes in the Changing Arctic

We have measured full water column depth Δ14C profiles for dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and suspended particulate organic carbon (POC) collected in 2008 at two sites in the Canada Basin in the Arctic Ocean. One site is seasonally ice-covered (CB-4; 75°N, 150°W) and the other is permanently ice-covered (CB-9; 78°N, 150°W). These samples provide an opportunity to study the current distribution of radiocarbon in different carbon pools and set a baseline for future investigations of the carbon cycle in this key oceanic region where climate change is anticipated to have a major and imminent impact on carbon storage and cycling. Our DIC results show similar features at both sites and demonstrate a well-ventilated surface layer overlying an older but recently ventilated deeper basin. The permanently ice-covered site exhibits relatively depleted DI14C values for the shallowest and deepest samples. Values range from greater than +50‰ in the surface 1000 m to less than -100‰ below 2000m. Each site has a mid-depth maximum at about 500m that corresponds to the temperature maximum. As in the open ocean, DO14C values are significantly reduced relative to DI14C with values ranging from approximately -200‰ at the surface to -450‰ at depth. The decrease is regular and does not show the mid-depth maximum observed in DI14C. PO14C values lie in between those of DIC and DOC, ranging from 0‰ at the surface to -250‰ at 3500m. We will discuss these results in the context of the hydrography of the Canada Basin and compare them to historical measurements made in the Canada Basin and the Atlantic Ocean.