Radiocarbon in the Canada Basin: Carbon Transfer Processes in the Changing Arctic

We are developing full water column depth [delta]14C profiles for dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and suspended particulate organic carbon (POC) collected in 2008 from the Canada Basin in the Arctic Ocean. 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 first DI14C depth profile from 75, 150 is similar to one taken in 1992 (Jones et al. 1994) in demonstrating a well-ventilated surface layer overlying an older but recently ventilated deeper basin. Significant increases in DI14C, up to 30 ppt, are observed in the mid-depth region between 500 to 1500 m, roughly coincident with a warm layer underlying cold surface waters. The differences that have occurred over 16 years may lend insight to the observed warming of Atlantic water in the Canada Basin over the past decades. We will present the first DO14C profile from the central Canada Basin. Measurements are being made using a UV oxidation system established at NOSAMS. Most of the samples collected for DO14C measurement were acidified to preserve them. Results from frozen duplicates for a few of the samples will be compared to validate the preservation technique. In most regions of the ocean, the shape of DO14C depth profiles parallel those of DI14C profiles but are shifted to significantly older values. This reflects the fact that general oceanographic circulation and remineralization processes dominate the overall profile, but that the sources of carbon to the DOC pool are more complex than those of DIC. It is unknown whether this will be the case in the Arctic Ocean which, while representing only ~1% of the worlds ocean volume, receives approximately 13% of the global flux of terrigeneous DOC. Jones, G. A. et al. (1994). NIMS B, 92, 426-430.