DO14C in the Canada Basin: Placing Limits on Carbon Transfer Processes in the Arctic
Arctic Research Initiative
2009 Funded Project
We propose to measure 13C and 14C, the rare stable and radioactive isotopes of carbon, on dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and suspended particulate organic carbon (POC) collected at two stations in the Canada Basin of the Arctic Ocean. In the Arctic region, where climate change is anticipated to have a major impact on carbon storage and cycling, these samples represent an opportunity to study carbon transport and cycling, to complement completed studies (Hwang et al. 2008; Raymond et al., 2007), and to set a baseline for future investigations of organic matter in this sensitive region. The ability to make radiocarbon measurements in DOC (DO14C) is a new capability at NOSAMS and the advent of this service coupled with the samples on hand provides us with a unique and timely opportunity to produce a data set crucial for our understanding of the carbon cycle in the Arctic Ocean.
Despite the recognized vulnerability of the arctic carbon cycle to anthropogenic perturbation (Freeman et al. 2004), our understanding of carbon cycling in this region remains rudimentary at best. The limited evidence available suggests that carbon inputs and dynamics in this region differ markedly from lower latitude regions. In particular, carbon cycling under seasonally and permanently ice-covered waters of the deep basin is poorly understood. During a cruise aboard the Canadian ice-breaker Louis St. Laurent last summer, MIT/WHOI JP student David Griffith collected full-ocean-depth samples for isotopic measurements of dissolved and suspended particulate organic and inorganic carbon from different locations within the Canada Basin. These samples were designed to complement those stemming from sediment trap activities that examine particle fluxes to the deep basin. While radiocarbon measurements on dissolved inorganic carbon and sinking POC have previously been reported, to our knowledge, no such information exists for DOC or for suspended POC. Moreover, the DI14C measurements were obtained more than 10 years ago, when carbon cycling in the central Arctic ocean may have differed from the present day. Due to the sensitivity of the arctic ocean, and in particular, the external forcing from both the surrounding margins and sea ice cover, more than any other ocean basin we are likely to detect change in the central arctic within a generation or less. Therefore, re-measurement of ocean DI14C profiles coupled with novel measurements on dissolved and suspended organic carbon pools will provide crucial new insights into the arctic ocean carbon cycle. Moreover, the samples analyzed as part of this study will prove important as a baseline data set for future isotopic studies in the region in the face of continued change.