Radiocarbon in Dissolved Organic Matter in the Arctic Ocean

University Of California-Irvine, Irvine CA

Investigators

Abstract

The average radiocarbon age of dissolved organic carbon (DOC) in the deep ocean ranges from 4000 - 6500 radiocarbon years. The data set used to estimate this range is based on only a few sites in the world ocean, none of which are in the Arctic. The objective of this proposal is to determine the radiocarbon signatures of bulk DOC in seawater from the Arctic Ocean to better understand the timescale of DOC cycling in the area that receives the highest amount of terrestrial DOC per unit volume than any other ocean. Participation in one cruise to the northern North Atlantic, and on two other cruises, to the Eurasian Basin and Canada Basin, is proposed to collect water samples from six detailed profiles. High-precision radiocarbon measurements are proposed using AMS (accelerator mass spectrometry) of DOC in water samples from each site. Two hypotheses will be tested: (1) bulk DOC in the deep Canada Basin (western Arctic) is several hundred radiocarbon years older than that in the deep Eurasian Basin (eastern Arctic), and these ages can be used to determine the cycling time of DOC in the deep Arctic Ocean; and (2) bulk DOC in the northern North Atlantic Ocean (61-62.5°N) is younger than in the Eurasian Basin, because of the presence of bomb radiocarbon in this region of deep water formation. These results will provide quantitative information on the timescale of DOC cycling in the Arctic Ocean. This grant will support the work of one graduate student and two undergraduate students and provide hands-on experience that will prepare them for careers as scientists and educators. The PI will conduct outreach and mentoring activities at several educational and professional levels.