Sources and Cycling of Particulate Organic Matter in Baffin Bay: A Multi-Isotope δ13C, δ15N, and Δ14C Approach

• Published in: Frontiers in Marine Science
• Main Authors: Fox, Aislinn, Walker, Brett D.
• Other Authors: Natural Sciences and Engineering Research Council of Canada
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2022
• Subjects: Ocean Engineering; Water Science and Technology; Aquatic Science; Global and Planetary Change; Oceanography; Arctic; Baffin Bay; Baffin Island; Greenland; Pacific; Baffin; Climate change; Davis Strait
• Online Access: http://dx.doi.org/10.3389/fmars.2022.846025; https://www.frontiersin.org/articles/10.3389/fmars.2022.846025/full

The Canadian Arctic is warming three times faster than the rest of the planet. The impact of climate change on the Arctic carbon cycle, and in particular for Baffin Bay, remains poorly constrained. Sinking particulate organic matter (POM sink ) is a key component of the biological carbon pump and provides a direct linkage between surface productivity and the preservation of carbon in marine sediments. While POM sink provides a rapid POM shunt to the deep ocean (days) the majority of marine POM is suspended (POM susp ) persists for years in the water column. Stable carbon (δ 13 C), nitrogen (δ 15 N) and radiocarbon (Δ 14 C) measurements are powerful tools for evaluating sources and cycling of POM. In this study, we measure depth-integrated (0-400m) POM susp stable carbon (δ 13 C), nitrogen (δ 15 N) and radiocarbon (Δ 14 C) values at 11 stations in Baffin Bay. We use POM C:N a ratios to evaluate its diagenetic state. POM susp δ 13 C and δ 15 N values ranged from −21.6‰ to −29.5‰, and +3.84‰ to +7.21‰, respectively. POM susp Δ 14 C values ranged from −41.8‰ to +76.8‰. Together, our results suggest Baffin Bay POM susp has multiple carbon and nitrogen sources. POM susp δ 13 C and Δ 14 C are strongly correlated to surface salinity, indicating surface water has a strong influence on POM susp isotopic composition and 14 C-age. POM susp from coastal Greenland stations have similar Δ 14 C values to surface dissolved inorganic carbon (DIC) and POM concentrations, consistent with primary production as the predominant POM susp source in Eastern Baffin Bay. Positive POM susp Δ 14 C values in central Baffin Bay suggest an accumulation of atmospheric “bomb” 14 C in the sub-polar gyre. POM susp exiting Davis Strait via the Baffin Island Current was determined to have a significant degraded, resuspended sediment component. Finally, POM susp δ 15 N values highlight two distinct N sources in Baffin Bay: Pacific and Arctic nutrients at Northern gateway stations vs. the influx of Atlantic nutrients via Davis Strait along coastal ...