Arctic Freshwater Sources and Ocean Mixing Relationships Revealed With Seawater Isotopic Tracing

Author:

Kopec Ben G.1ORCID,Klein Eric S.2ORCID,Feldman Gene C.3,Pedron Shawn A.4ORCID,Bailey Hannah5ORCID,Causey Douglas67ORCID,Hubbard Alun89ORCID,Marttila Hannu5ORCID,Welker Jeffrey M.61011ORCID

Affiliation:

1. Great Lakes Research Center Michigan Technological University Houghton MI USA

2. Geological Sciences University of Alaska Anchorage Anchorage AK USA

3. NASA Goddard Space Flight Center Greenbelt MD USA

4. Earth System Science University of California Irvine Irvine CA USA

5. Water, Energy and Environmental Engineering University of Oulu Oulu Finland

6. Biological Sciences University of Alaska Anchorage Anchorage AK USA

7. Harvard Kennedy School Belfer Center Arctic Initiative Harvard University Cambridge MA USA

8. Centre for Ice, Cryosphere, Carbon and Climate Institute for Geosciences UiT—The Arctic University of Norway Tromsø Norway

9. Geography Research Unit University of Oulu Oulu Finland

10. Ecology and Genetics Research Unit University of Oulu Oulu Finland

11. The University of the Arctic (UArctic) Rovaniemi Finland

Abstract

AbstractThe Arctic Ocean and adjacent seas are undergoing increased freshwater influx due to enhanced glacial and sea ice melt, precipitation, and runoff. Accurate delineation of these freshwater sources is vital as they critically modulate ocean composition and circulation with widespread and varied impacts. Despite this, the delineation of freshwater sources using physical oceanographic measurements (e.g., temperature, salinity) alone is challenging and there is a requirement to improve the partitioning of ocean water masses and their mixing relationships. Here, we complement traditional oceanographic measurements with continuous surface seawater isotopic analysis (δ18O and deuterium excess) across a transect extending from coastal Alaska to Baffin Bay and the Labrador Sea conducted from the US Coast Guard Cutter Healy in Autumn 2021. We find that the diverse isotopic signatures of Arctic freshwater sources, coupled with the high freshwater proportion in these marine systems, facilitates detailed fingerprinting and partitioning. We observe the highest freshwater composition in the Beaufort Sea and Amundsen Gulf regions, with heightened freshwater content in eastern Baffin Bay adjacent to West Greenland. We apply isotopic analysis to delineate freshwater sources, revealing that in the Western Arctic freshwater inputs are dominated by meteoric water inputs—specifically the Mackenzie River—with a smaller sea ice meltwater component and in Baffin Bay the primary sources are local precipitation and glacial meltwater discharge. We demonstrate that such freshwater partitioning cannot be achieved using temperature‐salinity relationships alone, and highlight the potential of seawater isotopic tracers to assess the roles and importance of these evolving freshwater sources.

Funder

National Science Foundation

Publisher

American Geophysical Union (AGU)

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