University of Alaska Anchorage and University of Oulu Professor, DIWA Investigator & UArctic Research Chair, Jeff Welker's research group has completed their second major research expedition into the Arctic Ocean quantifying the hydrologic linkages between northern landscapes, rivers and the Arctic Ocean using geochemistry tracers aboard the US Coast Guard’s icebreaker Healy, a program jointly supported by University of Alaska Anchorage, University of Oulu, and the Research Council of Finland (RCF) and U.S. National Science Foundation (NSF awards).
Fig. 1. DIWA research platform in the Arctic Ocean System during 2024 used by Professor Welker’s team, the US Coast Guard icebreaker Healy.
Welker’s team left the Aleutian Island Chain of West Alaska in late June and spent the next 35 days taking over 40 million continuous measurements of the ocean's surface water (10 m) isotope geochemistry (δ18O, δ2H, d-excess) as a means by which to verify major river inputs of isotopically distinct fresh water (snow and glacial ice melt) and melting sea ice inputs.
In addition, his source-sea research program is providing additional forensic data for differentiating water masses that exist in the complex Arctic Ocean system, including the northern migration of the warm Pacific current into the Arctic through the Bering Strait and the simultaneous transport of Eastern Eurasian current water south into the Pacific, as part of the bi-directional water mass fluxes through the Bering Strait Arctic Gateway System.
His team is delineating the transport of old, freshwater out of the Beaufort Gyre into the Canadian Arctic and its contribution to the freshening of the east Greenland Current and Arctic water mass fluxes over north Greenland and out of the Arctic through the Fram Strait and into the North Atlantic - connecting the western and eastern Arctic Basin (Fig. 2).
Fig. 2. The Arctic Ocean current system and depiction of the DIWA source to sea Healy track (in yellow) into the western side of the NW Passage.
Using their continuous sea water measurements, taken by their Picarro laser-based isotope measurement device called Neptune; Welker’s team found that the Yukon River contributes freshwater that makes up to 40% of the Bering Sea water in it’s massive plume. They also discovered that off the North coast of Canada, the MacKenzie River contributes freshwater that makes up more than 50% of the Beaufort Sea water as part of its plume extending >50 km into the Arctic Ocean. Freshening geochemical signals were also observed in the marginal ice zones as they entered the western edged of the NW Passage in the Amundson Gulf and the McClure Strait areas (Fig. 3)
Fig. 3. 5-minute average values of surface sea water continuously measured by Neptune over first 20+ days of the cruise: 3 July to 26 July.
Welker’s team has also just published their earlier Arctic Ocean Freshening findings from an earlier Healy icebreaker expedition that spanned the western and the central Arctic, supported by NSF, his UArctic Research Chairship, University of Oulu RCoF Arctic Interaction Profile 4 award and collaboration with the US Coast Guard icebreaker Healy. The finding from this expedition have just been jointly published by Welker’s University of Oulu and University of Alaska teams, including early career scientist, Dr. Ben Kopec, who was the lead-author on the paper in one of the world's premier oceanic research outlet: The Journal of Geophyscial Research-OCEANS
The 2021 Freshening expedition also traversed along western and northern Alaska coast line, but then passed through the entire NW Passage of the Canadian High Arctic, and spent weeks taking surface water isotope measurements all along the West Coast of Greenland, the East Coast of Baffin Island and back and forth across Baffin Bay, existing through the Davis Strait, and sampling across the Labrador Sea, reaching land in Halifax, Canada after 61 days at sea. During this study they took ~ 60 million water isotope measurements over the duration of the mission. This freshening package captured distinct Greenland Ice Sheet meltwater injections along the fjord systems of West Greenland and Baffin Island.
These Arctic hydrologic properties are not independent processes, but appear to have an influence on the marine food web. In the areas where the massive GrIS freshwater injections were occurring, they found that florescence values were higher, indicative of greater phytoplankton photosynthesis, the ocean acting as a C sink (Fig. 4). These connections between the abiotic hydrological processes with biological processes are likely due in part to the carbon, nitrogen and phosphorus that is dissolved in this melt water and are co-injected into the surrounding fjord, bays and nearshore coastal regions.
Fig. 4. Baffin Bay productivity collected by NASA collaborators during Welker’s 2021 Source-Sea Freshening and Fertilization program, central to the DIWA conceptual framework. Bright red indicates high phytoplankton, base of the food web, production inside the fjords and along the nearshore of west Greenland and Baffin Island.
Freshening of the Arctic Ocean is one of the most important processes to document today, because as recently reported: “Freshening of the Arctic may completely change the Earth's Climate" from the paper: Physics-based early warning signal shows that AMOC is on the tipping course: R Westen et al. Science Advances Feb. 2024.
These global alarm bells are ringing because this linkage that Welker’s team is stitching together and contributing to DIWA is a “connecting the dots” scenario: climate warming-ice melt- freshwater increases in rivers, more freshwater into the Arctic Ocean leading to a complex set of consequences that may include a weaking of the Atlantic Meridional Overturning Circulation (AMOC) that regulates the heat transport from the mid- to the high latitudes.