Six narwhals carrying oceanographic sensors have helped scientists document warm Atlantic water reaching glacier-front basins hundreds of kilometres inside East Greenland's fjords. The peer-reviewed study, published in Science Advances on August 26, used 2,060 dive profiles to fill a major observation gap in Scoresby Sound and nearby coastal systems, where ships face sea ice, icebergs and high operating costs.
Researchers from the Greenland Institute of Natural Resources, the University of Copenhagen and partner institutions attached conductivity, temperature and depth instruments to the animals. From August 2017 to July 2020, the devices recorded a profile whenever a whale dived at least 50 metres, with observations separated by at least 15 minutes. The six narwhals naturally entered remote waters that research vessels rarely sample, including during winter.
The team combined those measurements with historical ship observations in the World Ocean Database, covering records from 1891 to 2022. Its statistical model related temperature and salinity to depth and indicated that warmer, saltier Atlantic Intermediate Water has thickened while the upper layer of colder Polar Water has thinned. Traces of Atlantic water appeared as far as about 300 kilometres from the open coast.
The study found that deep glacier-front basins were generally exposed to warmer water than shallow coastal basins, especially between roughly 200 and 500 metres. Most Atlantic inflow occurred below 150 metres. The researchers said this subsurface heat can accelerate melting where glaciers meet deep water, including parts of Scoresby Sound, while glaciers ending in shallow basins face less direct exposure.
The results do not measure a single glacier's future retreat or by themselves establish how much sea level will rise. They instead provide previously scarce observations for improving ocean and climate models. Freshwater released by Greenland's ice can affect ocean circulation beyond the Arctic, making the pathways and changing thickness of water layers important inputs for projections.
Scientists said marine mammals can complement, rather than replace, ships and fixed instruments in inaccessible polar regions. This was the first narwhal deployment to measure salinity as well as temperature and depth, according to Eos. The University of Copenhagen's animal-care committee approved the work, and outside researchers stressed that such monitoring remains valuable only when animals are treated ethically.
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