Across some sections of the Arctic, seasonal sea ice is failing to reappear as temperatures rise.
Across some sections of the Arctic, seasonal sea ice is failing to reappear as temperatures rise. Public domain

It’s hard to know where one ocean starts and the next one begins. Though on maps we’re happy to chop up our maritime world into parcels, the water doesn’t really work that way, despite the occasional circulation of miscaptioned photographs that purport to show the dramatic meeting of two oceans. In fact, so far as the NOAA is concerned, there’s only one ocean, with four, or possibly five, ocean basins.

When geographers talk about what distinguishes one ocean from another, however, they’re interested in their geographical features and physical properties, such as salinity or temperature. What that means, too, is that ocean “boundaries” may shift with the features or properties of a given undersea area.

This is exactly what seems to be taking place in a region of the Arctic Ocean, northeast of Finland. In the Barents Sea, both salinity and ocean temperature are climbing at an alarming rate, according to a new study published this week in the journal Nature Climate Change. As sea ice vanishes, and fails to be replaced, the water is no longer being diluted as it once was, leading to this uptick in saltiness. All of this, the study says, means that the northern Barents is beginning to look much more like the Atlantic Ocean than the Arctic Ocean.

More than simply moving a line on a map, there are dramatic, and perhaps worrying, implications for the marine ecosystems of this region. As subzero Arctic water floods out of the Barents, and the seasonal sea ice disappears, the marine mammals, birds, and microorganisms that call it home may be displaced or die out altogether, to be replaced with Atlantic creatures who enjoy a balmier climate.

In earlier simulations, LiveScience notes, it seemed likely that the northern Barents Sea would eventually be indistinguishable from the Atlantic, though not before close to the end of the century. But the speed at which the zone is warming—2.7 degrees Fahrenheit since 2000—suggests that this may happen much, much sooner. “Unless the freshwater input should recover, the entire region could soon have a warm and well-mixed water column structure and be part of the Atlantic domain,” according to the study. Such a transition would be a “historically rare moment,” the researchers add.