Increasing temperatures aren’t the only factor to blame for dramatic Arctic sea ice loss. An international team of 16 scientists led by the International Arctic Research Center in Alaska discovered warm currents from the Atlantic Ocean are snaking up to the Arctic and melting ice from below. They call this phenomenon the Atlantification of the Arctic.
Scientists placed sensors in the Arctic seas in 2002, and the information they’ve gathered isn’t good. The Arctic Ocean’s behavior has undergone a massive shift, according to physical oceanographer Finlo Cottier of the Scottish Association for Marine Science, who was not part of the study.
Warm Atlantic currents have a lot to do with this change, according to research published online by Science yesterday. The scientists looked at the Eurasian basin, or one of two basins in the Arctic Ocean divided by a ridge far beneath the surface. The Eurasian basin is north of Europe and Asia. Scientists have long known warm Atlantic currents prevent ice formation on the western side of the Eurasian basin north of Scandinavia. But now it seems those currents are working against ice on the eastern side north of Siberia too.
Atlantic currents stream into the Arctic at depths of around 656 to 820 feet, with temperatures around four degrees Celsius higher than surface water. When they mix with surface water, which cools and falls in winter, the mixed water is a little warmer overall so the ocean has little sea ice. On the Eurasian basin’s eastern side a barrier known as the cold halocline layer (CHL) used to prevent much of that mixing. But now the eastern side is becoming more like the western side. Summer sea ice once helped form the CHL, but without that ice the ocean mixes more – and then not as much ice forms. Study lead author Igor Polyakov of the University of Alaska in Fairbanks told Science, “Previously this monster, Atlantic warm water, was well covered from the surface” by the CHL. “The new data show this layer has disappeared in winter.”
Cottier told Science, “Here we’re seeing an ocean basin changing on a generational timescale – or less.”