Arctic deep water protected from climate change

Although sea ice is melting rapidly on the surface of the Arctic Ocean, new research shows that the deep water that lies beneath remains relatively stable—for now.

A study led by researchers at Arizona State University and Columbia University in the United States found that a vast pool of deep Arctic water, sitting more than 1,500 metres below the surface, has remained largely isolated for roughly 450 years. The researchers found that only trace amounts of modern surface water have penetrated this layer, highlighting how slowly the deep Arctic Ocean circulates.

A cooler intermediate layer helps keep the warmer deep water from mixing upward toward the surface and the sea ice above. The new findings suggest that this layered structure remains largely intact, despite rapid warming and record-low levels of winter sea ice in recent years.

If continued warming weakens this separation and allows more mixing between the layers, warmer water from below could reach the surface and accelerate sea ice loss. Changes in deep-water circulation could also have far-reaching effects on global ocean circulation and potentially contribute to faster melting of Greenland’s ice sheet.

For now, however, researchers have found no indication that deep-water circulation has begun to change—a rare piece of encouraging news about the rapidly changing Arctic.