Newly published research suggests the amount of heat stored in a vast section of the Arctic Ocean has doubled over the last 30 years, adding another blow to sea ice that helps regulate the planet’s climate.
“The most likely outcome for this heat is that it will slow the growth of winter sea ice, which further compromises the Arctic sea ice pack,” said Mary-Louise Timmermans of Yale University.
Timmermans is one of the authors of a paper published Wednesday that examined 30 years worth of measurements at different depths in the Canada Basin, a large section of the Arctic Ocean west of Canada’s High Arctic Islands.
That ocean is composed of layers divided by both salinity and temperature. One of those layers, beginning at about 50 metres of depth, is both more saline and warmer than the surface waters.
That layer has probably always been there and comes from waters hundreds of kilometres to the south in the Chukchi Sea, said Timmermans.
Those waters move north through a natural current called the Beaufort Gyre. When they get far enough north, their higher salinity makes them heavier than the water around them and they sink below the surface.
But climate change means the Chukchi Sea has been losing sea ice in recent decades. That has allowed the sun to warm it up.
“We’re seeing more and more open water as the sea ice retreats in the summertime,” Timmermans said. “The sun is warming up the ocean directly, because it’s no longer covered by sea ice.”
The paper calculates that sea is now absorbing five times more solar energy than it did before.
That sun-warmed water has created what Timmermans calls “archived” heat in the Canada Basin.
“That layer of water is both increasing in temperature and also increasing in thickness. Overall, it’s increasing heat content.”
Some of that heat trickles up to the surface of the Canada Basin, one of the places that still has a summer ice cover. Timmermans said that heat will slow and weaken the formation of winter ice.
Although that water has only been warmed to a maximum temperature of about 0 C, the paper calculates there is currently enough new heat stored beneath the ocean surface to thin the ice cover of the entire basin by nearly a metre. It notes the amount of such “archived” heat will continue grow as the Chukchi loses more ice.
What’s happening in the Canada Basin is an example of how losing sea ice in one area can contribute to further sea ice losses in areas hundreds of kilometres away, the paper says.
The ultimate consequences are unknown, Timmermans said.
If the Chukchi water warms up enough, it may no longer sink. That could further affect sea ice, or it may change atmospheric circulation if the heat is lost to the air.
Scientists are still debating the impact of sea ice on the jet stream, a high-altitude river of air that has large effects on southern weather.
The future challenges are clear, she said.
“To understand heat transport, to understand limits and to keep measuring the whole Arctic system – atmosphere, ice, and ocean below so that we can do these kinds of analyses and use them to make viable projections.”