It may come as a shock to some, but as the global temperature has been rising, ice has been melting. In the Arctic ocean, this has meant a decline in multi-year sea ice. While conservatives have been busy pretending that the ice totally isn’t melting, climate scientists have been looking into what follows as the ice recedes. The news isn’t good:
There are a lot of feedback mechanisms that are starting to kick in and speed up the warming, but the easiest one to explain and understand is the albedo effect. For those who are unfamiliar, white ice reflects more sunlight than dark water. The more ice there is, the more light bounces back into space. The less ice there is, the more light is absorbed by the water, heating it up.
So the more ice we lose, the faster the planet warms.
This study shows that that process has been underway, and it shows that some of the extra heat is being pooled below the surface of the Arctic Ocean, and while there’s a layer of cold water currently separating it from the surface, the end result seems pretty clear:
The upper ocean in the Canadian Basin has seen a two-fold increase in heat content over the past 30 years, the researchers said. They traced the source to waters hundreds of miles to the south, where reduced sea ice has left the surface ocean more exposed to summer solar warming. In turn, Arctic winds are driving the warmer water north, but below the surface waters.
“This means the effects of sea-ice loss are not limited to the ice-free regions themselves, but also lead to increased heat accumulation in the interior of the Arctic Ocean that can have climate effects well beyond the summer season,” Timmermans said. “Presently this heat is trapped below the surface layer. Should it be mixed up to the surface, there is enough heat to entirely melt the sea-ice pack that covers this region for most of the year.”
Unfortunately, that scenario doesn’t end with the ice melting. It’s important to remember that each of these studies is a small piece of a planet-sized puzzle. The ice isn’t the only thing in the Arctic Ocean that will melt if temperatures rise. All over the planet there are sea floor deposits called hydrates that are kept stable by high pressure and low temperature. They keep a vast amount of methane out of the atmosphere – sealed in ice. If that pool of warmth in the Arctic reaches down, it could trigger a huge release of methane into the atmosphere, and things would get a lot hotter, a lot faster.
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Uh, how does wind drive subsurface water to locations beneath ice?
(Yes, I read the linked summary and the (publicly available -yay!) article from which it came. The latter, most of which roared over my head, even using a search for the few instances of “wind”, to my confused reading implicates ocean currents pouring through the Bering Strait, in combination with the tendencies of water with differing salinity to self-segregate, as the factors responsible.)
And I desperately hope I misread the “Implications and outlook” section, as I think it implies that a little more warming (which seems inevitable) in the just-below-the-ice water layer will break that thermal differentiation, leading to the whole ice cap melting very rapidly. That scares me silly…
Once you get a large volume of water moving, it tends to keep moving, and since water doesn’t like to pile up or leave holes, wind-driven surface currents can strongly influence (or become) sub-surface currents.
Dunc @ # 2 – I s’poze it has to work like that, sometimes, but I’ve so often noticed – &/or received dire warnings about – offshore currents running at cross angles to the prevailing winds.
Still, unless the field reports got everything wrong, those warm pockets under the ice got there somehow, and we don’t see anybody talking about Arctic-Circle hot springs and fumaroles…
It’s complicated, with lots of different factors interacting in often surprising ways. Near shore currents are largely determined by tide state and local geography / oceanography. i think you only see winds driving currents when you’re looking at larger scales.
Not positive, but I think the Arctic ocean has a sort of a “lid” of cold, dense water at the surface in addition to the ice, so it may be that that, plus the prevalence of short-term ice floes forces the warmer current down farther to the edges, so that it’s deeper by the time it reaches the center of the ocean basin.