Planetary climate change has already had significant observable effects on the environment, particularly in the ice covered regions of the world known as the cryosphere. Species are migrating (including humans) poleward, glaciers have shrunk and are receding rapidly, ice shelves in the Antarctic are collapsing, ice in rivers and lakes are breaking up earlier.
These are all the effects that were predicted by climate scientists that have now come to pass: loss of sea ice, intense and deadly heat waves, changing rainfall patterns and accelerating sea level rise.
The Arctic is warming twice as fast as any other place on Earth, and is reeling from the heat in spectacular ways.
The Barents Sea is located in the Arctic Ocean just north of Norway and Russia, and has abundant marine life with hydrocarbons under its shallow shelf. This region is already being exploited by the fishing and fossil fuel industries.
John Timmer, writing for ars Technica, notes that we have just passed a tipping point in the Barents Sea.
Many of the threats we know are associated with climate change are slow moving. Gradually rising seas, a steady uptick in extreme weather events, and more all mean that change will come gradually to much of the globe. But we also recognize that there can be tipping points, where certain aspects of our climate system shift suddenly to new behaviors.
The challenge with tipping points is that they're often easiest to identify in retrospect. We have some indications that our climate has experienced them in the past, but reconstructing how quickly a system tipped over or the forces that drove the change can be difficult. Now, a team of Norwegian scientists is suggesting it has watched the climate reach a tipping point: the loss of Arctic sea ice has flipped the Barents Sea from acting as a buffer between the Atlantic and Arctic oceans to something closer to an arm of the Atlantic.
Chris Mooney of the Washington Post notes that the same study results, published this week in Nature Climate Change by Lind Sigrid and two other researchers from Norway’s Institute of Marine Research and University of Bergen, make the crucial point that the “divide between the Atlantic and the Arctic isn’t just a geographical one — it’s physical in nature”.
While the Southern Barents is milder, the northern Barents has — until recently — had all the characteristics of an Arctic sea. It featured floating sea ice that, when it melted, helped to provide an icy, freshwater cap atop the ocean. This kept internal heat from escaping to the atmosphere, and also kept the ocean “stratified” — cold, fresher waters in the upper part of the ocean and warmer, Atlantic-originating waters down below.
There has been less and less sea ice in the Barents leaving just open ocean in its place, absorbing more solar energy and heating the intermediate water layer from above. Timmer explains that in addition, “the warm Atlantic water will heat it from below. As a result, the cold intermediate water has essentially vanished from the Barents Sea, turning the area into a basin dominated by Atlantic water. The entire water column, from surface to the sea floor, has both warmed and gotten saltier, all starting in the late-2000s.”
The precipitating event for these changes, the new study finds, is that floating ice is no longer being supplied as regularly to the Barents Sea region from higher Arctic climes.
Arctic sea ice breaks up and becomes more mobile in the warmer months of the year, but less has been flowing into the Barents Sea and melting, and that in turn has begun to break the hold of stratification on the ocean, as the Barents no longer contains enough freshwater to sustain it.
“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, a historically rare moment where we would witness a large body of water being completely transformed from Arctic to Atlantic type,” the study concludes.
While these changes are quite dramatic, that in and of itself doesn't make for a tipping point, states Timmer. He notes that the researchers make the argument that current conditions in the Barents “make it extremely difficult for the sea ice to re-establish itself during the winter: "Increased Atlantic Water inflow has recently enlarged the area where sea ice cannot form, causing reductions in the sea-ice extent." That is because the water is now warmer with high salt content, “making freezing more difficult”.
In a nutshell, the researchers “argue that the entire Barents Sea has started to behave as an arm of the Atlantic”.
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