Climate change impacts in the polar regions
WOR 6 The Arctic and Antarctic - Extreme, Climatically Crucial and In Crisis | 2019

Climate change impacts in the polar regions

Climate change impacts in the polar regions
> To date, global warming has affected the two polar regions in different ways. While the Arctic is undergoing fundamental changes and is gradually losing its distinctive polar character, the observable changes in the Antarctic are primarily focused on two regions: West Antarctica and the Antarctic Peninsula. East Antarctica, however, is also beginning to respond to the rising temperatures.
The pathways of heat © ddp images/Picture Press/Per-­Andre Hoffmann

The pathways of heat

> Climate change produces more visible traces in the polar regions than it does on other parts of the Earth. This is due in part to the special sensitivity to heat of these icy worlds. But another factor is that the warming due to greenhouse gas emissions is more strongly amplified in the Arctic by a number of positive feedback mechanisms, causing temperatures in the northern polar region to rise twice as fast as in the rest of the world.

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Retreating ice © Paul Zizka Photography

Retreating ice

> Where the atmosphere and oceans warm steadily, ice and snow retreat. In the polar regions, this has long since ceased to be just a theoretical concept. It is a stark everyday reality, especially in the Arctic, where the snow cover and sea ice are shrinking, glaciers are thinning, and the permanently frozen ground is thawing to greater depths. But climate change has also been impacting Antarctica for some time now, with consequences that are becoming evident on all the coastlines of the world.

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More heat – much less ice

The atmosphere is warming as a result of increasing greenhouse gas emissions and the greenhouse effect. But more importantly, the world ocean is warming. It has absorbed 93 per cent of the additional heat so far. Particularly in the polar regions the rising air and water temperatures are causing fundamental changes that are occurring earlier and more notice­ably in the Arctic than in the Antarctic. The Arctic region is ­warming twice as fast as the rest of the world ­because processes in the ice, land, sea and atmosphere of the polar regions are so closely interrelated that changes in one of these components has a direct effect on the others, and they reinforce one another. Scientists call this “Arctic amplification”. The effect is especially pronounced in winter. Many regions of the Arctic are receiving significantly less snow. At the same time, not as much sea ice is ­forming. Since 1979, the ice cover on the Arctic ­Ocean has lost more than 30 per cent of its area. Further­more, the sea ice today is younger and thus thinner, more fragile, and more mobile.
The rising temperatures also affect permanently frozen soils in the Arctic. The permafrost is warming to greater depths and thawing ever deeper and over larger areas in the summer. As a result, portions of the Alaskan and Siberian coasts are eroding, entire landscapes are subsiding, and the once-frozen subsurface is losing its load-bearing capacity, causing substantial damage to buildings, roads and other infrastructures.
The ice masses on land in the Arctic are undergoing substantial change. The Greenland Ice Sheet, as well as the glaciers in Alaska and Canada, are losing more ice than is being replaced by new snowfall. This is the result of melting processes on their upper surfaces and on the underside of the ice tongues where they are in contact with sea water.
In Antarctica, the atmosphere had only warmed noticeably by the end of the 20th century in the ­region of the Antarctic Peninsula. This was evidenced by the breakup of the northern ice shelves, and by a decline in sea ice on the western side of the peninsula. In all other regions of Antarctica the air temperature has only risen slightly or not at all – a situation that scientists attribute to the cooling effect of the Antarctic ozone hole. Nonetheless, warming in the Southern Ocean is causing profound changes in the Antarctic, with effects that vary from area to area. The loss of ice in West Antarctica gives major cause for concern. In recent decades, warm water from the Circumpolar Current has been penetrating far beneath the ice shelf in the Amundsen Sea and melting it from below. These ice masses are thus retreating at a record pace, a process that will ­probably not end until the part of the West Antarctic Ice Sheet that is resting on the sea floor has completely disappeared.
There are now signs of a similar development in East Antarctica, where the Totten Glacier is losing contact with the bottom, and in the Weddell Sea, where warm water is threatening Antarctica’s second-largest ice shelf. Overall, the rate of ice-mass loss in the Antarctic region has tripled since 2012. The share of its contribution to global sea-level rise has risen accordingly. At 3.34 millimetres per year, the global rate is twice as high as it was in 1990, whereby the rise is due mostly to the losses of ice in Greenland and glaciers outside of Antarctica, as well as to the thermal expansion of water. However, it is a fact that, because of the rising water levels, the decline of polar ice is becoming a threat to coastal regions around the globe.