Saturday, October 10, 2015

Arctic Sea Ice 2015 - update 11

Arctic sea ice extent has been growing rapidly recently. The image below shows extent up to October 9, 2015 (marked by red dot).

Below is a comparison of sea ice thickness as on October 6, for the years (from left to right) 2012, 2013, 2014 and 2015. The comparison shows that decline has been strongest where sea ice used to be the thickest, i.e. over 3 meters thick.

One of the reasons why the thickest Arctic sea ice has declined so dramatically over the years is the rising ocean heat that is melting the sea ice from underneath. The image below illustrates the situation on October 5, 2015, when sea surface temperature anomalies were as high as 6.4°C, 7.4°C and 7.3°C (11.5°F 13.2°F and 13.1°F) off the North American coast, and as high as 9.4°C (16.8°F) near Svalbard.

Water temperatures are very high in the Arctic, as further illustrated by the image below showing Arctic sea surface temperature anomalies as at October 9, 2015.

Rising ocean heat is further illustrated by the graph below, showing August sea surface temperature anomalies on the Northern Hemisphere over the years.
The situation is very dangerous, due to feedbacks and their interaction. The thicker sea ice used to act as a buffer, consuming ocean heat in the melting process. Without thicker sea ice, ocean heat threatens to melt the sea ice from below right up to the surface, causing the entire sea ice to collapse. As the sea ice declines, more open water will give rise to stronger winds and waves.

Furthermore, sunlight that was previously reflected back into space will instead be absorbed by the water, causing rapid rise of the temperature of the water. In places such as the East Siberian Arctic Shelf, the water is on a average only 50 m deep, so warmer water is able to reach the seafloor more easily there. As ocean heat keeps rising, there's a growing risk that heat will reach the Arctic Ocean seafloor and destabilize methane hydrates in sediments at the Arctic Ocean seafloor.

The image below shows a non-linear trend that is contained in the temperature data that NASA has gathered over the years, as described in an earlier post. A polynomial trendline points at global temperature anomalies of over 4°C by 2060. Even worse, a polynomial trend for the Arctic shows temperature anomalies of over 4°C by 2020, 6°C by 2030 and 15°C by 2050, threatening to cause major feedbacks to kick in, including albedo changes and methane releases that will trigger runaway global warming that looks set to eventually catch up with accelerated warming in the Arctic and result in global temperature anomalies of 16°C by 2052.

[ click on image to enlarge ]
The situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan.

Comparison of sea ice thickness on October 6, for the years (from left to right) 2012, 2013, 2014 and 2015, shows that...

Posted by Sam Carana on Saturday, October 10, 2015

1 comment:

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