The image below shows Arctic sea ice north of Greenland and around Ellesmere Island. This is the area where for thousands of years the sea ice has been the thickest, in many places remaining thicker than 5 meters (16.4 ft) throughout the year.
[ The once-thickest sea ice has gone – click on images to enlarge ]The image is a compilation of NASA Worldview images over seven days, from August 14 through to August 21, 2018. The least cloudy areas have been selected from each image to get the best insight in the magnitude of this catastrophe.
The loss of this sea ice indicates that the buffer is gone. Sea ice acts as a buffer that absorbs heat, while keeping the temperature at the freezing point of water, about zero degrees Celsius. As long as there is sea ice in the water, this sea ice will keep absorbing heat, so the temperature doesn’t rise at the sea surface.
Once the buffer is gone, further energy that enters the Arctic Ocean will go into heating up the water. The amount of energy absorbed by melting ice is as much as it takes to heat an equivalent mass of water from zero to 80°C.