Global floating ice in "constant retreat"

Reuters: The world's floating ice is in "constant retreat," showing an instability which will increase global sea levels, according to a report published in Geophysical Research Letters on Wednesday. Floating ice had disappeared at a steady rate over the past 10 years, according to the first measurement of its kind.

"It's a large number," said Professor Andrew Shepherd of the University of Leeds, lead author of the paper, estimating the net loss of floating sea ice and ice shelves in the last decade at 7,420 cubic kilometers. That is greater than the loss of ice over land from the Greenland and Antarctic ice sheets over the same time period, highlighting the impact of warming oceans on floating ice.

…The study did not shed new light on how soon the North Pole may be ice-free in summer, which many climate experts say could happen by 2050, perhaps even earlier. Melting of floating sea ice and ice shelves adds little to sea level rise, because their entire mass is already in the water. By contrast, ice on land which melts into the sea will add to levels according to the equivalent of its entire weight.

If all the world's floating ice melted it would add about 4 centimeters to sea levels. But this could have a bigger effect by unblocking glaciers over land, which could then slide faster into the sea, and also because open water reflects less sunlight than ice, warming the local area…

Isfjord, Ilulissat, Diskobay, West Greenland. Huge icebergs (up to 600 ft. high) and calv ice moving out of the Isfjord (Kangia) to the sea. In summer this movement is reaching a speed of 30 m. per day. July 1999. Shot by Michael Haferkamp, Wikimedia Commons, under the Creative Commons Attribution ShareAlike 3.0 License