A new study published in the journal Nature reports that glaciers along the coastline of both the Antarctic and Greenland ice sheets are rapidly thinning.

Lead author Dr Hamish Pritchard from British Antarctic Survey (BAS) said:

We were surprised to see such a strong pattern of thinning glaciers across such large areas of coastline — it’s widespread and in some cases thinning extends hundreds of kilometres inland. We think that warm ocean currents reaching the coast and melting the glacier front is the most likely cause of faster glacier flow. This kind of ice loss is so poorly understood that it remains the most unpredictable part of future sea level rise.

The authors conclude that this ‘dynamic thinning’ of glaciers now reaches all latitudes in Greenland, has intensified on key Antarctic coastlines, is penetrating far into the ice sheets’ interior and is spreading as ice shelves thin by ocean-driven melt. Ice shelf collapse has triggered particularly strong thinning that has endured for decades.

The National Snow and Ice Data Center reports that the Arctic melt season is now in high gear:

Through most of June, ice extent tracked close to two standard deviations below the long-term mean and just above the levels observed in 2007.

The graph above shows daily sea ice extent as of July 6, 2009. The solid blue line indicates 2009; the dashed green line shows 2007; and the solid gray line indicates average extent from 1979 to 2000. The gray area around the average line shows the two standard deviation range of the data.

NSIDC says that Arctic ice extent has been declining at a rate of 3.3% per decade:

Compared to previous Junes, ice extent in June 2009 was extremely close to the last two years, falling within 30,000 square kilometers (12,000 square miles) of the June extent in 2007 and 2008. The long-term trend indicates a decline of 3.3% per decade, an average of 40,100 square kilometers (15,500 square miles) of ice per year.

Monthly June ice extent for 1979 to 2009 shows a decline of 3.3% per decade.

In June, the Arctic saw warm temperatures over the Laptev Sea and the northern Beaufort Sea, while the Atlantic sector of the Arctic was slightly cooler than normal. The warm temperatures in the Laptev Sea corresponded to quickly declining ice concentrations in the area. NSIDC expects this region to become largely ice-free in the next few weeks.

The map of sea ice concentration from AMSR-E from July 5, 2009 shows low ice concentrations in the Laptev Sea, where atmospheric temperatures have been particularly warm in the month of June.

Arctic sea ice has thinned dramatically, some seven inches (17.8 centimeters) a year, or 2.2 feet (67 centimeters) between the winters of 2004 and 2008, according to a study by NASA and the University of Washington. The scientists also found that thicker, older ice, which has survived one or more summers, shrank by 42% – the equivalent of Alaska’s land area.

Thicker, older ice is less vulnerable than thinner ice to melting in the summer months. Less summer ice means more open water, which absorbs more heat, warming the ocean and further melting the ice.

Australian polar explorer Eric Philips reports:

Each year I guide ski expeditions across the pack ice to the North Geographic Pole and each year brings new surprises — severe storms rarely seen in these parts, vast tracts of first-year ice where there should be years of accumulation, pack ice drifting faster and farther than ever before.

The veneer of fractured ice over the Arctic Ocean is changing, disintegrating before my eyes.

From the National Snow and Ice Data Center:

After a slow start to the melt season, ice extent declined quickly in May. Scientists are monitoring the ice pack for signs of what will come this summer. The thinness of the ice pack makes it likely that the minimum ice extent will again fall below normal, but how far below normal will depend on atmospheric conditions through the summer.

Sea ice melt has now nealy caught up to the record 2007 season.

The ice bridge supporting the Wilkins ice shelf shattered yesterday (Saturday, April 4).

The last photo on the European Space Agency’s animated “webcam from space” shows the disintegrating ice.

David Vaughan, a glaciologist with the British Antarctic Survey, told Reuters:

It’s amazing how the ice has ruptured. Two days ago it was intact. We’ve waited a long time to see this.

My feeling is that we will lose more of the ice, but there will be a remnant to the south.

We believe the warming on the Antarctic Peninsula is related to global climate change, though the links are not entirely clear.

Temperatures on the Antarctic Peninsula, which snakes up toward South America, have risen by up to about 3 Celsius (5.4 Fahrenheit) in the past 50 years, the fastest rate of warming in the Southern Hemisphere.

Nine other shelves have receded or collapsed around the Antarctic Peninsula in the past 50 years, often abruptly like the Larsen A in 1995 or the Larsen B in 2002 further north.

The loss of the ice bridge, which was almost 100 km wide in 1950 and had been in place for hundreds of years at least, could allow ocean currents to wash away more of the Wilkins.

Great timing. On Monday the United States will be hosting a “polar conference” with representatives of 47 of the world’s governments. Climate change is to be a major focus of the talks, which are preparatory to the global talks in Copenhagen scheduled for December.