Rising Sea, Collapsing Ice

Articles in Nature Climate Change and The Cryosphere indicate that global sea levels have rising faster than previously thought, and that the Larsen C ice shelf in Antarctica is thinning from above and below.

Update (May 22):  A study published in Science indicates that glaciers along the southern Antarctic Peninsula coast have been losing about 56 billion tons of ice per year since 2009.  It's being driven by warmer water melting the undersides of ice shelves.

Update (July 10):  Looking at past warm periods, a study published in Science projects a 20 foot sea level rise even if warming is held to 2 degrees Celsius.  The melting will take at least 200 years with a loss of 48,000 square miles of land in the U.S. which is home to 15 percent of the population.

Peak global mean temperature, atmospheric carbon dioxide, maximum global mean sea level (GMSL), and source(s) of meltwater.  Light blue shading indicates uncertainty of GMSL maximum. Red pie charts over Greenland and Antarctica denote fraction (not location) of ice retreat

Update (July 20):  A study by lead author James Hansen (not yet peer reviewed) argues that sea level could rise by 10 feet by the end of this century.  Even 2 degrees Celsius of warming is considered "highly dangerous".

Update (July 23):  The study by Hansen, et al is blunt:

There is evidence of ice melt, sea level rise to [plus 5 through 9 meters], and extreme storms in the prior interglacial period that was less than 1 [degree Celsius] warmer than today.

A relatively rapid rise in sea level will be quite destructive.  The timing depends on how fast the rate of melting doubles.

Doubling times of 10, 20 or 40 years yield sea level rise of several meters in 50, 100 or 200 years.

Recent ice sheet melt rates have a doubling time near the lower end of the 10 [to] 40 year range. We conclude that 2 [degree Celsius] global warming above the preindustrial level, which would spur more ice shelf melt, is highly dangerous.

Update (July 27):  More from James Hansen.  I suppose this study deserved its own entry, but it's not in final form.  It suggests sea level rise may be greater and faster than already anticipated.

Update (November 13):  A study published in Science finds that the Zachariae glacier in northeast Greenland is rapidly retreating. By itself, it would contribute one and a half feet of sea level rise.

Update (November 19):  A study by lead author Catherine Ritz published in Nature seems to dispute a large contribution from Antarctica to sea level rise by 2100. A 10 cm contribution is given as the mostly likely outcome.

Update (January 17, 2016):  More about Zachariae and the Northeast Greenland Ice Stream.

Update (July 2, 2017):  An international study finds that the rate of sea level rise has increased from 2.2 millimeters per year in 1993 to 3.3 millimeters per year in 2014. Greenland's contribution to that rate of change increase from 5 percent in 1993 to 25 percent in 2014.

A separate study finds that Greenland's surface melting is driven by decreasing cloud cover more than just rising temperatures.