Summer Ice Melt On Antarctic Peninsula Is Now Nonlinear, Fastest In Over 1000 Years

Scientist: "The Antarctic Peninsula has warmed to a level where even small increases in temperature can now lead to a big increase in summer ice melt."

Credit: British Antarctic Survey

A new study finds "a nearly tenfold increase in melt intensity" on the Antarctic Peninsula in the last few hundreds years.

Here's the most worrisome news from this 1000-year reconstruction of "ice-melt intensity and mean temperature" published in Nature Geoscience:

The warming has occurred in progressive phases since about AD 1460, but intensification of melt is nonlinear, and has largely occurred since the mid-twentieth century. Summer melting is now at a level that is unprecedented over the past 1,000 years. We conclude that ice on the Antarctic Peninsula is now particularly susceptible to rapid increases in melting and loss in response to relatively small increases in mean temperature.

In short, while some mistakenly assert the climate is less sensitive than we thought, the fact is that polar ice loss is accelerating far beyond what the models had projected even a few years ago, and the whole region appears even more sensitive than previously thought.

It was just 2006 when Penn State climatologist Richard Alley explained that observations had indicated the great ice sheets appear to be shrinking "100 years ahead of schedule."

NASA's Jet Propulsion Laboratory reported in 2011 that polar ice sheet mass loss is speeding up and is on pace for 1 foot sea level rise by 2050.

What's happening at the South Pole, which has 90% of the world's ice. In 2009, we learned that Antarctica's Pine Island Glacier has been thinning 4 times faster than it was 10 years ago: "Nothing in the natural world is lost at an accelerating exponential rate like this glacier." The same year Naturereported that "Dynamic thinning of Greenland and Antarctic ice-sheet ocean margins is more sensitive, pervasive, enduring and important than previously realized."

As for the cause, we know that "deep ocean heat is rapidly melting Antarctic ice." And we knew that these warm ocean currents melting Antarctica were so intense that, seawater appears to "boil on the surface like a kettle on the stove." Last April, researchers reported in Nature that this melting from below "May Already Have Triggered A Period of Unstable Glacier Retreat." We learned in December that West Antarctica is warming three times faster than global average.

The key point is that the West Antarctic ice sheet (WAIS) is inherently far less stable than the Greenland ice sheet because most of it is grounded far below sea level. As I wrote in the "high water" part of my book:

rest http://thinkprogress.org/climate/2013/04/15/1864401/summer-ice-melt-on-antarctic-peninsula-is-now-nonlinear-fastest-in-over-1000-years/