Greenland's melt mystery unfolds, at glacial pace

[joshcryer]

HELHEIM GLACIER, Greenland – Suddenly and without warning, the gigantic river of ice sped up, causing it to spit icebergs ever faster into the ocean off southeastern Greenland.

Helheim Glacier nearly doubled its speed in just a few years, flowing through a rift in the barren coastal mountains at a stunning 100 feet (30 meters) per day.

Alarm bells rang as the pattern was repeated by glaciers across Greenland: Was the island's vast ice sheet, a frozen water reservoir that could raise the sea level 20 feet if disgorged, in danger of collapse?

Half a decade later, there's a little bit of good news — and a lot of uncertainty.

"It does seem that the very rapid speeds were only sustained for a short period of time although none of these glaciers have returned to the 'normal' flow speeds yet," says Gordon Hamilton, a glaciologist from the University of Maine, who's clocked Helheim's rapid advance using GPS receivers on site since 2005.

Understanding why Greenland's glaciers accelerated so abruptly in the first half of the decade — and whether they are now slowing down — is crucial to the larger question of how fast sea levels will rise as the planet warms.

More at link: http://news.yahoo.com/s/ap/20090910/ap_on_sc/climate_09_greenland_s_melt

---

This sort of thing is why I believe IPCC AR5 is going to be one scary report. One thing that many people don't know is that AR4 did *not* take into account any arctic melt off outside of glaciers. The "small number" oft quoted by global warming denialists only considers glaciers and the expansion of the oceans as they warm.

[NecklyTyler]

1. It looks like we are walking a tightrope for tipping points - without a net

There were record warm temperatures in the late '90.

Understanding why Greenland's glaciers accelerated so abruptly in the first half of the decade — and whether they are now slowing down — is crucial to the larger question of how fast sea levels will rise as the planet warms.

By grace, the slope of the warming curve hit a plateau in 2002 - 2003. I think we were right at the brink of a tipping point with the Greenland glaciers, but we have a temporary reprieve for the moment.

Global temperatures do not have to rise enough to melt all the ice. They only have to rise enough to upset the Arctic equilibrium. I think we have already destroyed the equilibrium, and things are going to get much worse, quickly, in the next 3 to 5 years.

[Nederland]

2. A Key problem in analyzing these things

We have no idea what "normal" is. We observe something for 30 or 40 years out of hundreds of millions, and call that "normal". There is so much we do not know and do not understand.