Tag: ice

The sound of failure/It’s dark… Is it always this dark?

Mackenzie.jpgForgive me this riff on impermanence. Last Sunday morning, my little group of middle-aged winos and winemakers (plus a professor or two) left the lodge in Martin’s Bay and crossed a serene Hollyford River on a jetboat. We walked along the edge of the bush on the spit, looking at Maori middens, layering in sand dunes, native plants and the succession from pingao to rimu, pondering the most recent ice age — which carved out the Hollyford valley — and the potential for rising seas to change this wonderful example of coastal ecology. Eventually we arrived at the site of the Mackenzie homestead – built in the 1870s by hardy settlers determined to make their lives in this wet and wild corner of what was then a new land to Europeans. All that remains is the stone fireplace, overgrown with grass, the vague outline of the walls, and some imported trees — the gums are doing very well. I pondered the lives of the settlers in the Hollyford and the scratches they left on the landscape, while New Zealand and the world grasped at bigger issues…

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Going, going, gone (by 2015)

One for the furry blogger with sharp teeth: the Winnipeg Free Press reports that University of Manitoba geoscientist David Barber is predicting that the Arctic will be ice free in summer in the next seven years.

“We’ll always have ice in the winter time in the Arctic, but it will always be first-year ice,” Barber said on Friday. He said he estimates the Arctic sea should see its first ice-free summer around 2015. “That has got industry very interested in the Arctic,” he said. “That will put more pressure there. The change is happening so quickly.”

Barber, who will be officially presenting his preliminary findings at the International Arctic Change 2008 conference in Quebec City next week, was the scientist in charge of the Circumpolar Flaw Lead System Study (CFL), a $40-million Arctic research project.

A newcomer to the form book, Barber’s track record is yet to be established. But he’s clearly a runner. And that sounds like a conference to watch…

(See also Spiegel Online – h/t S Bloom Esq)

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The cracks are showing #2 (polar notes)

wilkins26nov480.jpg

Summer’s arriving on the Wilkins ice shelf, and its disintegration continues. New cracks are threatening to destroy the ice “bridge” that’s been holding the ice shelf pinned between Charcot Island (top left) and the Antarctic peninsula. This picture, captured by the European Space Agency’s ENVISAT satellite on November 26, shows the new cracks (coloured lines) and the dates they first appeared (NASA version here). If the chunk of ice under “21 July” breaks away, the long thin bridge will lose support and follow suit, the ESA analysts say.

Meanwhile, a team lead by Richard Alley at Penn State has worked out that ice shelf calving – where icebergs break away at the edge of an ice shelf – is critically influenced by the rate at which the ice shelf is spreading out. The PSU release notes:

For iceberg calving, the important variable — the one that accounts for the largest portion of when the iceberg breaks — is the rate at which ice shelves spread, the team reports in the Nov. 28 issue of Science. When ice shelves spread, they crack because of the stresses of spreading. If they spread slowly, those cracks do not propagate through the entire shelf and the shelf remains intact. If the shelf spreads rapidly, the cracks propagate through the shelf and pieces break off.

When ice shelves break up, the glaciers that feed them can speed up noticeably, dumping more ice into the ocean. Over recent years, the role of water as a lubricant for glacier flow has been receiving a lot of attention (rubber ducks were recruited as under ice research tools in Greenland this year), and the BBC reports that a sub-glacial “flood” under the Byrd Glacier which feeds ice at the rate of about 20 billion tonnes a year into the Ross ice shelf caused that to increase to 22 billion tonnes over 2006. It has since returned to normal.

Up north, the NSIDC reports (Dec 3) that it continues to be warmer than average, even though the sea ice is now covering the whole Arctic ocean.

In the heat of the (Arctic) night

LWOct2008.gif Time for an Arctic update and a bit of “original” research. There’s been quite a bit of polar news around, and a rapid freeze-up is underway in the Arctic – so rapid that some are declaring that the sea ice is “back to normal” for the time of year, based on this graph from the Arctic Regional Ocean Observing System in Norway, which shows sea ice area climbing up towards to the average for 1979-2007, within one standard deviation (the grey area). On the other hand, if you look at the equivalent graph at Cryosphere Today, you’ll see that ice area is 1.25m km2 below the average – which in CT’s case is 1979-2000. So the ice is approaching normal, only if you define “normal” as including the significant ice reductions over the last seven years. How encouraging. But this autumn’s freeze-up has been pretty rapid. Does that mean that it’s been unusually cold up there? I thought I’d take a look…

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(The Village) Greenland Preservation Society

tintinmilou.jpeg The latest satellite data shows that this summer’s snowmelt in northern Greenland was “extreme”, according to Marco Tedesco, assistant professor of Earth & Atmospheric Sciences at The City College of New York. From the press release:

“Having such extreme melting so far north, where it is usually colder than the southern regions is extremely interesting,” Professor Tedesco said. “In 2007, the record occurred in southern Greenland, mostly at high elevation areas where in 2008 extreme snowmelt occurred along the northern coast.”

Melting was most pronounced near Ellesmere Island, where ice sheet collapses were observed, and around the Petermann glacier, which is also shedding ice. Melting lasted 18 days longer than average in these areas, and the melt index (area times days) was three times higher than the 1979-2007 average for the region.

Underlining the dramatic changes being seen in the far north, the National Oceanic & Atmospheric Administration (NOAA) released its second Arctic Report Card earlier this week…

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