Tasman Glacier (NZ) In Rapid Retreat - Hectare-Sized Chunk Falls Off During Rainstorm

[hatrack]

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Glaciologist Trevor Chinn said the development of lakes was a tipping point for glaciers. No amount of snow at the head of the glacier, the neve, would compensate the effect of the lake. He said wherever the lake flowed under a glacier it would be eaten away. The glacier would retreat to a point where it was above the lake. He speculated this could be somewhere around the Ball Hut (about 5km away).

Alpine Recreation guide Gottlieb Braun-Elwert said long flat glaciers, like the Godley and Tasman, lost thickness on the bottom. Once pools or puddles appeared the glacier's demise rapidly accelerated. Heat dynamics meant at 4.2C water was its most dense and sank to the bottom. As ice thawed the water became cooler and moved upwards to be replaced by warmer water. "As soon as you have puddles or lakes forming on ice you have a huge solar collector and unrestricted access of the sun's energy to melt the ice underneath."

He estimated in 15 years the lake could have expanded to cut off traditional Mt Cook access via the Tasman moraine near the former Ball Hut.

As the moraine wall grew higher climber access was made harder. The loss of the glaciers also increased danger. Glaciers applied lateral pressure to the sides of mountains and when they went, instability occurred. He believed loss of lateral pressure at the base of any mountains steeper than 28 degrees, the natural angle of recession, would affect stability right to the peak. This was demonstrated by the number of slips occurring on the Haast Ridge.

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http://www.stuff.co.nz/stuff/thepress/westcoast/4019158a10.html