Friday, June 7, 2013

Surging glaciers

While we were surveying glaciers in several mountain ranges, we had the opportunity to watch a vast variety of glaciers. While many are rapidly retreating, some are advancing and a few are experiencing a glacier surge. This is a phenomenon where a glacier increases its speed by a factor of ten or more for several months. It only happens on very few glaciers. Glacier surges happen periodically, every few years on some coastal glaciers and every few decades in the Alaska Range. So it's always a special treat to see one.

Turner Glacier (coming straight at us, across the bay) is the only tidewater glacier in Alaska that is surging. It has an unusually quick repeat cycle and this is its third surge in the last ten years.

The broken surface of Turner Glacier near its front

We noticed unusual crevasses on the Logan Glacier in March, and now they are even more pronounced.

The surge does not produce crevasses across the entire glacier, but there are distinct crevassed bulges on the side that indicate fast flow.

Logan Glacier

This is the Robertson or the Johnson Glacier in the Alaska Range. It is not known to surge, and I don't believe this is a real surge. But that fresh shear crevasse running along several kilometers is something I've never seen before on a glacier.

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