400 years is young for a Glacier

Three posts ago I discussed some plants emerging from 400 year old glaciers in the Canadian Arctic.  I expressed surprise, how could the Canadian Arctic glaciers be so young?

As I thought about the subject it occurred to me that most people do not have the local perspective I have when discussing glaciers.  If you haven’t seen glaciers up close, perhaps it’s difficult to grasp how time and temperature impact these spectacular pieces of moving ice.

Alaskans live with stories of Glaciers.  When one suddenly advances or retreats…it makes the news.   My history of living with and exploring glaciers is relatively small for a 40 year Alaska resident.

I have walked on 3 glaciers (Worthington, Matanuska and Columbia).  I have made repeated visits to two well known glaciers near my home, Exit Glacier and Portage Glacier.  Both Exit Glacier and Portage Glacier have, I believe, aided me in my understanding of time….climatically.

Exit Glacier is in Kenai Fjords National Park near Seward.

The 12 mile drive from Seward includes an 8 mile section up a wide valley.  The last mile and  a half cuts across the valley, following a stream to the visitor center.  A sign at the visitor center (1961) lets you know where the glacier was some 52 years ago.

Inside the visitor center, you learn that some 10,000 years ago the Glacier filled the valley you just entered.  A valley over a mile wide and almost 7 miles long.  That’s a lot of melting.

Portage Glacier offers a similar lesson.

When I first visited Alaska, Portage Glacier was a fresh water marine glacier.  The lake that fronted the glacier ended at a parking lot near where the Portage Glacier Visitor Center sits today.   Large icebergs piled up  in the lake near the parking lot…and in the winter you could walk on the lake and get a good look at these mountains of ice that had broken off the glacier.   That was in 1972.

Today the glacier no longer sits in the lake and is no longer receding.  The lake made the glacier unstable which aided in it’s rapid recession as the following graphic demonstrates:

Much of this area was discovered by Captain Cook on his third voyage in 1778.  Anchorage sits along Cook Inlet that was named for the famous explorer.   Portage Glacier sits near the end of Turnagain Arm.  Captain Cook was looking for a northerly passage back to the Atlantic.  When he got to the end of the arm he had too turn again….or so the legend goes.

It is said, he could see Portage Glacier from his boat in Turnagain Arm.   The Portage Glacier Visitor Center is some 7 miles inland.  That glacier must have been much bigger then than it is today…or was in 1911 when it first became a fresh water marine glacier.

Both Exit Glacier and Portage Glacier have been receding for thousands of years.   The thought of a 400 year old glacier in the Canadian Arctic seemed odd to me.

I suppose the lesson learned must have something to do with regional climate variations in the Arctic.  Still I am a bit surprised that a glacier that formed in the Arctic only 400 years ago required 250 years of warming to melt!?

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2 responses to “400 years is young for a Glacier

  1. I’ve been thinking about the young Canadian Glacier some more. Glaciers advance and decline for all sorts of reasons. Conditions could exist that would cause a glacier to advance 400 years ago and then take a long time to recede again. Arctic Canada, the location did surprise me. I would have expected South America or Antarctica, some place that has not experienced regional warming in the last 200 years. It shouldn’t have been so surprised, regional climate is a tricky subject.

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