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Retreating Alaskan Glacier Reveals Remains Of Medieval Forest

August 26, 2013

By Paul Homewood

 

h/t agfosterjr

 

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The Exit Glacier, Alaska

 

Reader agfosterjr sent me a link about the Exit Glacier, in southern Alaska, pointing out, as the glacier retreats, it is uncovering remains of a medieval forest, as this report from the National Park Office makes clear:-

 

The Little Ice Age (LIA) was a time of global cooling from approximately 1350 to 1870 AD. During this time glaciers expanded in the northern regions, moving down the mountains and scouring the  vegetation that had been in the valleys below. Park Service personnel recently discovered evidence of a buried forest  dating back to at least 1170 AD high in the Forelands near the current glacier’s edge.

http://www.nps.gov/kefj/naturescience/upload/The%20Retreat%20of%20Exit%20Glacier.pdf

 

This report, of course, tallies with studies of other Alaskan glaciers, which have also found similar tree remains. What I found equally intriguing though was this table, that was included in the report, showing how the rate of retreat has changed since the 19thC.

 

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http://www.nps.gov/kefj/naturescience/upload/The%20Retreat%20of%20Exit%20Glacier.pdf

 

The retreat began slowly after 1815, but really accelerated after 1889. The fastest rate was 1914-17, but since then the glacier has been retreating much more slowly.

I was puzzled though by the fact that the table finished in 1973, confused further by the fact that the bottom line mentions 1815-1999. The total retreat of 6549 ft for that whole period is the sum of the individual periods, so I wondered whether the retreat had stopped altogether since 1973.

[The National Park report is based on research undertaken in 2001, so logically the figures up to 1999 should be correct]

So I did some more research and found this study by Katie Baumann, based on National Park mapping.

 

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http://www.calvin.edu/admin/provost/sustainability/initiatives/ceap/academics/courses/GGES/222/posters/Baumann_Katie.pdf

[There may be a problem with this link]

 

Let’s home in on the right hand map. The retreat from 1950 to 1973 is very clear, but since then there has been no significant change. Indeed the current glacier extent seems to be greater than in 1985. As the footnote says, the last 35 years have seen a mixture of advance and retreat.

 

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This of course is only one glacier, and I certainly would not suggest that it is representative of all glaciers in Alaska. But it is clear that the Exit Glacier began retreating at the end of the LIA, retreated at a much faster pace between 1889 and 1917 than anything seen since, and stopped retreating 40 years ago.

9 Comments
  1. August 26, 2013 6:11 pm

    Very interesting post! I currently reside in Valdez, Alaska & we have a glacier that acts the same. It is called the Columbia Glacier that was actually named by a group of Columbia University students. I cool little fact about this glacier is that it is the most receding glacier in North America & comes close to being first in the world. I took a helicopter tour this past June or so & it was great to see it calving and how it spans quite an extraordinary amount of area. 🙂

  2. August 27, 2013 10:39 am

    So who do you suppose dug down through all that ice, just to bury a medieval forest?

  3. Ulric Lyons permalink
    August 27, 2013 11:34 am

    So all the retreats are during cold episodes with negative AO/NAO. Exactly the same as seen in Greenland: http://wattsupwiththat.com/2013/08/23/the-medieval-warm-period-in-the-arctic/#comment-1398577
    That’s why the retreat stopped in 1973.

  4. Don B permalink
    August 27, 2013 3:01 pm

    John MuirGlacier Bay was first surveyed in detail in 1794 by a team from the H.M.S. Discovery, captained by George Vancouver. At the time the survey produced showed a mere indentation in the shoreline. That massive glacier was more than 4,000 feet thick in places, up to 20 miles wide, and extended more than 100 miles to the St. Elias mountain range.

    By 1879, however, naturalist John Muir discovered that the ice had retreated more than 30 miles forming an actual bay. By 1916, the Grand Pacific Glacier – the main glacier credited with carving the bay – had melted back 60 miles to the head of what is now Tarr Inlet.

    http://www.glacierbay.org/geography.html

  5. Brian H permalink
    September 1, 2013 8:51 pm

    Oh, noes! We’re returning to the sweltering times when forests grew where we’ve now got nice ice! What to do, what to do?

  6. March 9, 2014 6:33 pm

    I came across this piece a while back–record setting LIA GIA: http://www.aeic.alaska.edu/input/chris/epsl_larsen.pdf
    –AGF

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