TERMINUS BEHAVIOR OF JUNEAU ICEFIELD GLACIERS 1948-2005.   

Mauri S. Pelto Dept. of Environmental Science, Nichols College, Dudley, MA 01571 mspelto@nichols.edu
Maynard M. Miller, Glaciological and Arctic Sciences Institute, University of Idaho, Moscow ID 83843 jirp@uidaho.edu

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Updated 3/11/2011

 

The Juneau Icefield Research Program has long monitored the mass balance of the Lemon Creek and Taku Glacier on the Juneau Icefield.  This program begun by Maynard Miller in 1946 and continuing through today has also monitored the terminus behavior of the icefields outlet glaciers.  Here we compare Google Earth Images from 2005 to the USGS maps based on 1948 and 1964 aerial photographs to indicate the state of the glaciers on the Alaskan side of the icefield, and simply Google Earth Images on the Canadian side.  Of the 17 glaciers discussed 5 have retreated more than 500 m since 1948, 11 more than 1000 m, and one glacier the Taku has advanced.  The comparison of maps and images provides a unique chance to observe the changes of an entire icefield to climate changes.  Google Earth Tour File-This is one of the selected tours for the GE Gallery. A You Tube video taking you through this google earth tour is at the bottom of this page.

 

 

Antler Glacier is a distributary glacier of the Bucher Glacier.  In 1948 it spilled over the lip of the valley from the Bucher and flowed kilometers downvalley to end in a proglacial lake.  In 2005 the glacier has retreated almost to the lip of the valley 5400 m which is 90% of it total length. 

 

 Note the Antler ending in the lake in this USGS map based on 1948 photographs.  The lake has since expanded greatly

Eagle Glacier is narrow and uncrevassed indicating the lack of movement near the terminus.  This glacier has retreated 700 m since 1948 when it ended on the shore of the lake.

 

Eagle Glacier is shown in contact with the lake in this USGS map based on a 1948 aerial photograph.

Field Glacier has retreated 800 m since 1948.  The lowest two kilometers of this glacier are debris covered and minimal crevassing, indicating stagnation.  There is an evident proglacial lake around the margin of the glacier in this lowest 2000 meters, indicating a rapid collapse like that seen on the Gilkey Glacier is likely.

 

Herbert Glacier has retreated 540 m since 1948.  There is an evident trimline on the north side of the glacier and considerable freshly deglaciated terrain.

 

Herbert Glacier in 1948 is in contact with a shallow proglacial lake, that has since largely filled in with glacial sediments. It shows up as the bright grayish outwash plain with three streams crossing it in the Google Earth Image.

Gilkey Glacier terminus area is breaking up into a series of large icebergs as the terminus area thins.  The lake which began forming after 1948 is now 3900 m long.  The lake is partly filled with large icebergs from disintegration of the Gilkey terminus.  The extensive debris cover and lack of crevassing in the lower 1500 meters of the glacier indicates that this section is stagnant and will break up soon.

 

 

 

Thiel Glacier used to join the Gilkey Glacier.  It has retreated 1700 m  from the Gilkey Glacier since 1948 and has extensive lateral moraines extending beyond the glacier terminus indicating the ongoing retreat.

 Battle Glacier in 1948 joined the Thiel Glacier and the two then merged with the Gilkey Glacier.   A retreat of 3200 m has created a glacier 70 % its former length.  The vast bare valley beyond the terminus is in stark contrast to the map above.

 

Lemon Creek Glacier has retreated continuously since its Little Ice Age maximum in 1750.  The glacier has retreated 1200 m since 1948.  Two lakes have formed since 1970 as the Lemon Creek Glacier has separated from the Thomas Glacier and the two have each retreated exposing a lake.  Lemon Creek Glacier has a long annual mass balance record measured from 1952-2005 by JIRP.  This record has become increasingly negative. 

 

Two new lakes are evident that were beneath the glacier in 1948.  The glacier has thinned more than 25 meters since 1948 based on remapping and the mass balance assessments.
Mendenhall Glacier has retreated 2800 meters since 1910 and 580 meters since 1948.  The trimline on the north side of the glacier is evident.  In this part of Alaska vegetation grows rapidly and bare deglaciated terrain usually develops substantial vegetation within 50 years. The peninsula in the lake that is so evident in the Google Earth Image is still beneath the ice in the map above.  The map is based on a 1964 photograph of the terminus.  The lake began to form in 1910 as the glacier retreat reached the southern margin of the lake. 

Norris  Glacier began retreating before 1890  and has continuously retreated 2050 m from its Little Ice Age maximum it continues to calve into a shallow proglacial lake.  The glacier has retreated 1100 meters since 1948.

The glacier until 1929 reached Grizzly bar and no proglacial lake was evident.  The map represents the 1964 terminus position. 
Taku Glacier has been advancing since 1890:  It advanced 5.3 km between 1890 and 1948, continuing its advance 2.0 km since 1948.   In 1948 the glacier stopped calving.  Just like finishing your mortgage payments would for your bank account, this created a significant positive balance allowing the advance to continue.  The annual balance has been measured by JIRP since 1946.  From 1946 to 1986 the glaciers positive balance drove continued advance.  Since 1986 the warming climate has caused a slightly negative balance.  On a glacier the size of the Taku Glacier this change will not be reflected by the terminus soon.  You can see the push moraine of the glacier advance.  The glacier did advance across the Taku River blocking the river in 1750.  With current climate the glacier will not be able to repeat this advance.  Hole in the Wall Glacier is a distributary terminus of the Taku Glacier.  Like the Taku Glacier it has advanced for a century.  The extensive crevassing and push moraine are evident at the head of the glacier.  In this respect it is like the Antler Glacier as it spills over the lip of a side valley.  In 1963 it reached the base of the valley wall and began to spread out onto the Taku River plain.
The Twin Glacier were joined until 1920.  They retreated from this point rapidly for twenty years.  From 1948-1964 there was only modest recession of 200 m.  A stillstand or small advance than occurred, which ended by 1986.  And retreat has once again begun.

The glacier retreated 1100 meters since 1948.  The calving terminus has an evident trimline adjacent to the glacier, 800 meters in the last 20 years.

The glacier has retreated from 500 m the 1948 position and is now reaching the head of the fjord where calving occurs.  The terminus is not heavily crevassed indicating the glacier will continue to retreat.

 

Tulsequah Glacier’s terminus is currently in a proglacial lake, which can be seen surrounding the glacier up to 2500 meters upglacier from the terminus. The glacier has retreated 1100 meters since 1948.  The thin termini, is stagnant and has no crevassing and will disintegrate in the lake soon.   This glacier has a glacier dammed lake that outbursts washing out any sign of a Little Ice Age moraine in the valley.  This lake is small and seldom forming now as the impounding glacier no long substantially dams Tulsequah Lake.

 

Sloko Glacier has retreated 2700 m and from its Little Ice Age position.  The terminus has minimal crevassing indicating continued retreat in the foreseeable future.

 

 

Llewellyn Glacier has several different termini.  The retreat of this glacier from its Little Ice Age position has been continuous with an average of 2800 m of retreat. 

 

Hobo Glacier is a minor terminus of the Llewellyn Glacier.  The glacier has retreated meters since the Little Ice Age.  The trimline is again evident.

 

 

ACKNOWLEDGEMENTS 

The support of NSF, NASA, U.S. Army Research Office, the Murdock Charitable Trust and University of Idaho have been essential to this project, as well as the Foundation for Glacier and Environmental Research, Pacific Science Center, Seattle, WA. 


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