Retreat of Yakutat Glacier
Located in the Brabazon Range of southeastern Alaska, Yakutat Glacier is one
of the fastest retreating glaciers in the world. It is the primary outlet for
the 810-square kilometer (310-square mile) Yakutat ice field, which drains into
Harlequin Lake and, ultimately, the Gulf of Alaska.
The Operational Land Imager on the Landsat 8 satellite captured this image of
the glacier and lake on Aug. 13, 2013. Snow and ice appear white and forests are
green. The brown streaks on the glaciers are lateral and medial moraines.
Over the past 26 years, the glacier’s terminus has retreated more than 5
kilometers (3 miles). What is causing the rapid retreat? University of Alaska
glaciologist Martin Truffer and colleagues pointed to a number of factors in
their 2013 study published in the Journal of Glaciology. The chief
cause is the long-term contraction of the Yakutat Ice Field, which has been
shrinking since the height of the Little Ice Age.
Once part of a much larger ice field, Yakutat has been contracting for
hundreds of years. As other nearby glaciers retreated, Yakutat ice field was cut
off from higher-elevation areas that once supplied a steady flow of ice from the
north. With that flow cut off, there simply is not enough snow falling over the
low-elevation Yakutat ice field to prevent it from retreating.
Beyond this natural change, human-caused global warming has hastened the
speed of the retreat. Between 1948–2000, mean annual temperatures in Yakutat
increased by 1.38° Celsius (2.48° Fahrenheit). Between 2000 and 2010, they rose
by another 0.48°C (0.86°F). The warmer temperatures encourage melting and
sublimation at all ice surfaces exposed to the air.
In the past few years, the breakdown of a long, floating ice tongue has
triggered especially dramatic changes in the terminus of Yakutat glacier. For
many years, Yakutat’s two main tributaries merged and formed a 5-kilometer
(3-mile) calving face that extended far into Harlequin Lake. In the past decade,
satellites observed a rapid terminus retreat and the breakup of the ice tongue
in 2010. As a result, the calving front divided into two sections, with one
running east-west and another running north-south.
Image Credit: NASA Earth Observatory image by Robert Simmon, using
Landsat data from the U.S. Geological Survey
Caption: Adam Voiland
Caption: Adam Voiland
NASA
Guillermo Gonzalo Sánchez Achutegui
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