Upsala Glacier Retreat
This photograph by an astronaut on the International Space Station highlights
the snout of the Upsala Glacier (49.88°S, 73.3°W) on the Argentine side of the
North Patagonian Icefield. Ice flow in this glacier comes from the north (right
in this rotated image). Dark lines of rocky debris (moraine) within the ice give
a sense of the slow ice flow from right to left.
A smaller, side glacier joins Upsala at the present-day ice front -- the wall
from which masses of ice periodically collapse into Lago (Lake) Argentino. In
this image, the 2.7 kilometer-wide ice front casts a thin, dark shadow. The
surface of Lago Argentino is whitened by a mass of debris from a recent collapse
of the ice wall. Larger icebergs appear as white dots on the lake surface at
image left.
Remotely sensed data, including astronaut images, have recorded the position
of the ice front over the years. A comparison of this October 2013 image with
older data (January 2004 and January 2001, as well as October 2009) indicates
that the ice front has moved backwards -- upstream -- about 3 kilometers (2
miles). This retreat is believed by scientists to indicate climate warming in
this part of South America. The warming not only causes the ice mass to retreat,
but also to thin. A study of 63 glaciers by Rignot et al has shown that this is
a general trend in Patagonia.
The water color in Lago Argentino is related to the glacier flow. The lake
receives most of the ice from the glacier and thus receives most of the “rock
flour” -- rocks ground to white powder by the ice scraping against the rock
floor of the valley. Glacial flour turns the lake a gray-green hue in this
image. The darker blue of the smaller lakes (image bottom) indicates that they
are receiving much less rock flour.
This image was taken on Oct. 2, 2013, with a Nikon D3 digital camera using a
300 millimeter lens, and is provided by the ISS Crew Earth Observations
experiment and Image Science & Analysis Laboratory, Johnson Space Center. It
has been cropped and enhanced to improve contrast, and lens artifacts have been
removed.
Image Credit: NASA
Caption: M. Justin Wilkinson, Jacobs at NASA-Johnson Space Center
Caption: M. Justin Wilkinson, Jacobs at NASA-Johnson Space Center
NASA
Guillermo Gonzalo Sánchez Achutegui
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