This pair of MISR images of the Pine Island Glacier in western
Antarctica was acquired on December 12, 2000 during Terra
orbit 5246. At left is a conventional, true-color image from
the downward-looking (nadir) camera. The false-color image at
right is a composite of red band data taken by the MISR forward
60-degree, nadir, and aftward 60-degree cameras, displayed in
red, green, and blue colors, respectively.
Color variations in the left (true-color) image highlight spectral
differences. In the multi-angle composite, on the other hand,
color variations act as a proxy for differences in the angular
reflectance properties of the scene. In this representation,
clouds show up as light purple. Blue to orange gradations on the
surface indicate a transition in ice texture from smooth to rough.
For example, the bright orange "carrot-like" features are rough
crevasses on the glacier's tongue. In the conventional nadir view,
the blue ice labeled "rough crevasses" and "smooth blue ice"
exhibit similar coloration, but the multi-angle composite reveals
their different textures, with the smoother ice appearing dark purple
instead of orange. This could be an indicator of different mechanisms
by which this ice is exposed. The multi-angle view also reveals
subtle roughness variations on the frozen sea ice between the glacier
and the open water in Pine Island Bay.
To the left of the "icebergs" label are chunks of floating ice.
Additionally, smaller icebergs embedded in the frozen sea ice are
visible below and to the right of the label. These small icebergs are
associated with dark streaks. Analysis of the illumination geometry
suggests that these streaks are surface features, not shadows. Wind-
driven motion and thinning of the sea ice in the vicinity of the
icebergs is one possible explanation.
Recently, Robert Bindschadler, a glaciologist at the NASA Goddard Space
Flight Center discovered in Landsat 7 imagery a newly-formed crack
traversing the Pine Island Glacier. This crack is visible as an
off-vertical dark line in the MISR nadir view. In the multi-angle
composite, the crack and other stress fractures show up very clearly
in bright orange. Radar observations of Pine Island Glacier in the
1990's showed the glacier to be shrinking, and the newly discovered
crack is expected to eventually lead to the calving of a major iceberg.
Image credit: NASA/GSFC/LaRC/JPL, MISR Team.
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