Geology Reference
In-Depth Information
Land
Smooth
FY ice
Land
FY ice
Shear
line
MY ice
FY ice
Ice
island
Ridged
FY ice
MY ice
HH-image
VV image
HV image
Figure 7.33 Radarsat‐2 image from the Quad‐pol mode acquired on 21 May 2010 over the west coast of Ellef
Ringnes Island in the Arctic (lat., 78.917 N; long., 104.683W), showing different ice types and the shear line
between the land‐fast ice and the mobile ice (at previous dates). The three backscatter imagery components HH,
VV, and HV are shown (© MDA, Canada).
equal appearance in both co‐polarization images. The
cross‐polarization signal enhances the appearance of
ridges and rubble fields. This is demonstrated by the visibly
linear features within the FY ice floes. Discrimination
between MY ice and rough FY ice can be achieved from
any polarization combinations, especially in the cross‐
polarized signal. The linear features are not visible within
the MY ice floes because ridges in this ice types have
eroded during summer melt and turned into hummocks
with mild slopes. Hummocks do not trigger the multi-
bouncing scattering mechanism that amplifies the co‐
polarized backscatter. Backscatter from MY ice is normally
high in both the co‐ and cross‐polarization with identifia-
ble rich texture generated by the volume scattering from
the no‐uniform air bubbles distribution in the subsurface
layer (significantly more number of bubbles exists in hum-
mock compared to depression ice). Volume scattering
causes backscatter in both co‐ and cross‐polarization sig-
nals to be relatively high, though higher from the co‐polar-
ization. The shear line visible in each image in Figure 7.33
marks the edge of the land‐fast ice. Physically speaking,
the shear ridge features broken ice pieces that result from
crushing the mobile ice against the fast ice. The rough ridge
appears bright in all images though brighter in the cross‐
polarized image (stronger depolarized scattering). The
undulating surface of the ice island (which was broken off
the Warden Hunt Ice Shelf located at the northern tip of
Ellesmere Island) appears with the same texture in the
three images (more on ice shelf from which this ice island
was detached is presented in section 5.2).
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