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ABSTRACT. Glacier facies from the Greenla nd ice sheet a nd the Wrangell St EliasMounta ins, Alas ka, are ana lyzed using multi-temporal synthe ti c aperture ra d a r (SAR) data from the Europea n Space Agency ERS-l satellite. Distinct zones and facies a r e visible in multi-temporal SAR d a ta, including the dry-snow facies, the combined p ercolation and wet-sn ow facies, the ice facies, transient m elt areas and m or a ine. In Greenl a nd and so uth-centra l Alas ka, ver y simil ar multi-temporal signatures a re evident fo r the same facies, a ltho ug h these fac ies a r e found at lower a ltitude in ' Nes t Greenland where the equilibrium lin e appea rs to be fo und at sea level a t 71°30' N during the yea r ana lyzed , proba bl y because of the cooling effect of the eruption of M ount Pinatubo. In Greenland, both the percolatio n a nd dry-snow facies a re excellent distributed ta rgets fo r sensor calibration, with backscatter coefficients stable to within 0.2 dB. H owever, th e p ercolation facies near the top orMount Wrangell are m or e complex a nd less easily delineated th an in Greenland , a nd at high altitude the glacier facies have a multi-temporal signa ture which depends sen sitively on slop e orientation.

[1] Arctic sea ice plays a key role in the climate system, by acting as the interface between a warm ocean and a cold atmosphere. Establishing the true pattern of recent behavior of the sea ice in this region is critical to simulating the role of sea ice in future climate. Recently released operational ice charts from the U.S. National Ice Center provide insight into the late twentieth century behavior of Northern Hemisphere sea ice, providing more reliable ice concentrations during summer and freeze-up than those available from the passive microwave record. The major winter and summer modes of ice concentration variability observed from empirical orthogonal function analysis covering the period 1972-1994 are shown to indicate, respectively, the 1-year lagged response of the sea ice to the North Atlantic Oscillation and the winter preconditioning of summer sea ice coverage in the eastern Arctic by the North Atlantic Oscillation. Feedback to the atmosphere is suggested in each case by zero-lag cyclone frequency relationships to these two sea ice modes of variability.

ABSTRACT. Glacier facies from the Greenla nd ice sheet a nd the Wrangell St EliasMounta ins, Alas ka, are ana lyzed using multi-temporal synthe ti c aperture ra d a r (SAR) data from the Europea n Space Agency ERS-l satellite. Distinct zones and facies a r e visible in multi-temporal SAR d a ta, including the dry-snow facies, the combined p ercolation and wet-sn ow facies, the ice facies, transient m elt areas and m or a ine. In Greenl a nd and so uth-centra l Alas ka, ver y simil ar multi-temporal signatures a re evident fo r the same facies, a ltho ug h these fac ies a r e found at lower a ltitude in ' Nes t Greenland where the equilibrium lin e appea rs to be fo und at sea level a t 71°30' N during the yea r ana lyzed , proba bl y because of the cooling effect of the eruption of M ount Pinatubo. In Greenland, both the percolatio n a nd dry-snow facies a re excellent distributed ta rgets fo r sensor calibration, with backscatter coefficients stable to within 0.2 dB. H owever, th e p ercolation facies near the top orMount Wrangell are m or e complex a nd less easily delineated th an in Greenland , a nd at high altitude the glacier facies have a multi-temporal signa ture which depends sen sitively on slop e orientation.

roughness can be measured unambiguously from the wave-form data, but estimations of other parameters, such as grain-size, snow density, and snow temperature are found to be ambiguous because different surface parameters have a similar influence on the shape of the return. Despite this, the derived estimates compare well with ground-based observations and suggest that the satellite altimeter may have an important role to play in providing information on the surface properties of the ice sheets.