| Summary: | Changes in the area of volume of polar ice sheets are intricately linked to changes in global climate and may severely impact the densely populated coastal regions on Earth. An ice sheet's velocity is a critical parameter, which, together with ice thickness, allows the determination of discharge rates. Using moderate-resolution satellite images such as Landsat, the velocity of floating ice can be measured quickly and relatively inexpensively by tracing crevasse patterns on shelves and ice tongues. Errors in measured velocities are as little as 0.02 km per year, if the following criteria are met: (1) the time interval is longer than 10 years; (2) the velocity is higher than 0.5 km per year; (3) the coregistration points are well dispersed and enclose the area to be measured; and (4) the image pair includes a Landsat 4 or 5 image. The fewer of these conditions that are met, the less accurate the results become; but even for poor conditions, the velocities are generally reliable to near 0.1 km per year. We are in the process of obtaining velocities of all ice shelves and ice tongues along the Bakutis and Ruppert coasts, wherever suitable crevasse patterns exist. So far, we have obtained velocities for the Thwaites and Land glacier tongues.
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