Satellite Image Analyses for US ITASE Route Selection and Sampling Strategy

Planning an overland traverse in Antarctica is a little different from planning your family's summer vacation road trip. We can't just visit our local AAA office and pick up a road map and a guidebook to places of interest along the way. Unfortunately, most of the interior of Antarctica is unmapped. But by using satellite imagery we can make our own maps for planning the traverse routes.

There are two important considerations in our work:

Crevasses as seen using satellite imagery.

First, we want to choose the safest route possible. The Antarctic Ice Sheet is constantly moving. Most of the ice sheet moves quite slowly but in some places the ice moves fast enough to form crevasses, or cracks, at the surface. Crevasses can be quite large: several feet wide and up to 160 feet (50 m) deep. Despite their large size, they are often very difficult to detect when driving along on the ice sheet surface. Quite often their presence is disguised by a thin covering of snow over the crack, making crevasses look just like the surrounding ice sheet. These snow bridges are quite thin, however, and a vehicle traveling over the top might be heavy enough to break the snow bridge and fall into the crevasse. Obviously we don't want that to happen. Fortunately, crevasses are usually large enough to be visible on images collected by satellites orbiting Earth. We use satellite imagery collected over West Antarctica to plan our traverse routes and very carefully map the position of crevasses near the proposed routes so that they can be avoided in the field.

Satellite imagery helps us understand the topography of the ice sheet.

Second, we want to visit the most interesting scientific places and know something about the places we will visit before we go there. Satellite images of ice sheets reveal all kinds of interesting features that are not always visible from ground level. These features might include flow divides (crests on the ice sheet where ice flows in opposite directions on either side), flow stripes (indicating enhanced flow in a particular direction) and relict features that suggest the presence of active flow sometime in the past. The textured, shadowy appearance in satellite imagery also tells us something about the topography of ice sheet surfaces. This information is useful for planning ice core sites. For example, we might want to obtain an ice core from the slope of an undulation or we might want to know what kind of terrain an ice core site has flowed through on its way to its present location.