While aircraft and satellite data provide great spatial coverage of Antarctic snow and ice cover, hands-on measurements of ice conditions are still needed to verify and further calibrate the radar data. To improve future snow accumulation measurements conducted directly from satellites, the SEAT (Satellite Era Accumulation Traverse) project collected radar measurements and compared to snow core data which compiled an in-situ database for estimating snow accumulation from space.
Funded by NSF and NASA, the SEAT team (consisting of team members from NASA Goddard Space Flight Center, USRA/GESTAR, and universities) recorded radar and elevation measurements along a 400-mile traverse which includes ice core drilling and snow pit measurement sites. The Ku-band radar and C-band Snow radar collected data by peering into the top 20-30 meters of the ice sheet, imaging the snow layers accumulated over the years. As one of the team members explained it, "Like rings in a tree tell you the age of a tree, firn (snow that has persisted through one melt season) layers tell you the age of the layer of the ice sheet."
Researchers use a specially designed ice core drill to retrieve samples from the ice sheet. In addition to ice, the cores can also contain ash, salts, and dust. The core is weighed to determine the density and its electrical conductivity is measured, to help determine chemical composition. Electrical conductivity can detect the presence of volcanic ash which when associated with a known volcanic event, can be used to set a point in time along the core. Isotope measurements using a mass spectrometer can also determine the age of ice along the core.