Abstract
In East Antarctica surface mass balance data can only be obtained from the sparselydistributed ice cores when considering time periods greater than a few decades.Observations of internal layers measured by airborne ice penetrating radar, in principle,permit extrapolation of mass balance information from these ice cores. We use radarsurvey lines gathered in the 1970s, and a three‐dimensional numerical model, toinvestigate the feasibility of such extrapolation, seeking to match the calculations ofenglacial layer geometry with observations. First, we justify the use of a three‐dimensionalmodel by showing that simple vertical flow models cannot explain all the observationsand that horizontal advection is a significant glacial process. Then we examine processesthat affect calculations of layer geometry, finding that spatial accumulation ‐rate patternsare extremely important while geothermal heat flux and flow mode (sliding or internaldeformation) are of substantially less importance. Where the layer is from the Last GlacialMaximum (17.5 ka), we find a very good match between the spatial pattern ofaccumulation rates inferred from this layer and the modern spatial pattern of accumulationrates. When considering deeper layers from beyond the current interglacial, we find that adifferent spatial accumulation‐rate pattern must have existed, in addition to the knownchange in accumulation rate from ice cores. The glacial spatial accumulation‐ ratepattern would have had proportionally greater accumulation at the South Pole than now,compared with the Vostok and Dome C ice cores.
Leysinger Vieli, Gwendolyn