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Norwegian-American Scientific Traverse of East Antarctica

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Accumulation rates

Determination of accumulation rates from combined analysis of shallow radar and DEP data, by the Norwegian Polar Institute and the University of Oslo.

Science Objectives

We will determine accumulation rates using a combination of shallow radar and ice core studies:
Ice cores yield high-resolution information at the drilling location, whereas radar layers allow for mapping of spatial variations and connection of drilling sites. Yet ice core data are mandatory to calibrate the radar data.

Methods

  • Ice cores will be dated by volcanic chronology derived from DEP records; a depth-age scale will thus be established.
  • The depth-age scale will be transferred to tracked radar layers
  • Density will be determined along the ice cores and hence the cumulative mass (mass of the overlying snow/firn up to the depth of the layer) can be calculated
  • With knowledge of age and cumulative mass of a layer, the accumulation rates can be calculated

Example: (a) Depth-age scale derived from a dated firn core
(b) Tracked layers from radar data
Combining (a) and (b) allows calculation of accumulation rates along the radar profile and discussion of spatial variations.

Dated internal layers


As the calculation of accumulation rates relies on accurate dating and conversion of travel-time of the radar signal to depth and cumulative mass, it is important to accurately log the ice cores after drilling.Core logging

Using the techniques described above, we will determine the spatial and temporal variability
of accumulation rates in Dronning Maud Land. GPS data will deliver important information about surface features controlling accumulation variability on different scales.
The results will help to understand the still uncertain contribution of East Antarctica to sea-level change and will also serve as validation for satellite data.

Logging a drilled ice core in the field



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