Talk by Lars B. Larsen, Centre for Ice and Climate – Niels Bohr Institute - University of Copenhagen

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Talk by Lars B. Larsen, Centre for Ice and Climate

Surface elevation change artifact at the NEEM ice core drilling site, North Greenland

The NEEM deep drilling site (77.45◦N 51.06◦W) is located at the main ice
divide in North Greenland. For the ice core drilling project, a number
of buildings was erected and left on the snow surface during the
five-year project period. The structures created snowdrifts that formed
accordingly to the predominant wind direction on the lee side on the
buildings and the overwintering cargo. To get access to the buildings,
the snowdrifts and the accumulated snow were removed and the surface in
the camp was leveled with heavy machinery each summer. In the camp a GPS
reference pole was placed as a part of the NEEM strain net, 12 poles
placed in three diamonds at distances of 2,5 km, 7,5 km and 25 km they
were all measured with high precision GPS every year. Around the
reference pole, a 1 km x 1 km grid with a spacing of 100 m was measured
with differential GPS each year.

In this work, we present results from the GPS surface topography
measurements in and around the camp- site. The mapping of the topography
in and around the campsite shows how the snowdrifts evolve and are the
reason for the lift of the camp site area.The accumulated snow drifts
are compared to the dominant wind directions from year to year. The
annual snow accumulation at the NEEM site is 0.60 m. The reference pole
in the camp indicates an additional snow accumulation of 0.50 m per year
caused by collected drifting snow. The surface topography mapping shows
that this artificially elevated surface extends up to several kilometers
out in the terrain. This could have possible implications on other
glaciological and geophysical measurements in the area i.e. pit and snow
accumulation studies.