Mass balance and surface movement of the Greenland ice sheet at Summit, Central Greenland

Geophysical Research Letters, Vol. 24, No. 18, p. 2307-2310, 1997

C.S. Hvidberg
Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen.
K. Keller
National Survey and Cadastre, Rentemestervej 8, DK-2400 Copenhagen NV, Denmark.
N.S. Gundestrup, C.C. Tscherning
Departement of Geophysics, The Niels Bohr Institute of Astronomy, Physics and Geophysics, University of Copenhagen.
R. Forsberg
National Survey and Cadastre, Rentemestervej 8, DK-2400 Copenhagen NV, Denmark.

ABSTRACT.
During the GRIP deep drilling in Central Greenland, the ice sheet topography and surface movement at Summit has been mapped with GPS. Measurements of the surface velocity are presented for a strain net consisting of 13 poles at distances of 25-60 km from the GRIP site. Some results are: The GRIP site is located approximately 2 km NW of the topographic summit; the surface velocity at the GISP 2 site is 1,7 m/yr in the W direction. The present mass balance at Summit is calculated to be +0,03+- 0,04 m/yr, i.e. close to steady state. This result is the best now available for Summit. A small thinning rate might be a transient response of the Greenland Ice Sheet due to the temperature increase at the Wisconsin-Holocene transition.