Comparison of direct and geodetic mass balances on an annual time scale A. Fischer1, H. Schneider2, G. Merkel3, and R. Sailer4 1Institute of Meteorology and Geophysics, University of Innsbruck, Austria 2Institute of Mathematics, University of Innsbruck, Austria 3Faculty of Geoinformation, University of Applied Sciences – Fachhochschule München, Germany 4Institute of Geography, University of Innsbruck, Austria
Received: 13 Jan 2011 – Revised: 03 Feb 2011 – Accepted: 04 Feb 2011 – Published: 14 Feb 2011
Abstract. Very accurate airborne laserscanning (ALS) elevation data was used to
calculate the annual volume changes for Hintereisferner and Kesselwandferner
in the Ötztal Alps, Austria for 2001/2002–2008/2009. The comparison of
the altitude of 51 recently GPS surveyed ground control points showed that
the accuracy of the ALS DEMs is better than 0.3 m. The geodetic mass balance
was calculated from the volume change using detailed maps of the firn cover
and applying corrections for the seasonal snow cover. The maximum snow height
at the time of the elevation data flight was 0.5 m averaged over the glacier
surface. The volume change data was compared to in situ mass balance data for
the total area and at the stakes. For the total period of 8 yr, the
difference between the geodetic and the direct mass balance is 2.398 m w.e.
on Hintereisferner and 1.380 m w.e. on
Kesselwandferner, corresponding to about two times the mean annual mass
balance. The vertical ice flow velocity was measured and found to be on the
same order of magnitude as the mass balance at KWF. This is an indicator that
volume change data does not allow the calculation of ablation or accumulation
rates without detailed measurements or models of the vertical ice flow
velocity. Therefore, only direct mass balance data allow process studies or
investigation of the climatic controls of the resulting mass changes.
Citation: Fischer, A., Schneider, H., Merkel, G., and Sailer, R.: Comparison of direct and geodetic mass balances on an annual time scale, The Cryosphere Discuss., 5, 565-604, doi:10.5194/tcd-5-565-2011, 2011.