Abstract
Abstract. Absolute gravity measurements have been regularly performed in the Austrian Eastern Alps since 1985. A gravity increase of 300 nm s−2 has been observed so far. The gravity trend is explained by ablation effects within surrounding glaciers. Ice thickness changes derived from 3 successive glacier inventories of 1969, 1997 and 2006 are used for quantitative 3-D modeling based on rectangular prisms with basis areas of ≤ 8 m × 8 m. Local topographic changes due to man-made mass displacements close to the measuring site are modeled by a polyhedron approach. Two-thirds (2/3) of the observed gravity increase can be explained by the ablation model response and man-made effects. A positive trend of about 100 nm s−2 remains. The origin of the residual trend remains open. Correcting for geodynamical processes like Alpine uplift or postglacial deformation is expected to cause a slight increase of this trend. The observed gravity signal shows seasonal gravity variations as well, which are probably due to snow cover effects but cannot be quantified due to the lack of appropriate snow cover information.
Highlights
Global warming and associated climate change during the recent decades is one of the main reasons for glacier retreat in the Alps. Memin et al (2009) quantified the gravity effects of present-day ice thinning in the vicinity of the Mont Blanc region (France) and the Svalbard (Norway) glaciers both due to the Newtonian and the deformation signal
To our knowledge for the first time, observed gravity variations and relate them quantitatively to ice mass balance information derived from glacier inventories in the Eastern Alps
10 % of the gravity effect is due to the other glaciers
Summary
Global warming and associated climate change during the recent decades is one of the main reasons for glacier retreat in the Alps. Memin et al (2009) quantified the gravity effects of present-day ice thinning in the vicinity of the Mont Blanc region (France) and the Svalbard (Norway) glaciers both due to the Newtonian and the deformation signal. One of the absolute gravity stations has been established in the central part of the Eastern Alps which is known to exhibit moderate recent uplift of roughly 1 mm yr−1 (Hoggerl, 2001; Ruess and Hoggerl, 2002). This estimate results from repeated leveling observations performed in Austria between 1948 and 1962 and between 1966 and 1990. Supporting geodynamical and tectonic investigations of the area by absolute gravity observations is the main purpose of this inner-Alpine station It has been established in the small village Obergurgl (Tyrol, Austria), surrounded by glacier-capped mountains of the so-called Otztal Alps and Stubai Alps (Fig. 1). We calculate the associated gravity response of these nearby ice mass losses to explain the observed gravity trend
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