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Abstract:
>Absolute gravity (AG) measurements have been performed at Mt. Zugspitze (2960 m height, Northern Limestone Alps) from 2004 to 2019. For this 15 years’ time span, the deduced gravity variations at the two summit stations are in the order of ‑0.30 μm/s² with a standard uncertainty of 0.04 μm/s². In addition, two stations in the Ester Mountains about 15 km apart of Mt. Zugspitze were occupied to serve as a reference and for validation. These stations at the mountain Wank (base site at an altitude of 735 m and summit site at 1738 m) show no significant gravity variation. The vertical stability of Mt. Wank summit is monitored by GNSS since 2004 and the results confirm its stability. Because a small mountain uplift due to Alpine orogeny cannot explain the gravity decrease at Mt. Zugspitze, the dominating geophysical contribution is assumed to be induced by glacial retreat due to climate warming. The modelled gravity effect from the diminishing glaciers between epochs 1999 and 2018 shows a linear trend of ‑0.012 μm/s² per year at the AG sites on Mt. Zugspitze and explains 60% of the observed gravity variation. Long-term variations on inter-annual and climate-relevant decadal scale are under investigation and are complemented by superconducting gravimetry (initiated in 2019) and new GNSS equipment.
