Introduction of a Superconducting Gravimeter as Novel Hydrological Sensor for the Alpine Research Catchment Zugspitze

Abstract

Abstract. The Zugspitze Geodynamic Observatory Germany has been set up with a worldwide unique installation of a superconducting gravimeter at the summit of Mount Zugspitze. With regard to hydrology, this karstic high-alpine site is largely dominated by high precipitation amounts and a long seasonal snow cover period with significant importance for water supply to its forelands, while it shows a high sensitivity to climate change. However, regarding the majority of alpine regions worldwide there is only weak knowledge on temporal water storage variations due to only sparsely distributed hydrological and meteorological point sensors and the large variability and complexity of alpine signals. This underlines the importance of well-equipped areas such as Mount Zugspitze serving as natural test laboratories for an improved monitoring, understanding and prediction of alpine hydrological processes. The observatory superconducting gravimeter OSG 052 supplements the existing sensor network as a novel hydrological sensor system for the direct observation of the integral gravity effect of total water storage variations in the alpine research catchment Zugspitze. Besides the experimental setup and the available datasets, the required gravimetric prerequisites are presented such as calibration, tidal analysis and signal separation of the superconducting gravimeter observations from the first 2 years. The snowpack is identified as primary contributor to seasonal water storage variations and thus to the gravity residuals with a signal range of up to 750 nm/s2 corresponding to 1957 mm snow water equivalent measured at a representative station at the end of May 2019. First hydro-gravimetric sensitivity analysis are based on simplified assumptions of the snowpack distribution within the area around Mount Zugspitze. These reveal a snow-gravimetric footprint of up to 4 km distance around the gravimeter with a dominant gravity contribution from the snowpack in the Partnach spring catchment. This study already shows that the hydro-gravimetric approach can deliver important and representative integral insights into this high-alpine site. This work is regarded as a concept study showing preliminary gravimetric results and sensitivity analysis for upcoming long-term hydro-gravimetric research projects.

Geodetic-Gravimetric Monitoring of Mountain Uplift and Hydrological Variations at Zugspitze and Wank Mountains (Bavarian Alps, Germany)

“…Since then, the SG has been in nominal mode. The continuous time series of gravity residuals from the OSG#052 so far provides seasonal minimum gravity values on 1 October 2019 and 20 September 2020 after reduction of Earth's body and ocean tides, polar motion, and atmospheric mass movements [15] which is consistent with the absolute gravity measurements. The time series gives evidence that the periods of absolute gravity observations at late September were well chosen to keep the aliasing effects as small as possible.…”

“…These parameters have been determined from continuous recordings with the GWR superconducting gravimeter (SG) OSG#052 since 1st of January, 2019 (15 months length). For details on the OSG#052, see [15]. SGs are manufactured by GWR Instruments, Inc., San Diego.…”

“…Due to technical demands in the Environmental Research Station Schneefernerhaus the absolute point 200, see [32], was relocated to an adjacent place in 2011 (new point 202 This was possible with the help of a witness point nearby which was set up in 2004. I addition to the absolute point from 2004 in an old telecommunication building (Telekom on the summit of Zugspitze, a second point in the Zugspitze Geodynamic Observator Germany (ZUGOG, GFZ Potsdam, [15]) was established very close to the Telekom site i September 2018. ZUGOG is located in an oddly shaped building that will not allow an snow cover on its steep roof (Figure 2).…”

“…In September 2018, the Zugspitze Geodynamic Observatory Germany has been set up by GFZ at the summit of Mt. Zugspitze including the observatory superconducting gravimeter (SG) OSG#052 by GWR Instruments, Inc., a permanent GNSS station and a local hydro-meteorological sensor network [15]. During the first simultaneous measurements of the absolute gravimeter FG5-220 and the OSG#052 at the end of September 2018, the SG showed an instrumental malfunction accompanied by a large negative drift of some nm/s 2 /day and several steps after being transported at operating temperatures of 4 K from GFZ to Mt.…”

“…Therefore, absolute gravimetry, superconducting gravimetry and GNSS are complementary measuring techniques in geodesy, which is exploited in this paper, cf. [15].…”