Metadata of 32 wells and temperature-depth profiles of the shallow subsurface between 1992 and 2019 in Bavaria, Germany

While this is expected to manifest as a gradual warming in groundwater temperature time series, such continuous long-term recordings are scarce. As an alternative, the present work examines the use of repeated temperature-depth profiles of 32 wells in southern Germany, that were logged during campaigns in the early 1990s and in 2019.

It is revealed that the temperatures have increased in nearly all cases. We find a moderate to good depth-dependent correlation to trends in air temperature, which however is strongly influenced by local hydrogeological and climate conditions. While during the last three decades, air temperatures have increased by a rate of 0.35 K (10a)-1 on average, the temperature increase in the subsurface is decreasing with depth, with median values of 0.28 K (10a)-1 in 20 m and only of 0.09 K (10a)-1 in 60 m depth.