Thermodynamic coupling between atmosphere and ground yields increasing aquifer temperatures as a consequence of global warming. 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. Still, the slow and damped warming of the groundwater bodies are remarkable, especially considering naturally very minor temperature changes in pristine groundwater bodies and predictions of atmospheric temperatures. This entails implications for temperature-dependent ecological and hydro-chemical processes, and also for the heat stored in the shallow ground. Moreover, it is demonstrated that the annual heat gain in the groundwater bodies below 15 m due to climate change is in the range of one third of the state’s heat demand, which underlines the geothermal potential associated with the change in natural heat fluxes at the ground surface.

由于全球变暖，大气和地面之间的热力学耦合导致含水层温度升高。虽然预计这将表现为地下水温度时间序列的逐渐变暖，但这种连续的长期记录却很少。作为替代方案，本工作研究了德国南部32口井的重复温度深度剖面的使用，这些剖面是在1990年代初和2019年的运动期间测得的。据揭示，温度几乎在所有情况下都升高了。我们发现与气温趋势呈中等至良好的深度相关关系，但是受到当地水文地质和气候条件的强烈影响。在过去的三十年中，气温上升了0.35 K（10a）^-1平均而言，地下温度的升高随着深度的增加而降低，在20 m中的中位数为0.28 K（10a）^-1，而只有0.09 K（10a）^-1在60 m的深度。尽管如此，地下水体缓慢而潮湿的增温还是很明显的，特别是考虑到原始地下水体的温度变化自然很小以及对大气温度的预测。这对依赖温度的生态和水化学过程以及浅层土壤中存储的热量具有影响。此外，事实证明，由于气候变化，在15 m以下的地下水体中，每年的热量增加在该州热量需求的三分之一范围内，这突显了与地面自然热通量变化相关的地热潜力表面。