datasheet1_Climate Change Yields Groundwater Warming in Bavaria, Germany.zip

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.

受全球变暖影响，大气与地表的热力学耦合作用会导致含水层温度持续升高。尽管该升温现象预计会在地下水温度时序数据中呈现为缓慢的升温过程，但这类连续长期的观测记录却十分匮乏。作为替代方案，本研究针对德国南部32口观测井的重复温度-深度剖面（temperature-depth profiles）展开分析，这些剖面分别于1990年代初与2019年的测量活动中获取。研究结果显示，几乎所有观测井的含水层温度均出现了上升。我们发现，地下水温度变化与气温趋势之间存在中等至较强的深度依赖性相关性，但该相关性受局地水文地质与气候条件的强烈调控。过去三十年间，区域气温平均以每10年0.35开尔文的速率上升，而地下温度的升幅则随深度增加而递减：20米深度处的升温中值为每10年0.28开尔文，60米深度处仅为每10年0.09开尔文。尽管如此，地下水水体缓慢且受抑制的升温现象仍十分显著，尤其是对比原生地下水体（pristine groundwater bodies）近乎无自然温度波动的背景，以及当前大气温度的预测增幅而言。这一现象对依赖温度的生态过程与水化学过程，以及浅层地下储存的热能均具有重要影响。此外，研究还证实，因气候变化导致的15米以下地下水体的年增热量，约占该联邦州热能需求的三分之一，这凸显了地表自然热通量变化所关联的地热开发潜力。