资源环境科技发展态势分析平台

Deep meteoric waters comprise a key component of the hydrologic cycle, transferring water, energy, and life between the earth’s surface and deeper crustal environments, yet little is known about the nature and extent of meteoric water circulation. Using water stable isotopes, we show that maximum circulation depths of meteoric waters across North America vary considerably from <1 to 5 km, with the deepest circulation in western North America in areas of greater topographic relief. Shallower circulation occurs in sedimentary and shield‐type environments with subdued topography. The amount of topographic relief available to drive regional groundwater flow and flush saline fluids is an important control on the extent of meteoric water circulation, in addition to permeability. The presence of an active flow system in the upper few kilometers of the Earth’s crust and stagnant brines trapped by negative buoyancy offers a new framework for understanding deep groundwater systems.

Deep circulation of waters, coming from precipitation, connects the Earth’s surface with deeper subsurface environments, transferring water, energy and life critical for key processes, such as deep mineral weathering and release of nutrients, and geothermal energy systems. Deeper, more saline groundwater is typically only weakly connected to the rest of the hydrologic cycle. The penetration depth of precipitation‐derived waters and the bottom of the more active hydrologic cycle is relatively unknown. This study shows the depth of meteoric water circulation varies considerably across North America as a function of topography and fluid density, in addition to permeability. Study results help constrain locations of deeper meteoric water penetration and potential hydrologic connections to the earth’s surface, which has important implications for the extent of water resources and transport and long‐term storage of anthropogenic contaminants in the subsurface.

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