Collaborative Research: Terrestrial hydrology during the last deglaciation

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Water, critical to life on Earth, moves between the atmosphere, oceans, lakes and wetlands, groundwater, rivers, permafrost, and glaciers and ice sheets. Earth?s finite amount of water means that whenever one of these reservoirs fills, the others must empty to balance it. This simple principle - conservation of mass - has powerful implications for society's ability to understand past climate and sea-level change, and potentially for predicting these into the future. To understand the impacts of past changes in water and climate, the researchers ask a simple and fundamental set of questions: First, how did the global water balance respond to the climate of the last glacial period? Second, how did that response in turn impact the climate system through evaporation from the land, runoff into the ocean, and ecological change linked with the global distribution and function of wetlands? In this project the researchers will develop a new model that links these components of the hydrological cycle, and apply this to the recent geological past when vast ice sheets covered the high latitudes and lakes filled now-dry basins. By connecting this new model with geological data, the researchers hope to understand how changes in past sea level are distributed among ice sheets and water on the continents, including groundwater, lakes, and wetlands. They will also investigate how sudden freshwater release can impact ocean circulation and global climate. In parallel with this research, they will communicate the importance of water in the environment by sharing their digitally reconstructed ancient land- and water-scapes online, developing a watershed board game for educators, and contributing their findings to scientific journals and Wikipedia.Terrestrial water storage plays a crucial role in climate, ecosystems, land-atmosphere interactions, and sea level. To date, most studies of the last deglaciation focus on changes in the ice sheets, but overlook the other components of the terrestrial hydrologic system: lakes, rivers, wetlands, groundwater, and permafrost. As a result the magnitude and pace of change of non-glacial terrestrial water storage - and its potential impact on the climate system - remains unknown. Here the researchers propose to reconstruct the global hydrologic environment during the last deglaciation. To do so, they will: (a) compile, integrate, and synthesize proxies for terrestrial paleohydrology since the Last Glacial Maximum (LGM); (b) develop a coupled model linking glacial isostatic adjustment, lakes and rivers, and groundwater; and (c) integrate data and model to quantify the time evolution of global terrestrial hydrology. This output will allow them to quantify: (1) the migration, expansion, and contraction of surface water bodies; (2) the total amount of water stored on land and its impact on sea-level records and ice-sheet reconstructions; and (3) water inputs to the ocean through evapotranspiration and submarine groundwater discharge, alongside their potential to reconcile ice-sheet reconstructions with records of sea level and past ocean circulation. In conjunction with these research activities, the researchers will deliver their paleohydrologic reconstructions as maps available on Wikimedia Commons and Flyover Country, build instructional materials on past environments, and improve Wikipedia's coverage of hydrologic and paleoclimate science.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.