Sedimentary records of lake-level fluctuations have long provided unambiguous evidence of past hydrologic changes. Here, we synthesize geomorphic and sedimentological evidence of late-Quaternary lake-level changes across North America and show that currently moist regions were commonly drier than today. Many lakes across humid or snow-dominated areas of North America were lower than today or totally desiccated for prolonged periods but rose to their current levels following climate changes in recent millennia. Maps of 173 records show that hydroclimates responded to deglacial dynamics and orbital changes but that regional hydrology changed even under the modest forcing and temperature variability of the past 8,000 years. Submerged paleoshorelines, ubiquitous across humid regions, reveal that North America's ecosystems and critical zone existed in a drier-than-modern state for much of the Quaternary and that continental moisture gradients often differed from today. The hydrologic changes underscore the climatic risk to many societally critical water supplies.
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We thank C. Oviatt and an anonymous reviewer for helpful feedback on the manuscript and J. Mercer for support with graphics. Data related to this paper is available through the National Centers for Environmental Information on the National Oceanic and Atmospheric Administration website (https://www.ncdc.noaa.gov/paleo/study/28771). The data can also be viewed through an interactive map (https://uwyo.maps.arcgis.com/apps/opsdashboard/index.html#/db6d2d21e3844a37b19c47ed474a2a9a). The analyses were performed in R.
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- water resources