GIS-BASED RECONSTRUCTIONS OF PALEOLAKE AREA AND VOLUMES IN THE WESTERN UNITED STATES AND CENTRAL ANDES: IMPLICATIONS FOR PALEOCLIMATE INTERPRETATIONS

Examining past lake level changes in ancient lake basins can tell us about past changes in climate. In particular, the ancient, closed-basin lakes of the western United States and central Andes are ideally suited for reconstructing past changes in precipitation and evaporation. Previous studies have focused on past changes in lake area as a proxy for hydrological change, but few have used the geometry of basins to provide additional context on the sensitivity and rate of response of lakes to such changes. Here we present a dataset of basin hypsometry curves from various basins in the western U.S. and central Andes. We use GIS and digital elevation models to create contours matching various paleoshoreline features observed in aerial imagery in order to reconstruct paleolake areas and volumes.

Our preliminary results show that while the relationship between lake level elevation and volume change is similar in character across most lake basins, the relationship between lake level elevation and lake area can vary and is dependent on basin geometry. Adjusting the model for various values of precipitation and evaporation, we explore the realm of feasible climates which may have resulted in the paleoshorelines for several basins, and examine which of these climates are realistic.

In addition, using the hydrological lake model by Huybers et al. (2015), we illustrate how lake basin geometry in our study regions determines the rate at which a lake reaches a new equilibrium in response to a climatic change. With this work, we hope that our estimates of the transient response of different lake basins to past abrupt changes can help us understand the timescales at which lake levels are most sensitive.