T116 Pluvials, Atmospheric Rivers, Monsoons, and Water Availability in Western North America from the Quaternary into the Future: Modeling, Observations, and Paleo Reconstructions of Hydroclimate Extremes

Monday, 26 September 2016
10:00 AM - 12:00 PM
Room 404

ATMOSPHERIC MOISTURE TRANSPORT TO WESTERN NORTH AMERICA DURING THE LAST GLACIAL MAXIMUM AND DEGLACIATION

Paper number: T116-3
Program: Technical Sessions
Time: 10:30 AM – 10:45 AM

Authors

Abstract

Proxy reconstructions of the late Pleistocene paleoclimate of western North America indicate that the southwest was considerably wetter during the Last Glacial Maximum (LGM; ~21 ka) than in the present, while the Pacific Northwest received less rainfall. Pluvial paleolake systems existed in regions that today are arid, from the Great Basin down to the modern Mojave Desert. Many lakes grew to highstands during the early deglaciation, before quickly falling to near-modern levels of dryness around 15 ka, around the same time when moisture in the northwest increased. The timing and distribution of these shifts observed in hydroclimate proxies have been hypothesized to reflect changes in the position of the polar jet stream or the seasonality of precipitation, but the source and delivery processes of the water feeding these regions are debated. Using results from a range of climate models and reanalyses, we explore the role of atmospheric rivers in delivering water to western North America during the glacial, as well as the evolution of water delivery during the deglaciation. Due to the presence of continental ice sheets, deepened Aleutian Low and weakened North Pacific High pressure systems concentrated water transport in atmospheric rivers into California relative to the present, enhancing moisture and precipitation in the southwest and shifting it away from the northwest. As the ice sheets receded, a rapid reorganization of the atmospheric circulation, accompanied by abrupt changes of the semi-permanent pressure systems, precipitated drying and moistening of southwestern and northwestern North America, respectively. We find that during this interval, changes in the water budget of western North America are attributable to the intensity of moisture transport into the continent, and not to the position of the jet stream.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-281946

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.