RECONSTRUCTIONS OF LATEST PLEISTOCENE GLACIERS AND PALEOCLIMATE IN THE RUBY-EAST HUMBOLDT MOUNTAINS, NEVADA, USA

During the last glaciation, the largest system of valley glaciers in the central Great Basin was in the Ruby-East Humboldt Mountains of northeastern Nevada (total ice surface area of ~275 km²). Although knowledge of the extent and chronology of Pleistocene glaciation in this area has improved, little is known about the climate during the last glaciation in the central Great Basin, especially compared to surrounding regions in the western U.S. Here, we use numerical modeling of valley glaciers in the Lamoille Canyon of the Ruby Mountains to infer climate during the Angel Lake Glaciation, the last Pleistocene glaciation in the Great Basin.

The modeling approach computes the net annual mass balance of a glacial valley based on monthly estimates of temperature, precipitation, radiation balance, and several other meteorological parameters at all points in the valley. These parameters are deviated from the modern to approximate full-glacial conditions, and the resulting mass balance is combined with an ice-flow model to simulate the areal ice extent in the glacial valley. Meteorological data are sparse in the Lamoille Canyon, but lapse rates and precipitation-elevation gradients are estimated from data collected at NRCS SNOTEL stations and the PRISM data set (http://www.prism.oregonstate.edu/). Based on our characterization of the modern climate, the model computes a spring and net annual mass balance in the Lamoille Canyon consistent with observations of perennial snow fields near the head of the canyon. If west-east atmospheric circulation was dominant during the last glaciation as it is today, as suggested by previous studies, then this characterization of climate is a useful approximation for modeling experiments that can be used to infer climate during the Angel Lake Glaciation.

Modeling experiments simulate the maximum extent of glaciers in the Lamoille Canyon during the Angel Lake Glaciation over a broad range of temperature and precipitation combinations. We discuss the significance of these model results in the context of previous estimates of glacial climates in the Great Basin.