The rapid rate of global warming currently underway highlights the need for a deeper understanding of abrupt climate change. The Younger Dryas is a Late-Glacial climate event of widespread and unusually rapid change whose study can help us address this need for increased understanding. Reconstructions from the glacial record offer important contributions to our understanding of the Younger Dryas due to (among other things) the direct physical response of glaciers to even minor perturbations in climate. Because the glacier equilibrium line altitude (ELA) provides a more explicit comparison of climate than properties such as glacier length or area, ELA methods lend themselves well to paleoclimate applications and allow for more direct comparisons in space and time. Here we present a physically based ELA model for alpine paleoglacier climate reconstructions that accounts for differences in glacier width, glacier shape, bed topography and ice thickness, and includes error estimates using Monte Carlo simulations. We validate the ELA model with published mass balance measurements from 4 modern glaciers in the Swiss Alps. We then use the ELA model, combined with a temperature index model, to estimate the changes in temperature and precipitation between the Younger Dryas (constrained by 10Be surface exposure ages) and the present day for three glacier systems in the Graubünden Alps. Our results indicate an ELA depression in this area of 320 m ±51 m during the Younger Dryas relative to today. This ELA depression represents annual mean temperatures 2.29 °C ±1.32 °C cooler relative to today in the region, which corresponds to a decrease in mean summer temperatures of 1.47 °C ±0.73 °C. Our results indicate relatively small changes in summer temperature dominate over other climate changes for the Younger Dryas paleoglaciers in the Alps. This ELA-based paleoclimate reconstruction offers a simple, fast, and cost-effective alternative to many other paleoclimate reconstruction methods. Continued application of the ELA model to more regions will lead to an improved understanding of the Younger Dryas in the Alps, and by extension, of rapid climate events generally.
College and Department
Physical and Mathematical Sciences; Geological Sciences
BYU ScholarsArchive Citation
Keeler, Durban Gregg, "Development and Validation of a Physically Based ELA Model and its Application to the Younger Dryas Event in the Graubünden Alps, Switzerland" (2015). Theses and Dissertations. 6142.
Younger Dryas, ELA model, paleoclimate, Swiss Alps, cosmogenic radionuclide ages