What sets the pace of glacier change in a warming world? Examining the roles of climate, geometry, and dynamics

Abstract

Glaciers are fundamentally sensitive to climate. Following a perturbation in either precipitation or temperature, their extent on the landscape must change in order to re-balance accumulation and melt. This equilibrium response is fairly straightforward, but in the con- text of anthropogenic warming, contemporary glacier change is fundamentally a transient problem. This dissertation focuses on basic physical controls on this transient response. First, I use a recently-developed statistical model to identify modes of climate variability that drive anomalies in glacier mass balance, and assess their effects on decadal trends. The remainder of the dissertation investigates glacier response times using a combination of numerical and analytical models. This work extends the theoretical basis of glacier response times into a framework for addressing practical questions about ongoing glacier change. These include the current disequilibrium of mountain glaciers, the relative impact of ocean vs. atmospheric forcing on marine-terminating glaciers, and the challenge of attributing glacier changes to natural or anthropogenic forcing. In each case, the results depend on fundamental constraints related to the glacier’s geometry and climate setting. While the particular parameters vary by glacier, these constraints arise from basic principles of ice flow, and are thus very robust. While there will always be details specific to any particular glacier, these experiments clarify fundamental processes that will affect glacier change in any setting.