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Timescales of Glacier Responses to Environmental Perturbations: What They Mean for the 21st Century

Timescales of Glacier Responses to Environmental Perturbations: What They Mean for the 21st Century
Type: 
Parallel
Time: 
17 March 2010 - 9:55am - 10:10am
Jeffrey S. Kargel1, Gregory Leonard2
1Hydrology & Water Resources, University of Arizona, Harshbarger Building, Tucson, AZ, 85721, USA, Phone 520-780-7759, jeffreyskargel [at] hotmail [dot] com
2Hydrology & Water Resources, University of Arizona, Harshbarger Building, Tucson, AZ, 85721, USA, Phone 520-449-4683, gleonard [at] email [dot] arizona [dot] edu

Much debate concerns the timescales of glacier responses to environmental change. Glaciers respond with multiple glacier dynamical mechanisms which may have distinct response times. In an idealized case of a cold-based, debris-free glacier, the response time, tau, given by J&oacutehanneson et al. (1989) is tau = H/-b, where H is a thickness parameter (e.g., thickness near the equilibrium line altitude), and b is the ablation rate near the terminus. Raper and Braithwaite (2009) made a modification to account for a crude measure of glacier hypsometry. A logical consequence is that for those glaciers indicating a lingering response to the Little Ice Age and post-Little Ice Age warming (sometimes thought to be a cause of ongoing wastage), the more we can expect 21st Century glacier responses to be an inexorable acceleration of wastage as they begin to lose memory of the Little Ice Age and increasingly respond to industrially modified climate of the 20th and 21st Centuries. Where basal melting and basal sliding occurs (in most temperate glaciers) the response time to an anomalous weather event can be just hours or days. For the shorter response timescales, consistent with basal sliding and deforming till, and kinematic wave propagation, we can expect glacier changes to be more tightly coupled to climate variations, which means that there will be many reversals of general temporal trends due to natural decadal climate oscillations. However, surges can lead to overextended and subsequently stagnating ice, and the recovery to equilibrium can be very slow along the lines of J&oacutehanneson et al. (1989). The behavior can be very complex: stagnant debris-covered glacier tongues may respond with different timescales within the same glacier due to heterogeneous debris loads. These considerations derived from mainly temperate glaciers point to a complex evolution of response times in polar glaciers as climate warms, as basal sliding initiates, and as supraglacial debris production increases. The behavior of polar ice will eventually depart from historical behavior and slow responses and take on increasingly complex behavior of surge-and-waste cycles, stagnating debris-covered lobes, supraglacial lake formation, and fast responses that are today more associated with Alaskan and Himalayan glaciers. Response times in Greenland and the Canadian Arctic may be lengthy until the transition to temperate behavior occurs, when responses will become extremely rapid.

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National Science Foundation | Division of Arctic Sciences
National Science Foundation
National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
International Arctic Systems for Observing the Atmosphere
International Arctic Systems for Observing the Atmosphere
Study of Environmental Arctic Change
Study of Environmental Arctic Change
Arctic System Science Program
Arctic System Science Program
US Arctic Research Commission
US Arctic Research Commission
North Slope Science Initiative
North Slope Science Initiative
International Arctic Science Committee
International Arctic Science Committee
Arctic Ocean Sciences Board
Arctic Ocean Sciences Board
Alaska Ocean Observing System
Alaska Ocean Observing System
Department of Energy
Department of Energy
National Aeronautics and Space Administration
National Aeronautics and Space Administration
World Wildlife Fund
WWF
Association of Polar Early Career Scientists
Association of Polar Early Career Scientists
Bureau of Land Management
Bureau of Land Management
International Study of Arctic Change
International Study of Arctic Change
ArcticNet
ArcticNet
DAMOCLES
Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies

This work is supported by the National Science Foundation (NSF) under the ARCUS Cooperative Agreement ARC-0618885. Any opinions, findings, and conclusions or recommendations expressed do not necessarily reflect the views of the NSF.