Mendenhall seminar on Arctic bluff retreat

Mendenhall Research Seminar

Arctic bluff retreat and coastal inundation in relation to a changing  climate

Li Erikson, USGS, Santa Cruz, CA

Wednesday, February 22, 2012 – at 12 Noon
USGS National Center, Reston, VA – Room 4C315

ABSTRACT

The coastline of Alaska’s North Slope is undergoing extensive changes, likely in response to a warming climate.  Arctic air temperatures have increased by nearly 4oC over the past 50-100 years, almost twice the global average rate.  This warming trend has been accompanied by shrinking of the perennial ice sheet covering the North Pole and much of the Arctic Ocean, an extension of the open water season, which typically extends from mid-June through early October, and possibly an increase in storm magnitude and frequency.  Some of the changes, such as elevated sea surface and air temperatures, changes in the active layer depth and permafrost, later freeze-up and earlier break-up of the arctic ice sheet, and intensity and frequency of storm activity, are thought to be directly responsible for increasing bluff recession rates and flooding events.

In this study the dominant processes by which permafrost-rich bluffs erode and low lying tundra and Arctic barrier islands undergo expansive inundation are being investigated.  Analysis of limited available data, supplemented with numerical modeling, suggest that the mechanisms by which Arctic bluffs erode are highly dependent on ice content and frequency of exposure to storm waves and surge events.  Numerically modeled time-series and event-based wave hind-casts from 1954 through 2004 show that the wave climate was strongly modulated by large-scale atmospheric circulation patterns and that mean and extreme wave conditions increased during the same time-period.  Since the mid-1980’s, the increase in wave severity was not due to an increase in fetch offered by the decreased sea-ice extent, but rather an increase in storm intensity.  Ice-cover extent is also shown to have little influence on elevated water levels associated with storm surges.  On average, 80% of the total storm surge can be attributed to atmospheric pressure gradients and speed of low pressure system migration, and the remainder due to wind set-up.

More Seminars…same time, same place
February 29, 2012 (W): John Loperfido – Effects of stormwater management strategy on water quantity and water quality in small urban watersheds located in the Chesapeake Bay Watershed
March  7, 2012 (W): Sean Bemis – Evidence for Quaternary faulting along the Gales Creek fault zone, northwest Oregon
March 14, 2012 (W): Brian Ebel – Rainfall-Infiltration-Runoff Processes for Soil Affected by Wildfire
March 21, 2012 (W): Joseph Long – Improving Coastal Change Forecasts by Assimilating USGS Data and Models
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Rama K. Kotra, Ph.D.
Office of Science Quality and Integrity (OSQI)
U.S Geological Survey, MS 911, Reston, VA 20192, USA
Tel: 703-648-6271 (USGS), 703-966-2610 (Cell/Mobile),
Fax: 703-648-6683, E-mail: rkotra@usgs.gov
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USGS: http://www.usgs.gov
OSQI: http://www.usgs.gov/quality_integrity/
USGS Mendenhall  Program: http://geology.usgs.gov/postdoc
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