Meeting:Abstract 2013 CSDMS meeting-077


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CSDMS all hands meeting 2013

Modeling of Waves and Storm Surge along the Arctic Coast of Alaska

Irina Overeem, University of Colorado Boulder Colorado, United States.
Katy Barnhart, University of Colorado Boulder Colorado, United States.
Robert Anderson, University of Colorado Boulder Colorado, United States.

[[Image:|300px|right|link=File:]]Arctic coasts have been impacted by rapid environmental change over the last 30 years. Warming air and water temperatures and the increased duration of the open water season, correlate with increases in the rate of already rapid erosion of ice-rich bluffs along the Beaufort Sea coast. To investigate longer-term changes in near-shore wave dynamics and storm surge set up as a result of sea-ice retreat, we coupled two simple modules.

Following Dean and Dalrymple (1991), we model wind-driven setup as a function of wind speed and direction, azimuth relative to the shore-normal, fetch and bathymetry. The wave module calculates the wave field for fetch-limited waves in shallow water based on the Shore Protection Manual (1984). For a given wind speed, dynamic water depth and fetch, we predict the significant wave height and wave period. Both modules require fetch as a controlling parameter. Sea-ice influenced coasts, are unique in that fetch is spatially variable due to the geometry of the shoreline and temporally variable as the location of the sea ice edge moves through the sea ice free season. We determine the distance to the sea ice edge using daily Nimbus 7-SMMR/SSM/I and DMSP SSMI Passive Microwave Sea Ice Concentration data. The sea ice edge is defined at a threshold sea ice concentration of 15%. We find a good match between the model predictions and our observed records of meteorological conditions and nearshore water level and waves along the Beaufort Coast in the summers of 2009 and 2010.

Over the period 1979-2012, fetch has increased significantly. In our study area near Drew Point, Alaska, the open water season itself lengthened from ~45 days to ~90 days. In the 1980’s and early 1990’s wave dynamics were fetch-limited during a significant period of the open water season. More recently, the distance from the coast to the sea ice edge shifts extremely rapidly (often 100’s of km over 1-2 weeks); fetch therefore only minimally influences wave dynamics as offshore distance exceeds the 140 km threshold over most of the open water season. Wave heights and surge set-up events on average have not changed in magnitude significantly, but storm surge set up events have increased in frequency.