Understanding coastal dynamics along a permafrost affected coastline in northwestern Alaska, USA

• Main Authors: Farquharson, Louise M., Mann, Daniel H., Grosse, Guido, Jones, Benjamin, Swanson, David, Romanovsky, V. E.
• Format: Conference Object
• Language: unknown
• Published: University of Lisbon and University of Evora 2014
• Subjects: Arctic; Barrier Islands; Chukchi Sea; Beaufort Sea; Chukchi; Climate change; Ice; permafrost; Sea ice; Seward Peninsula; Thermokarst; wedge*; Alaska
• Online Access: https://epic.awi.de/id/eprint/35916/; https://hdl.handle.net/10013/epic.43832

Some of the highest coastal erosion rates in the world are now occurring along non-bedrock, permafrost affected coastlines in the Arctic. Understanding how vulnerable Arctic coastlines are to current and future climate change is critical for resource management, subsistence hunting and gathering, and quantifying the flux of carbon and sediment from a terrestrial to marine environment. Observations since the 1970’s, show that pan-Arctic sea ice extent is decreasing by approximately 12 % per decade, with 2012 exhibiting the longest ice-free season on record. As a result, Arctic coastlines are vulnerable to wave-driven erosion for longer periods. Permafrost borehole temperatures show an overall warming trend, increasing susceptibility to thaw. While several studies already exist pointing at accelerating coastal erosion along the Beaufort Sea coast, studies for the Chukchi Sea coast of NW Alaska have remained inconclusive for the 1950-2003 period. Did recent dramatic changes in sea ice extent, with several sea ice minimum records since the mid 2000’s have an impact on the patterns and processes of coastal dynamics of the Chukchi Sea coast? Here we report on coastal change rates and key geomorphological processes occurring between 2003 and 2013 in comparison to coastal dynamics between 1950 and 2003 along the northern shoreline of the Seward Peninsula, Alaska, USA. Previous studies in our study area, focusing on 1950 to 2003, show rates of change ranging from -5.84 to 2.57 meters per year, indicating the occurrence of both erosion and aggradation. Our study shoreline is a complex system of barrier islands, sand spits, yedoma bluffs and drained thermokarst lake basins. The 1950-2003 coastal change data is based on aerial imagery covering 3 time steps (ca. 1950, ca. 1978, and 2003) that was analyzed by Lestak et al. 2010. To place recent coastal change dynamics since then in a spatial context, we conducted geomorphological analysis using 22 sub-meter resolution panchromatic World View 2 images from June 2013 and a five-meter resolution interferometric synthetic aperture radar derived digital elevation model acquired in summer 2012. We identified key geomorphological processes associated with coastal change and analyzed sediment redistribution between yedoma bluffs, lagoons and spits. Although relatively stable, ice wedge degradation was observed in yedoma bluff areas. Barrier islands, tidal channels, and overwash deposits showed significant variation in morphology during the study period. We further collected weather station data from Shishameref and Kotzebue, the two closest climate stations to the study area, and plan to extract sea ice and sea surface temperature data for the immediate region offshore our study coast. Our results illustrate the heterogeneous nature of coastal dynamics along the Arctic coastline and the need to acknowledge this when modelling future coastal response to sea ice decline and climate change.