Temporal and spatial variations in coastal dynamics along the Yukon coast, Canada

The Arctic is warming. This results in longer open-water periods during which waves can interact with the shore, and extends the duration in which the land and the sea are exposed to positive temperatures. Increasing active layer depths compound the effectiveness of wave action on the coast that is often composed of ice-bound and fine-grained sediments. As permafrost soils contain approximately twice as much carbon as is currently circulating in our atmosphere, the Arctic is one of the key areas requiring study to better understand global climate change processes. Due to the fact that Arctic permafrost coasts make up one third of the World’s coasts, their dynamics are of particular interest. We investigated spatio-temporal shoreline dynamics of the Yukon Coast, characterized by very ice-rich soils and a variety of coastal landforms. Over one hundred aerial photographs from the 1950’s, the 1970’s, and the 1990’s were georeferenced on the base of GeoEye and WorldView satellite imageries from 2011. By digitizing the shoreline for each time step and performing analyses using the Esri ArcGIS extension DSAS (Digital shoreline analysis system), we classified regions according to their rate and variability of coastal erosion. Some regions are very dynamic, showing phases of fast acceleration and deceleration of coastal retreat, others appear to be very stable with little change through time. Such regions may be directly adjacent. By coupling these spatial coastal dynamics data with LiDAR (Light Detection And Ranging) data from 2012 and 2013, we calculated the volumetric erosion along the Yukon coast. Additionally, we investigated infrared theodolite and real time kinematic GPS measurements from eight coastal monitoring sites maintained by the Geological Survey of Canada, covering the last 20 years. Together, these data allow us to measure coastal evolution over the last 60 years. The temporally better resolved ground survey data indicates that coastal erosion rates, in general, show a decelerating trend over the last 20 years. However, within the last three years rates of coastal erosion along some sites (e.g. the Yukon-Alaskan Border and Stokes Point West) are increasing at unprecedented rates up to 18 m/a. These first results will help to quantify the amount of carbon released by coastal erosion along the Yukon coast and identify the contribution of coastal processes operating along the Yukon coast to regional and global nutrient cycles