Coastal erosion and resulting impacts along the ice-rich permafrost coast of the Yukon Territory, Canada

Due to its fine grained and very ice-rich sediments, the coast of the Yukon Coastal Plain forms a very dynamic landscape. Changing climatic conditions add to this by lengthening open water periods and increasing permafrost temperature, which contributes to an increase of coastal erosion. Even though the Yukon Territory has no permanent settlements along its Beaufort coast, this region is of exceptional value as it serves as a calving area for the Porcupine Caribou Herd and it comprises numerous archaeological sites which are rare remains of the rich human history of this region. The importance of this area is underpinned by the fact that about two third of the coast of the Yukon Territory is protected as part of the Ivvavik National Park, which in turn is a candidate for the UNESCO world heritage site status. Additionally, recurring plans to develop oil and gas-related infrastructure would dramatically change the nature of the coastal environment. Yet, no up-to-date information is available on the erosion of this long coastal stretch, which is detrimental to both environmental and industrial planning in the area. Here, we present initial results of an assessment of shoreline dynamics and their influence on the coastal system in the Ivvavik National Park area. We first quantified shoreline changes of the approximately 150 km long coast by means of remote sensing data. We geocoded aerial photographs from the 1950s, the 1970s and the 1990s to a GeoEye scene from 2011 and digitized the respective shorelines. We then analyzed spatial and temporal shoreline dynamics by using the Esri ArcGIS extension DSAS (Digital Shoreline Analysis System). Then, we coupled these results with a large range of ecological and cultural datasets, including ecological units, freshwater habitat extents and archaeological site positions, in order to determine the vulnerability of the coastal environment of the Ivvavik National Park. Our initial results show that coastal erosion is prevailing along most parts of the coast and only very limited coastal stretches experience accumulation. The analyses allow us to draw initial conclusions about which habitats are most affected by arctic coastal changes and which archaeological sites are prone to get lost in the near future

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

Variability of coastal change along the western Yukon Coast

Because the Yukon coast along the Beaufort Sea has the highest ground ice contents in the Canadian Arctic and, in addition, faces the direction of most effective storms, this section of coast is considered to be highly vulnerable to the effects of climate change. In order to gain insight into the regional coastal dynamics, a quantification of coastal change was undertaken that allowed the determination of spatial and temporal variability of coastal change along a 35 km long section of coast, stretching from Komakuk to the international border. Shorelines from several years between 1951 and 2009 were digitized from georeferenced aerial photographs and an ortho-rectified SPOT image. Shoreline change statistics were subsequently calculated using the Digital Shoreline Analysis System (DSAS) extension for Esri ArcGIS. Theodolite and real-time kinematic GPS data that was collected during several surveys between 1991 and 2012 at two Geological Survey of Canada (GSC) monitoring sites (Border site and Komakuk site) were analysed to provide higher temporal resolution of coastal change for the last two decades. Additionally, the field survey data enabled an assessment to be made of the contribution of geomorphic variables (i.e. beach slope, beach width, cliff slope, absolute cliff height, relative cliff height) towards explaining changes of coastal erosion. According to the findings, the mean annual erosion along the western Yukon coast has been -1.2 ± 0.4 m/a over the entire period of study, with the rates decreasing through time from -1.4 ± 0.6 m/a between 1951 and 1972, to -1.2 ± 0.5 m/a between 1972 and 2009. However, site specific investigations show that there are differences in the mean erosion rates and in temporal trends. To the west at the Border site, the mean annual erosion rate is -1.3 ± 0.3 m/a, and the rates have recently accelerated, while at Komakuk in the east of the study area, the mean annual erosion rate is -0.9 ± 0.2 m/a, with the rates decelerating over time. A comparison of these findings to erosion rates from the Alaskan Beaufort Sea coast indicates that there is a general spatial pattern of decreasing erosion rates from the west to the east. The quantified erosion rates also enabled the calculation of mean annual land loss between 1951 and 2009, which amounted to 4.5 ha/a. An analysis of the influence of shore profile parameters on mean annual erosion rates showed a statistically significant correlation between beach widths and erosion rates (r=0.84) at the Border site. There is also a strong but insignificant correlation between absolute cliff heights and erosion rates at the Border, but no correlations of shore profile parameters with erosion could be distinguished for the Komakuk site

New insights into coastal erosion rates along the Yukon coast, Canada

Approximately twice as much carbon is stored in permafrost (perennially frozen ground) as is in the Earth’s atmosphere. Globally, nearly one third of all coasts are affected by permafrost processes. Erosion of these coasts causes re-mobilization of the stored carbon which then becomes available for the conversion into greenhouse gasses, such as methane and carbon dioxide. The Yukon Coastal Plain in the western Canadian Arctic is typically composed of ice-rich and unconsolidated sediments, including massive ice bodies for example in the form of ice wedges and segregated ice. This composition and morphology make it highly susceptible to erosion. Recent changes in environmental conditions such as record low summer sea ice extents in the years of 2007 and 2012, and rising sea- and ground temperatures, suggest an increase in coastal retreat and thus an increase in the re-mobilization of carbon. We present the initial results of a regional study focused on the spatial and temporal changes of coastal retreat along a 200 km coastal stretch of the Yukon Coastal Plain, reaching from the USA-Canada border to Shingle Point. Aerial photography from 1951 to 1996, as well as SPOT and GeoEye satellite imagery from the years of 2009 and 2011, form the basis for GIS analyses using the Digital Shoreline Analysis System (DSAS). The results are supplemented by ground observations at seven coastal monitoring sites maintained by the Geological Survey of Canada. Infrared theodolite and real time kinematic global positioning system data, together with LiDAR (Light Detection And Ranging) data from 2012 and 2013, allow us to estimate the total volumetric land loss along the Yukon coast that occurred over the last 60 years. The temporal and spatial variability in coastal erosion shows that erosion occurs at rates up to 10 m/a around Stokes Point. Western study sites show much lower erosion rates of less than 2 m/a which appear to more adequately represent the overall erosional trend of the coast. The acceleration or deceleration of coastal retreat is highly dependent on the specific location, and varies from west to east. As the overall erosional behavior of the coast is very diverse, no clear response of the coast to changing environmental conditions can be distinguished yet. Further field investigations are planned, to gain a better understanding of how the Yukon coast is responding to environmental changes

Variability of Arctic coastal erosion along the western Yukon coast

Arctic coastal erosion can have substantial impacts on coastal infrastructure, sometimes prompting the need for aggressive adaptation strategies. It can also induce the release of large quantities of organic carbon and nutrients directly into the nearshore with potential impacts on the ecosystem and/or transformation into greenhouse gases upon contact with sea water. The recent major changes in summer sea ice extent, as well as the warming of sea temperature could potentially lead to greater erosion rates and amplify these processes, yet few studies have quantified erosion in the Canadian Arctic over the period including the 2007 and 2012 minima in sea ice. In this study, we present erosion rates for the western Yukon coast, a 35 km long stretch between the Komakuk Beach Distant Early Warning Line station in the east and the Canada-USA border in the west. Shoreline position data from 44 aerial photographs as well as a SPOT image were analyzed to determine rates spanning 58 years (1951-2009). These remote sensing data were analyzed with the Digital Shoreline Analysis System (DSAS) extension for ESRI ArcGIS. Additionally, total station and real time kinematic global positioning system survey data from coastal monitoring sites maintained by the Geological Survey of Canada at Komakuk Beach and at the border were used to compute rates for the time period between 1991 and 2012. These two datasets together with LiDAR (Light Detection And Ranging) data collected in 2012 and 2013 allowed us to measure shoreline evolution and total volumetric land loss over the past 61 years. Mean annual volumetric land loss for the whole coastal stretch between 1951 and 2009 was calculated to be 250,000 m3/a. DSAS results show rates of coastal erosion in the region have not changed significantly over time. A comparison of the mean annual erosion from 1951 to 1972 to the time period of 1972 to 2009 shows a slight deceleration from 1.4 m/a to 1.2 m/a. A clearer trend towards decreasing erosion was distinguished at the Komakuk Beach study site, where mean annual erosion decelerated from 1.92 m/a to 0.49 m/a during the time from 1951 to 2009. By contrast, coastal erosion at the Canada-USA border increased during the same time period from 1.3 m/a to 1.8 m/a. Work is under way to better understand these local differences and the overall nature of erosion along the Yukon coast

Coastal retrogressive thaw slumps along the Yukon Coast (Canada), link to shapefile

Aerial photographs from the National Air Photo Library, Canada. GeoEye-1 and WorldView-2 imagery from the Yukon Coast, 2011