Observing Muostakh disappear: permafrost thaw subsidence and erosion of a ground-ice-rich island in response to arctic summer warming and sea ice reduction

Abstract

Abstract.Observations of coastline retreat using contemporary very high resolution satellite and historical aerial imagery were compared to measurements of open water fraction, summer air temperature, and wind. We analysed seasonal and interannual variations of thawing-induced cliff top retreat (thermo-denudation) and marine abrasion (thermoabrasion) on Muostakh Island in the southern central Laptev Sea. Geomorphometric analysis revealed that total ground ice content on Muostakh is made up of equal amounts of intrasedimentary and macro ground ice and sums up to 87 %, rendering the island particularly susceptible to erosion along the coast, resulting in land loss. Based on topographic reference measurements during field campaigns, we generated digital elevation models using stereophotogrammetry, in order to block-adjust and orthorectify aerial photographs from 1951 and GeoEye, QuickBird, WorldView-1, and WorldView-2 imagery from 2010 to 2013 for change detection. Using sea ice concentration data from the Special Sensor Microwave Imager (SSM/I) and air temperature time series from nearby Tiksi, we calculated the seasonal duration available for thermo-abrasion, expressed as open water days, and for thermo-denudation, based on the number of days with positive mean daily temperatures. Seasonal dynamics of cliff top retreat revealed rapid thermo-denudation rates of −10.2 ± 4.5 m a −1 in mid-summer and thermo-abrasion rates along the coastline of −3.4 ± 2.7 m a −1 on average during the 2010-2013 observation period, currently almost twice as rapid as the mean rate of −1.8 ± 1.3 m a −1 since 1951. Our results showed a close relationship between mean summer air temperature and coastal thermo-erosion rates, in agreement with observations made for various permafrost coastlines different to the East Siberian Ice Complex coasts elsewhere in the Arctic. Seasonality of coastline retreat and interannual variations of environmental factors suggest that an increasing length of thermo-denudation and thermo-abrasion process simultaneity favours greater coastal erosion. Coastal thermoerosion has reduced the island's area by 0.9 km 2 (24 %) over the past 62 years but shrank its volume by 28 × 10 6 m 3 (40 %), not least because of permafrost thaw subsidence, with the most pronounced with rates of ≥ −11 cm a −1 on yedoma uplands near the island's rapidly eroding northern cape. Recent acceleration in both will halve Muostakh Island's lifetime to less than a century.

Coastal dynamics and submarine permafrost in shallow water of the central Laptev Sea, East Siberia

“…Much of the Chukchi and Beaufort seas' coastlines are similarly ice-rich and can be expected to be subject to the same mechanisms of geomorphologic change in response to shifts in environmental drivers of coastal dynamics (Ping et al, 2011). Regionally, relevant shifts in the energy and water balances at the land-atmosphere interface (Boike et al, 2013), increases in Lena River discharge (Fedorova et al, 2015) and increases in the duration of open water and coastal erosion (Günther et al, 2015) have recently been observed, matching similar circumpolar observations (Barnhart et al, 2014).…”

“…Ships leaving Tiksi, one of the major ports on the Northeast Passage, travel within sight of Muostakh Island, and it has therefore long been an object of research, from as early as the late nineteenth century. This research includes studies of coastal dynamics, and coastline erosion rates observed at Muostakh Island in the central Laptev Sea include some of the highest observed in the Arctic (Grigoriev et al, 2009 Günther et al, 2015), polygenetic in origin and characterized at the ground surface by the polygonal network of ice wedges formed over thousands of years by meltwater infiltration into cold winter thermal contraction cracks (Schirrmeister et al, 2011b). Coastal thermo-erosion on Muostakh Island varies widely in intensity (from close to 0 to over 25 m a −1 ) over a relatively small region (Grigoriev et al, 2009;Günther et al, 2015).…”

“…This research includes studies of coastal dynamics, and coastline erosion rates observed at Muostakh Island in the central Laptev Sea include some of the highest observed in the Arctic (Grigoriev et al, 2009 Günther et al, 2015), polygenetic in origin and characterized at the ground surface by the polygonal network of ice wedges formed over thousands of years by meltwater infiltration into cold winter thermal contraction cracks (Schirrmeister et al, 2011b). Coastal thermo-erosion on Muostakh Island varies widely in intensity (from close to 0 to over 25 m a −1 ) over a relatively small region (Grigoriev et al, 2009;Günther et al, 2015). The spatial variability of coastal retreat rates along the island's coastline offers an opportunity to investigate its influence on submarine permafrost development while other aspects of environmental forcing are similar.…”

“…The time since inundation was determined using coastlines digitized from remotely sensed imagery. In addition to the remote sensing dataset used by Günther et al (2015), we increased temporal resolution by adding coastal erosion observations based on a CORONA KH-4B satellite image dating from 24 July 1969, a HEXAGON image from 17 July 1975 and a SPOT-4 image taken on 1 July 2001. After stitching image tiles of the CORONA and HEXAGON images and pansharpening of the SPOT scene, each image was orthorectified to mean sea level using specific sensor models.…”

Arctic in Rapid Transition: Priorities for the future of marine and coastal research in the Arctic

“…The permanently frozen ground extends below sea level on the shallow Arctic shelves as submarine permafrost. There is evidence in northern Alaska and the Laptev Sea area for recent acceleration in the rate of coastal erosion (e.g., Günther et al, 2015) related in parts to more open water and higher wave energy due to reduced sea-ice coverage, rising sea level, and more rapid thermal abrasion along coasts with high volumes of ground ice. Nearshore zones are transient zones for terrigenous matter, which arrives via coastal erosion, river discharge, and sea ice (e.g., Forbes, 2011).…”