15.4.6 Coastal zone and small islands

15.4.6.1 Arctic coastal erosion

Coastal stability in polar regions is affected by factors common to all areas (exposure, relative sea-level change, climate and lithology), and by factors specific to the high latitudes (low temperatures, ground ice and sea ice). The most severe erosion problems affect infrastructure and culturally important sites in areas of rising sea level, where warming coincides with areas that are seasonally free of sea ice or where there is widespread ice-rich permafrost (Forbes, 2005). Ice-rich permafrost is widespread in the western Canadian Arctic, northern Alaska and along much of the Russian Arctic coast (e.g., Smith, 2002; Nikiforov et al., 2003). Wave erosion and high summer air temperatures promote rapid shoreline retreat, in some cases contributing a significant proportion of regional sediment and organic carbon inputs to the marine environment (Aré, 1999; Rachold et al., 2000). Communities located on resistant bedrock or where glacio-isostatic rebound is occurring are less vulnerable to erosion.

Coastal instability may be further magnified by poorly adapted development. For example, in places such as Varandey (Russian Federation) industrial activity has promoted erosion, leading to the destruction of housing estates and industrial facilities (Ogorodov, 2003). Interacting human and natural effects may also increase the sensitivity to coastal erosion. For example, in Shishmaref (Alaska, USA) and Tuktoyaktuk (Northwest Territories, Canada), the combined effects of reduced sea ice, thawing permafrost, storm surges and waves have led to significant loss of property, and this has led to relocation or abandonment of homes and other facilities (Instanes et al., 2005). Despite a cultural aversion to moving from traditional sites, these changes may ultimately force relocation. Although clear evidence for accelerated erosion is sparse, there has been a documented increase in erosion rates between 1954-1970 and 1970-2000 for coastal terrain with very high ground-ice content at Herschel Island, Canada (Lantuit and Pollard, 2003). A modelling exercise (Rasumov, 2001) suggested that erosion rates in the eastern Siberian Arctic could increase by 3-5 m/yr with a 3°C increase in mean summer air temperature. Furthermore, the projected reduction of sea ice would also contribute to increased erosion, as has been observed at Nelson Lagoon in Alaska (Instanes et al., 2005).