The effect of changing sea ice on the physical vulnerability of Arctic coasts

Abstract

Abstract. Sea ice limits the interaction of the land and ocean water in the Arctic winter and influences this interaction in the summer by governing the fetch. In many parts of the Arctic, the open-water season is increasing in duration and summertime sea-ice extents are decreasing. Sea ice provides a first-order control on the physical vulnerability of Arctic coasts to erosion, inundation, and damage to settlements and infrastructures by ocean water. We ask how the changing sea-ice cover has influenced coastal erosion over the satellite record. First, we present a pan-Arctic analysis of satellite-based sea-ice concentration specifically along the Arctic coasts. The median length of the 2012 open-water season, in comparison to 1979, expanded by between 1.5 and 3-fold by Arctic Sea sector, which allows for open water during the stormy Arctic fall. Second, we present a case study of Drew Point, Alaska, a site on the Beaufort Sea, characterized by ice-rich permafrost and rapid coastal-erosion rates, where both the duration of the open-water season and distance to the sea-ice edge, particularly towards the northwest, have increased. At Drew Point, winds from the northwest result in increased water levels at the coast and control the process of submarine notch incision, the rate-limiting step of coastal retreat. When open-water conditions exist, the distance to the sea ice edge exerts control on the water level and wave field through its control on fetch. We find that the extreme values of water-level setup have increased consistently with increasing fetch.

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).…”

Impacts of a lengthening open water season on Alaskan coastal communities: deriving locally relevant indices from large-scale datasets and community observations

“…It is well documented that a lengthened period of open water leaves Arctic shorelines more vulnerable to erosion from fall storms (Barnhart et al, 2014;Overeem et al, 2011). Moreover, along the Alaskan coast during the open water period, we have found the number of wind events capable of doing geomorphological work or creating hazards to habitat or infrastructure (as defined by Atkinson, 2005) is increasing at all three communities in this study (Fig.…”

“…Over the 36-year time period examined, Kotzebue has had an approximate increase from 39 to 46.2 total wind events, while Shishmaref has seen an increase from an average of 49 to 52.6 events. In addition, wind direction is very important to determine whether a particular wind event is able to set up water along the coastline enough to cause flooding, increased coastal erosion, or infrastructure damage (Barnhart et al, 2014). The average number of high-wind events from the quadrant favorable for erosion at Utqiaġvik is approximately 4.61 with a significant increasing trend of 0.14 per year.…”

“…We have also counted the number of high-wind events as defined by Atkinson (2005) (greater than 10 m s −1 for at least 6 h) but have an added restriction that winds conducive to erosion must be blowing from directions within a 90 arcdeg between normal to the coastline and alongshore with the coast to the right of the wind. High winds from these directions favor both wave generation and water setup along the coastline (i.e., increase in local sea level) and can therefore be particularly damaging to a community in terms of increasing erosion rates (Barnhart et al, 2014) and possible infrastructure damage due to flooding. Winds from between 225 and 315 • satisfy both the alongshore and onshore requirements at Utqiaġvik.…”

“…It is at the center of animal migration routes and is also the center of a complex food-distribution system based in subsistence hunting practices (Marino, 2012). It is highly vulnerable to erosion, which has been exacerbated by declining sea ice cover protecting the coastline (Barnhart et al, 2014). The members of Shishmaref have voted twice to permanently relocate the village due to this problem, but the funds are not available for doing so, even though the community will eventually have to move (Department of Commerce, Community, and Economic Development, 2017).…”