Coastal Erosion Resource Brief for the Arctic Network

Portions of the coast in Bering Land Bridge National Preserve and Cape Krusenstern National Monument are steep slopes of thawing and eroding permafrost above narrow beaches.

ShoreZone, www.shorezone.org

The 5 Arctic parks collectively referred to as the Arctic Network: Bering Land Bridge National Preserve, Cape Krusenstern National Monument, Noatak National Preserve, Kobuk Valley National Park, and Gates of the Arctic National Park and Preserve.

Status and trends of coastal erosion in the Arctic Network

The coastlines of Bering Land Bridge National Preserve and Cape Krusenstern National Monument have eroded in most areas over the past seven decades, but accretion (seaward advance of the shore) has occurred in some places. A comparison of images taken between 1950 and 2014 show that long-term erosion rates are generally higher in Bering Land Bridge NP than in Cape Krusenstern NM, and average rates of erosion have not changed much over time. However, the amount of variation from place-to-place has recently increased, meaning locally both more erosion and more accretion than before. This is probably because of the increased duration of ice-free open water when wave action can occur. Erosion at rates of over 1 meter per year continue in many areas and could threaten archeological sites. Vegetation cover on barrier islands has held stead steady or increased, and we did not observe an increase in breaches of the barriers.

The shoreline has moved inland due to erosion over most of Bering Land Bridge National Preserve and Cape Krusenstern National Monument. In some areas the shoreline moved more inland than 164 feet (50 meters) between 1950 and 2014.

Satellite image shows the erosion line position on the shoreline bluff at four different measurement times in Bering Land Bridge NP. The coast in this area retreated about 130 feet (40 meters) between 1950 and 2014. Ice wedge polygons on the shore show that this is an area of ice-rich permafrost.

Satellite image by Worldview-2 satellite by Maxar

Why coastal erosion is important

Coastal environments within Bering Land Bridge National Preserve and Cape Krusenstern National Monument are experiencing rapid environmental changes in the form of coastal erosion, bluff retreat, beach accretion, sediment deposition and permafrost thaw. The coastal zone may change rapidly as Arctic warming lengthens the ice-free season, causes sea-level rise, increases seawater temperature and alters storm frequency and severity. A variety of near-shore habitats – including sandy shores, barrier spits and islands, lagoons, bays and inlets, tundra bluffs, dunes, estuaries, and salt marshes – are threatened by coastal erosion. Such areas provide habitat for unique plants, fish, birds, and marine mammals, including migratory stopover sites. Coastal zone changes will also impact human activities and cultural resources such as travel routes, fishing, and hunting. Many of the important archeological sites within these park units occur on the coast and could be threatened by erosion.

An eroding shoreline in Bering Land Bridge National Preserve.

How we monitor coastal erosion

Every 10 years we acquire and analyze of aerial photographs or satellite images. We trace the position of the shoreline on a computer screen and use specialized software to calculate erosion and accretion rates from the digitized shorelines.

Barrier islands and spits face the ocean over much of Bering Land Bridge NP and Cape Krusenstern NM. Coastal dunes covered with grass rise behind the beach, with salt marshes behind adjacent to lagoons. The pristine condition of these barriers helps protect the land from erosion.

Shorezone, www.shorezone.org

How monitoring coastal erosion helps park managers protect parks in the Arctic Network

The coastal zone harbors many different kinds of wildlife, including fish, migratory birds, and mammals. Tracking coastal change over time and space will allow park managers to better understand changes in the habitat for wildlife, including important subsistence species. By identifying areas of rapid erosion, we can target these areas for special management of archeological resources.

For more information, contact:

Dave Swanson
907-455-0665
[e-mail]