Geoelectric observations of the degradation of nearshore submarine permafrost at Barrow (Alaskan Beaufort Sea)

Abstract

Submarine permafrost degradation rates may be determined by a number of interacting processes, including rates of sea level rise and coastal erosion, sea bottom temperature and salinity regimes, geothermal heat flux and heat and mass diffusion within the sediment column. Observations of ice‐bearing permafrost in shelf sediments are necessary in order to determine its spatial distribution and to quantify its degradation rate. We tested the use of direct current electrical resistivity to ice‐bearing permafrost in Elson Lagoon northeast of Barrow, Alaska (Beaufort Sea). A sharp increase in electrical resistivity was observed in profiles collected perpendicular to and along the coastline and is interpreted to be the boundary between ice‐free sediment and underlying ice‐bearing submarine permafrost. The depth to the interpreted ice‐bearing permafrost increases from <2 m below sea level to over 12 m below sea level with increasing distance from the coastline. The dependence of the saline sediment electrical resistivity on temperature and freezing was measured in the laboratory to provide validation for the field measurements. Electrical resistivity was shown to be effective for detection of shallow ice‐bearing permafrost in the coastal zone. Historical coastal retreat rates were combined with the inclination of the top of the ice‐bearing permafrost to calculate mean vertical permafrost degradation rates of 1 to 4 cm yr−1.