Assessing Drivers of Coastal Tundra Retreat at Point Hope, Alaska

Abstract

Shoreline erosion over the last few decades along the Point Hope, Alaska, USA coastline has led to considerable loss of tundra behind the beach. Analysis of available remote sensing, morphology, and hydrodynamic datasets are used to inform the time scales and mechanisms of coastal land loss at Point Hope, in part through integration of these data into an analytical retreat model originally developed for coastal foredunes. At shorter time scales, these analyses indicate that steeper local beach slopes influence higher wave runup that can enhance the scale of tundra retreat at a particular section of coast. Coastal stretches that are most vulnerable to wave attack of the tundra scarp appear to shift with time related to complex spatio-temporal variability in shoreline change rates. These local beach erosion rates primarily control the retreat of the tundra at decadal scales. However, independent of the fronting beach morphology, the largest erosion events throughout the region generally occur when there is the coincidence of both high wave energy and elevated still water levels. Additional exploratory modeling results indicate that future changes to sea level and changes in wave energy will further enhance the magnitude of tundra erosion.