Rapid coastal erosion of ice-bonded deposits on Pelly Island, southeastern Beaufort Sea, Inuvialuit Settlement Region, western Canadian Arctic

Abstract

This paper quantifies rates of shoreline change and investigates the influence of surficial geology on shoreline dynamics between 1950 and 2018 on Pelly Island, located 10 km off the Mackenzie Delta. Long-term changes in shoreline position were calculated using imagery analysis and Analysing Moving Boundaries Using R (AMBUR). The influence of shoreline exposure to predominant storm direction and influence of surficial geology were examined for Northwest and Southeast zones. The average annual linear regression rate (LRR) rate during the 1950-2018 observation period was -3.8 m∙a-1. The end point rate (EPR) was calculated for six observation periods: 1950-1972, 1972-1985, 1985-2000, 2000-2018, 2013-2018. A mean EPR of -5.5 ± 0.7 m∙a-1 was calculated for the 2000-2018 period, and a maximum retreat rate of 46.7 ± 2.1 m∙a-1 was recorded during the 2013-2018 observation period. By comparing the rate of change for sections of historical shorelines with differing surficial geology and exposure to storms, it was possible to draw conclusions on why Pelly Island continues to have the highest retreat rates in the Mackenzie-Beaufort region. Greater retreat rates were observed in lacustrine deposits (5.3 m∙a-1) compared to moraine deposits (2.7 m∙a-1). In addition, shoreline exposure to the predominant storm direction from the Northwest was found to be a major influence on rates of shoreline change in all observation periods.