Sea-Ice mediated beach ridge development along the Hudson Bay lowland coast

Abstract

Satellite remote sensing is used here to examine the development of sequences of raised beach ridges, composed of gravel and rock, that form the characteristic stripes roughly parallel to the shoreline, an integral part of the emerging landscape of the Hudson Bay Lowlands (HBL). A novel observation is that beach ridge formation is initiated in the intertidal zone on the marine tidal flats and then ridges physically grow while migrating towards the shore up to 1 km over 20 years due to the impact of sea-ice bulldozing. Observations reveal significant changes over the 2000 to 2020 period in the ridges located on the tidal flats in their areas, lengths, and locations relative to the coastline. Repeated interaction between sea ice, forced by tides and wind, and the ridges resulted in a gradual build-up of sedimentary material, which increased individual ridge areas between 0.04 and 0.77 km2 over the 20 years. The ridges also underwent a significant increase in length, the dimension roughly parallel to the shore, by 0.3 to 2.8 km net change over 20 years. The rate of shoreward migration of ridges was found to be inversely related to their change in area and length. Coupled with the isostatic uplift of the landmass, the ridges eventually stabilize on the coast, whereafter they become impervious to further modification by sea ice and play a long-term role in the development of the salt marshes, wetlands, and peatlands that characterize the HBL landscape.