Arctic Land-Ocean Interactions - Permafrost land-ocean interactions in the Arctic: from coastal to submarine permafrost including gas hydrates

Abstract

Most Arctic coasts are permafrost coasts. There is regional evidence in northern Alaska and the Laptev Sea area for recent acceleration in the rate of coastal erosion. This is related in part to more open water and higher wave energy due to reduced sea ice coverage, rising sea level, and more rapid thermal abrasion along coasts with high volumes of ground ice. Nearshore zones are a sensitive source and temporary storage for terrigenous matter inputs onto the shelves via coastal erosion, river discharge, and sea ice. Recent flux estimates of sediment and organic carbon from coastal erosion into the Arctic Ocean are around 430 Tg (Tg = 10^12 gram) sediment per year and 4.9-14.0 Tg organic carbon per year. However, the fate of the terrestrial material, the contribution to greenhouse gas emissions and ocean acidification, and the impact on nearshore ecosystems is poorly constrained. As sea levels in the Arctic continue to rise, warming ocean water and seawater intrusion enhance the degradation of submarine permafrost. Submarine permafrost is thought to act as a barrier to rising gases from depth, thus, as permafrost degrades, it allows the release of methane gas from dissociating gas hydrates into the water column. Because the Arctic coastal waters are very shallow, escaping greenhouse gases may pass through the water column, and enter the atmosphere directly. Apart from regional to global consequences of a changing environment along Arctic coasts, immediate local implications for coastal communities and indigenous peoples are becoming more apparent. Nearshore ecosystems located in traditional hunting and fishing grounds might be impacted by high loads of sediments and nutrients released from eroding coasts. Coastal retreat leads to a loss of natural habitat for flora and fauna and of cultural heritage from the early explorers and indigenous peoples. In the Arctic coastal zone, the impacts of environmental change on local communities, on ecosystem services, and socioeconomic dynamics have not been quantified yet.