Thermokarst is a land surface characterised by very irregular surfaces of marshy hollows and small hummocks formed as ice-rich permafrost thaws, that occurs in Arctic areas, and on a smaller scale in mountainous areas such as the Himalayas and the Swiss Alps.
Walter's research focuses on methane and carbon dioxide emissions from arctic and temperate lakes and wetlands in Alaska and Siberia, and the processes involved in greenhouse gas emissions from lakes, including thermokarst (permafrost thaw), industrial plant emissions, geology, and changes in lake area.