CRYOSPHERE | Sea Ice

Abstract

Sea ice is any form of ice found at sea that originated from the freezing of seawater. It is the most visible feature of the polar seas, with its extent waxing and waning with the seasons. Ice thickness is highly variable, ranging from a thin veneer to tens of meters. While the existence of sea ice reflects the cold conditions inherent to high latitudes, sea ice also strongly modulates the energy budget and climate of the polar seas and beyond, particularly because of its high albedo and through acting as a lid, insulating the underlying ocean from a generally much colder atmosphere. Sea ice extent and thickness are in turn influenced by changing climate conditions. Arctic sea ice extent and thickness as observed at the end of the melt season have declined significantly over the past several decades. In contrast, Antarctic sea ice extent has expanded slightly.