Past polar sea ice variability Sea ice is a fundamental component of the Earth's climate system. Changes in sea ice extent and thickness have a strong influence on albedo, the hydrologic cycle, ocean and [...] diatoms (diatoms) to reconstruct sea ice cover. Projects Arctic Ocean Arctic Ocean mean sea ice concentration (Graphic: NSIDC) Southern Ocean Southern Ocean mean sea ice concentration (Graphic: NSIDC) [...] and, more recently, biomarker-based reconstruction of sea ice, which provides important information on: natural (non-anthropogenically induced) sea ice variability and associated climate variability; Changes