This work package deals with what lies below the surface and adds a long-term perspective to the processes studied in the other work packages. Past variability of the Arctic climate and environment is reconstructed through the analyses of geological archives such as marine sediment cores, acoustic surveying data, and climate models. The focus is on past changes in ocean circulation, temperature, salinity, and sea ice cover, as well as ice sheet dynamics and the interactions between them. These studies are based on a wide variety of methods, including geochronology (radiocarbon dating and event stratigraphy), micropaleontology (study of fossil diatoms and foraminifera), geophysics (modelling, sea floor mapping, and sub-bottom imaging), sedimentology (grain size and physical properties), and geochemistry (organic biomarkers and mineralogy). In addition to this focus on Arctic paleoclimatology and paleoceanography, this work package also covers subjects ranging from geomicrobiology and the study of pollutants, including their pathways and fate in the geological record.