The Arctic Realm is rapidly changing at a pace exceeding the average rate of the ongoing global warming. Particularly sensitive to this change is the cryosphere, including both Arctic sea ice, glaciers and the Greenland Ice Cap. Melting of ice has large impact on the radiative energy budget and sea level. At the same time, the meltwater discharge may affect oceanic circulation. Many of these processes and feedbacks operate on time scales too long for instrumental observations and the sensitivities and natural variation in key Earth System Components in the Arctic can be best studied on natural experiments from the geological past. In this session, we invite contributions from a range of disciplines and across time scales, including observational data, proxy data, model simulations and forecasts. The common denominator of these studies will be their focus on a better understanding of the involved processes and their impacts.