Poleward ocean heat transport is a key process in the earth system. We detail and review the northward Atlantic Water (AW) flow, Arctic Ocean heat transport and heat loss to the atmosphere since 1900, in relation to sea ice cover. Our synthesis is largely based on a sea ice-ocean model forced by a reanalysis atmosphere (1900-2018) corroborated by a comprehensive hydrographic database (1950-), AW inflow observations (1996-), and key long-term time series. The Arctic Seas, including the Nordic and Barents Seas, have warmed since the 1970s, especially on the shelves. This warming is congruent with increased ocean heat transport and sea ice loss, and has contributed to the retreat of marine terminating glaciers on Greenland. Heat loss to the atmosphere is largest in the Nordic Seas (60% of total): with large variability linked to the frequency of Cold Air Outbreaks and cyclones in the region, but the long-term positive trend is small. Heat loss from the Barents Sea (~30%) and Arctic Seas farther north (~10%) is overall smaller, but have large positive trends. The AW inflow, heat loss to the atmosphere, and dense outflow have thus all increased since 1900. These are consistently related through theoretical scaling, but the AW inflow increase is also wind-driven. The Nordic, Barents and other Arctic Seas CO2 uptake constitutes ~8% of the global uptake and seems largely driven by heat loss. This uptake has increased by ~30% over the last century - consistent with Arctic sea ice loss allowing more regional air-sea interaction.