Multi-scale temperature variability in the Arctic Mediterranean between 1958 to 2023 – from surface to abyss 

The temperature of the Arctic Ocean and adjacent areas has increased over recent decades and is expected to continue to increase through this century. Discrepancies between previous studies based on different periods, domains, and datasets suggest that the warming of the Arctic Ocean is nonlinear and characterized by large temporal and spatial variability. The behavior of this warming signal has numerous local effects on aspects from sea ice cover and surface fluxes to ecosystems, all of which react differently to linear warming compared to episodic warming events. The spatiotemporal warming pattern will also play a role in defining the product of dense-water formation in the region, which feeds into the lower limb of the Atlantic Meridional Overturning Circulation. Utilizing the ORAS5 reanalysis, the Arctic Subpolar gyre sTate Estimates, as well as in-situ observations, we present an overview of the warming of the Arctic Ocean and the Nordic Seas between 1958 and 2023. We shed light on the variability of trends and seasonal signals across the Arctic Ocean, from surface to abyss. This analysis provides a solid baseline for detecting regional changes in the mean state and variability of the Arctic Ocean with global warming and exploring the physical mechanisms causing the warming trend. As such, it will be key for grounding investigations of future changes in heat budgets for the Arctic Ocean and the Nordic Seas.