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Abstract

The Barents-Kara region is an Arctic warming hotspot. It has experienced increased water column and lower troposphere temperatures, pronounced sea ice loss, and ecosystem change. Ocean stratification here is a pertinent focus for study: the strength of density stratification controls vertical mixing and the fluxes of quantities, including heat and salt, which determine the properties (temperature, salinity, and density) of water throughout the water column. At the surface, these properties influence sea ice processes and heat loss to the atmosphere in a region ostensibly linked to Northern Hemisphere mid-latitude weather. More generally, they govern the characteristics and behaviour of water masses, undergoing transformation in the BKS, that participate in Arctic and North Atlantic circulation. We use the potential energy anomaly (PEA), a metric of density stratification, to investigate changes in the region from 1993 to present day. Representing the energy required to hypothetically mix stratified water to vertical homogeneity (strongly stratified water columns require more energy to mix), PEA is calculated spatio-temporally from the ARMOR-3D reanalysis product. The rate of change of PEA with time can be expressed as the sum of contributions from physical processes that increase stratification (e.g., surface heating and sea ice melting) or decrease it (e.g., wind-driven mixing and tidal stirring), each of which can be computed from reanalysis products or model outputs. We thus determine the processes dominating BKS stratification and identify those driving long-term trends in parts of the region. Implications for ocean-atmosphere coupled interactions, water masses, and broader circulation are discussed.