Sea ice thickness affects a wide range of processes in the Arctic, but remains poorly constrained by observations. This study focuses on the northwestern Barents Sea, an area where sea ice is highly variable and affected both by local processes and ice transport from the adjacent Central Arctic Ocean. Satellite-derived sea ice age and back-trajectories indicate that sea ice was transported from the Central Arctic Ocean into the northwestern Barents Sea during 7 of 15 ice seasons between 2009–2024. Three of these seasons (2019–2021) coincided with moored in situ sea ice draft observations in the area. In these seasons, the arrival of ice from the Central Arctic Ocean coincided with a local transition to thicker and more uniform ice – a seasonal evolution that could not be explained by local thermodynamic forcing alone. Satellite-derived sea ice thickness and modelled thermodynamic ice growth along back-trajectories indicate that the Central Arctic-origin ice grew along its pathway within the Transpolar Drift, and had acquired its thickness before entering the Barents Sea. While intermittent at the study area, an advection-driven shift to thicker and older ice between February and June occurs at the margin between the Barents Sea and the Nansen Basin in the 2011–2023 climatology. The driver appears to be a seasonal progression of the atmospheric pressure configuration over the Atlantic sector of the Arctic Ocean. Large-scale patterns of sea ice transport are a key control on the pronounced interannual variability of summer sea ice thickness in the region, with implications across the marine system.