Abstract: The warm Pacific Summer Water (PSW) is one of the important factors impacting sea ice in the Canada Basin. In summer, the temperature of the PSW was found to be highly correlated with sea ice concentration, indicating that it provided heat to promote ice melting. In winter, the heat release process of the PSW and its impact on winter sea ice need further research. Base on the hydrographic profiles collected by the Ice Tethered Profilers in Canada Basin, we analyzed the relationship between heat release from the PSW layer into the mixed layer and its impact on sea ice during winter. We found that heat restored in the PSW layer can be entrained into the mixed layer thought Ekman upwelling, resulting in an increase in mixed layer heat content. This process, when combined with intense ice-ocean interface friction, results in a rise in the under-ice oceanic heat flux, interrupting heat balance at ice bottom and impeding sea ice growth. The occurrence of strong heat release events in 2013, 2016 and 2021 coincided with thinner ice in those years. What’s more, the PSW is over 0.5 °C warmer than previous state since 2019, in the meantime, there is a significant increase on the winter Ekman upwelling induced entrainment heat flux and under-ice oceanic heat flux during the period from 2019 to 2023 compared to previous period from 2005 to 2018, with the regional averages rising from 0.9 W/m² to 1.6 W/m², and 1.1 W/m² to 2.4 W/m², respectively. The regional average value corresponding to the reduction in the growth rate of sea ice due to the under-ice oceanic heat flux has increased from 4×10⁻⁹ m/s to 1.0×10⁻⁸ m/s. More vertical heat mixing would be triggered with the prominently warmer PSW under the same external forces such as atmospheric forcing and sea ice motion, exerting bigger influence on winter sea ice mass balance.