Changes in Internal Wave‐Driven Mixing Across the Arctic Ocean: Finescale Estimates From an 18‐Year Pan‐Arctic Record

The Arctic climate is changing rapidly, with dramatic sea ice declines and increasing upper‐ocean heat content. While oceanic heat has historically been isolated from the sea ice by weak vertical mixing, it has been hypothesized that a reduced ice pack will increase energy transfer from the wind into the internal wave (IW) field, enhancing mixing and accelerating ice melt. We evaluate this positive ice/internal‐wave feedback using a finescale parameterization to estimate dissipation, a proxy for the energy available for IW‐driven mixing, from pan‐Arctic hydrographic profiles over 18 years. We find that dissipation has nearly doubled in summer in some regions. Associated heat fluxes have risen by an order of magnitude, underpinned by increases in the strength and prevalence of IW‐driven mixing. While the impact of the ice/internal‐wave feedback will likely remain negligible in the western Arctic, sea‐ice melt in the eastern Arctic appears vulnerable to the feedback strengthening. Plain Language Summary The Arctic is changing rapidly, with dramatic declines in sea ice and warming of upper‐ocean waters. Historically, weak ocean mixing has prevented the melting of sea ice by oceanic heat. Scientists have hypothesized that as sea ice melts and open water is exposed to the wind, more energetic internal waves will result. These waves cause mixing in the upper ocean, which can bring heat upwards to the surface and melt more sea ice, thus creating a positive feedback loop. To test the importance of this feedback, we use ocean measurements to estimate “dissipation,” a proxy for the internal wave energy that is available to cause mixing. The measurements cover much of the Arctic Ocean for the years 2002–2019. We find that dissipation has increased during summer in recent years. Summer heat transport toward the sea ice has also increased, on average by a factor of 10, as internal wave‐driven mixing became stronger and more prevalent. We estimate that the western Arctic is unlikely to experience significant future sea‐ice melt due to this positive feedback; however, the eastern Arctic may be vulnerable to accelerated sea‐ice melt as increases in dissipation continue. Key Points Dissipation in the central Arctic has nearly doubled in summer while declining in winter; no interannual trends are found in any region Summer heat flux in the central Arctic has risen by an order of magnitude due to stronger and more prevalent internal wave‐driven mixing The eastern Arctic appe