Turbulent Mixing in a Changing Arctic Ocean

Abstract

Historically, the Arctic Ocean has been considered an ocean of low variability and weak turbulent mixing. However, the decline in seasonal sea ice cover over the past couple of decades has led to increased coupling between the atmosphere and the ocean, with potential enhancement of turbulent mixing. Here, we review studies that allow identifying energy sources and pathways that lead to turbulent mixing in an increasingly ice-free Arctic Ocean. We find that the evolution of wind-generated, near-inertial oscillations is highly sensitive to the seasonal sea ice cycle, but the response varies greatly between the continental shelves and the abyssal ocean and between the eastern and western ocean basins. There is growing interest in the role of tides and continental shelf waves in driving mixing over sloping topography. Both dissipate through the development of unsteady lee waves. The role eddies play in transporting shelf water into the basins and in supporting mixing has become more apparent as technological advances have permitted higher resolution observations of sea ice retreat. The importance of the dissipation of unsteady lee waves and of eddies in driving mixing highlights the need for parameterizations of these phenomena in regional ocean models and climate simulations.

A Synthesis of the Upper Arctic Ocean Circulation During 2000–2019: Understanding the Roles of Wind Forcing and Sea Ice Decline

“…It was also found that only about 20% of the increased Atlantic Water concentration above the 34.8 isohaline in the Eurasian Basin can be attributed to the Fram Strait branch (Wang et al, 2019b). Therefore, although sea ice decline can increase vertical mixing (e.g., Rainville and Woodgate, 2009;Polyakov et al, 2020b;Rippeth and Fine, 2022), thus increasing halocline salinity through mixing saline Atlantic Water upwards, this process is not the major contribution to the salinification of the halocline in the Eurasian Basin. In addition, the positive salinity anomaly in the Barents Sea induced by sea ice decline could contribute to the positive salinity anomaly in the eastern Eurasian Basin too, but the larger salinity anomaly associated with sea ice decline in the eastern Eurasian Basin than in the upstream Barents Sea implies that this contribution is small (Figure 12F).…”

Winter Vertical Diffusion Rates in the Arctic Ocean, Estimated From 7Be Measurements and Dissipation Rate Profiles

“…The highly intermittent nature of turbulence requires both long sampling periods to obtain representative average values, and a high sampling frequency to capture short-term variability in response to environmental forcing. Especially in the rapidly changing Arctic, repeated sampling campaigns are necessary to assess the response of turbulent transport to climate change, as vertical mixing in the Arctic Ocean is expected to increase in response to trends in the environmental conditions, with implications for the future maintenance of sea ice and Arctic Ocean primary production (e.g., Rippeth & Fine, 2022). The method comparison presented in this paper was initiated by Dr. David Kadko.…”

Atlantic Water Boundary Current Along the Southern Yermak Plateau, Arctic Ocean

“…The high‐frequency variability is beyond the scope of this study. Peterson (2017) and Wang et al. (2022), have described the near‐inertial and the tidal variability, respectively, using the data from the moorings used here.…”