Wind, Ice, and Tide Controls on the Dynamics of Mixing, Stratification, and Internal Waves in the Canadian Arctic Archipelago

Abstract

The Canadian Arctic Archipelago (CAA) plays a vital role in the global climate as a major oceanic gateway between the Arctic and Atlantic Oceans. Barrow Strait, a high-latitude, seasonally ice-covered channel with complex bathymetry, accounts for 30 – 50 % of the volume transport through the CAA and is located within the ecologically significant Tallurutiup Imanga National Marine Conservation Area. Despite its recognized importance, how waters are mixed and modified in the region remains poorly constrained. This dissertation addresses this knowledge gap by investigating the variability in stratification and wind- and tide-driven dynamics within Barrow Strait, processes widely recognized to contribute to ocean mixing and internal wave activity.

Analyses integrate in situ observations, including ocean and ice velocities, water column stratification, and sea ice draft, from four locations across the Strait spanning up to 18 years (1998 – 2011 and 2017 – 2022), together with reanalysis products, including wind velocity, surface buoyancy fluxes, and ice concentration. These datasets are complemented by idealized models, including a one-dimensional ice-ocean coupled slab model and three-dimensional sloping channel tidal simulations. In Chapter 2, a potential energy anomaly framework is used to diagnose seasonal density stratification and assess the contributions of local surface buoyancy forcing and vertical mixing. Stratification is found to be predominantly determined by local and upstream sea ice melt and growth. Chapters 3 and 4 examine the wind- and tide-driven internal wave field. Barrow Strait lies at the critical latitude of the semidiurnal tide, coupling wind-driven near-inertial waves and semidiurnal internal tides. Near-inertial motions are elongated along the channel, influenced by its geometry. They also exhibit a marked seasonal increase from July through October, arising from the kinematic effects of mixed layer depth and modulation of wind stress by sea ice. Diurnal subinertial tides are bottom-amplified during periods of westward low-frequency flow and increased stratification, while the semidiurnal near-inertial tide is strongly damped in the ice-ocean boundary layer, enhancing near-surface and bottom shear with implications for mixing. Overall, this dissertation presents an unprecedented and detailed characterization of stratification variability and of near-inertial and tidal dynamics utilizing long-term datasets within Barrow Strait.