The role of waves in the autumn Arctic Ocean

• Main Author: Smith, Madison
• Other Authors: Thomson, Jim
• Format: Thesis
• Language: English
• Published: 2019
• Subjects: Arctic Ocean; sea ice; surface waves; Physical oceanography; Geophysics; Civil engineering; Arctic; Pancake; Beaufort Sea; Sea ice
• Online Access: http://hdl.handle.net/1773/44760

Thesis (Ph.D.)--University of Washington, 2019 Recent decline of sea ice coverage in the Arctic Ocean has resulted in a substantial seasonal wave climate. Waves generated in the open water are attenuated far into the sea ice, but are a defining feature of the marginal ice zone (MIZ). In autumn, waves in the MIZ can be large due to the significant open water area following the minimum ice extent. Waves are expected to affect ice cover development through both kinematic and thermodynamic processes. In this research, I use observations from 2015 in the Beaufort Sea region to improve understanding of key feedbacks between waves and sea ice, and describe implications for autumn ice formation. In the MIZ, where surface waves are often present, much of the ice forms through the 'pancake cycle'. Gradients in wave orbital velocities across the surface cause small ice crystals to be herded into increasingly larger, rounded floes. Modeling the relative motion between ice floes is the basis for describing pancake ice growth, as well as the attenuation of wave energy associated with their motion. Here, existing models for ice motion and growth are evaluated using coincident measurements of waves and pancake sea ice made using shipboard stereo video. The observations are well captured by existing models, and relative velocities of floes are typically small compared to the mean orbital velocities. The models for relative motion of pancake sea ice due to waves can be subsequently used to estimate attenuation of wave energy due to floe motion. Under the conditions observed, estimates of wave energy loss from ice-ocean turbulence are much larger than those from pancake collisions, and can account for most of the observed wave attenuation. In addition to the general trends of sea ice growth in the Arctic in autumn, ice edge advance can be temporarily reversed as a result of upper ocean mixing by wind and waves. Observations during a high wind and wave event demonstrate how heat released from the upper ocean can melt significant ...