Pancake sea ice kinematics and dynamics using shipboard stereo video

Abstract

In the marginal ice zone, surface waves drive motion of sea ice floes. The motion of floes relative to each other can cause periodic collisions, and drives the formation of pancake sea ice. Additionally, the motion of floes relative to the water results in turbulence generation at the interface between the ice and ocean below. These are important processes for the formation and growth of pancakes, and likely contribute to wave energy loss. Models and laboratory studies have been used to describe these motions, but there have been no in situ observations of relative ice velocities in a natural wave field. Here, we use shipboard stereo video to measure wave motion and relative motion of pancake floes simultaneously. The relative velocities of pancake floes are typically small compared to wave orbital motion (i.e. floes mostly follow the wave orbits). We find that relative velocities are well-captured by existing phase-resolved models, and are only somewhat over-estimated by using bulk wave parameters. Under the conditions observed, estimates of wave energy loss from ice–ocean turbulence are much larger than from pancake collisions. Increased relative pancake floe velocities in steeper wave fields may then result in more wave attenuation by increasing ice–ocean shear.

SAR image wave spectra to retrieve the thickness of grease-pancake sea ice using viscous wave models

“…For γ 7, the pancake layer becomes essentially inextensible. Field measurements by 39 support the modelling assumption. In general, the pancake layer acts as an additional source of tangential stress on the grease ice The dispersion relation for the model is obtained by imposing continuity of the stresses at the interface between the layers.…”

Three-dimensional imaging of waves and floe sizes in the marginal ice zone during an explosive cyclone

“…Images were recorded with resolution 2448×2048 pixels and a sampling rate 2 Hz during daylight on the 4th July (from 07:00 to 14:00 UTC). Acquisition was performed over ≈ 30 mins intervals (≈ 6 times longer than Smith and Thomson [24]).…”

“…1c). The WASS system captures ≈ 150 m×200 m snapshots of the ocean surface (≈ 5 times larger than Smith and Thomson [24]). The system operated from 07:00 to 14:00 UTC but images acquired in the early hours of the day (07:00-08:00 UTC) lacked contrast and light to reconstruct sea surface elevation.…”

“…To date, use of stereo-imaging techniques for wave measurements in sea ice has been limited in scope. Campbell et al [23] and Smith and Thomson [24] both use stereo-camera systems to derive one-dimensional wave spectra and bulk wave properties (peak periods and significant wave heights) from images over small domains (order 100 m 2 ) for small waves propagating through pancake ice. Campbell et al [23] use a camera system on a fixed platform on the edge of a lake, whereas Smith and Thomson [24] use a camera system on a moored vessel in the Arctic MIZ, and hence have to correct the images for wave-induced ship motions.…”

Identification of large-scale sea ice ridge areas in the Arctic using ASCAT data

“…о возможности идентификации крупномасштабных областей всторошенного льда… часто образующихся при формировании льда из начальных его видов в условиях сильного волнения ). В полыньях такое волнение маловероятно (Smith, Thomson, 2019), а вот в прикромочной ледовой зоне разделение возможных причин повышения яркости требует анализа временной изменчивости полей УЭПР.…”