Observations of surface waves interacting with ice using stereo imaging

Abstract

A powerful Automated Trinocular Stereo Imaging System (ATSIS) is used to remotely measure waves interacting with three distinct ice types: brash, frazil, and pancake. ATSIS is improved with a phaseonly correlation matching algorithm and parallel computation to provide high spatial and temporal resolution 3-D profiles of the water/ice surface, from which the wavelength, frequency, and energy flux are calculated. Alongshore spatial frequency distributions show that pancake and frazil ices differentially attenuate at a greater rate for higher-frequency waves, causing a decrease in mean frequency. In contrast, wave propagation through brash ice causes a rapid increase in the dominant wave frequency, which may be caused by nonlinear energy transfer to higher frequencies due to collisions between the brash ice particles. Consistent to the results in frequency, the wavelengths in pancake and frazil ices increase but decrease in brash ice. The total wave energy fluxes decrease exponentially in both pancake and frazil ice, whereas the overall energy flux remain constant in the brash ice due to thin layer thickness. The spatial energy flux distributions also reveal that wave reflection occurs at the boundary of each ice layer, with reflection coefficient decaying exponentially away from the ice interface. Reflection is the strongest at the pancake/ice-free and frazil/brash interfaces and the weakest at the brash/ice-free interface. These high resolution observations measured by ATSIS demonstrate the spatially variable nature of waves propagating through ice.

Airborne Remote Sensing of Wave Propagation in the Marginal Ice Zone

“…Direct measurement of requires spatio‐temporal measurements of the sea surface which remain technically difficult to make, particularly over the range of scales typically present at the sea surface. Current efforts are largely focussed on stereo imaging (e.g., Benetazzo, ; Campbell et al, ) and X‐band radar (e.g., Campana et al, ; Young et al, ), but both types of measurement have challenges regarding scale and/or interpretation. Instead it is more common to make measurements of projections of .…”

Pancake sea ice kinematics and dynamics using shipboard stereo video

“…Observations of pancake ice in the Central Arctic basin have become more commonplace with seasonal sea ice retreat in recent years (Thomson and others, 2018). Pancake ice has also been observed in large bodies of freshwater, including a number of northern lakes and rivers (e.g., Rumer and others, 1979; Campbell and others, 2014).…”

In situ measurements of an energetic wave event in the Arctic marginal ice zone

“…The wave effects on ice are mostly mechanical in nature: flexing and fracturing of continuous ice and floes, calving of ice edges, convergence or divergence of ice fields, and forcing collisions between floes [ Wadhams , ; Squire , , and references within]. Ice is often heterogeneous in nature and varied in form which greatly impacts wave‐ice interaction [e.g., Campbell et al ., ].…”