Abstract
We provide the first in situ observations of floe size distributions (FSD) resulting from wave-induced sea ice break-up. In order to obtain such data, an unmanned aerial vehicle was deployed from the Canadian Coast Guard Ship Amundsen as it sailed in the vicinity of large ice floes in Baffin Bay and in the St. Lawrence Estuary, Canada. When represented as probability density functions weighted by the surface of ice floes, the FSDs exhibit a strong modal shape which confirms the preferential size hypothesis debated in the scientific community. Both FSDs are compared to a flexural rigidity length scale, which depends on ice properties, and with the wavelength scale. This comparison tends to show that the maximal distance between cracks is preferentially dictated by sea ice thickness and elasticity rather than by the wavelength. Temporal analysis of one fracture event is also done. Results show that the break-up advances almost as fast as the wave energy and that waves responsible for the break-up propagate following the mass loading dispersion relation. Moreover, our experiments show that thicker ice can attenuate wave less than thinner ice. This method thus provides key information on the wave-induced FSD, clarifies theoretical aspects from the construction of the FSD to its implementation in models and brings new knowledge regarding the temporal evolution of sea ice break-up.
Highlights
The marginal ice zone (MIZ) is the ice-covered region that is affected by waves, usually found in the periphery of the polar 15 and subpolar oceans
In order to obtain such data, an unmanned aerial vehicle was deployed from the Canadian Coast Guard Ship Amundsen as it sailed in the vicinity of large ice floes in Baffin Bay and in the St
When represented as probability density functions weighted by the surface of ice floes, the floe size distributions (FSD) exhibit a strong modal shape which confirms the preferential 5 size hypothesis debated in the scientific community
Summary
The marginal ice zone (MIZ) is the ice-covered region that is affected by waves, usually found in the periphery of the polar 15 and subpolar oceans. 55 Large-scale spectral WIMs (Dumont et al, 2011; Williams et al, 2013a, b; Zhang et al, 2016; Bennetts et al, 2017; Boutin et al, 2018; Bateson et al, 2020; Boutin et al, 2020) use a power-law FSD to estimate sea ice morphological properties such as the mean floe size Such statistical moments are dependent on the shape of the FSD and are further used to parameterize numerous MIZ processes, namely wave-induced break-up. Observations of sea ice break-up by waves in the natural environment are needed to test the flexural rigidity-dependent preferential size hypothesis and to better understand the overall FSD generated by this process Determining such details from observations would help to develop physically-based parameterizations of wave-induced break up in WIMs. 100 Few studies about break-up have been made yet mainly because the MIZ is an arduous area to sample directly from.
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