Spectral attenuation of ocean waves in pack ice and its application in calibrating viscoelastic wave-in-ice models
<p>We investigate a case of ocean waves through a pack ice cover captured by Sentinel-1A synthetic aperture radar (SAR) on 12 October 2015 in the Beaufort Sea. The study domain is 400 km by 300 km, adjacent to a marginal ice zone (MIZ). The wave spectra in this domain wer...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-06-01
|
| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/14/2053/2020/tc-14-2053-2020.pdf |
| Summary: | <p>We investigate a case of ocean waves through a pack ice
cover captured by Sentinel-1A synthetic aperture radar (SAR) on 12 October 2015 in the Beaufort Sea. The study domain is 400 km by 300 km, adjacent to a
marginal ice zone (MIZ). The wave spectra in this domain were reported in a
previous study (Stopa et al., 2018b). In that study, the authors divided the
domain into two regions delineated by the first appearance of leads (FAL)
and reported a clear change of wave attenuation of the total energy between
the two regions. In the present study, we use the same dataset to study the
spectral attenuation in the domain. According to the quality of SAR-retrieved wave spectrum, we focus on a range of wave numbers corresponding to
9–15 s waves from the open-water dispersion relation. We
first determine the apparent attenuation rates of each wave number by pairing
the wave spectra from different locations. These attenuation rates slightly
increase with increasing wave number before the FAL and become lower and more
uniform against wave number in thicker ice after the FAL. The spectral
attenuation due to the ice effect is then extracted from the measured
apparent attenuation and used to calibrate two viscoelastic wave-in-ice
models. For the Wang and Shen (2010b) model, the calibrated equivalent shear
modulus and viscosity of the pack ice are roughly 1 order of magnitude
greater than that in grease and pancake ice reported in Cheng et al. (2017).
These parameters obtained for the extended Fox and Squire model are much
greater, as found in Mosig et al. (2015) using data from the Antarctic MIZ.
This study shows a promising way of using remote-sensing data with large
spatial coverage to conduct model calibration for various types of ice
cover.<br/><br/><strong>Highlights.</strong> Three key points:
</p><ol><li>
<p id="d1e139">The spatial distribution of wave number and spectral attenuation in pack ice
are analyzed from SAR-retrieved surface wave spectra.</p></li><li>
<p id="d1e143">The spectral attenuation rate of 9–15 s waves varies around
10<span class="inline-formula"><sup>−5</sup></span> m<span class="inline-formula"><sup>2</sup></span> s<span class="inline-formula"><sup>−1</sup></span>, with lower values in thicker semicontinuous ice fields
with leads.</p></li><li>
<p id="d1e180">The calibrated viscoelastic parameters are greater than those found in
pancake ice.</p></li></ol> |
|---|---|
| ISSN: | 1994-0416 1994-0424 |