Contents lists available at ScienceDirect Applied Ocean Research journal homepage: www.elsevier.com/locate/apor An experimental study of gravity waves through segmented foating viscoelastic covers Dharma K.K. Sree a,b , Adrian Wing-Keung Law a,b, ⁎ , Hayley H. Shen a,c a Environmental Process Modelling Centre (EPMC), Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, 1 CleanTech Loop, CleanTech One, #06-08, Singapore 637141 b School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 c 132 Rowley Laboratories, Civil and Environmental Engineering, Clarkson University, Potsdam, NY, USA 13699-5710 ARTICLE INFO Keywords: Viscoelastic PDMS Wave dispersion Attenuation Segmented foating covers ABSTRACT With climate changes and global warming, the extent of Marginal Ice Zone (MIZ) in the polar region is widening, and there is now more research attention on the wave interactions with broken ice covers within the zone to gain insights into its future sea conditions. Towards this objective, the dispersion and attenuation of surface waves propagating through segmented foating viscoelastic covers was investigated experimentally in this study. The covers were made of oil-doped Polydimethylsiloxane (PDMS) material, with diferent curing agent percentages to vary their rheological properties. For stifer covers, the measurements showed that the efect of segmentation on wavelength modifcation was signifcant, and the dispersion relation agreed generally with the existing theoretical predictions for discrete foating elastic segments despite the presence of the additional viscosity for the material. At the same time, the earlier empirical formula based on the concept of “equivalent rigidity” to represent the segmented elastic cover, did not work well for the conditions investigated. With more fexible covers, however, the efect of segmentation became insignifcant for thin cover thickness. Given the present experimental conditions, we confrmed that the efect of scattering was negligible, and the wave attenuation should be attributed to the various dissipative mechanisms. An empirical relation for the attenuation was es- tablished based on the experimental results, to quantitatively relate the attenuation coefcient to the incident wave characteristics and cover properties. The relation identifes a signifcant inverse relationship with the viscosity of cover material, and thus confrms the essential role of viscoelastic representation for the attenuation predictions. 1. Introduction With climate changes and global warming, foating ice covers in the polar region are thinning and are more prone to break up. The possi- bility is now increasing that new sea routes through the Arctic Ocean would appear in the coming decades [1,2], adjacent to or through the extremely dynamic transitional zone with broken ice covers i.e. the Marginal Ice Zone (MIZ) which is the region between the open water and continuous ice cover. Although the extent of MIZ varies during the year, records had already shown that the width had increased by 39% during the summer for the past three decades with also increasing amounts of thinner and thus weaker sea ice [3]. Within the MIZ, diverse ice covers exist, from fragmented ice sheets to grease/pancake ice [4,5]. The type of ice cover governs how waves evolve within (in terms of directional energy redistribution), and also disperse and attenuate after passage. A better understanding on the wave-ice interactions with segmented foating covers is hence desirable to aid the future predictions of the polar sea conditions. In particular, feld observations had shown various complex patterns regarding wave attenuation. Stopa et al. [6] used SAR imagery to determine the wave attenuation over a 400 km stretch of ice cover in the MIZ and found signifcant variations with diferent ice conditions. A strong correlation between the ice cover type and attenuation profle was also observed in the feld data by Rogers et al. [7]. To reduce the complexity, attempts had been made to construct simplifed theoretical and laboratory models based on a few signifcant factors. These simplifed models can then be implemented in global wave models, such as WAVEWATCH III, to improve the forecasts for ice-covered seas. Rogers et al. [8] provided detailed discussion of the current state-of-the-art of the performance of various wave-in-ice models against feld data in the MIZ. Sea ice models for the MIZ could be broadly classifed into con- tinuum models and discrete foe models [9–11]. Continuum models https://doi.org/10.1016/j.apor.2020.102233 Received 26 October 2019; Received in revised form 22 April 2020; Accepted 27 May 2020 ⁎ Corresponding author. E-mail address: cwklaw@ntu.edu.sg (A.W.-K. Law). Applied Ocean Research 101 (2020) 102233 0141-1187/ © 2020 Elsevier Ltd. All rights reserved. T