A Mechanism of Ice-Band Pattern Formation Caused by Resonant Interaction between Sea Ice and Internal Waves: A Theory

Abstract

Ice bands are frequently observed over marginal ice zones in polar seas. A typical ice-band pattern has a regular spacing of about 10 km and extends over 100 km in the marginal ice zone. Further, the long axis of an ice band lies to the left (right) with respect to the wind direction in the Northern (Southern) Hemisphere. Here, the study shows that the resonance between ice-band pattern propagation and internal inertia–gravity waves below the sea ice well explains the ice-band pattern formation. Internal waves are generated by the difference between the stress on the open water and the stress on ice-covered water. This in turn reinforces the formation of an ice-band pattern with a regular band spacing. Specifically, the authors have found the following: 1) A band spacing on the order of 10 km is selected by the resonance condition in which the ice-band pattern propagation speed coincides with the phase speed of internal inertia–gravity waves. 2) The ice bands tend to develop favorably when the wind direction and the band propagation direction are nearly parallel. The velocity acceleration caused by the periodic differential stress associated with the ice bands, driven by the wind parallel to the band propagation direction, is important. The wind direction may turn to the left (right) slightly in the Northern (Southern) Hemisphere as a result of the Coriolis force acting on ice. Satellite images confirmed that the band spacing of the ice-band pattern in the polar seas is consistent with this theory.

Laboratory Experiments on Internal Solitary Waves in Ice‐Covered Waters

“…The parameter range investigated was limited by the scale of the facility, but nevertheless the observations show that the physical interactions of ISWs with ice could have important implications for dissipation of wave energy and consequent mixing in the polar oceans and point to the need for further more detailed investigations. Moreover, the observation that an ISW can transport ice horizontally suggests that a series of ISWs may well constitute a mechanism by which sea ice banding can occur as proposed theoretically by Saiki and Mitsudera (2016).…”

“…IWs are known to cause flexure of sea ice (Czipott et al, 1991;Marchenko et al, 2010), and theoretical studies (Muench et al, 1983;Saiki & Mitsudera, 2016) suggest they are responsible for the formation of ice bands in the marginal ice zone. The annual variation of the Arctic ice edge is monitored carefully (i) to assess climate change and (ii) for a variety of practical reasons involving sea traffic, fisheries, offshore operations, and military marine activities.…”

Multi-scale satellite observations of Arctic sea ice: new insight into the life cycle of the floe size distribution

“…Increased open water areas generate stronger ocean surface waves [ 45 ] that further fragment weakened ice floes into smaller floes [ 36 , 40 – 42 ] and the lateral melt intensifies among small floes [ 3 , 46 ] (hereafter we call this period ‘melt/wave fragmentation’). The final stage would be a complete melt out of the floes in the presence of ice bands [ 47 , 48 ]. In this study, we hypothesize that the seasonal life cycle of the floe size distribution can be conceptualized in three stages: fracturing, transition and melt/wave fragmentation and each stage of the life cycle has unique floe size distribution characteristics across scales.…”

Interactions Between Internal Solitary Waves and Sea Ice

“…Lamb (1997) used weakly nonlinear ISW models to analyze how small particles ( L f ≪ λ , where L f is float length, and λ is wavelength) at the surface would be transported by ISWs. At larger scales relevant to sea ice, horizontal gradients in ISW‐induced vertical velocity has been observed causing the flexure of sea ice in the field (Czipott et al., 1991; Marchenko et al., 2010) and the ice banding effect in the marginal ice zone has also been theoretically attributed to IW activity (Muench et al., 1983; Saiki & Mitsudera, 2016). This indicates that ISWs are capable of inducing movement of sea ice on the order of the ice floe length scales, and here, laboratory experiments are used alongside fully nonlinear models to investigate both small and much larger floating structures.…”