Thesis or Dissertation A mechanism of ice-band pattern formation caused by resonant interaction between sea ice and internal waves [an abstract of entire text]

佐伯, 立

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 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 we show 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, as well as the difference in the angle between these stresses. This in turn reinforces to form ice band pattern with a regular band spacing. Using a 1.5-layer model we have specifically found that: 1. A band spacing on the order of 10 km is selected for 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. A continuously stratified ocean model, coupled with an sea-ice model, is also used to examine the above theoretical results. Satellite images also confirmed that the band spacing of the ice-band pattern in the polar seas is consistent with this theory and numerical results.
Hokkaido University(北海道大学). 博士(環境科学)

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