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海氷漂流と内部波伝播の共鳴相互作用によるアイスバンドパターン形成
佐伯, 立;三寺, 史夫;馬目, 歩美;木村, 詞明;浮田, 甚郎;豊田, 威信;中村, 知裕
Permalink : http://hdl.handle.net/2115/91745
JaLCDOI : 10.14943/lowtemsci.82.195
KEYWORDS : アイスバンド;海氷;内部波;共鳴相互作用;連続成層;ice band;sea ice;internal wave;resonant interaction;continuously stratification
Abstract
氷縁域は海氷の融解・再凍結を通して地球規模の気候変動に敏感であるといえる. アイスバンドのパターン形成は氷縁における現象の一つであり, 帯状のバンドパターンの短軸方向に10km程度の規則的間隔で数100km以上連なり, バンドパターンの長軸は風向きに対して反時計回りに傾くという特徴を持つ. これまでその理由については未解明であったが本研究では簡単な1.5層の理論モデルを使って海面を動く海氷と慣性内部重力波の共鳴相互作用の観点からこれを説明し, 連続成層モデルの数値実験, 衛星観測結果に対しても整合的な結果を得ることができた. ただし, 連続成層下では共鳴可能な内部波のモードは風速に応じて別のモードの内部波との共鳴にシフトする場合のあることも分かっている.
Signals of the global climate change may be easy to appear around the ice-edge area, because melting and refreezing are often occurred in such field. Ice-band pattern formation is a phenomenon in the ice-edge area. Ice-band patterns have two basic features, one is the regular size (about 10km) band-spacing to the short axis direction of ice-band pattern, another is suitable wind direction which is slightly turn to the counterclockwise with respect to the perpendicular to the long axis of ice-band pattern. However, there have been no certain explanation about two basic characters. Thus, we try to examine from a point of view of the resonant-interaction between sea-ice drift and internal-wave propagation using 1.5-layer simple theoretical model. In consequence, we confirm that our theoretical results associated with two basic features correspond with the results of numerical experiments and satellite observation data. Further, we found that the resonance mode is necessary to be shifted with respect to the wind speed change in a continuously stratification case.
Signals of the global climate change may be easy to appear around the ice-edge area, because melting and refreezing are often occurred in such field. Ice-band pattern formation is a phenomenon in the ice-edge area. Ice-band patterns have two basic features, one is the regular size (about 10km) band-spacing to the short axis direction of ice-band pattern, another is suitable wind direction which is slightly turn to the counterclockwise with respect to the perpendicular to the long axis of ice-band pattern. However, there have been no certain explanation about two basic characters. Thus, we try to examine from a point of view of the resonant-interaction between sea-ice drift and internal-wave propagation using 1.5-layer simple theoretical model. In consequence, we confirm that our theoretical results associated with two basic features correspond with the results of numerical experiments and satellite observation data. Further, we found that the resonance mode is necessary to be shifted with respect to the wind speed change in a continuously stratification case.
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