Thick Sea-ice Floes

This paper examines how sea ice floes of thickness exceeding 6 m can be formed in the Arctic. Such floes have been observed by a Soviet drifting station, by a submarine at the North Pole, and at three sites in the Canadian Arctic Archipelago. The Maykut and Untersteiner model of sea ice growth predicts an equilibrium thickness of 3m under normal conditions, but if the oceanic heat flux is set to zero and the annual snowfall is increased to 1 m growth will continue to at least 12 m thickness over tens of years. The conclusion is that thick floes grow as 'plugs' of fast ice in constricted channels of shallow water at high latitudes, and that they break out into the Arctic Ocean only after many years of growth in place. Their history in some respects resembles that of Arctic ice shelves. RfiSUMl?. Les contraintes de cisaillement ou de convergence sont gentralement a l'origine d'une kpaisseur exceptionelle de la banquise, sous la forme de rides ou de monticules de glace, auparavent ecrasee. Bien que I'epaisseur normale de la glace de mer, formee par les forces thermodynamiques, soit de 3 metres dans les regions polaires, des rapports ca et la, signalent des epaisseurs de I'ordre de 10 metres de glace d'origine thermodynamique. L'auteur etudie ces observations.