STRUCTURAL CHARACTERISTICS OF CONGELATION AND PLATELET ICE AND THEIR ROLE IN THE DEVELOPMENT OF ANTARCTIC LAND-FAST SEA-ICE
STRUCTURAL CHARACTERISTICS OF CONGELATION AND PLATELET ICE AND THEIR ROLE IN THE DEVELOPMENT OF ANTARCTIC LAND-FAST SEA-ICE
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DOI：
10.3189/s0022143000015884
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发表时间：
1993-01-01
影响因子：
3.4
通讯作者：
MORRIS, K
中科院分区：
文献类型：
--
作者：
JEFFRIES, MO;WEEKS, WF;MORRIS, K
1990年1月，从麦克默多海峡的陆固冰中获得冰芯，以研究结构、组构、子结构、组成和发展的变化。观察到两种主要的冰类型，冰粒和血小板，以及少量的碎冰。凝结冰的生长先于片晶冰的增长。凝结冰织物显示频繁的中度到强烈的对齐，这种现象被认为是由于水流控制选择性冰晶生长。板状冰起源于冰隙的底部，最初是由板状冰晶组成的多孔晶格，随后通过间隙水的渗透而固结。间质膨胀-冰织物通常很少或没有对齐，表明在凝固之前血小板晶格内电流的影响减小。片状晶体结构的范围从小的，波浪形边缘的形式到大的，叶片状的形式。片状晶体组构表明，除了随机取向外，片状晶格通常包括许多晶体，其平坦的（0001）面平行于和垂直于上覆冰的底部。板宽数据表明，间质骨钙素生长速率与上覆骨钙素生长速率相似。这种生长速率的有效增加可能是因为在冻结界面之前聚集的血小板的晶格结构确保了血小板层内的水处于凝固点，并且对于给定厚度的血小板生长，从富含血小板的水中去除的热量比从无血小板的水中去除的热量少。与麦克默多湾的血小板冰形成相关的负海洋热通量解释了为什么麦克默多湾的坚冰比罗斯海的浮冰厚，也解释了为什么它比在类似的极地海洋气候中生长的北极坚冰厚。然而，从麦克默多海峡冰川的板块宽度来看，它的增长速度并不比北极冰川快。
Ice cores were obtained in january 1990 from the land-fast ice in McMurdo Sound for a study of variations in texture, fabric, sub-structure, composition and development. Two primary ice types were observed, congelation and platelet, with a minor amount of frazil ice. Congelation ice growth precedes platelet-ice accretion. Congelation-ice fabrics show frequent moderate to strong alignments, a phenomenon believed to be due to water-current control of selective ice-crystal growth. Platelet ice originates at the base of the congelation ice, initially as a porous latticework of tabular ice crystals which subsequently consolidate by congelation of the interstitial water. Interstitial congelation-ice fabrics generally have little or no alignment, indicating the reduced effect of currents within the platelet latticework prior to solidification. Platelet-crystal textures range from small, wavy-edged forms to large, blade-like forms. Platelet-crystal fabrics indicate that, in addition to being randomly oriented, the platelet latticeworks commonly include many crystals with their flat (0001) faces oriented both parallel and normal to the base of the overlying ice. Plate-width data suggest that the interstitial congelation ice-growth rates remain similar to those of the overlying congelation ice. This effective increase in growth rates probably happens because the latticework of accumulating platelets ahead of the freezing interface ensures that the water within the platelet layer is at the freezing point and less heat has to be removed from platelet-rich water than from platelet-free water for a given thickness of congelation ice to grow. The negative oceanic heat flux associated with platelet-ice formation in McMurdo Sound explains why McMurdo Sound fast ice is thicker than Ross Sea pack ice, and also why it reaches a greater thickness than Arctic fast ice grown in a similar polar marine climate. Plate widths in the McMurdo Sound congelation ice suggest, however, that it grows no faster than Arctic congelation ice.