Snow-ice growth: a fresh-water flux inhibiting deep convection in the Weddell Sea, Antarctica
Snow-ice growth: a fresh-water flux inhibiting deep convection in the Weddell Sea, Antarctica
复制标题
雪冰生长：抑制南极洲威德尔海深层对流的淡水通量
作者：
V. Lytle;S. Ackley
摘要在1994年7月的一次田间试验中，R.V.Nathaniel B.帕尔默号停泊在南极洲威德尔海的一块浮冰上，收集海冰和雪的特征数据。我们报告的演变的冰生长在一个新打开的铅。正如预期的那样，在寒冷的大气条件下，冰最初在铅中形成。随后的积雪和巨大的海洋热通量导致冰的底部融化，并增强了冰面上的积雪。这些被淹没的雪随后冻结，并且，在铅打开后5天，所有的冰都融化了，形成了26厘米的雪冰。我们使用测量的海冰和雪的盐度，厚度和新形成的铅冰的氧同位素值来计算盐通量的海洋。虽然有一个盐通量的海洋作为冰最初的增长，我们计算了一个小的净淡水输入到上层海洋结束的5天期间。类似的基底融化和表面冰雪形成过程也发生在周围较厚的海冰上。威德尔海这一区域的海洋学研究表明，海冰形成的排盐作用可能会增强海洋垂直温盐环流，并从海洋深处释放热量，融化冰盖。这种类型的深对流被认为是导致威德尔冰穴形成的原因，这种现象直到20世纪70年代才被观测到。我们的研究结果表明，冰盖可以在没有盐输入海洋的情况下形成，这提供了一种机制，可能有助于解释最近没有威德尔冰穴的原因。
Abstract During a field experiment in July 1994, while the R.V. Nathaniel B. Palmer was moored to a drifting ice floe in the Weddell Sea, Antarctica, data were collected on sea-ice and snow characteristics. We report on the evolution of ice which grew in a newly opened lead. As expected with cold atmospheric conditions, congelation ice initially formed in the lead. Subsequent snow accumulation and large ocean heat fluxes resulted in melt at the base of the ice, and enhanced flooding of the snow on the ice surface. This flooded snow subsequently froze, and, 5 days after the lead opened, all the congelation ice had melted and 26 cm of snow ice had formed. We use measured sea-ice and snow salinities, thickness and oxygen isotope values of the newly formed lead ice to calculate the salt flux to the ocean. Although there was a salt flux to the ocean as the ice initially grew, we calculate a small net fresh-wlter input to the upper ocean by the end of the 5 day period. Similar processes of basal melt and surface snow-ice formation also occurred on the surrounding, thicker sea ice. Oceanographic studies in this region of the Weddell Sea have shown that salt rejection by sea-ice formation may enhance the ocean vertical thermohaline circulation and release heat from the deeper ocean to melt the ice cover. This type of deep convection is thought to initiate the Weddell polynya, which was observed only during the 1970s. Our results, which show that an ice cover can form with no salt input to the ocean, provide a mechanism which may help explain the more recent absence of the Weddell polynya.