Calculating the rate of Antarctic Bottom Water formation using new theory, fine-scale modelling and observations

利用新理论、精细尺度建模和观测计算南极底层水形成率

• 批准号: NE/I025867/1
• 负责人: Paul Holland
• 金额: $ 28.12万
• 依托单位: British Antarctic Survey
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI025867%2F1
• 关键词: Calculating; rate; Antarctic; Bottom; Water

The equatorial regions of the Earth receive more solar energy than the polar regions. The extra heat is transported polewards in approximately equal parts by the circulations of the atmosphere and ocean. Warm surface waters enter the polar regions, where they release their heat. As these surface waters cool, they can begin to freeze to form sea ice and this releases dense brine into the ocean. The combination of surface cooling and brine release causes the surface waters to become sufficiently dense to sink. The cold bottom waters so formed then flow equatorward, balancing the poleward surface flow. The location and mechanism of bottom water production affects the spatial distribution and intensity of the ocean circulation, which helps determine the weather.Evidence from climate models and observations suggest that bottom water formation around Antarctica will be affected by global warming and will influence the climate and weather in both the Southern and Northern hemispheres. In order to accurately predict future climate change, climate models require an adequate representation of bottom water formation around Antarctica, which is presently lacking. As a result of their limited spatial resolution and simplified physics, climate models are unable to represent adequately the small-scale processes responsible for the formation of bottom water. Climate models typically produce too little bottom water and this water is too warm and fresh, which has been ascribed to inadequate representation of winter freezing of seawater to form sea ice, which releases brine into the upper ocean. This proposal will use high resolution numerical modelling of the sea ice and ocean, combined with field observations to improve our understanding of the processes controlling bottom water formation around Antarctica.We will focus on a particular region, over the continental shelf north of the Ronne Ice Shelf, since this region is believed to be responsible for about a third of the bottom water formed around Antarctica, is representative of other regions of bottom water formation around Antarctica, and because, relative to other areas in the Southern Ocean, we have a lot of data with which to test our model. We will explore the role of the Ronne polynya, an open water region in the sea-ice cover caused by winds blowing off Antarctica, and frazil ice formation, in controlling the bottom water formation in this region. Frazil ice consists of millimetre-sized ice crystals that form and grow when the seawater is below its freezing point. We will include the physics of frazil ice formation into our models. We will test our models with recently-acquired oceanographic and atmospheric data and satellite observations. We will use our models, which will be the most physically-sophisticated, and highly-calibrated, models to date, to calculate the rate of bottom water formation over the Ronne continental shelf. The models, once calibrated for the Ronne continental shelf, will be used to calculate total bottom formation around the whole of Antarctica. In addition to new estimates for bottom water formation, we will develop new model physics and identify the optimal representation of ocean mixing.

地球的赤道地区比极地地区接收更多的太阳能。额外的热量通过大气和海洋的环流以大致相等的比例向极地输送。温暖的表面沃茨进入极地地区，在那里它们释放热量。随着这些表面沃茨冷却，它们可以开始冻结形成海冰，这将向海洋释放密集的盐水。表面冷却和盐水释放的结合导致表面沃茨变得足够稠密而下沉。这样形成的冷的底层沃茨然后向赤道流动，平衡了向极地的表面流动。底层水的形成位置和机制影响着海洋环流的空间分布和强度，而海洋环流的空间分布和强度又决定着气候的变化。气候模式和观测的证据表明，南极洲周围的底层水的形成将受到全球变暖的影响，并将影响南半球和北方的气候和天气。为了准确地预测未来的气候变化，气候模型需要充分代表南极洲周围的底层水形成，这是目前缺乏的。由于空间分辨率有限和物理学简化，气候模型无法充分反映造成底层水形成的小尺度过程。气候模型通常产生太少的底层水，这些水太温暖和新鲜，这被归因于冬季海水冻结形成海冰，将盐水释放到上层海洋的代表性不足。这项建议将利用海冰和海洋的高分辨率数值模拟，结合实地观测，以提高我们对控制南极洲周围底层水形成的过程的理解，我们将重点关注伦讷冰架以北大陆架上的一个特定区域，因为据信该区域是南极洲周围形成的大约三分之一底层水的来源，代表了南极洲周围其他地区的底层水形成，因为相对于南大洋的其他地区，我们有很多数据来测试我们的模型。我们将探讨伦讷冰间湖的作用，这是一个开放的水域，在海冰覆盖的风吹离南极洲，和frazil冰的形成，在控制底层水的形成在这一地区。冰柱冰由毫米大小的冰晶组成，当海水低于冰点时形成并生长。我们将把冰形成的物理过程纳入我们的模型。我们将用最近获得的海洋和大气数据以及卫星观测来测试我们的模型。我们将使用我们的模型，这将是最复杂的物理，高度校准，模型到目前为止，计算底层水形成的速度超过伦讷大陆架。这些模型一旦针对伦讷大陆架进行校准，就将用于计算整个南极洲周围的海底形成总量。除了对底层水形成的新估计外，我们还将开发新的物理模型，并确定海洋混合的最佳表示。

项目成果

Eddy-Driven Exchange between the Open Ocean and a Sub-Ice Shelf Cavity

公海与冰架下空腔之间的涡流驱动交换

• DOI: 10.1175/jpo-d-13-0137.1
• 发表时间: 2013
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Nicholls K

Study of the Impact of Ice Formation in Leads upon the Sea Ice Pack Mass Balance Using a New Frazil and Grease Ice Parameterization

使用新的 Frazil 和油脂冰参数化研究铅中冰的形成对海冰包质量平衡的影响

• DOI: 10.1175/jpo-d-14-0184.1
• 发表时间: 2015
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Wilchinsky A