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

基本信息

批准号：
NE/I023708/1
负责人：
Daniel Feltham
金额：
$ 21.51万
依托单位：
University College London
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%2FI023708%2F1
关键词：
Calculating rate Antarctic Bottom Water

项目摘要

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.

地球的赤道区域比极地区域获得的太阳能更多。额外的热量通过大气和海洋的循环在大约相等的部分将极点传递。温暖的地表水进入极地区域，在那里释放热量。随着这些地表水的冷却，它们可以开始冻结以形成海冰，并将稠密的盐水释放到海洋中。表面冷却和盐水释放的结合使地表水变得足够致密。如此形成的冷底水流动赤道，平衡了极向表面流量。底部水生产的位置和机制会影响海洋循环的空间分布和强度，这有助于确定天气。气候模型和观察结果表明，南极周围的底水形成将受到全球变暖的影响，并会影响南部和北半球的气候和天气。为了准确预测未来的气候变化，气候模型需要足够的南极底水形成，目前缺乏。由于它们有限的空间分辨率和简化的物理学，气候模型无法充分代表负责形成底水的小规模过程。气候模型通常会产生太少的底部水，而这种水太温暖和新鲜，因此归因于冬季冻结海水以形成海冰的代表不足，从而将盐水释放到上大洋中。该提案将使用海冰和海洋的高分辨率数值建模，再加上现场观察，以提高我们对控制南极周围底水形成的过程的理解。我们将集中于一个特定地区，在罗恩冰架以北的大陆架子上，因为该地区被认为是底部水的三分之一，并且在底部的三分之一范围内代表了Antarctica的三分之一，是代表Antarctica的三分之一，是Antarctica的代表。对于南大洋的其他地区，我们有很多数据可以测试我们的模型。我们将探讨罗恩·波利尼亚（Ronne Polynya）的作用，罗恩·波尼亚（Ronne Polynya）是由吹南极的风和弗拉西尔冰形成的海冰覆盖中的开放水域，在控制该地区的底水形成中。 Frazil冰由毫米大小的冰晶组成，当海水低于冰点时，形成并生长。我们将将弗拉西尔冰形成的物理学包括在我们的模型中。我们将通过最近获得的海洋学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，该模型将是迄今为止最有理由且高度校准的模型，以计算罗恩大陆架上的底水的速率。这些模型曾经为罗恩大陆架进行了校准，将用于计算整个南极洲周围的总底部形成。除了对底水的新估计值外，我们还将开发新的模型物理，并确定海洋混合的最佳表示。