Sea ice Processes and Mass Balance in the Bellingshausen Sea

南极海冰厚度可以说是我们对气候系统了解的最大差距。虽然在过去30年里收集的卫星图像中冰层范围的快速变化是显而易见的，但我们几乎没有信息来评估冰层的厚度。了解海冰及其积雪的厚度分布对于理解广泛的气-海-冰相互作用至关重要。它随时间的演变为极地地区对气候变化和可变性的反应提供了一个敏感的衡量标准，它控制着控制海-气相互作用和水团转化的热量、盐分和淡水的通量。虽然我们正在接近从太空测量北极海冰厚度的“圣杯”，但由于厚厚的积雪，这种方法在南极受到严重限制。此外，我们对控制南极冰雪厚度的过程的了解还不够充分。这项建议有两条互补的研究路线：(1)确定一系列冰类的积雪深度、冰层厚度和干舷分布之间的可靠统计关系。如果我们能够从太空确定雪的深度或冰的厚度，了解这些关系是至关重要的--这是确定大范围雪和海冰厚度、趋势和可变性的唯一可行手段。(2)量化关键南极海冰过程在控制冰层厚度演变及其对气候强迫的响应中所起的作用。这只能通过同时对表面地形和冰底进行详细的测量来实现。我们将首次在任何地方获得各种冰层类型和条件的表面(从机载激光雷达)和底部(从AUV安装的多波束声纳)的一致3D地形图。由于每个采样站有100多万个单独的测量值，数据集的丰富度将比传统方法高出几个数量级。这将使我们能够第一次确定雪深和冰厚度空间变异性之间的可靠统计关系。这些数据将使我们能够对卫星估算南极海冰厚度和各种冰层条件下积雪深度的方法的可行性和准确性进行明确评估。此外，我们将部署前所未有的数量(20个)的新型冰质量平衡浮标(IMB)，以监测整个年度海冰周期中雪和海冰的演变。大量的IMB部署将使首次对南极海冰的积雪速率和冰块平衡进行区域评估。为了实现这些目标，我们已经在詹姆斯·克拉克·罗斯号上安排了一次为期30天的专门巡航，计划于2010年11月进行，并使用BAS双水獭在冰站和周围地区执行空中激光雷达任务。作为BAS核心方案的一部分提供的这些平台，以及项目伙伴免费提供的支助和仪器，是一个独特的机会，也是对超过1,000,000 GB实物捐助的重要影响。对于英国来说，这是一个前所未有的机会，可以领导一项协调行动，以确定雪和海冰厚度分布的最终图景，并在整个年度周期中持续监测控制这些分布的过程。我们的计划将使我们对冰雪厚度分布的了解向前迈进一大步。它将促进我们对南极海冰过程的理解，并提高我们监测冰盖演变和大范围大气-冰-海相互作用的能力。这将改善海冰在大规模和全球气候模型中的表现，并最终提高我们对南极冰盖对当前和未来气候变化和可变性的反应的理解。

Antarctic sea ice thickness is arguably the largest gap in our knowledge of the climate system. While rapid changes in ice extent are evident in satellite imagery collected over the last three decades, we have little information with which to assess the thickness of the ice. Knowledge of the thickness distribution of sea ice and its snow cover is critical in understanding a wide range of air-sea-ice interactions. It's evolution over time provides a sensitive measure of the response of the polar regions to climate change and variability, and it controls the fluxes of heat, salt, and freshwater that govern air-sea interactions and water mass transformation. Whilst we are moving closer to the 'holy grail' of measuring Arctic sea ice thickness from space, such methods are severely limited in the Antarctic due to the deep snow cover. Moreover, our understanding of the processes that control Antarctic snow and ice thickness is inadequate. This proposal has two complementary lines of investigation: (1) To determine robust statistical relationships between snow depth, ice thickness, and freeboard distribution for a range of ice classes. Understanding these relationships is critical if we are to be able to determine either snow depth or ice thickness from space - the only viable means of determining large-scale snow and sea ice thickness, trends, and variability. (2) To quantify the role that key Antarctic sea ice processes play in controlling the ice thickness evolution and its response to climate forcing. This can only be achieved through detailed simultaneous measurements of both the surface topography and ice underside. We will obtain, for the first time anywhere, coincident 3D topography maps of both the surface (from airborne Lidar) and underside (from AUV mounted multibeam sonar) for a variety of ice types and conditions. With over 1 million individual measurements per sampling station, the richness of the data set will be several orders of magnitude more than is possible with traditional methods. This will allow us to determine, for the first time, robust statistical relationships between snow depth and ice thickness spatial variability. These data will allow a definitive assessment of the feasibility and accuracy of satellite methods for estimating Antarctic sea ice thickness and snow depth for a range of ice conditions. In addition we will deploy an unprecedented number (20) of novel ice mass balance buoys (IMBs) to monitor the evolution of the snow and sea ice throughout the annual sea ice cycle. The large number of IMB deployments will allow the first regional assessment of snow accumulation rates and ice mass balance of Antarctic sea ice. To achieve these goals we have secured a 30-day dedicated cruise aboard the James Clark Ross, scheduled for November 2010, as well as use of a BAS Twin Otter for airborne Lidar missions over ice stations and the surrounding region. These platforms, provided as part of the BAS core programme, along with support and instrumentation provided by project partners at no cost, represent a unique opportunity, and a significant leverage of over £1,000,000 of in-kind contribution. This is an unprecedented opportunity for the UK to lead a coordinated campaign to produce a definitive picture of snow and sea ice thickness distribution, and to continuously monitor the processes that control these distributions throughout the annual cycle. Our programme will deliver a major step forward in our knowledge of the snow and ice thickness distribution. It will advance our understanding of Antarctic sea ice processes and improve our ability to monitor the evolution of the ice cover and air-ice-ocean interactions on a large scale. This will allow improved representation of sea ice in large-scale and global climate models, and ultimately improve our understanding of the response of the Antarctic ice cover to current and future climate change and variability.