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知识的最大空白。虽然从过去三十年收集的卫星图像中可以明显看出冰的范围在迅速变化，但我们几乎没有信息来评估冰的厚度。了解海冰的厚度分布及其积雪对于理解大范围的空气-海冰相互作用至关重要。随着时间的推移，它的演变为极地地区对气候变化和变异的反应提供了一个敏感的衡量标准，它控制着热、盐和淡水的通量，这些通量控制着海气相互作用和水团转化。虽然我们离从太空测量北极海冰厚度的“圣杯”越来越近，但由于南极覆盖着厚厚的积雪，这种方法在南极受到严重限制。此外，我们对控制南极积雪和冰层厚度的过程的理解是不充分的。本提案有两个互补的调查方向：(1)确定一系列冰类的雪深、冰厚和干舷分布之间的可靠统计关系。如果我们想要从太空确定雪深或冰厚，理解这些关系是至关重要的——这是确定大尺度雪和海冰厚度、趋势和变异性的唯一可行方法。(2)量化南极海冰过程在控制冰厚演变及其对气候强迫响应中的作用。这只能通过同时详细测量地表地形和冰层底部来实现。我们将首次在任何地方获得各种冰类型和条件下的表面（来自机载激光雷达）和底部（来自安装在水下航行器上的多波束声纳）的一致3D地形图。由于每个采样站有超过100万次单独测量，数据集的丰富程度将比传统方法高出几个数量级。这将使我们第一次确定雪深和冰厚空间变异性之间可靠的统计关系。这些数据将使我们能够对卫星方法在一系列冰况下估计南极海冰厚度和雪深的可行性和准确性作出明确的评估。此外，我们将部署数量空前（20个）的新型冰质量平衡浮标（imb），以监测整个年度海冰循环中雪和海冰的演变。大量IMB的部署将使人们能够首次对南极海冰的积雪率和冰质量平衡进行区域评估。为了实现这些目标，我们计划在2010年11月在詹姆斯·克拉克·罗斯号上进行为期30天的专门巡航，并使用BAS双水獭在冰站和周围地区进行机载激光雷达任务。这些平台作为BAS核心项目的一部分，与项目合作伙伴免费提供的支持和仪器一起，代表了一个独特的机会，以及超过100万英镑实物捐款的重要杠杆作用。对于英国来说，这是一个前所未有的机会，可以领导一场协调一致的运动，绘制出雪和海冰厚度分布的明确图像，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了解，并提高我们在大范围内监测冰盖演变和空气-冰-海洋相互作用的能力。这将改善海冰在大尺度和全球气候模式中的表现，并最终提高我们对南极冰盖对当前和未来气候变化和变率的响应的理解。

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.