Ocean processes over the southern Weddell Sea shelf using seal tags

南极底层水(AABW)是世界深海冷却和通风的重要水团。AABW的主要来源之一源于冬季威德尔海西南部大陆架上的海冰产生的冷水和稠水的产生。然而，对于控制最初将源水输入大陆架和将稠密水从大陆架制度出口的过程，仍然存在很大的不确定性。不确定性源于威德尔海南部极具挑战性的海冰状况，尤其是在冬季。冬季有关区域的条件对于任何船基工作都是异常困难的，在相对不那么困难的夏季月份部署在海洋中的仪器，留下来监测冬季期间的水性质，很容易受到经过冰山的疏浚。我们将使用一种最近成熟的技术来解决这个问题。我们建议在韦德尔海豹(Leptonychotes Wedellii)身上贴上电导-温度-深度(CTD)标签，这是一种微型海洋仪器。这些标签有一个卫星发射器，将海豹潜水期间收集的海洋数据与潜水位置一起转发。使用标准的海洋双组分环氧树脂将标签粘在动物的毛皮上，对身体无害，大约11个月后，在一年一度的换羽过程中，标签再次脱落。英国南极调查局进行的一项初步研究涉及对四只海豹进行标记，其中三只提供了过冬数据集。尽管只有三个标签的覆盖率令人印象深刻，强调证实了该技术的实用性，但感兴趣的区域面积近500,000平方公里2，而且一个全面的数据集需要更多的标记动物。我们将在2010/2011年澳大利亚夏末期间，在费尔奇纳-罗恩冰架以北的搁板东端标记20只韦德尔海豹。冬季动物潜水所产生的数据集将给出迄今为止最全面的威德尔海南部大陆架上的海洋状况。通过绘制海底附近的水温图，我们将确定密集水离开陆架的位置，以及涉及的过程：要么是在重力作用下顺着斜坡向下流动，要么是在陆架边缘最初与来自陆架外的水混合，然后从斜坡下降。我们还将能够确定源水进入大陆架的位置。韦德尔海豹是非常有造诣的潜水员，长时间反复潜水，经常深入到搁置的海底。在南极海豹中，韦德尔海豹也生活在最南端的水域，冬季当冰向北扩展时，它们会留在浮冰中。这些特性使韦德尔海豹非常适合进行这项拟议的研究。虽然主要是一个海洋学项目，但海豹生物学家对威德尔海豹的运动和潜水行为非常感兴趣，他们希望了解南极洲不同地区的不同行为。在试验期间被标记的动物的异常不同的行为，以及与之前在南极其他地区跟踪到的这种物种的比较，都有力地证明了这些变化。在试点研究期间追踪到的一些海豹所显示的远距离移动对该物种来说是不典型的，至少在南极其他地方是不典型的，可能与当地的海洋条件有关。人们普遍认为，像这里提出的这样的多学科研究将为我们提供工具，以更好地预测不断变化的海洋和气候条件可能如何影响种群的分布、行为和最终的种群状况。

Antarctic Bottom Water (AABW) is an important water mass in the cooling and ventilation of the World's deep ocean. One of the principal sources of AABW has its roots in the production of cold, dense water that results from wintertime sea-ice production over the continental shelf of the southwestern Weddell Sea. However, there remains great uncertainty about the processes controlling the initial import of the source waters onto the continental shelf, and the export of the dense waters from the shelf regime. The uncertainty results from the extremely challenging sea ice conditions existing in the southern Weddell Sea, especially during winter. Conditions in the area of interest during winter are exceptionally difficult for any ship-based work, and instruments deployed in the ocean during the rather less difficult summer months, and which are left to monitor the water properties over the Winter period, are vulnerable to dredging by passing icebergs. We will tackle the problem using a technology that has recently come of age. We propose to attach conductivity-temperature-deph (CTD) tags, miniaturised oceanographic instruments, to Weddell seals (Leptonychotes weddellii). The tags have a satellite transmitter that relays the oceanographic data collected during the seals' dives, together with the dive location. The tag is glued harmlessly to the animal's fur using standard marine two-component epoxy and comes off again during the annual moult about eleven months later. A pilot study undertaken by the British Antarctic Survey involved the tagging of four seals, three of which supplied over-winter datasets. Although the coverage was impressive from only three tags, emphatically confirming the practicality of the technique, the region of interest is nearly 500,000 km^2 in area and a comprehensive dataset requires substantially more tagged animals. We will tag 20 Weddell seals at the eastern end of the shelfbreak north of the Filchner-Ronne Ice Shelf during the late Austral summer of 2010/2011. The resulting dataset resulting from the animals' dives during the winter will give the most comprehensive picture to date of the ocean conditions over the southern Weddell Sea continental shelf. By mapping the temperature of the water near the sea floor we will determine the locations where dense waters leave the shelf, and the processes involved: either a direct flow down the slope under gravity, or initially mixing at the shelf edge with waters from off the shelf before descending down the slope. We will also be able to determine where the source waters come on to the shelf. Weddell seals are very accomplished divers, diving repeatedly for long periods and to depths regularly reaching the on-shelf seafloor. Among Antarctic seals, Weddell seals also inhabit the southernmost waters, and remain within the pack-ice in winter when the ice expands northward. These characteristics make Weddell seals ideally suited for the proposed study. Although primarily an oceanographic project, the movements and diving behaviour of Weddell seals is of great interest to seal biologists who wish to understand differing behaviours in different parts of Antarctica. These variations were ably demonstrated by the extraordinarily diverse behaviour of the animals tagged during the pilot, and by comparisons with previous tracking of this species in other parts of the Antarctic. The long-ranging movements displayed by some of the seals tracked during the pilot study are untypical for the species, at least at other Antarctic locations, and may be related to the local oceanographic conditions. It is widely recognised that multidisciplinary studies such as proposed here will provide us with the tools to better predict how the distribution, behaviour and ultimately population status may be affected by changing ocean and climate conditions.