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的主要来源之一是来自威德尔海西南部大陆架上冬季海冰产生的冷而稠密的水。但是，控制最初将源沃茨输入大陆架和从大陆架制度输出密集沃茨的程序仍然存在很大的不确定性。这种不确定性是由于威德尔海南部存在极其具有挑战性的海冰条件，特别是在冬季。在冬季，感兴趣区域的条件对于任何基于船舶的工作来说都是非常困难的，在夏季的几个月里部署在海洋中的仪器，以及在冬季监测水的性质，很容易受到通过冰山的疏浚。我们将使用一种最近成熟的技术来解决这个问题。我们建议附加电导率-温度-深度（CTD）标签，微型海洋仪器，威德尔海豹（Leptonychotes weddellii）。标签上有一个卫星发射器，可以传递海豹潜水时收集的海洋学数据以及潜水位置。标签是无害地粘在动物的毛皮使用标准的海洋双组分环氧树脂和脱落再次在年度换羽约11个月后。英国南极调查局进行的一项试点研究涉及对四只海豹进行标记，其中三只海豹提供了越冬数据集。尽管仅用三个标签就能获得令人印象深刻的覆盖率，这有力地证实了该技术的实用性，但感兴趣区域的面积接近50万平方公里，一个全面的数据集需要更多的标记动物。我们将在2010/2011年南半球夏末在菲尔希纳-罗恩冰架北部的断架东端标记20只威德尔海豹。从动物在冬季的潜水中得到的数据集将提供迄今为止威德尔海南部大陆架海洋状况的最全面的图片。通过绘制海底附近的水温图，我们将确定密集的沃茨离开大陆架的位置，以及所涉及的过程：在重力作用下直接沿斜坡流下，或者在大陆架边缘与来自大陆架外的沃茨混合，然后沿斜坡流下。我们还将能够确定源沃茨从哪里到达大陆架。威德尔海豹是非常熟练的潜水员，长时间反复潜水，并定期到达大陆架海底的深度。在南极海豹中，威德尔海豹也栖息在最南端的沃茨，当冰层向北扩展时，它们会在冬季呆在浮冰中。这些特点使威德尔海豹非常适合拟议的研究。虽然主要是一个海洋学项目，但威德尔海豹的运动和潜水行为对希望了解南极洲不同地区不同行为的海豹生物学家非常感兴趣。这些变化在试点期间被标记的动物的异常多样的行为中得到了很好的证明，并与以前在南极其他地区对该物种的跟踪进行了比较。在试点研究期间追踪到的一些海豹所显示的长距离移动对该物种来说是不典型的，至少在南极其他地点是这样，可能与当地的海洋条件有关。人们普遍认为，这里提出的多学科研究将为我们提供更好地预测海洋和气候条件变化如何影响分布，行为和最终人口状况的工具。

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.