SEEBECK - using the Seebeck effect to power sea-ice instrumentation

冰要融化了！1979至2007年间，北极夏季海冰面积减少了一半，从800多万平方公里减少到400多万平方公里。此外，从潜艇上的测量表明，它的厚度骤降了约40%。至于未来，政府间气候变化专门委员会(IPCC)最新报告中使用的所有气候预测模型都一致认为，这种减少将继续下去，到本世纪末，北极夏季可能不再有冰。然而，观察表明，这些模型在空间和时间上都严重低估了这种减少，北极最早可能在2040年实现无冰。这些模型是错误的，因为我们没有完全了解海冰是如何生长、移动和消融的。我们无知的一个原因是，海冰的性质在不断演变，受到当地环境条件变化的推动，如气温、雪深、海洋温度等。我们根本没有足够的测量数据来完善我们的理解，建造和测试更好的模型，这些测量分布在北极和全年。这部分是因为成本、后勤困难和缺乏人力，部分是因为我们还没有廉价、简单和可靠的自动化仪器，可以大量分布在北极各地，能够挺过漫长的极地冬季。我们计划在这项工作中解决的一个关键问题是，在极地冬季没有太阳能可供调用的情况下，如何为我们需要的仪器供电。传统的解决方案使用风力发电机和/或大型汽车电池，这两种电池在遇到的极端条件下都不可靠。电池也是一种污染危险，我们可以很好地将其降至最低。我们建议开发、测试和部署利用塞贝克效应的热电发电机。这种发电机将冷热水库之间的热流转化为电力，已被广泛应用于航天工业，但迄今尚未在极地地区使用。一个问题是，当热水库(在我们的案例中是冰下的海洋)和冷水库(海冰上方的空气)之间的温差只有几十度时，发电机的效率非常小。然而，现代极地仪器是非常节能的，我们的计算表明，在大多数情况下，一个中等大小的塞贝克效应发电机将能够在冬季提供足够的能量。典型的仪器包括垂直的传感器链(已经根据NERC赠款开发)，连接到小型卫星发射器，未经培训的操作员可以很容易和有机会地在冰中部署这些传感器。来自这些链的测量正在用于改进现有的海冰模型及其与海洋和大气的相互作用：因此，它们将在阐明海冰与全球气候变化之间的相互作用方面发挥重要作用。

The ice is melting! Between 1979 and 2007 the summer sea ice extent in the Arctic has halved, from over 8 million square km to just over 4 million square km. Moreover, measurements from submarines suggest that its thickness has plummeted by some 40%. As to the future, there is unanimous agreement between all the climate prediction models used in the latest report of the Intergovernmental Panel on Climate Change (IPCC) that this reduction will continue, and that the Arctic could be ice free in summer by the end of this century. However, observations suggest that these models are significantly under-representing this reduction, in both space and time, and that the Arctic could become ice free as early as 2040. The models are wrong because we do not fully understand how sea ice grows, moves and decays. One reason for our ignorance is that the properties of sea ice are constantly evolving, driven by changes in local environmental conditions such as air temperature, snow depth, ocean temperature and so on. We simply do not have enough measurements, spread out over the Arctic and throughout the year, to refine our understanding and build and test better models. This is partly because of the combination of cost, difficult logistics and lack of man-power, and partly because we do not yet have cheap, simple and reliable automatic instruments that can be scattered round the Arctic in large numbers, and that can survive the long polar winter. A key problem, which we plan to address in this work, is how to power the instruments that we need during the polar winter, when there is no solar energy to call upon. Traditional solutions have employed wind generators and/or large car batteries, both of which are unreliable in the extreme conditions encountered. Batteries are also a pollution hazard which we could well do to minimise. We propose to develop, test and deploy thermo-electric generators that exploit the Seebeck Effect. Such generators, converting a flow of heat between a hot and a cold reservoir into electricity, have been widely used in the space industry, but have not been used so far in the polar regions. One problem is that the efficiency of the generator is quite small when the temperature difference between the 'hot' reservoir (the sea beneath the ice in our case) and the cold reservoir (the air above the sea ice) is only a few tens of degrees. However, modern polar instruments are very energy efficient and our calculations show that a Seebeck Effect generator of modest size will, in most cases, be able to supply sufficient energy during the winter months. Typical instruments consist of vertical chains of sensors (already being developed under NERC grants), connected to small satellite transmitters, that can be easily and opportunistically deployed through the ice by untrained operators. The measurements from these chains are being used to improve existing models of sea ice and its interaction with ocean and atmosphere: as such they will play an important role in elucidating the interaction between sea ice and global climate change.