Sea ice physical properties and their application to ocean-atmosphere interaction

长期以来认为海-气相互作用不能通过海冰发生的观念是无效的。我们现在了解到，海冰为海洋-大气交换提供了一条不同的有效管道，特别是对二氧化碳来说。现在人们认为，海冰(取决于其温度)在形成或生长过程中可能会产生二氧化碳，这些二氧化碳可能被困在冰中，最终被输出到深海。这些相互作用受其液体和气体包裹体的形状、位置和连通性的影响，其固有性质受冰内垂直温度梯度的控制，还取决于海冰的类型和年龄。我们的目标是表征海冰中液体和气体包裹体的大小、形状、位置和连通性，以及它们从形成到融化的变化。这些结果对于确定极地海洋在一个年度周期内通过海冰过程和作为海冰过程的结果可能被封存的大气二氧化碳的数量至关重要。 这项工作的一个重大障碍是海冰采样的传统方法。也就是说，从更大的体积中垂直移除海冰核心，并随后将其存储在-20°C。一旦海冰样本向上拉出漂浮在海洋中的海冰，它就不再连接海洋和大气，控制我们感兴趣的大部分物理的垂直温度梯度受到不可挽回的影响。这与海冰的底部尤其相关，它通过向上延伸的液体通道沐浴在海水中。一个有用的类比是从水槽中取出的海绵。将海绵从水槽中取出，然后将其切开，看看里面有多少水，可能不会产生逼真的效果。 这个项目的首要目标是方法论的发展。海冰取芯和样品存储的局限性早已为人所知；我的学生和我将努力利用其他领域长期使用的现有成像技术，开发新的最先进的方法，以非侵入性测量海冰包裹体的形状、位置和类型。我们想要量化的是，当海绵漂浮在水槽中时，海绵中有多少液体和空气。 这项工作将极大地扩展关于海冰如何影响极地海洋和大气之间的生物地球化学过程和二氧化碳通量的现有知识。这项工作的结果将包括一个长期寻求的观测得出的海冰渗透率数据库，根据自然大范围的物理条件，按阶段(包括液体卤水、气体和固体盐)相对划分出不同的海冰发育阶段。这些结果对于验证现有的海冰卤水滞留、卤水排放和温室气体通过海冰向下方海洋输送的理论近似和模型至关重要。

The long-standing concept that ocean-atmosphere interaction cannot occur through sea ice is invalid. We now understand sea ice provides a variably effective conduit for ocean-atmosphere exchange, particularly for CO2. It is now thought that sea ice (depending on its temperature) may produce CO2 as it forms or grows, which may be trapped within the ice and eventually exported to the deep ocean. These interactions are modulated by the shape, location and connectivity of its liquid and gas inclusions, the intrinsic properties of which are controlled by a vertical temperature gradient within the ice and depend also on the sea ice type and age. We aim to characterize the size, shape, location and connectedness of liquid and gas inclusions in sea ice and changes therein from formation to melting. These results are imperative in determining how much atmospheric CO2 may be sequestered in polar oceans over an annual cycle both through, and as a result of, sea ice processes. A significant obstacle to this work is the traditional methodology for sea ice sampling. That is, the vertical removal of a sea ice core from a larger volume and its subsequent storage at -20°C. Once a sea ice core sample is pulled upward and out of sea ice floating in the ocean, it’s no longer connecting the ocean and atmosphere, and the vertical temperature gradient that controls much of the physics we’re interested in is irreparably affected. This is especially relevant to the bottom portion of the sea ice bathed in ocean water through liquid channels extending upward into it. A useful analogy is a sponge removed from a sink of water. Removing the sponge from the sink and slicing it up it to see how much water it contained may not yield realistic results. The overarching goal of this program is methodological development. The limitations of sea ice coring and sample storage have been known for a long time; my students and I will endeavour to employ existing imaging techniques long used in other areas, and develop new state-of-the-art methods for the non-invasive measurement of the shape, location and type of sea ice inclusions. We would like to quantify how much liquid and air are in the proverbial sponge when it is floating in the sink, while it is floating in the sink. This work will greatly expand current knowledge on how sea ice affects the biogeochemical processes and CO2 fluxes between the ocean and atmosphere in polar seas. Results of this work will include a long-sought observationally-derived library of permeability data for sea ice, partitioned relatively by phase, (including liquid brine, gases and solid salts) for a variety of sea ice stages of development as a function of naturally wide ranging physical conditions. These results are vitally important for verification of existing theoretical approximations and modeling of sea ice brine retention, brine drainage and greenhouse gas transport through sea ice to the ocean below.