Ocean-ice Interaction in the Ross Sea during Past Warm Periods

过去温暖时期罗斯海的海冰相互作用

基本信息

批准号：
NE/R018219/1
负责人：
Tina Van De Flierdt
金额：
$ 3.2万
依托单位：
Imperial College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2018
资助国家：
英国
起止时间：
2018 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FR018219%2F1
关键词：
Ocean ice Interaction Ross Sea

项目摘要

The two polar ice sheets in Greenland and Antarctica contain enough ice to raise global sea levels by ~65 metre. In total, 58 metre of sea level equivalent ice is tied up in Antarctica, of which ~4m is located in West Antarctic areas that are particularly vulnerable to environmental change. These are areas where the ice rests on a bed several hundred meters below sea level, meaning the ice is in direct contact with the warming ocean. In such a set up the ice sheet is not just melting from the top down by means of higher atmospheric temperatures and surface melting, but also from the bottom up, via contact with warmer ocean water. Recent estimates on how fast West Antarctica may lose most of its ocean terminating ice range from a few hundred to a few thousand years into the future. The lower end of this range is just a few generations away, and is something that becomes increasingly likely under unabated carbon dioxide emissions, increased atmospheric carbon dioxide concentrations and resulting global warming. We can make detailed observations on how the ice sheet reacts to ongoing environmental change. But what we can't observe with our own eyes is what will happen to the ice when global temperature are 1, 2, 4 or even 8 degrees warmer than today. As Earth Scientists we love our detective stories. Figuring out the response of the Antarctic ice sheets to warmer climates is something we can do by using the mud deposited at the bottom of the ocean. Just like an old-fashioned tape recorder, this mud preserves an environmental signal from times in the past, where earth's climate was warmer and atmospheric carbon dioxide levels were higher than today. It is such records that we want to recover when we set sail on Expedition 374 of the International Ocean Discovery Program in January 2018 to March 2018. My role on the expedition will be to look at the chemical fingerprint in the mud. Every rock that gets crushed by the overlying ice sheet and transported from the continent to the ocean has a typical fingerprint, just like every human being has a very specific DNA. We can use this fingerprint to decipher where the material was located on the continent, which in turn can tell us about the location of the ice margin that scrapes off the mud. You can imagine that back in times of greater warmth that location was not the same as it is today. Another part of the climate system that changes with changing environmental conditions is how the oceans circulate and transport heat and carbon around the globe. We are all used to thinking about the Gulf Stream that brings warm waters to the shores of Northern Europe. Down south, next to the giant Antarctic continent, another process comes into play: Freezing of surface waters and interaction of warmer water with cold floating ice shelves creates very salty, cold and dense water, which sinks to the bottom of the ocean. Such waters are called Antarctic Bottom Waters and fill up 30-40% of our global oceans. Will this be the same in a warming world? Or will the retreat of the Antarctic ice sheets also have a major impact on global ocean circulation? Another question we can tackle as Earth Science detectives by looking at the chemical fingerprint of mud. IODP Expedition 374 is going to be a great opportunity to collect unique material and advance our basic understanding of polar ice sheets and ocean circulation in a warmer world -a world which may just look like the one we are headed towards.

格陵兰岛和南极洲的两个极地冰原所含的冰足以使全球海平面上升约 65 米。南极洲总共有 58 米相当于海平面的冰，其中约 4 米位于特别容易受到环境变化影响的西南极地区。这些区域的冰位于海平面以下数百米的床上，这意味着冰与变暖的海洋直接接触。在这样的设置中，冰盖不仅通过较高的大气温度和表面融化从上到下融化，而且通过与温暖的海水接触从下到上融化。最近对未来几百年到几千年西南极洲失去大部分海洋终止冰层的速度进行了估计。距离这个范围的下限只有几代人的时间，并且在二氧化碳排放量不减、大气二氧化碳浓度增加以及由此导致的全球变暖的情况下，这种情况变得越来越有可能。我们可以详细观察冰盖对持续环境变化的反应。但我们无法用肉眼观察到，当全球气温比现在高1、2、4甚至8度时，冰会发生什么变化。作为地球科学家，我们喜欢我们的侦探故事。我们可以利用海底沉积的泥浆来弄清楚南极冰盖对气候变暖的反应。就像老式的录音机一样，这些泥土保存了过去时代的环境信号，当时地球的气候更加温暖，大气中的二氧化碳含量也比今天更高。当我们于 2018 年 1 月至 2018 年 3 月启航国际海洋发现计划 374 号探险队时，我们想要恢复的正是这些记录。我在这次探险中的角色将是观察泥浆中的化学指纹。每块被冰盖压碎并从大陆运到海洋的岩石都有一个典型的指纹，就像每个人都有一个非常特定的 DNA 一样。我们可以使用这个指纹来破译该物质在大陆上的位置，这反过来又可以告诉我们刮掉泥浆的冰缘的位置。您可以想象，在更加温暖的时代，那个位置与今天不一样。随着环境条件变化而变化的气候系统的另一部分是海洋如何在全球范围内循环和运输热量和碳。我们都习惯于想到将温暖的海水带到北欧海岸的墨西哥湾流。在南方，紧邻巨大的南极大陆，另一个过程开始发挥作用：地表水结冰以及温暖的海水与寒冷的漂浮冰架相互作用，产生了非常咸、寒冷和稠密的水，这些水沉入海底。这些水域被称为南极底层水域，占全球海洋的 30-40%。在变暖的世界中，情况也会如此吗？或者南极冰盖的退缩也会对全球海洋环流产生重大影响？作为地球科学侦探，我们可以通过观察泥浆的化学指纹来解决另一个问题。 IODP 374 号探险将是一个绝佳的机会，可以收集独特的材料，并增进我们对温暖世界中极地冰盖和海洋环流的基本了解——这个世界可能看起来就像我们即将走向的世界。