The role of Arctic sea ice in climatic and ecological processes

在上个世纪，北极海冰的范围和厚度都有所减少。这一趋势已经加速，预计未来几十年夏季北冰洋将无冰。这代表海冰融化的规模和速度发生了前所未有的变化，至少在数千年内是独一无二的，也可能在人类文明史上是独一无二的。预计海冰融化的影响范围很广，从改变当地陆地和海洋动物和植物群的分布，到改变地球的气候系统和海洋循环模式：海洋动物和浮游生物分布的大幅度变化、北极熊等关键物种的栖息地减少，或北极-中纬度气候联系增强导致欧洲冬季变冷，都是这些影响的一部分。海冰是北极气候和生态的重要组成部分。它的白色表面就像一面镜子，可以反射入射的太阳光线，这些光线大部分被反射回太空，而不是穿透海洋并被困在我们的星球上。海冰的减少增加了进入地球的热量，进一步加速了变暖。海冰融化也会产生大量的淡水，干扰全球海洋循环。因此，北极海冰的减少在北极进一步变暖（北极变暖的速度比低纬度地区快得多）方面发挥了重要作用。这促进了植物的生长，导致冻土带的巨大变化。此外，许多植物和动物在海冰的景观中进化，现在正在发生变化。这对北极熊、北极狐、北极鲸和北极海豹以及北极植物等动物的影响仍然知之甚少。由于北极生物学家和气候学家所面临的过去环境条件的信息很少，因此，迄今为止，对气候和生态的预期巨大影响在很大程度上无法量化。北极长期环境记录的汇编将使人们能够检验关于迅速变化的环境的影响的许多问题。因此，缺乏整个北极海冰状况的长期（覆盖数千年）记录。拟议项目的目的是制作它来回答对我们社会有直接影响的关键问题，即：北极海冰的变化如何影响全球气候和高纬度生物群，以及我们可以从中学到什么？过去的海冰状况是通过分析在北极收集的材料推断出来的，这些材料构成了过去海冰存在或不存在的证据（海冰代理）。这种物质包括海洋底部过时的沉积物中的分子和微生物，受海冰影响的冰芯和树木年轮，海滩上冰造成的疤痕，以及动物和植物遗骸，如鲸鱼骨头或浮木。该项目提出了一项合作努力，将所有这些信息联合收割机结合起来，制作一幅完整的北极过去海冰动态图。在所有海冰代理中，漂流木是唯一一个不仅能提供过去海冰状况，而且能提供海冰从进入海洋到沉积在北极海滩上的漂流路线的代理。由于北极非常寒冷，漂流木被完好地保存了一万多年。将使用新技术分析现有材料，这些技术可以更精确地了解过去的海冰范围和漂流路线。将组织北极考察，收集关键区域和关键时期的新材料，这将有助于科学界回答有关海冰在北极气候和生物中的作用及其全球影响的问题。它还将把当前的变化放在一个更大的框架中，并提高我们对这种巨大的环境变化将对我们星球产生的影响的理解，这是我认为这项研究计划最重要和最令人兴奋的地方。

In the last century Arctic sea ice has declined, both in extent and thickness. This trend has accelerated to the point where a summer ice-free Arctic Ocean is expected in the next decades. This represents an unprecedented change in scale and speed of sea ice-melt, unique for at least millennia, and also possibly in the history of human civilisation.The impacts of melting sea-ice are predicted to be wide-ranging, from alterations in the distribution of local terrestrial and marine fauna and flora, to changes to the earth's climate systems and ocean circulatory patterns: large shifts in the distribution of marine fauna and plankton, reductions in the habitat of key species such as the polar bear, or an enhanced Arctic-mid-latitudes climate connection responsible for colder winters in Europe are amongst these impacts. Sea ice is a key part of Arctic climate and ecology. Its white surface acts as a mirror for the incoming solar rays, which are largely reflected back into space, instead of penetrating the ocean and getting trapped in our planet. Sea ice loss increases the amount of heat entering our planet, further accelerating warming. Sea ice melt also creates great volumes of freshwater, interfering with the global oceanic circulation. Arctic sea ice loss thus plays a big role in further warming the Arctic (which warms much faster than lower latitudes). This enhances plant growth, causing large changes in the tundra. Plus, many plants and animals have evolved in landscapes with sea ice that are now changing. The consequences of this for animals such as the polar bear, the Arctic fox, Arctic whales and seals, and Arctic plants remain poorly understood.The anticipated large effects on climate and ecology are to date largely unquantified, due to the fact that Arctic biologists and climatologists are confronted with scarce and short information of past environmental conditions. The compilation of long environmental records for the Arctic would allow testing many questions about the effects of a rapidly changing environment. A much needed long (covering thousands of years) record of sea ice conditions for the whole Arctic is thus lacking.The aim of the proposed project is to produce it to answer key questions with direct implications for our society, namely: how changes in Arctic sea ice affect the global climate and the high latitude biota, and what can we learn from this for the future?Past sea ice conditions are inferred from the analysis of material collected in the Arctic that constitutes evidence of past sea ice presence or absence (sea ice proxies). This material consists of molecules and microscopic organisms in dated sediment at the bottom of the ocean, ice cores and tree rings affected by sea ice, scars made by ice on beaches, and animal and plant remains like whale bones or driftwood. This project proposes a collaborative effort to combine all this information and produce a full Arctic picture of past sea ice dynamics.Of all sea ice proxies, driftwood is the only one informing not only of past sea ice condition, but also of the drift routes sea ice took to deliver driftwood from the moment it entered the ocean to the moment it got deposited on Arctic beaches. Since the Arctic is so cold, driftwood is well preserved for more than 10,000 years. Existing material will be analysed using new techniques that can inform with improved precision about past sea ice extent and drift routes. Arctic expeditions will be organized to collect new material for key regions and periods.This will help the scientific community to answer questions about the role of sea ice in Arctic climate and biology and its global consequences. It will also put current changes in a larger framework and improve our understanding of the effects that this huge environmental change will have on our planet, which is what I find most important and exciting about this research proposal.