Terrestrial Holocene climate variability on the Antarctic Peninsula

南极大陆是地球系统的重要组成部分，影响并响应全球海洋和大气环流。冰盖在海平面变化中起着重要作用，目前相当于全球海平面上升70米。因此，监测南极洲气候、冰冻圈和生物圈的变化是了解和预测未来全球变化的一个关键因素。在过去的50年里，南极洲大部分地区的气候保持相对稳定，但南极半岛是地球上变暖速度最快的地区之一，自1950年代以来，气温上升了3摄氏度，有些地方的冬季气温甚至更高。气温的迅速上升与海冰范围缩小、冰架崩塌、冰川退缩和冰流速度加快以及陆地和海洋生态系统的变化有关。然而，最近温度变化的原因和背景尚不清楚，尽管人们认为平流层臭氧消耗和温室气体增加都是重要的。目前，全球气候模式还不能充分捕捉到观测到的变化。理解和归因南极气候变化的一个关键问题是，与过去的自然气候变率相比，半岛上记录的变化是否不同寻常。然而，这个问题无法解决，因为仪器记录太短，现有的代用气候记录不适合定位，无法追踪随时间变化的空间特征。本文提出的项目将利用苔藓银行作为一个新的代理气候档案，以测试三个关键假设：1）最近的温度上升在南极半岛是前所未有的晚全新世。2)变化的空间格局与以往气候变化期间出现的格局相似。3)植物群落正在通过增长率的增加和季节性生长模式的改变来应对最近的气候变化。苔藓滩是重建南极半岛陆地表面气候变化的理想沉积物，因为它们的位置与记录的温度变化有关，它们的年龄，以及它们作为档案的属性。在过去的5-6000年里，苔藓银行在整个南极洲半岛西部的各个地点积累了泥炭。它们仅由一个或两个物种组成，每年的生长可以在表面的泥炭中追踪，苔藓的保存情况良好。我们将使用过去气候的多代理指标（稳定同位素，衰变措施，有壳变形虫和苔藓形态），以重建气候变率从69 °和61 ° S之间的温度变化率的观测梯度的关键位置。虽然这些技术在世界上较温和的地区得到了试验和检验，但它们尚未在南极洲使用。我们在西尼岛进行了试点研究，结果表明，这些代理人在南极的苔藓银行工作得很好，所以我们知道我们的方法将产生有价值的结果。我们的工作还将包括通过一项地表取样和测量方案，增进我们对代理-气候关系的了解。将使用涵盖仪器观察期的年度解析记录校准记录。与Signy Island的记录一起，作为研究团队成员监督的当前BAS博士项目的一部分，来自James Ross Island的BAS冰芯和一些更高分辨率的海洋沉积物记录的新兴结果，我们的数据也将为更全面地了解更广泛地区的晚全新世气候变化提供基础。建立在BAS过去气候和化学方案的基础上，旨在重建和了解南极半岛全新世气候变化。

The Antarctic continent is an important part of the Earth system, both influencing and responding to global ocean and atmospheric circulation. The ice sheet plays a major role in sea-level change and currently holds the equivalent of 70m of global sea-level rise. Monitoring change in the climate, cryosphere and biosphere of Antarctica is therefore a critical element in understanding and predicting future global change. Over the past 50 years, the climate over most of Antarctica has remained relatively stable, but the Antarctic Peninsula has experienced one of the highest rates of warming anywhere on Earth, with increases of 3oC since the 1950s, and even higher rates for winter in some locations. The rapid increase in temperature has been associated with decreased sea-ice extent, ice-shelf collapse, glacier retreat and increased ice flow rates, and changes in ecosystems on land and sea. However, the causes and context of the recent temperature changes are unclear, although it is thought that stratospheric ozone depletion and increasing greenhouse gases are both important. Current global climate models do not capture the observed changes adequately at present. A key question in understanding and attribution of Antarctic climate change is whether the recorded changes on the Peninsula are unusual compared with past natural climate variability. However, this question cannot be addressed because the instrumental records are too short and existing proxy-climate records are not suitably located to be able to trace the spatial signature of change over time. The project proposed here will exploit moss banks as a new proxy-climate archive to test three key hypotheses: 1) The recent temperature rise on the Antarctic Peninsula is unprecedented in the late Holocene. 2) The spatial pattern of variability is similar to that which occurred during previous periods of climate change. 3) Plant communities are responding to recent climate change by increases in growth rates and altered seasonal growth patterns. Moss banks are ideal deposits for reconstructing climate change over the land surface of the Antarctic Peninsula because of their location in relation to recorded temperature changes, their age, and their attributes as archives. The moss banks have accumulated peat over the past 5-6000 years at locations throughout the western Antarctic Peninsula. They are formed of only one or two species, annual growth can be traced in the surface peats and preservation of moss remains is good. We will use multi-proxy indicators of past climate (stable isotopes, measures of decay, testate amoebae and moss morphology) to reconstruct climate variability from critical locations across the observed gradient in rate of temperature change between 69o and 61o S. Although these techniques are tried and tested in more temperate regions of the world, they have not been employed in the Antarctic. We carried out pilot studies on Signy Island which show that these proxies work well for the moss banks in the Antarctic so we know that our approach will produce valuable results. Our work will also involve improving our understanding of proxy-climate relationships by a programme of surface sampling and measurement. The records will be calibrated using annually resolved records covering the period of instrumental observations. Together with records from Signy Island being produced as part of a current BAS PhD project supervised by members of the research team, emerging results from the BAS ice core at James Ross Island and some of the higher resolution ocean sediment records, our data will also provide the basis for a more complete understanding of late Holocene climate variability in the broader region, building on the BAS Past climate and Chemistry programme directed at reconstructing and understanding Holocene climate variability in the Antarctic Peninsula.