ULTRA-HIGH-RESOLUTION PROXY RECORD OF LAST MILLENNIUM NORTH ATLANTIC TEMPERATURE ANOMALIES ('ULTRA')

许多海洋双壳类软体动物，特别是Arctica islandica的外壳，包含年度生长带。在北极的乐队是年度的事实已经证明了稳定的氧同位素分布在整个增长增量，这表明海水温度的季节性周期，并通过标记活的个人和检查的增量增长后，反复夺回。计算这些增量表明，这个物种具有非凡的寿命：班戈尔小组在2006年从冰岛沃茨收集的一个活标本，将成为这里提出的研究的中心板块，每年至少有500个增量。这被认为是科学界已知的最长寿的非殖民动物。此外，我们已经能够交叉匹配的增长系列，从这些活的个人与死贝壳疏浚从海底构建长的绝对年表。交叉匹配表明，一个区域内的个体对相同的环境，可能是气候，刺激作出反应。在冰岛北部，我们已经确定生长增量的宽度与海水温度之间存在显着的统计关系，在温暖的年份会出现更广泛的增量。我们现在已经构建了一个交叉匹配的记录，涵盖了这个地区过去1000年的历史，我们建议在这个项目中使用的就是这个已经组装好的档案。我们将分析年生长增量中所含的稳定氧同位素。通过仔细比较同位素测量与当地仪器记录的海水温度和过去50年收集的其他变量，我们将能够可靠地将同位素数据转换为温度重建。这将有助于测试单独基于增量宽度的重建的鲁棒性。我们有初步的数据表明，在过去的1000年里，冰岛北部有重大的水文变化，特别是北大西洋极地锋（NAPF）的迁移，将温暖的Irminger电流与寒冷的东冰岛电流分开。这些变化与北大西洋更广泛的环流直接相关。正是这种环流系统-北大西洋纬向翻转环流（AMOC）-目前提供的热量控制了西北欧的气候。通过重建，在非常详细的，在冰岛北部的NAPF的位置在过去的1000年中的北极记录的氧同位素的变化，我们将提高我们的理解如何频繁的翻转系统，以及如何快速这些过渡。对AMOC的直接测量只有几年的时间。更长的记录--这对于确定AMOC对扰动的敏感性至关重要，特别是流入海洋的淡水流量的增加--依赖于代理记录。政府间气候变化专门委员会第四次评估报告（IPCC，2007）强调了生成此类记录的重要性。气候小组指出，过去1300年来各种仪器和代用气候记录的汇编提供了大尺度平均地表温度变化的关键证据，并明确强调了最近变暖的突出性，特别是在过去二三十年中。然而，IPCC也认识到，迫切需要通过更新现有记录（其中许多记录是在20年前收集的）和生成更多的，特别是早期的，地理覆盖范围更广的古气候系列来减少这种汇编的不确定性。该提案旨在通过对Arctica islandica年增量的氧同位素分析生成独特的1000年古温度记录来促进这一目标，以确定与北冰岛大陆架NAPF的纬向迁移有关的温度异常的自然变化。

The shells of many marine bivalve molluscs, in particular Arctica islandica, contain annual growth bands. The fact that the bands in Arctica are annual has been demonstrated by stable oxygen isotope profiles across the growth increments, which show seasonal cycles of seawater temperature, and by marking live individuals and examining the incremental growth after repeated recaptures. Counting the increments demonstrates that this species has extraordinary longevity: one live specimen from Icelandic waters collected by the Bangor group in 2006, and which will form a central plank in the research proposed here, has at least 500 annual increments. This is considered the longest-lived non-colonial animal known to science. Furthermore, we have been able to cross-match the growth series from such live individuals with dead shells dredged from the seabed to construct long absolute chronologies. Cross-matching demonstrates that individuals within a region respond to the same environmental, possibly climatic, stimuli. North of Iceland we have established that there is a significant statistical relationship between the width of the growth increments and seawater temperature, with wider increments being laid down in warmer years. We have now constructed a cross-matched record covering the last 1000 years from this region and it is this already assembled archive that we propose to use in this project. We will analyse the stable oxygen isotopes contained within the annual growth increments. By carefully comparing the isotope measurements with local instrumental records of seawater temperature and other variables collected over the last 50 years, we will be able to convert reliably the isotope data into temperature reconstructions. This will help test how robust the reconstructions based on increment width alone are. We have preliminary data which suggest that there were major hydrographic changes north of Iceland during the last 1000 years, notably the migration of the North Atlantic Polar Front (NAPF) separating the warm Irminger Current from the cold East Icelandic Current. These changes are directly linked to the wider circulation of the North Atlantic. It is this circulation system - the North Atlantic meridional overturning circulation (AMOC) - that currently provides the heat that controls the climate of NW Europe. By reconstructing, in great detail, the variability in the position of the NAPF north of Iceland over the last 1000 years from the oxygen isotopes in the Arctica record, we will enhance our understanding of how frequent the flips in the system are and how quickly these transitions take. Direct measurement of the AMOC have only been available for a few years. Longer records - which are crucial for identifying the sensitivity of the AMOC to perturbations, notably increases in freshwater flux to the ocean - rely on proxy records. The importance of generating records such as this was highlighted in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2007). IPCC stated that the compilation of various instrumental and proxy climate records over the last 1300 years provides critical evidence of the variations in average large-scale surface temperatures, and clearly emphasize the prominence of the recent warming, especially in the last two to three decades. However, IPCC also recognise that there is an urgent need to reduce the uncertainty in such compilations, via the update of existing records, many of which were assembled up to 20 years ago, and the generation of additional, especially early, palaeoclimate series with much wider geographic coverage. This proposal seeks to contribute to this goal through the generation of a unique 1000-year palaeotemperature record based on oxygen isotopic analysis of annual increments of Arctica islandica in order to identify the natural variability of temperature anomalies linked to the meridional migration of the NAPF on the north Icelandic shelf.