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

上个千年北大西洋温度异常的超高分辨率代理记录（“ULTRA”）

• 批准号: NE/H023356/1
• 负责人: Christopher Richardson
• 金额: $ 36.21万
• 依托单位: Bangor University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH023356%2F1
• 关键词: ULTRA; RESOLUTION; PROXY; RECORD; LAST; ULTRA; RESOLUTION; PROXY; RECORD; LAST

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.

许多海洋双壳类软体动物的贝壳，尤其是阿西卡岛岛，都包含年度生长带。在整个生长增量中，稳定的氧同位素剖面证明了arctica中的乐队，这一事实证明了海水温度的季节性周期，并标记了活个体并检查了重复重复后的增量生长。计算增量表明该物种具有非凡的寿命：班戈集团在2006年收集的冰岛水域的一个活标本，它将在此处提出的研究中形成一个中央木板，至少有500个年度增量。这被认为是寿命最长的非殖民动物。此外，我们已经能够从从海床上挖出的死壳的现场壳的活人穿越增长系列，构建了长期的绝对时间表。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）做出了反应。冰岛以北，我们已经确定，增长宽度和海水温度之间存在显着的统计关系，在温暖的年份中，增量越来越大。现在，我们已经构建了一个交叉匹配的记录，该记录涵盖了最近的1000年，正是我们建议在该项目中使用的已经组装的档案。我们将分析年增长增量中包含的稳定氧同位素。通过将同位素测量值与过去50年来收集的海水温度和其他变量的局部仪器记录进行仔细比较，我们将能够可靠地将同位素数据转换为温度重建。这将有助于测试仅基于增量宽度的重建程度。我们有初步数据表明，在过去的1000年中，冰岛以北有重大的水文变化，尤其是北大西洋极地阵线（NAPF）的迁移，将温暖的irminger电流与冷冰岛冰岛电流分开。这些变化与北大西洋的更广泛循环直接相关。正是这种循环系统 - 北大西洋子午翻转循环（AMOC） - 目前提供了控制欧洲西北欧洲气候的热量。通过详细地重建冰岛北部NAPF北部位置的变异性在过去的1000年中，阿西卡记录中的氧同位素的变化，我们将增强对系统中逆转的频率以及这些过渡的速度的理解。直接测量AMOC仅可用几年。较长的记录（对于确定AMOC对扰动的敏感性，特别是淡水通量对海洋至关重要 - 依靠代理记录至关重要。政府间气候变化小组的第四次评估报告中强调了产生诸如此类记录的重要性（IPCC，2007年）。 IPCC指出，在过去的1300年中，各种工具和代理气候记录的汇编提供了对平均大型表面温度的差异的关键证据，并清楚地强调了最近的变暖的突出性，尤其是在过去的两到三十年中。但是，IPCC还认识到，迫切需要通过更新现有记录来减少此类汇编的不确定性，其中许多记录是在20年前组装的，并且生成了额外的，尤其是早期的古气候系列，并具有更广泛的地理覆盖范围。该提案旨在通过基于氧气同位素分析的氧气同位素分析来确定与NAPF在北冰岛架子上NAPF的子午线迁移相关的温度异常的自然变异性，从而生成了独特的1000年古温度记录来为这一目标做出贡献。