Holocene Land-Ocean-Atmosphere Interactions on the Eastern Seaboard of North America

北美东海岸全新世陆地-海洋-大气相互作用

• 批准号: NE/G019851/1
• 负责人: Paul Hughes
• 金额: $ 24.83万
• 依托单位: University of Southampton
• 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%2FG019851%2F1
• 关键词: Holocene; Land; Ocean; Atmosphere; Interactions

Past terrestrial responses to climate-ocean interactions in the North Atlantic region are a critical research priority because they show how changes in key aspects of climate that will be affected by future global warming, such as ice sheet volume & ocean circulation, may be translated into phenomena of socio-economic importance, including the atmospheric water balance & soil moisture availability. Although we are beginning to understand the nature & magnitude of changes in the circulation of the North Atlantic over the last 10,000 years, terrestrial responses to these events are still poorly understood in terms of timing, magnitude & spatial pattern. It is imperative to rectify this deficiency in order to generate & test hypotheses to explain the processes of change, to understand the strength of relationships between oceanic & terrestrial climate change, & to enable future soil conditions & water resources to be predicted using computer models. Plan of work This project will investigate four sites located on a transect along the eastern seaboard of North America, from northern Newfoundland to Maine. This region was highly sensitive to past changes in ice sheet mass balance & ocean circulation. The selected sites are all raised (rain-fed) peat bogs, which provide superb climate archives. Plant & animal (testate amoebae) fossils preserved in well-dated cores extracted from these bogs will be used to reconstruct past changes in Bog Surface Wetness (an index of surface water balance) over the last 8500 years, at a time resolution of 10-100 years. The same core samples will be analysed for stable isotopes of oxygen & hydrogen. The spatial & temporal distribution of the heavy isotopes of these elements in precipitation is related to air temperature, & hence to atmospheric circulation. The isotope signal captured in the cellulose fraction of Sphagnum moss closely tracks that of the precipitation used by the plant for cellulose synthesis. Hence, fossil Sphagnum from raised peat preserves a clear signal of past changes in climate & atmospheric circulation. Modern precipitation along the eastern seaboard of North America is derived mainly from the Atlantic Ocean. A strong temperature contrast exists between the Arctic waters of the Labrador Current, which flows southwards along this coast, & the warm waters of the Gulf Stream further offshore. Past isotopic ratios in precipitation falling over coastal areas will have been strongly influenced by changes in these ocean currents & in the heat transport by the Gulf Stream. By combining the oxygen & hydrogen isotope records, we will estimate the deuterium excess, an index of the conditions prevailing at the sea surface when evaporation occurred, including the extent of sea ice. The stable isotope data will be compared with isotope measurements on ice cores from Greenland & Canadian ice caps, and more cautiously, with estimated isotope values for surface seawater & lakes that have been derived from sediment analyses. Hence, analyses of fossils & stable isotopes from the same core levels will allow us to reconstruct the timing, magnitude & spatial pattern of the terrestrial response, as well as exploring the impact of different causal factors such as meltwater discharges, changes in atmospheric & ocean circulation & solar variability on the climate of the study area. In this way, insight will be gained into the mechanisms that have driven climate change over the last 8500 years. Hypotheses to be tested: 1) Between 8500 & 6800 years ago, the climate of the study area was strongly influenced by repeated discharges of glacial meltwater from the decaying North American Ice Sheet to the north, resulting in cooling & increased bog wetness. 2) After the disappearance of the ice sheet, 6800 years ago, the climate of the study area was indirectly influenced by cyclical variations in sea ice extent, ocean currents & deepwater formation north of Iceland.

北大西洋地区过去陆地对气候-海洋相互作用的反应是一个关键的研究重点，因为它们表明了未来全球变暖将影响气候的关键方面的变化，如冰盖体积和海洋环流，可能会转化为具有社会经济重要性的现象，包括大气水平衡和土壤水分可用性。虽然我们开始了解过去10，000年来北大西洋环流变化的性质和幅度，但就时间，幅度和空间模式而言，对这些事件的陆地反应仍然知之甚少。必须纠正这一缺陷，以产生和测试假设来解释变化过程，了解海洋和陆地气候变化之间关系的强度，并使未来的土壤条件和水资源能够使用计算机模型进行预测。工作计划本项目将调查位于北美东海岸沿着从北方纽芬兰到缅因州的一个样带上的四个地点。这一地区对过去冰盖质量平衡和海洋环流的变化非常敏感。所选的地点都是由雨水灌溉的泥炭沼泽，提供了极好的气候档案。从这些沼泽中提取的保存在年代久远的岩心中的植物和动物（有遗嘱的变形虫）化石将用于重建过去8500年来沼泽表面湿度（地表水平衡指数）的变化，时间分辨率为10-100年。将对相同的岩心样品进行氧和氢的稳定同位素分析。降水中这些元素的重同位素的时空分布与气温有关，从而与大气环流有关。泥炭藓的纤维素组分中捕获的同位素信号密切跟踪植物用于纤维素合成的沉淀。因此，从凸起的泥炭中提取的泥炭藓化石保留了过去气候和大气环流变化的明确信号。北美东海岸沿着的现代降水主要来自大西洋。拉布拉多海流的北极沃茨沿着海岸向南流动，与墨西哥湾流的温暖沃茨之间存在强烈的温度对比。过去落在沿海地区的降水中的同位素比率将受到这些洋流的变化的强烈影响&墨西哥湾流的热量输送。通过结合氧和氢同位素记录，我们将估计氘过量，这是蒸发发生时海面上普遍存在的条件的指数，包括海冰的范围。稳定同位素数据将与格陵兰和加拿大冰帽冰芯的同位素测量结果进行比较，并更谨慎地与从沉积物分析中得出的地表海水和湖泊的估计同位素值进行比较。因此，对来自相同核心水平的化石和稳定同位素的分析将使我们能够重建陆地响应的时间，幅度和空间模式，以及探索不同因果因素的影响，如融水排放，大气和海洋环流的变化以及太阳变率对研究区域的气候。通过这种方式，我们将深入了解过去8500年来推动气候变化的机制。待检验的假设：1）在8500年至6800年前，研究区域的气候受到来自北美冰盖的冰川融水向北反复排放的强烈影响，导致冷却和沼泽湿度增加。2)6800年前冰盖消失后，研究区的气候间接受到海冰范围、洋流和冰岛北部深水形成的周期性变化的影响。

项目成果

Transatlantic distribution of the Alaskan White River Ash

• DOI: 10.1130/g35945.1
• 发表时间: 2014-10-01
• 期刊: GEOLOGY
• 影响因子: 5.8
• 作者: Jensen, Britta J. L.;Pyne-O'Donnell, Sean;Pilcher, Jonathan R.
• 通讯作者: Pilcher, Jonathan R.

Drivers of Holocene peatland carbon accumulation across a climate gradient in northeastern North America

• DOI: 10.1016/j.quascirev.2015.05.012
• 发表时间: 2015-08-01
• 期刊: QUATERNARY SCIENCE REVIEWS
• 影响因子: 4
• 作者: Charman, Dan J.;Amesbury, Matthew J.;Mauquoy, Dmitri
• 通讯作者: Mauquoy, Dmitri

Towards a Holarctic synthesis of peatland testate amoeba ecology: Development of a new continental-scale palaeohydrological transfer function for North America and comparison to European data

• DOI: 10.1016/j.quascirev.2018.10.034
• 发表时间: 2018-12-01
• 期刊: QUATERNARY SCIENCE REVIEWS
• 影响因子: 4
• 作者: Amesbury, Matthew J.;Booth, Robert K.;Warner, Barry G.
• 通讯作者: Warner, Barry G.

The 8.2-ka BP event in north-eastern North America: first combined oxygen and hydrogen isotopic data from peat in Newfoundland

• DOI: 10.1002/jqs.2870
• 发表时间: 2016-05-01
• 期刊: JOURNAL OF QUATERNARY SCIENCE
• 影响因子: 2.3
• 作者: Daley, T. J.;Barber, K. E.;Street-Perrott, F. A.
• 通讯作者: Street-Perrott, F. A.

Simultaneous determination of stable carbon, oxygen, and hydrogen isotopes in cellulose.

• DOI: 10.1021/ac502557x
• 发表时间: 2015
• 期刊: Analytical chemistry
• 影响因子: 7.4
• 作者: N. Loader;F. Street-Perrott;T. Daley;P. Hughes;Á. Kimák;T. Levanič;Gerald P. Mallon;D. Mauquoy;I. Robertson;T. Roland;S. van Bellen;M. Ziehmer;M. Leuenberger