Palaeoclimate reconstructions from Tierra Del Fuego to detect Land-Ocean-Atmosphere Interactions

火地岛古气候重建以探测陆地-海洋-大气相互作用

• 批准号: NE/I023104/1
• 负责人: Neil Loader
• 金额: $ 17.45万
• 依托单位: Swansea University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI023104%2F1
• 关键词: Palaeoclimate; reconstructions; Tierra; Del; Fuego

The nature of future human induced climate change is highly uncertain with projected global temperature increases in 2100 spanning 0.3-6.4 Celsius (IPCC 2007, AR4). Part of this large uncertainty is due to the paucity of climate & proxy-climate data to validate climate models & constrain Earth System sensitivity to simulated forcing, particularly in the Southern Hemisphere (SH). A key component of variability of the SH atmosphere is the Southern Annular Mode (SAM), which is an oscillation of atmospheric mass that results in changes in the westerly winds over the Southern Ocean. The SH westerly winds modify the upwelling of carbon-rich deep water & therefore influence the global balance of carbon dioxide between the ocean and the atmosphere. It is uncertain whether the recently observed intensification of the southern westerlies will cause the Southern Ocean to be a net source or sink of atmospheric carbon dioxide. Little is known about the long-term past variability of the southern westerlies & atmospheric carbon dioxide, making it difficult to separate internally & externally-forced fluctuations. It is imperative to rectify this deficiency in order to generate & test hypotheses to explain the processes of change in the strength of the southern westerlies & how these are related to (inter-)hemispheric climate change during known periods of contrasting climate change, for example the Medieval Climatic Anomaly & the Little Ice Age. This project will investigate four new sites located in southern South America (SSA). This region is located in the core of the southern westerlies and is ideally located to capture changes in their intensity. SSA terrestrial peatland-based palaeoclimate archives are capable of recording long-term changes in the westerlies, given that wind intensity affects precipitation mainly produced in winter by fronts & low-pressure systems embedded in the prevailing westerly circulation. The selected sites are all rain-fed peat bogs, which provide excellent climate archives. Plant & protozoan (testate amoebae) fossils preserved in well-dated cores extracted from these bogs will be used to reconstruct past changes in Bog Surface Wetness (BSW, an index of surface water balance) over the last ~2000 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. The stable isotope data will be compared with isotope measurements from moss banks & ice cores from the maritime Antarctic and Antarctic Peninsula, in addition to stable water isotope data & BSW reconstructions from eastern North America. Analyses of fossils & stable isotopes from the same core levels will allow us to reconstruct the timing, magnitude & spatial pattern of the regional terrestrial response, as well as exploring the impact of different causal factors such as 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 ~2000 years. Hypotheses to be tested: 1 Climate changes during the last ~2000 years in SSA are in phase with climate changes identified in eastern North America & NW Europe, & represent inter-hemispheric teleconnections. 2 Climate changes in SSA during the last ~2000 years are in antiphase with Northern Hemisphere climate changes & represent a bipolar seesaw. 3 Climate changes in SSA during the last ~2000 years are uncorrelated with Northern Hemisphere climate changes.

未来人类引起的气候变化的性质具有很大的不确定性，预计2100年全球气温将上升0.3-6.4摄氏度（IPCC 2007，AR 4）。这种巨大的不确定性部分是由于缺乏气候和代理气候数据来验证气候模型并限制地球系统对模拟强迫的敏感性，特别是在南半球。南半球大气变化的一个关键组成部分是南半球环形模态（SAM），这是一种大气质量的振荡，导致南大洋西风的变化。南半球西风改变了富碳深水的上升流，从而影响了全球海洋和大气之间的二氧化碳平衡。目前还不确定最近观测到的增强的南部西风带是否会导致南大洋成为大气二氧化碳的净源或汇。对南方西风带和大气二氧化碳的长期变化知之甚少，这使得很难将内部和外部强迫波动分开。必须纠正这一缺陷，以产生和测试假设来解释南部西风带强度的变化过程，以及这些变化如何与已知的气候变化对比时期的（间）半球气候变化相关，例如中世纪气候异常和小冰期。该项目将调查位于南美洲南部（SSA）的四个新地点。这个区域位于南部西风带的核心，是捕捉其强度变化的理想位置。SSA陆地泥炭地为基础的古气候档案能够记录长期的变化，西风带，风强度影响降水主要是在冬季由嵌入在盛行西风环流的前和低压系统。所选的地点都是雨水灌溉的泥炭沼泽，提供了极好的气候档案。保存在从这些沼泽中提取的年代久远的岩心中的植物和原生动物（有壳变形虫）化石将用于重建过去2000年来沼泽表面湿度（BSW，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。稳定同位素数据将与来自海洋南极和南极半岛的苔藓银行和冰芯的同位素测量结果进行比较，此外还将与来自北美东部的稳定水同位素数据和BSW重建进行比较。对来自相同岩心水平的化石和稳定同位素的分析将使我们能够重建区域陆地响应的时间，幅度和空间模式，并探索不同因果因素的影响，如大气和海洋环流的变化以及太阳变率对研究区域气候的影响。通过这种方式，将深入了解过去2000年来推动气候变化的机制。待检验的假设：1近2000年来，SSA的气候变化与北美东部和欧洲西北部的气候变化同步，代表了半球间的遥相关。2近2000年来，SSA的气候变化与北方气候变化呈反位相，表现为两极跷跷板。3近2000年来，SSA的气候变化与北方气候变化无关。

项目成果

Late-Holocene climate dynamics recorded in the peat bogs of Tierra del Fuego, South America

• DOI: 10.1177/0959683615609756
• 发表时间: 2016-03
• 期刊: The Holocene
• 作者: S. van Bellen;D. Mauquoy;Paul D.M. Hughes;T. Roland;T. Daley;N. Loader;F. Street-Perrott;Emma M. Rice;V. Pancotto;Richard J Payne

Investigating late Holocene variations in hydroclimate and the stable isotope composition of precipitation using southern South American peatlands: an hypothesis

利用南美南部泥炭地研究全新世晚期水文气候的变化和降水的稳定同位素组成：一个假设

• DOI: 10.5194/cp-8-1457-2012
• 发表时间: 2012
• 期刊: Climate of the Past
• 影响因子: 4.3
• 作者: Daley T

Testate amoebae as a proxy for reconstructing Holocene water table dynamics in southern Patagonian peat bogs

将变形虫作为重建巴塔哥尼亚南部泥炭沼泽全新世地下水位动态的代理

• DOI: 10.1002/jqs.2719
• 发表时间: 2014
• 期刊: Journal of Quaternary Science
• 影响因子: 2.3
• 作者: VAN BELLEN S

Significance testing testate amoeba water table reconstructions

• DOI: 10.1016/j.quascirev.2016.01.030
• 发表时间: 2016-04
• 期刊: Quaternary Science Reviews
• 影响因子: 4
• 作者: R. Payne;K. Babeshko;S. Bellen;J. Blackford;R. Booth;D. Charman;Megan R. Ellershaw;D. Gilbert;P. Hughes;V. Jassey;Łukasz Lamentowicz;M. Lamentowicz;E. Malysheva;D. Mauquoy;Y. Mazei;E. Mitchell;G. Swindles;A. Tsyganov;T. Turner;R. Telford

An alternative approach to transfer functions? Testing the performance of a functional trait-based model for testate amoebae

• DOI: 10.1016/j.palaeo.2016.12.005
• 发表时间: 2017-02
• 期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
• 作者: S. Bellen;D. Mauquoy;R. Payne;T. Roland;P. Hughes;T. Daley;N. Loader;F. Street-Perrott;Emma M. Rice;V. Pancotto