Collaborative research: Nonlinearities in the Arctic climate system during the Holocene

合作研究：全新世北极气候系统的非线性

• 批准号: 0908200
• 负责人: Mark Abbott
• 金额: $ 14.14万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0908200&HistoricalAwards=false
• 关键词: Collaborative; research; Nonlinearities; Arctic; climate

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Abstract Rapid changes in the arctic climate system that occurred in the relatively recent past can be compared with the output of climate models to improve the understanding of the processes responsible for nonlinear system change. This study focuses on the transition between the Holocene thermal maximum (HTM) and the onset of Neoglaciation, and on the step-like changes that occurred subsequently during the late Holocene. The millennial-scale cooling trend that followed the HTM coincides with the decrease in Northern Hemisphere summer insolation driven by slow changes in Earth?s orbit. Despite the nearly linear forcing, the transition from the HTM to the Little Ice Age (1500-1900 AD) was neither gradual nor uniform. To understand how feedbacks and perturbations result in rapid changes, a geographically distributed network of proxy climate records will be used to study the spatial and temporal patterns of change, and to quantify the magnitude of change during these transitions. The researchers of this collaborative project will use lacustrine sediments to produce 13 new high-resolution proxy climate records of the past 8000 years. The study sites form two focus regions (eastern Beringia and the NW Atlantic) that generally coincide with the nodes of the surface temperature expression of the Arctic Oscillation (AO). This effort will nearly double the number of high-resolution lacustrine records that extend through the last two millennia, and will generate some of the first high resolution records that capture the HTM. During the HTM, summer sea-ice cover over the Arctic Ocean was likely the smallest of the present interglacial period; certainly it was less extensive than at any time in the past 100 years, and therefore affords an opportunity to investigate a period of warmth similar to what is projected during the coming century. This study focuses on lakes because lakes are the most widely distributed sources of proxy climate records that consistently extend through the post-glacial interval. Because climate change is amplified in the Arctic, the climate signal preserved in arctic lake sediments should be stronger than elsewhere. The proxy records generated in this project will use conventional and newly emerging techniques to document the spatio-temporal patterns of abrupt environmental changes, and to derive quantitative estimates of past summer temperature and hydroclimate variables. Most lakes have been cored previously and show potential for generating high-quality proxy records. Five of the lakes contain laminated sediment with annually resolved records; others have high sedimentation rates (0.5 mm yr-1) for sub-decadal resolution across the climate transitions. Confidence in the paleoclimate reconstructions will be bolstered by a multi-proxy approach, and by replicate lake records in each of the focus regions that will be used to distinguish basin-scale thresholds from regional-scale climate shifts. This project builds on on-going climate-modeling experiments that use NCAR?s Climate System Model (CCSM3) to study the sensitivities of the arctic system to volcanism and solar variability. A new data-model comparison proposed for this study will test whether the most prominent changes in the arctic system during the past 8 ka, as reconstructed from the proxy records, can be explained by a plausible combination of system-component conditions coincident with prolonged volcanism. The experiments, conducted with NCAR collaborators, will focus on the elements of the Arctic system (e.g., AO and extent of sea ice) that participate in abrupt transitions, and that might elicit nonlinear changes in the future.

该奖项是根据2009年《美国复苏与再投资法》（公法111-5）资助的。可以将北极气候系统的抽象快速变化与最近较新的过去发生的北极气候系统变化与气候模型的输出进行比较，以提高对负责非线性系统变化的过程的理解。这项研究的重点是全新世热最大（HTM）与新凝胶开始之间的过渡，以及随后在全新世晚期期间发生的阶梯状变化。 HTM之后的千禧一代冷却趋势与北半球的夏季日光降低相吻合，这是由于地球轨道的缓慢变化而驱动的。尽管强迫几乎是线性的，但从HTM到小冰河时代（1500-1900年）的过渡既不是渐进的也不是统一的。为了了解反馈和扰动如何导致快速变化，将使用代理气候记录的地理分布式网络来研究变化的空间和时间模式，并量化这些过渡期间的变化幅度。该协作项目的研究人员将使用湖间沉积物来生成过去8000年的13个新的高分辨率代理气候记录。研究地点形成了两个重点区域（东部贝林亚和西北大西洋），通常与北极振荡的表面温度表达（AO）相吻合。这项工作将几乎是过去两千年来延伸的高分辨率湖泊记录的数量，并将产生一些捕获HTM的第一个高分辨率记录。在HTM期间，北极海上的夏季海冰覆盖可能是目前冰间时期的最小。当然，它比过去100年的任何时候都不那么广泛，因此提供了一个机会，可以调查与未来世纪预计的温暖时期。这项研究的重点是湖泊，因为湖泊是代理气候记录的分布最广泛的来源，该来源始终延伸到冰川后间隔。由于气候变化在北极地区放大，因此在北极湖沉积物中保存的气候信号应比其他地方更强。该项目生成的代理记录将使用常规和新兴的技术记录突然环境变化的时空模式，并得出过去夏季温度和氢化气候变量的定量估计。大多数湖泊以前已经被批准，并显示出产生高质量代理记录的潜力。其中五个湖泊包含层压沉积物，每年都有解决记录；其他人的沉积率（0.5 mm yr-1）用于整个气候过渡的亚少数分辨率。对古气候重建的置信度将通过多种方法的方法来加强，并通过在每个焦点区域中复制湖泊记录，这些区域将用于区分盆地规模的阈值和区域尺度气候变化。该项目基于使用NCAR气候系统模型（CCSM3）来研究北极系统对火山和太阳可变性的敏感性的持续气候模型实验。本研究提出的新的数据模型比较将测试过去8 ka期间最显着的变化（如从代理记录中重建）是否可以通过系统成分条件的合理组合来解释。与NCAR合作者进行的实验将重点关注参与突然过渡的北极系统（例如AO和海冰的范围）的要素，这可能会在未来引起非线性变化。