Collaborative Research: A Synthesis of the Last 2000 Years of Climatic Variability from Arctic Lakes

该项目通过将20世纪的气候变化置于过去2000年的年代际气候变率的长期背景下，有助于了解北极系统。该项目的核心是对北美北极地区湖泊的标准化、高分辨率代用气候记录的综合，这将促进我们对北极在地球系统中的作用的理解。最近的结果表明，北极的代用气候记录保留了夏季温度的特征，这与全球平均变暖和北极涛动都有关。这一结论是基于对过去600年的综合研究得出的。目前，从小冰期到以前的暖期的现有记录太少，无法充分确定地捕捉到变率模式。这些模态的较长期演变可在年代际解析的代理记录中识别出来，并应保存在年代际到多年代际解析的较长记录中。这种年到年代际气候变率的综合将贯穿中世纪时期的关键暖期。目前北极地区可获得的高分辨率、2000年代用气候记录的数量将增加近三倍，气候重建的确定性将大大提高。该项目通过标准化方法和为授权合作者及其学生举办研讨会来促进结果的整合。这项对北极系统的紧密集中的综合研究将直接整合到气候建模工作中，以探索火山活动和太阳辐照度波动与气候系统内部调整及其内在变率模式的作用，以解释在代理气候数据中观察到的模式。在整个北极地区，湖泊档案包含了过去2000年最容易获取和分布最广泛的代理记录。这项工作侧重于PIs的30个最高优先级、最有希望的湖泊，几乎所有这些湖泊之前都已被记录。站点网络包括两个区域焦点（阿拉斯加和北大西洋西北部），它们通常包含北极涛动地表温度表达的节点，从而促进了这种变率模式的重建。一半的湖泊含有层状沉积物，具有每年解决记录的潜力；其他湖泊在5至30年的样品分辨率下具有较高的沉积速率。大多数湖泊的代理数据可以与附近的树木年轮记录或仪器数据进行比较，或者可以应用传递函数来产生温度或其他气候变量的定量估计。作为正在进行的研究的一部分，大多数岩心的低分辨率分析已经开始。来自这些湖泊的初步数据表明，它们具有很大的气候重建潜力。

This project contributes to understanding the Arctic system by placing 20th century climatic change into a longer-term context of inter-decadal climatic variability spanning the last 2000 yr. The centerpiece of the project is a synthesis of standardized, high-resolution proxy climate records from lakes across the North American Arctic that will advance our understanding of the role of the Arctic within the Earth system.Recent results have demonstrated that proxy climate records from the Arctic preserve a signature of summer temperature that is related to both global mean warming and the Arctic Oscillation. This conclusion was based on a synthesis limited to just the last 600 yr. Available records that extend beyond the Little Ice Age to previous warm intervals are currently too few to capture modes of variability with adequate certainty. The longer-period evolution of these modes is identifiable in decadally resolved proxy records, and should be preserved in longer records of annual to multi-decadal resolution.This synthesis of annual to inter-decadal climatic variability will extend through the key warm interval of Medieval time. The certainty of the climate reconstruction will be significantly improved by nearly tripling the number of high-resolution, 2000-yr-long, proxy climate records currently available in the Arctic. The project facilitates integration of results by standardizing the methodologies and by holding workshops for vested collaborators and their students. This tightly focused synthetic study of the Arctic system will be integrated directly into a climate-modeling effort to explore the role of volcanism and solar irradiance fluctuations versus internal adjustments of the climate system and its inherent modes of variability to explain observed patterns in the proxy climate data.Across the Arctic, lacustrine archives contain the most accessible and widely distributed proxy records for the past 2000 yr. This work focuses on 30 of the PIs' highest-priority, most-promising lakes, nearly all of which have been cored previously. The network of sites includes two regional foci (Alaska and the NW North Atlantic) that generally encompass the nodes of the surface temperature expression for the Arctic Oscillation, thereby facilitating the reconstruction of this mode of variability. Half of the lakes contain laminated sediment with potential for annually resolved records; others have high sedimentation rates for sample resolution of 5 to 30 yr. The proxy data from most lakes can be compared with nearby tree-ring records or instrumental data, or can be applied to transfer functions to yield quantitative estimates of temperature or other climatic variables. Analyses at low-resolution have already begun on most of the cores as part of on-going research. Preliminary data from these lakes indicate their high potential for climate reconstructions.