Calibration and Reconstruction of Past Temperature Changes from Glacial Varved Sediments

巴芬岛的多纳德湖（donard Lake）每年都有由夏季融化的驯鹿冰川（Caribou Glacier）产生的层状沉积物，而驯鹿冰川目前在其集水区占主导地位。多纳德湖层状沉积物是典型的冰川湖相沉积物，包含了夏季温度变化的记录，可能追溯到距今5000年前。先前使用单个岩心校准唐纳湖阀门厚度的努力显示阀门厚度与温度相关（r=0.57），但也有大量无法解释的方差。当温度和阀门厚度数据被平滑为三年平均值时，相关性大大提高（r=0.82），这表明年度数据的低相关性是由单芯阀门年表中包含的误差和随机噪声引起的。对其他北极湖泊中变异沉积物的研究表明，对多个岩心的测量结果进行平均对于精确的校准研究是必要的，这可以消除年表中的误差，并减少单个岩心中随机变化带来的噪音。详细的校准数据集对于提高层状沉积物记录作为古温度代用物的效用至关重要，无论是对单个地点温度变化幅度的精确定量重建，还是对整个北极地区古气候记录的综合空间网络的发展。首席研究员将使用一套5个新的沉积物岩心，在沉积物-水界面完好无损的情况下，为多纳德湖构建一个高质量的多岩心阀年表。多个岩心的相互关联将提供精确的层数年表，用于使用独立测年方法（包括137cs和210Pb）的组合来确认年沉积。交叉相关年表还将允许在几个岩心之间平均每年的阀门厚度测量，从而提供一个全湖范围的阀门厚度记录，该记录受单个岩心随机噪声的影响要小得多。该阀门厚度记录将使用附近Cape Dyer的每月仪器气象数据校准为夏季温度，从而为唐纳湖阀门提供精确和准确的温度校准关系。气象数据还将用于研究降水对阀门厚度的可能影响。用于校准阀门厚度和温度的多芯阀门年表将在新岩心中延长至大约500年前。加拿大东部北极地区500年来的温度变化新记录将为小冰期结束时变暖的精确幅度提供重要的量化，并将有助于区分全球气候变化的自然和人为强迫。此外，古温度记录的年际性质还可以精确地确定过去五个世纪的变化和变化率，并将最近的气候变化置于自然变率的长期视角中。巴芬岛的多纳德湖（donard Lake）每年都有由夏季融化的驯鹿冰川（Caribou Glacier）产生的层状沉积物，而驯鹿冰川目前在其集水区占主导地位。多纳德湖层状沉积物是典型的冰川湖相沉积物，包含了夏季温度变化的记录，可能追溯到距今5000年前。先前使用单个岩心校准唐纳湖阀门厚度的努力显示阀门厚度与温度相关（r=0.57），但也有大量无法解释的方差。当温度和阀门厚度数据被平滑为三年平均值时，相关性大大提高（r=0.82），这表明年度数据的低相关性是由单芯阀门年表中包含的误差和随机噪声引起的。对其他北极湖泊中变异沉积物的研究表明，对多个岩心的测量结果进行平均对于精确的校准研究是必要的，这可以消除年表中的误差，并减少单个岩心中随机变化带来的噪音。详细的校准数据集对于提高层状沉积物记录作为古温度代用物的效用至关重要，无论是对单个地点温度变化幅度的精确定量重建，还是对整个北极地区古气候记录的综合空间网络的发展。首席研究员将使用一套5个新的沉积物岩心，在沉积物-水界面完好无损的情况下，为多纳德湖构建一个高质量的多岩心阀年表。多个岩心的相互关联将提供精确的层数年表，用于使用独立测年方法（包括137cs和210Pb）的组合来确认年沉积。交叉相关年表还将允许在几个岩心之间平均每年的阀门厚度测量，从而提供一个全湖范围的阀门厚度记录，该记录受单个岩心随机噪声的影响要小得多。该阀门厚度记录将使用附近Cape Dyer的每月仪器气象数据校准为夏季温度，从而为唐纳湖阀门提供精确和准确的温度校准关系。气象数据还将用于研究降水对阀门厚度的可能影响。用于校准阀门厚度和温度的多芯阀门年表将在新岩心中延长至大约500年前。加拿大东部北极地区500年来的温度变化新记录将为小冰期结束时变暖的精确幅度提供重要的量化，并将有助于区分全球气候变化的自然和人为强迫。此外，古温度记录的年际性质还可以精确地确定过去五个世纪的变化和变化率，并将最近的气候变化置于自然变率的长期视角中。

ABSTRACTHughenOPP-0096751Donard Lake, Baffin Island, contains annually laminated sediments produced by the summer melting of the Caribou Glacier, which currently dominates its catchment. Donard Lake laminated sediments are classic glacio-lacustrine varves and contain a record of summer temperature variations, potentially as far back as 5,000 years before present. Previous efforts to calibrate Donard Lake varve thickness using a single core showed a correlation of varve thickness to temperature (r=0.57), but also a large amount of unexplained variance. The correlation was greatly improved when both temperature and varve thickness data were smoothed into three-year averages (r=0.82), suggesting that the low correlation for annual data was caused by error and random noise contained in the single-core varve chronology. Research on varved sediments in other Arctic lakes has shown that averaging together measurements from multiple cores is necessary for accurate calibration studies, to eliminate errors in the annual chronology and to reduce noise from random variability contained within individual cores. Detailed calibration data sets are critical to improving the utility of laminated sediments records as paleotemperature proxies, both for accurate quantitative reconstructions of the magnitude of temperature change at individual locations, as well as for the development of integrated spatial networks of paleoclimate records throughout the Arctic.The Principal Investigator will use a suite of five new sediment cores, retrieved with the sediment-water interfaces intact, to construct a high-quality, multiple-core varve chronology for Donard Lake. Cross correlation of the multiple cores will provide a precise layer-count chronology for confirmation of annual deposition using a combination of independent dating methods, including 137 Cs and 210Pb. The cross-correlated chronology will also allow averaging of each year's varve thickness measurements between several cores, providing a lake-wide varve thickness record that is much less influenced by random noise from individual cores. This varve thickness record will be calibrated to summer temperature using monthly instrumental meteorological data from nearby Cape Dyer, resulting in precise and accurate temperature calibration relationships for Donard Lake varves. The meteorological data will also be used to investigate the possible influence of precipitation on varve thickness. The multiple-core varve chronology used to calibrate varve thickness to temperature will be extended back in the new cores for approximately 500 years. This new, 500-year record of temperature change in the eastern Canadian Arctic will provide important quantification of the precise magnitude of warming at the end of the Little Ice Age, and will help efforts to discriminate between natural and anthropogenic forcing of global climate change. In addition, the annual nature of the paleotemperature record will also allow precise determination of variance and rates of change during the past five centuries and place recent climatic changes into a longer-term perspective of natural variability.ABSTRACTHughenOPP-0096751Donard Lake, Baffin Island, contains annually laminated sediments produced by the summer melting of the Caribou Glacier, which currently dominates its catchment. Donard Lake laminated sediments are classic glacio-lacustrine varves and contain a record of summer temperature variations, potentially as far back as 5,000 years before present. Previous efforts to calibrate Donard Lake varve thickness using a single core showed a correlation of varve thickness to temperature (r=0.57), but also a large amount of unexplained variance. The correlation was greatly improved when both temperature and varve thickness data were smoothed into three-year averages (r=0.82), suggesting that the low correlation for annual data was caused by error and random noise contained in the single-core varve chronology. Research on varved sediments in other Arctic lakes has shown that averaging together measurements from multiple cores is necessary for accurate calibration studies, to eliminate errors in the annual chronology and to reduce noise from random variability contained within individual cores. Detailed calibration data sets are critical to improving the utility of laminated sediments records as paleotemperature proxies, both for accurate quantitative reconstructions of the magnitude of temperature change at individual locations, as well as for the development of integrated spatial networks of paleoclimate records throughout the Arctic.The Principal Investigator will use a suite of five new sediment cores, retrieved with the sediment-water interfaces intact, to construct a high-quality, multiple-core varve chronology for Donard Lake. Cross correlation of the multiple cores will provide a precise layer-count chronology for confirmation of annual deposition using a combination of independent dating methods, including 137 Cs and 210Pb. The cross-correlated chronology will also allow averaging of each year's varve thickness measurements between several cores, providing a lake-wide varve thickness record that is much less influenced by random noise from individual cores. This varve thickness record will be calibrated to summer temperature using monthly instrumental meteorological data from nearby Cape Dyer, resulting in precise and accurate temperature calibration relationships for Donard Lake varves. The meteorological data will also be used to investigate the possible influence of precipitation on varve thickness. The multiple-core varve chronology used to calibrate varve thickness to temperature will be extended back in the new cores for approximately 500 years. This new, 500-year record of temperature change in the eastern Canadian Arctic will provide important quantification of the precise magnitude of warming at the end of the Little Ice Age, and will help efforts to discriminate between natural and anthropogenic forcing of global climate change. In addition, the annual nature of the paleotemperature record will also allow precise determination of variance and rates of change during the past five centuries and place recent climatic changes into a longer-term perspective of natural variability.