NOAA/WDS Paleoclimatology - Luckman - Athabasca Glacier 2 - PCEN - ITRDB CANA430

We present a significant update to a millennial summer temperature reconstruction (1073-1983) that was originally published in 1997. Utilising new tree-ring data (predominantly Picea engelmannii), the reconstruction is not only better replicated, but has been extended (950-1994) and is now more regionally representative. Calibration and verification statistics were improved, with the new model explaining 53% of May-August maximum temperature variation compared to the original (39% of April-August mean temperatures). The maximum latewood density data, which are weighted more strongly in the regression model than ringwidth, were processed using regional curve standardisation to capture potential centennial to millennial scale variability. The reconstruction shows warm intervals, comparable to twentieth century values, for the first half of the eleventh century, the late 1300s and early 1400s. The bulk of the record, however, is below the 1901-1980 normals, with prolonged cool periods from 1200 to 1350 and from 1450 to the late 19th century. The most extreme cool period is observed to be in the 1690s. These reconstructed cool periods compare well with known regional records of glacier advances between 1150 and the 1300s, possibly in the early 1500s, early 1700s and 1800s. Evidence is also presented of the influence of solar activity and volcanic events on summer temperature in the Canadian Rockies over the last 1,000 years. Although this reconstruction is regional in scope, it compares well at multi-decadal to centennial scales with Northern Hemisphere temperature proxies and at millennial scales with reconstructions that were also processed to capture longer timescale variability. This coherence suggests that this series is globally important for the assessment of natural temperature variability over the last 1,000 years.

本研究对1997年首次发表的千年尺度夏季温度重建序列（1073年至1983年）进行了重要更新。本研究采用了以恩格曼云杉（Picea engelmannii为主的全新树轮数据，该重建序列不仅复本质量得到提升，且将重建时段拓展至950年至1994年，区域代表性显著增强。校准与验证统计结果均得到优化，新模型可解释53%的5月至8月最高温度的变率，而原模型仅可解释39%的4月至8月平均温度的变率。相较于树轮宽度数据，最大晚材密度数据在回归模型中拥有更高权重，本研究通过区域曲线标准化方法对其进行处理，以捕捉百年至千年尺度的潜在变率。该重建序列显示，11世纪上半叶、13世纪末与14世纪初存在与20世纪相当的暖期。不过，该序列的大部分时段均低于1901年至1980年的气候基准值，其中1200年至1350年以及1450年至19世纪末存在持续冷期。最极端的冷期出现在1690年代。上述重建冷期与已知的1150年至13世纪的区域冰川推进记录高度吻合，同时也与16世纪初、17世纪初及19世纪的冰川推进记录相符。本研究还揭示了过去1000年以来太阳活动与火山事件对加拿大落基山脉地区夏季温度的影响。尽管该重建序列具有区域范围，它在年代际至百年尺度上与北半球温度代用资料吻合良好，在千年尺度上也与同样以捕捉更长时间尺度变率的重建序列高度一致。这种一致性表明，该序列对于评估过去1000年的自然温度变率具有全球重要性。