NOAA/WDS Paleoclimatology - Porter - Peel Channel Mackenzie Delta - PCGL - ITRDB CANA516

We present a reconstruction of June-July minimum temperatures since AD 1245 for the Mackenzie Delta region based on a 29-site network of white spruce (Picea glauca) ring-width series. Most but not all trees experienced a divergent temperature-growth response, similar to the divergence that has affected other white spruce trees across Yukon and Alaska. However, divergence in the study region began as early as AD 1900 and we have documented our methods to avoid including divergent signals in the reconstruction. Calibration/verification testing based on local temperature data, and multi-century coherence with nearby and large-scale temperature proxy records, confirm that our reconstruction is robust. The reconstruction shows cool conditions in the late 13th, early 18th and early 19th centuries, corresponding with solar minima and increased volcanism. These cool periods are interrupted by warm periods consistent with early to mid-20th century warmth. The late 20th century is the warmest interval, and the last decade is estimated to be 1.4C warmer than any decade before the mid-20th century. The reconstructed climate history corroborates other proxy-based inferences and supports the notion that high-latitude regions such as the Mackenzie Delta have experienced rapid warming in recent decades that is exceptional in the last eight centuries.

本研究基于覆盖29个采样点的白云杉（Picea glauca）年轮宽度序列，重建了公元1245年以来马更些三角洲地区6-7月最低气温序列。多数（而非全部）树木呈现温度-生长响应分歧现象，这与育空地区及阿拉斯加境内其他白云杉所受的分歧影响特征相似。但本研究区域的分歧现象早在公元1900年便已出现，我们已明确研究方法以规避重建过程中纳入分歧信号的风险。基于局地气温数据开展的校准/验证检验，以及与邻近区域及大尺度气温代用记录之间的多世纪一致性验证，均证实本重建结果具备稳健性。重建结果显示，13世纪末、18世纪初及19世纪初区域气候偏冷，这与太阳极小期及火山活动增强的时段高度吻合。这些冷期被与20世纪早中期暖期特征一致的暖期所打断。20世纪晚期为研究时段内最暖的时段，且近十年的气温较20世纪中期之前的任何十年均高出1.4℃。本重建的气候历史与其他代用指标推论结果相互印证，进一步支持了马更些三角洲等高纬度地区近数十年快速变暖的结论——这一变暖速率在过去8个世纪中均属罕见。