NOAA/WDS Paleoclimatology - Boswijk - St Paul's College - AGAU - ITRDB NEWZ107

It is not known how global warming will affect the El Niño/Southern Oscillation (ENSO). The instrumental record is too short to discern centennial-scale trends and modelling results are inconclusive1, 2, 3, 4, 5. Proxy reconstructions indicate that ENSO activity was relatively high during the late twentieth century6, 7, 8, 9, 10, but whether this was unusual in the millennial context remains uncertain. Here we present insights into these issues derived from rings of the kauri tree (Agathis australis), a rare long-lived conifer endemic to the forests of northern New Zealand. Our results indicate that the twentieth century was the most ‘ENSO-active’ century of the past 500 years, but may not be unique in the context of the past 700 years, and that ENSO activity comparable to or elevated above that experienced during the late twentieth century is plausible under warmer-than-present conditions. We also find evidence that there may have been significant changes in the ENSO teleconnection to the New Zealand region during the fourteenth and fifteenth centuries, and of multi-decadal fluctuations in ENSO-related activity building up to the present day. Although these two features may delay the expression of increased ENSO activity in the New Zealand region, our results indicate that New Zealand climate is likely to be more dominated by ENSO-related inter-annual variability as the world continues to warm.

目前尚不清楚全球变暖将如何影响厄尔尼诺-南方涛动（El Niño/Southern Oscillation，ENSO）。器测记录时长过短，难以辨识百年尺度的变化趋势，且相关模拟结果尚无定论1,2,3,4,5。代用重建结果显示，20世纪后期ENSO活动相对活跃6,7,8,9,10，但该现象在千年尺度的气候背景下是否反常仍未明确。本研究基于新西兰北部森林特有分布的稀有长寿命针叶树——贝壳杉（Agathis australis）的年轮，为上述问题提供了新的认知。研究结果表明：20世纪是过去500年中ENSO活动最为活跃的世纪，但在过去700年的气候背景下未必独一无二；在较当前更为温暖的气候条件下，出现堪比或超过20世纪后期的ENSO活动合乎情理。本研究还发现，14至15世纪期间，ENSO与新西兰区域的遥相关可能发生了显著变化，且ENSO相关活动存在年代际波动，直至当前仍在持续。尽管这两类特征可能会延缓ENSO活动增强在新西兰区域的显现，但本研究结果显示，随着全球持续变暖，新西兰气候或将更多受到ENSO相关年际变率的主导。