NOAA/WDS Paleoclimatology - Lorrey - 26/28 Wynyard Street, Auckland - AGAU - ITRDB NEWZ115

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）。仪器观测记录时长过短，难以识别百年尺度的变化趋势，且模拟结果尚无定论1,2,3,4,5。代用重建资料显示，20世纪后期ENSO活动相对较强6,7,8,9,10，但这一现象在千年尺度的气候背景下是否属于异常，仍未明确。本研究依托新西兰北部森林特有的珍稀长寿针叶树种贝壳杉（Agathis australis）的年轮数据，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年的背景下，这一情况并非独有；且在比当前更温暖的气候条件下，出现与20世纪后期相当甚至更强的ENSO活动是合理的。本研究还发现，14至15世纪期间，ENSO与新西兰区域的遥相关关系可能发生了显著变化，且直至今日，与ENSO相关的活动存在年代际尺度的波动。尽管这两个特征可能会延缓新西兰区域ENSO活动增强的信号显现，但研究结果显示，随着全球持续变暖，新西兰气候将更易受到ENSO相关年际变率的主导影响。