Climatic and volcanic forcing of tropical belt northern boundary over the past 800 years
Climatic and volcanic forcing of tropical belt northern boundary over the past 800 years
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DOI：
10.1038/s41561-018-0242-1
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发表时间：
2018-10
影响因子：
18.3
通讯作者：
R. Alfaro‐Sánchez;Hanh Nguyen;S. Klesse;A. Hudson;S. Belmecheri;N. Köse;H. Diaz;R. Monson;R. Villalba;V. Trouet
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作者：
R. Alfaro‐Sánchez;Hanh Nguyen;S. Klesse;A. Hudson;S. Belmecheri;N. Köse;H. Diaz;R. Monson;R. Villalba;V. Trouet
热带北方边界的位置影响着北方半球许多干旱和半干旱地区的水文气候。自1970年代以来，热带的加宽主要归因于人类活动的强迫。然而，在此之前，对热带带扩张和收缩的自然驱动因素的相对影响知之甚少。利用北方5个中纬度地区的树轮宽度资料，重建了近800年来（ad 1203 -2003）早春热带带北方边界的运动。我们的重建解释了45%的年际变化的纬度范围内的哈德利环流，度量的热带边界的位置。我们发现，在厄尔尼诺南方涛动和太平洋北美遥相关模式的正（负）阶段，热带收缩（扩大）。在大规模火山活动将硫注入平流层后，热带也大幅收缩。持续时间最长的热带扩张发生在世纪晚期，也就是小冰期最冷的时期之一。我们的研究结果警告说，未来热带带宽度的变化，由自然气候变化或平流层气溶胶注入，无论是火山或人工驱动的潜在社会经济后果。
The position of the northern boundary of the tropical belt affects the hydroclimate of many arid and semi-arid regions in the Northern Hemisphere. Widening of the tropical belt since the 1970s has largely been attributed to anthropogenic forcing. However, the relative influence of natural drivers of tropical belt expansion and contraction before this time is poorly understood. Here we use data on tree-ring widths from five mid-latitude regions in the Northern Hemisphere to reconstruct the movement of the northern boundary of the early spring tropical belt over the past 800 years (ad1203–2003). Our reconstruction explains 45% of the interannual variance in the latitudinal extent of the Hadley circulation, a metric of the position of the tropical belt boundary. We find that the tropical belt contracted (expanded) during positive (negative) phases of the El Niño Southern Oscillation and Pacific North American teleconnection patterns. The tropical belt also contracted significantly following major volcanic events that injected sulfur into the stratosphere. The longest period of persistent tropical belt expansion occurred in the late sixteenth century, during one of the coldest periods of the Little Ice Age. Our results warn of potential socio-economic consequences of future variations in tropical belt width driven by natural climate variability or stratospheric aerosol injections, whether volcanic or artificial.