Cintra Bruno B L, Gloor Manuel, Boom Arnoud, Schöngart Jochen, Baker Jessica C A, Cruz Francisco W, Clerici Santiago, Brienen Roel J W
School of Geography, University of Leeds, Garstang North Building, Leeds, LS2 9JT UK.
Institute of Biosciences, University of São Paulo, Rua do Matão 14, São Paulo, 05508-090 Brazil.
Clim Dyn. 2022;59(5-6):1401-1414. doi: 10.1007/s00382-021-06046-7. Epub 2021 Nov 26.
Extant climate observations suggest the dry season over large parts of the Amazon Basin has become longer and drier over recent decades. However, such possible intensification of the Amazon dry season and its underlying causes are still a matter of debate. Here we used oxygen isotope ratios in tree rings (δO) from six floodplain trees from the western Amazon to assess changes in past climate. Our analysis shows that δO of these trees is negatively related to inter-annual variability of precipitation during the dry season over large parts of the Amazon Basin, consistent with a Rayleigh rainout model. Furthermore δO increases by approximately 2‰ over the last four decades (~ 1970-2014) providing evidence of an Amazon drying trend independent from satellite and in situ rainfall observations. Using a Rayleigh rainout framework, we estimate basin-wide dry season rainfall to have decreased by up to 30%. The δO record further suggests such drying trend may not be unprecedented over the past 80 years. Analysis of δO with sea surface temperatures indicates a strong role of a warming Tropical North Atlantic Ocean in driving this long-term increase in δO and decrease in dry season rainfall.
The online version contains supplementary material available at 10.1007/s00382-021-06046-7.
现有气候观测表明，近几十年来，亚马逊流域大部分地区的旱季变得更长且更干燥。然而，亚马逊旱季这种可能的加剧及其潜在原因仍存在争议。在此，我们利用来自亚马逊西部六个河漫滩树木年轮中的氧同位素比率（δO）来评估过去气候的变化。我们的分析表明，这些树木的δO与亚马逊流域大部分地区旱季降水的年际变化呈负相关，这与瑞利降雨模型一致。此外，在过去四十年（约1970 - 2014年）中，δO增加了约2‰，这为与卫星和实地降雨观测无关的亚马逊干旱趋势提供了证据。利用瑞利降雨框架，我们估计全流域旱季降雨量减少了多达30%。δO记录还表明，这种干旱趋势在过去80年中可能并非前所未有。对δO与海表温度的分析表明，热带北大西洋变暖在推动δO的这种长期增加以及旱季降雨量减少方面发挥了重要作用。
在线版本包含可在10.1007/s00382-021-06046-7获取的补充材料。
