Instituto de Geociências, Universidade de São Paulo, São Paulo 05508-090, Brazil.
Department of Atmospheric and Environmental Sciences, University at Albany, Albany, New York 12222, USA.
Sci Rep. 2016 Apr 21;6:24762. doi: 10.1038/srep24762.
The South American Monsoon System (SAMS) is generally considered to be highly sensitive to Northern Hemisphere (NH) temperature variations on multi-centennial timescales. The direct influence of solar forcing on moisture convergence in global monsoon systems on the other hand, while well explored in modeling studies, has hitherto not been documented in proxy data from the SAMS region. Hence little is known about the sensitivity of the SAMS to solar forcing over the past millennium and how it might compete or constructively interfere with NH temperature variations that occurred primarily in response to volcanic forcing. Here we present a new annually-resolved oxygen isotope record from a 1500-year long stalagmite recording past changes in precipitation in the hitherto unsampled core region of the SAMS. This record details how solar variability consistently modulated the strength of the SAMS on centennial time scales during the past 1500 years. Solar forcing, besides the previously recognized influence from NH temperature changes and associated Intertropical Convergence Zone (ITCZ) shifts, appears as a major driver affecting SAMS intensity at centennial time scales.
南美季风系统（SAMS）通常被认为对北半（NH）球多百年时间尺度上的温度变化高度敏感。另一方面，太阳辐射对全球季风系统中水汽辐合的直接影响在模式研究中得到了很好的探讨，但在 SAMS 地区的代用数据中尚未记录。因此，人们对 SAMS 在过去一千年中对太阳辐射的敏感性知之甚少，也不知道它如何与主要由火山活动引起的 NH 温度变化竞争或建设性地相互作用。在这里，我们提出了一个新的 1500 年长的石笋氧同位素记录，该石笋记录了过去 SAMS 核心未采样区域降水的变化。该记录详细说明了在过去 1500 年中，太阳变化如何在百年时间尺度上持续调节 SAMS 的强度。除了先前认识到的 NH 温度变化和相关热带辐合带（ITCZ）变化的影响外，太阳辐射似乎是影响 SAMS 百年时间尺度强度的主要驱动因素。
