Low oxygen isotope values of fossil cellulose indicate an intense monsoon in East Asia during the late Oligocene
Low oxygen isotope values of fossil cellulose indicate an intense monsoon in East Asia during the late Oligocene
复制标题
DOI：
10.1016/j.palaeo.2021.110556
复制
发表时间：
2021-07
期刊：
影响因子：
--
通讯作者：
J. Ren;B. Schubert;W. Lukens;C. Quan
中科院分区：
文献类型：
--
作者：
J. Ren;B. Schubert;W. Lukens;C. Quan
渐新世晚期是理解东亚季风强度未来变化的一个重要的深部时间模拟：它代表了比今天更温暖的气候，但伴随着始新世时期西藏-喜马拉雅造山作用的初步抬升。在这里，我们根据从中国南部现代和化石木材中提取的纤维素(δ180cell)的新氧同位素测量结果来量化季风强度。树木年轮δ180O以前被用来追踪东亚全新世的气候变化，因为δ180O主要受大气降水δ18O(δ180兆瓦)和相对湿度的控制。我们发现，在现代样品(25.7VSMOW到29.1VSMOW)上测得的δ180Ocell值与现代季风气候下生长在中国南部的树木的其他‰180Ocell值一致。然而，化石木材的VSMOW值(21.0VSMOW21.0VSMOW24.1VSMOW值)明显低于该地区活树的δ180cell值，与现代高纬度和高海拔地区的值重叠。我们发现，这些低的δ180cell值最好的解释是晚渐新世中国南部的降雨量要大得多，根据现代关系，每月的雨季降雨量可能比今天多出约60%。这些数据代表了中国南部地区在渐新世晚期的第一次季节性降雨量估计，并标志着该地区目前的季风降雨模式的加强。因此，我们推测，在气候变暖的情况下，该地区的季风降雨量可能会大幅增加。
The late Oligocene is an important deep-time analog for understanding future changes in the strength of the East Asian monsoon: it represents a climate warmer than today, yet follows the nascent uplift of the Tibetan–Himalayan orogeny during the Eocene Epoch. Here we quantify monsoon strength based on new oxygen isotope measurements on cellulose (δ18Ocell) extracted from modern and fossil wood from southern China. Tree-ring δ18Ocellvalues have previously been used to track Holocene climate variations in East Asia, as δ18Ocellvalues are primarily controlled by meteoric water δ18O (δ18OMW) and relative humidity. We find the δ18Ocellvalues measured on the modern samples (25.7 to 29.1‰ VSMOW) are consistent with other δ18Ocellrecords from trees growing in southern China under the present-day monsoon climate. However, fossil wood δ18Ocellvalues (21.0 to 24.1‰ VSMOW) are significantly lower than those from living trees in the region, and instead overlap with values from modern high latitudes and high elevations. We show that these low δ18Ocellvalues are best explained by much higher rainfall amounts in southern China during the late Oligocene, with monthly wet-season rainfall that may have been ~60% greater than today based on modern relationships. These data represent the first seasonal rainfall estimates for southern China during the late Oligocene and signify an intensification of the region's current monsoonal rainfall patterns. We speculate that significantly greater monsoon rainfall is therefore possible in the region under a warmer climate.