Paleoclimatic reconstruction for sediment core SO139-74K

A multiproxy record has been acquired from a piston core (SO139-74KL) taken offshore southern Sumatra, an area which is situated in the southwestern sector of the tropical Indo-Pacific Warm Pool. The high-resolution data sets (X-ray fluorescence, total organic carbon, and C37 alkenones) were used to track changes in paleoproductivity, freshwater budget, and sea surface temperature (SST) of the tropical climate system at orbital time scales over the past 300 ka. Our paleoclimatic data show that enhanced marine paleoproductivity was directly related to strengthening of coastal upwelling during periods of increased boreal summer insolation and associated SE monsoon strength with a precessional cyclicity. Changes in freshwater supply were primarily forced by precession-controlled changes in boreal NW winter monsoon rainfall enclosing an additional sea level component. SST variations of 2°-5°C occurred at eccentricity and precessional cyclicity. We suggest that the sea surface temperature variability off southern Sumatra is predominantly related to three major causes: (1) variations in upwelling intensity; (2) an elevated freshwater input into the southern Makassar Strait leading to reduced supply of warmer surface waters from the western Pacific and increased subsurface water transport via the Indonesian Throughflow into the Indian Ocean; and (3) long-term changes in the intensity or frequency of low-latitude climate phenomena, such as El Niño-Southern Oscillation.

本研究从取自苏门答腊南部近海的活塞岩芯（SO139-74KL）中获取了多代理记录，该区域位于热带印度-太平洋暖池（Tropical Indo-Pacific Warm Pool）的西南片区。研究采用高分辨率数据集（X射线荧光光谱（X-ray fluorescence）、总有机碳（total organic carbon）与C37长链烯酮（C37 alkenones）），追踪了过去30万年轨道时间尺度下热带气候系统的古生产力、淡水收支与海表温度（SST）变化。本研究的古气候数据表明，在北半球夏季太阳辐射增强、伴随东南季风强度提升的岁差周期阶段，海洋古生产力提升与沿岸上升流增强直接相关。淡水供给变化主要受岁差驱动的北半球西北冬季风降水变化调控，同时叠加了海平面分量的影响。海表温度存在2℃至5℃的波动，其周期对应偏心率与岁差周期。我们认为苏门答腊南部近海的海表温度变化主要由三大因素导致：（1）上升流强度的变化；（2）望加锡海峡南部淡水输入增加，导致西太平洋暖水补给减少，同时印尼贯穿流（Indonesian Throughflow）向印度洋的次表层水输送增强；（3）低纬度气候现象（如厄尔尼诺-南方涛动（El Niño-Southern Oscillation））的强度或频率长期变化。