Bulk mineralogy and membership degrees of sediments from the Heihai lake area

Extra-tropical circulation systems impede poleward moisture advection by the Indian Summer Monsoon. In this context, the Himalayan range is believed to insulate the south Asian circulation from extra-tropical influences and to delineate the northern extent of the Indian Summer Monsoon in central Asia. Paleoclimatic evidence, however, suggests increased moisture availability in the Early Holocene north of the Himalayan range which is attributed to an intensification of the Indian Summer Monsoon. Nevertheless, mechanisms leading to a surpassing of the Himalayan range and the northern maximum extent of summer monsoonal influence remain unknown. Here we show that the Kunlun barrier on the northern Tibetan Plateau [~36°N] delimits Indian Summer Monsoon precipitation during the Holocene. The presence of the barrier relocates the insulation effect 1,000 km further north, allowing a continental low intensity branch of the Indian Summer Monsoon which is persistent throughout the Holocene. Precipitation intensities at its northern extent seem to be driven by differentiated solar heating of the Northern Hemisphere indicating dependency on energy-gradients rather than absolute radiation intensities. The identified spatial constraints of monsoonal precipitation will facilitate the prediction of future monsoonal precipitation patterns in Central Asia under varying climatic conditions.中高纬度环流系统（extra-tropical circulation systems）会阻碍印度夏季风（Indian Summer Monsoon）向极地的水汽平流。在此背景下，学界普遍认为喜马拉雅山脉可阻隔南亚环流免受中高纬度环流的影响，并划定印度夏季风在中亚地区的北界。然而古气候证据表明，喜马拉雅山脉以北地区在全新世早期（Early Holocene）的水汽供给量有所提升，这一现象被归因于印度夏季风的增强。尽管如此，促使夏季风影响翻越喜马拉雅山脉并抵达其北界最大范围的具体机制仍未明确。本研究证实，青藏高原北部约北纬36度的昆仑山脉屏障（Kunlun barrier）限定了全新世期间印度夏季风降水的影响范围。该屏障的存在将阻隔效应向北推移了1000公里，使得一支强度较弱的大陆性印度夏季风分支得以形成，并在整个全新世期间持续存在。其北界的降水强度似乎受北半球差异化太阳加热所驱动，这表明该降水强度依赖于能量梯度而非绝对辐射强度。本研究明确的季风降水空间约束机制，将有助于预测不同气候情景下中亚地区未来的季风降水格局。