张 旭 研究员
Paleoclimate proxy records have shown a close coupling between millennial-scale climate variability and insolation-induced orbital-scale climate evolutions during the Pleistocene Epoch. However, it remains elusive whether there exists a direct dynamic link between insolation changes and millennial-scale climate variability. Here, by using a comprehensive fully coupled climate model, we show that orbitally-induced insolation changes alone can give rise to millennial-scale spontaneous climate oscillations under intermediate glacial conditions. Our results demonstrate that increases in low-latitude boreal summer insolation (controlled by eccentricity-modulated precession) can trigger abrupt climate transitions from warm interstadial to cold stadial conditions by increasing freshwater budget in the North Atlantic via a reduction of the tropical Atlantic-to-Pacific atmospheric moisture export. Meanwhile, decreases in high-latitude mean insolation (controlled by obliquity) also trigger these transitions by cooling and expanding sea-ice cover in the key convection sites of the northern North Atlantic. Of particular importance is existence of unforced AMOC oscillations under constant orbital settings that modulate thermohaline balance between the tropical and subpolar North Atlantic by exerting contrast effects over them on the strength of Atlantic overturning circulation. These results advance our insights of governing dynamics of climate instability, broadening Milankovitch theory and providing a basis to commence a coherent framework for understanding origins of abrupt glacial climate changes during the Pleistocene Epoch.
张旭，男，生于1986年1月，研究员，博士生导师。长期从事古气候变化的机理研究，主攻气候突变事件及其全球遥相关的动力机理，高纬度冰-海-气反馈对气候演变的调制机理和中低纬度水循环时空演变的动力机理。现共发表论文50余篇，其中在《Nature》（5篇）、《Science》（1篇）、《Nature Geoscience》（4篇）等NSP顶级学术刊物发表15篇论文，第一通讯作者单篇文章引用达200余次。曾任Past Climate Change杂志大洋环流与碳循环专刊主编，现任《Science Bulletin》，《中国科学-地球科学》编委，《Geosystems and Geoenvironment》副主编。