Collaborative Research: P2C2--Reconstructing Deglacial and Holocene Climate Variability in Southeast Asia Using Speleothems and Isotope-Enabled Model Simulations

亚洲季风系统是全球气候系统的重要组成部分，在从热带向高纬度地区输送热量和水分方面起着重要作用。即使是季节性降雨强度和/或时间上的微小变化，也会对生活在亚洲季风区内的数十亿人产生重大影响，但气候模式对未来季风变化的预测仍然不确定。虽然古气候记录大大提高了我们对某些地区夏季季风变异的认识，但我们对东南亚季风变异的范围和机制仍然知之甚少。这项研究是加州大学欧文分校和新泽西州威廉·帕特森学院的科学家们共同努力的成果，将在老挝（印度和东亚季风系统交界的关键地点）产生过去2万年水文气候变化的高分辨率洞穴（洞穴方解石沉积物）记录。新的氧同位素记录将在次年代际到轨道时间尺度上记录东南亚季风强度的变化，填补热带古气候记录中一个关键的时空空白。通过整合古气候代理数据、仪器气候数据和气候模式分析，该项目将解决三个主要问题：(1)在过去2万年中，东南亚季风强度如何响应轨道强迫、千年尺度突变气候事件和年际至多年代际气候模式而变化？(2)老挝降水和洞穴氧同位素在年际-轨道时间尺度上的控制机制；(3)老挝洞穴记录与热带印度洋-太平洋地区、亚洲季风区和高纬度地区过去气候变化的更广泛的时空格局有何关系？除了科学成果外，该项目还将为研究生和本科生提供研究机会，并将纳入旨在改善代表性不足群体参与地球科学的推广工作。例如，美国国家科学基金会资助的美国印第安人夏季地球系统科学研究所将于每年夏天在加州大学欧文分校举办一次关于古气候、气候变化和本土文化的实地和实验室实践活动。

The Asian Monsoon system is an important component of the global climate system that plays a major role in the transport of heat and moisture from the tropics to higher latitudes. Even small variations in the strength and/or timing of seasonal rainfall can have significant impacts on the billions of people living within the Asian monsoon domain, yet climate model projections of future monsoon changes still remain uncertain. While paleoclimate records have significantly advanced our understanding of summer monsoon variability in some regions, we still know very little about the range and mechanisms of monsoon variability in Southeast Asia. This research, a collaborative effort between scientists from the University of California, Irvine and William Patterson College of New Jersey, will generate high-resolution speleothem (cave calcite deposit) records of past hydroclimate variability over the last 20,000 years from Laos, a key site at the interface between the Indian and East Asian monsoon systems. The new oxygen isotope records will document changes in Southeast Asian monsoon strength on sub-decadal to orbital timescales, filling in a key spatial and temporal gap in the paleoclimate record of the tropics. Through integrating paleoclimate proxy data, instrumental climate data, and climate model analyses, the project will address three main questions: (1) How has Southeast Asian monsoon intensity varied over the past 20,000 years in response to orbital forcing, millennial-scale abrupt climate events, and interannual to multi-decadal climate modes?; (2) What are the mechanisms that control precipitation and speleothem oxygen isotopes on interannual to orbital timescales in Laos?; and (3) How do the Laos speleothem records relate to broader spatial and temporal patterns of past climate variability in the tropical Indo-Pacific, the Asian monsoon region, and high latitudes? In addition to the scientific outcomes, this project will provide research opportunities for graduate and undergraduate students and will be incorporated in outreach efforts aimed at improving the participation of underrepresented groups in the geosciences. For instance, a hands-on field and laboratory exercise on paleoclimate, climate change, and native culture will be developed for the NSF funded American Indian Summer Institute in Earth System Science held at the University of California, Irvine each summer.