Mostapha Bousmina, President of the Euro Mediterranean University of Fes and Chancellor of the Hassan II Academy of Science and Technology.
Driss Ouazar, Professor of Civil Engineering, Head of LASH: HydroSystems Analysis Laboratory, National Research Council Associate Laboratory.
Lindsey Gillson, Dept of Biological Sciences, University of Cape Town, Rondebosch, South Africa.
Timothy Lenton, University of Exeter, Exeter, UK.
Yoshi Maezumi, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands.
Hai Cheng, School of Human Settlement and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
High and low latitude climate interactions at multiple timescales
Earth’s natural climate system varies persistently at multiple timescales with different dynamics. While we outline a sustainable future for a climate context, detailed case studies of past climate variations on various timescales are important, which however, haven’t yet been fully developed. In the last two decades, significant advances in understanding the climatic controls on d18O in atmosphere and cave environment together with landmark developments in U-Th dating techniques have propelled speleothems to the forefront of paleoclimatology and substantially improved our view of our planetary climate system on a wide range of timescales. I will present here speleothem data across multiple timescales, providing detailed case study in the context of high and low latitude climate interactions. On orbital-scale, a set of cave d18O records from different climate domains suggest that precession-induced changes in summer insolation in producing distinct climate variability in the ice-sheet proximal and distant regions via the (delayed) ice-volume forcing and in-phase CO2 feedback/forcing, and the direct summer insolation forcing and CH4 feedback in driving the climate variability at low-latitude monsoon regimes. On millennial-scale, we used a combination of well-dated speleothem and ice core records to pinpoint the timings of the Younger Dryas event onsets and terminations in various climatic domains around the world. We show that the event occurred first at high northern latitudes then propagated southward into the tropical monsoons belt within a few decades, eventually reaching Antarctica before reversing the course to its eventual termination. It appears that changes in Antarctic and/or low-latitude hydroclimate might have served as precursors of the YD termination or Holocene onset. On centennial-decadal scales, new high-resolution record of the 8.2 kyr event from the Southern Indian Ocean reinforce the double peak structure centered at ~8.2 and 8.1 kyr BP, withstanding the interhemispheric anti-phased relationship. Importantly, the significance of the 8.1 kyr BP peak is prominent in Southern than Northern Hemisphere proxy records, likely implying a different mechanism. There is a large array of hydroclimate events worldwide around 4.2-3.9 kyr BP, the so-called ‘4.2 kyr event’. These events are not representative of one synchronous event globally, and it remains unclear whether the events are indeed a manifestation of one time-transgressive event in different geographical regions. I will conclude by briefly presenting the annual resolution speleothem record across the ‘Chongzhen Drought’ event (~1637–1644 CE) and its wide social-economic impacts. The case studies are fundamental for gaining insights into the inner workings of the earth’s climate system for a sustainable future.
About the speaker:
Hai Cheng has been a professor at the Xi’an Jiaotong University since 2010. He received his PhD in geochemistry in 1988 from Nanjing University. He joined the Institute of Geology at the Chinese Academy of Sciences in 1988 and was a Senior Research Scientist at the University of Minnesota from 1993 to 2010. Hai Cheng has received many honors and awards, including appointment as a Geochemical Fellow of the Geochemical Society and European Association of Geochemistry (2015), AGU Fellow (2017), and the AGU Emiliani Lecturer (2019). He has been at the leading edge in developing U-series dating techniques and provided innumerable U-Th dates for collaborators who have made discoveries about paleoclimatic change worldwide. He played a world-leading role in paleoclimate studies of global speleothems, including the longest East Asian (640 kyr) and Indian (280 kyr) monsoon records, the longest Westerly climate records from central Asia (500 kyr) and North America (335 kyr), and the longest record from the Amazon Basin (250 kyr).
Pascale Braconnot, Lab. des Sciences du Climat et de l’Environnement, CEA-CNRS, Gif-Sur-Yvette, France.
Jean-Jacques Hublin, Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
Maisa Rojas, Department of Geophysics, University of Chile, Santiago, Chile.