EC‐Earth Simulations Reveal Enhanced Inter‐Hemispheric Thermal Contrast During the Last Interglacial Further Intensified the Indian Monsoon

• Published in: Geophysical research letters 2022-03, Vol.49 (6), p.n/a
• Main Authors: Chen, Kaiqi, Axelsson, Josefine, Zhang, Qiong, Li, Jianping, Wang, Lanning
• Format: Article
• Language: English
• Subjects: Anomalies; Archives & records; Climate change; Climate models; Future climates; General circulation models; Geographical distribution; Geographical locations; Global warming; Greenhouse effect; Greenhouse gases; Indian summer monsoon; inter-hemispheric thermal contrast; Interglacial periods; Last Interglacial; Monsoons; Northern Hemisphere; ocean feedback; Oceans; Paleoclimate; Paleoclimatology; Radiation; Rain; Rainfall; Rainfall simulators; Simulation; Solar radiation; Summer; Summer monsoon; Temperature gradients; Wind
• ISSN: 0094-8276; 1944-8007; 1944-8007
• DOI: 10.1029/2021GL094551

Paleoclimate proxy data indicate a stronger Indian summer monsoon (ISM) during the Last Interglacial (LIG) than in the present day. This is largely attributed to orbital forcing induced high seasonal and latitudinal insolation anomalies in the Northern Hemisphere during LIG. According to the general circulation model EC‐Earth3, the simulated ISM rainfall is increased by approximately 28% during the LIG compared to the pre‐industrial period as a result of the orbital forcing and the amplified land‐sea contrast due to both local and remote ocean feedbacks. Although the LIG is often portrayed as a potential analogue of future warmer climates, our study suggests that the enhanced inter‐hemispheric thermal gradient during the LIG strengthened the ISM, in opposition to the observed weakening of ISM under present‐day warming. Plain Language Summary One way to understand the future climate change is to learn from the past warm periods. The period of the Last Interglacial (LIG) is often referred to as a potential analogue for what a future climate may look like. However, paleoclimate archives such as speleothems show a stronger Indian summer monsoon (ISM) during the LIG, in contrast to an observed weakening trend in ISM in the past century. In this study, we use the climate model simulations from EC‐Earth3 to explain why the opposite changes happened in ISM during LIG and the current global warming period. The warming in the LIG was caused by a changed distribution of solar radiation over the Earth; in contrast, the current warming results from increased greenhouse gas concentrations in the atmosphere. The changes in the ISM are mainly determined by the thermal differences between land and ocean in the region. Due to its special geographical location, that is, the north‐south orientation of land and ocean, the solar radiation changes in the LIG enhanced the land‐sea temperature gradient, and thus intensified the ISM. Therefore, the response in the ISM to the present‐day warming climate is different from that to the warm LIG climate. Key Points The EC‐Earth model simulations demonstrate a 28% increase in Indian summer monsoon rainfall during the Last Interglacial (LIG) Orbital forcing in the LIG increased the inter‐hemispheric thermal gradient and enhanced the land‐sea contrast in South Asia The Indian summer monsoon during the LIG was further amplified by feedbacks in the equatorial Indian Ocean and Pacific Ocean