Tropical temperature variations during the last glacial cycle from stalagmite fluid inclusions

Abstract

Low latitudes play a key role in the Earth's climate system, receiving the highest amount of solar energy that is redistributed across the globe through atmospheric and oceanic circulation. The MIS 5a – 4 boundary, characterized by global cooling and increased ice volume marks the glacial inception. The last glacial cycle has been characterized by millennial-scale climate oscillations, the Dansgaard-Oeschger events, marked by large and rapid temperature swings in the North Atlantic region accompanied by opposite and smaller temperature variations in the Southern Hemisphere. Tropical land temperatures’ response to the last glacial inception remains to be quantitatively estimated. In the context of these millennial-scale climate events, this thesis seeks to understand the tropical climate behavior, determining whether it followed the Northern Hemisphere pattern or the Southern Hemisphere pattern and atmospheric CO2. In this study, nucleation-assisted microthermometry (Krüger et al., 2011) was used to determine stalagmite formation temperatures based on fluid inclusion liquid-vapor homogenization. The method was applied to SC03, a stalagmite from Secret Cave (Gunung Mulu National Park, northern Borneo), previously studied for hydroclimate (Carolin et al., 2013). A quantitative land temperature record has been reconstructed, covering selected Dansgaard-Oeschger cycles during MIS 3 (42-50 ka) as well as during MIS 5a and MIS 4 (60-81 ka). Findings suggest that tropical temperature did not follow Northern Hemispheric patterns but there appears to be a strong relationship with Antarctic temperatures and atmospheric CO2 levels. This aligns with previous findings from the last glacial termination, derived from another stalagmite from the same cave (Løland et al., 2022). Additionally, a short-lived cooling in northern Borneo and Quaternary’s largest volcanic eruption are occurring simultaneously. Thus, a potential correlation has been investigated. This thesis contributes to a broader understanding of the interplay between low and high-latitude climates during millennial-scale reorganizations of the global climate system.