Comparison of interglacial tropical climate variability during the past 300,000 years

• Applicant: Dr. Sophie Warken
• Subject Area: Palaeontology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512385350

On the regional scale, the hydroclimate does not respond uniformly to climatic forcing, which has strong implications for future predictions. Therefore, the study of past climate variability in different regions is particularly relevant. Over the past c. 800,000 years, climate has approximated present-day conditions during several previous warm periods, including the present (Holocene). Due to their relative warmth, these so called past interglacial periods may be considered comparable to a future, warmer state in terms of potential climate impacts and ecosystem feedbacks at the regional scale, especially over centennial-to-millennial timescales that are often not covered by climate model simulations. Investigations of past interglacial climates have shown that both the relative intensity of these periods as well as regional precipitation patterns are spatially not coherent, and the terrestrial and tropical regions, including the western tropical Atlantic region, are under-represented in the record. To address this research gap, we propose to investigate the last four interglacial phases (the last 300,000 years) using multi-proxy speleothem records from Larga Cave, Puerto Rico, to reconstruct the relative intensity and intra-interglacial climate variability of these phases and investigate their relevance to climate change in the tropical Americas. Marine isotope stages (MIS) 1 (11.8ka BP to pre-industrial), MIS 5e (ca. 130 - 116ka BP), MIS 7a/c (ca. 214 to 197 ka) and 7e (ca. 255 to 236 ka), and MIS 9 (ca. 340 - 310 ka BP) not only comprise three of the four warmest periods of the last 800,000 years, but their diversity also makes them suitable for testing the dependence of intra-interglacial climate variability on the background climate state. The δ18O and δ13C values of stalagmites from Larga Cave and measurements of trace elements, e.g., Mg/Ca or Cu/Ca, provide excellent archives of past hydroclimatic variations such as changes in precipitation amount or convective activity. In addition, stable water isotope analyses of fluid inclusions provide a method for quantifying the cave temperatures at the time of speleothem formation. These proxy records - as well as quantification of the inherent variability of the analyzed parameters - will allow us to place the current regional climate into context, and to assess the sensitivity of precipitation patterns to different warm background climate states. This project will improve quantitative and qualitative understanding of precipitation intensity and variability during past warm interglacials, and help estimate the sensitivity of the Earth system to different forcing mechanisms and assess the rate and magnitude of current climate change relative to natural variability.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partner: Professor Dr. Amos Winter
• Co-Investigator: Professorin Dr. Kira Rehfeld