[M-IS04] Evolution and variability of the Asian Monsoon and Indo-Pacific climate during the Cenozoic Era

[MIS04-06] Impact of long-term monsoon dynamics on Cenozoic-Mesozoic climate and ecosystems

*Masayuki Ikeda¹, Kazumi Ozaki², LEGRAND Julien³ (1.University of Tokyo, 2.Toho University, 3.Shizuoka University)

Keywords:monsoon

Earth’s orbital variations on timescales of 10⁴ to 10⁵ years, known as Milankovitch cycles, have played a critical role in pacing climate change and ecosystem dynamics during the Cenozoic and Mesozoic, through glacial and monsoon dynamics. However, the climatic and biotic consequences of these cycles on much longer 10⁷ years timescales remain unclear, due to a lack of long proxy records with precise age constraints.
Here, we show 10 Myr scale variations in Triassic Jurassic records of lake level, desert distribution, biogenic silica burial flux, atmospheric CO2 levels, and sea surface temperature, SST. Their phase relationships, coupled with carbon cycle modeling results, suggest that orbitally paced summer monsoon dynamics modulates changes in terrestrial weatherability, affecting changes in pCO2 of up to 500 to 1000 ppmv and 3 to 7 C SST. We also infer that these 10 Myr scale climatic variations could have been causally linked to biotic turnover, size variations in dinosaur footprints, and tetrapod dispersal, potentially through spatio temporal variations in resource availability and arid hot climatic barriers at low middle latitudes.