October 9 (CLIM) Parish, TBD

Meredith Parish, George Mason University 

Title: Forcings of Indo-Pacific Warm Pool Climate During the Past One Million Years

October 9 2024, 1:30pm 

Planetary Hall 224 and via Zoom (for link, email lortizur@gmu.edu) 

Host: Xiaojing Du 

The past one million years encompasses major changes in the Earth’s glacial-interglacial cycles, with a shift from 41- to 100-kyr cycles during the Mid-Pleistocene Transition (MPT), followed by an increase in interglacial CO2 across the Mid-Brunhes Transition (MBT). Terrestrial paleoclimate records spanning these climate transitions from within the Indo-Pacific Warm Pool (IPWP) are scarce, which limits our ability to diagnose the dominant climate forcings of Maritime Continent (MC) climate. We produced long, orbitally-resolved climate and vegetation reconstructions to identify the primary climate forcing mechanisms in the IPWP, a region with global importance through transport of heat to higher latitudes. We used branched glycerol dialkyl glycerol tetraethers (brGDGTs) and leaf wax isotopes (δ²Hwax, δ¹³Cwax) measured in sediment cores from Lake Towuti, Indonesia as proxies for temperature, hydroclimate and vegetation. We find that temperature variability increased after ~750 ka, coinciding with the emergence of 100-kyr cycles after the MPT. Hydroclimate exhibited significant 19-13-kyr cycles prior to the MPT, and then remained stable until the MBT (~430 ka) when significant 41- and 100-kyr cycles emerged. Insolation has long been presumed as the dominant forcing of hydroclimate in the tropics, yet our data points to glacial-interglacial cycles as the primary forcing of MC hydroclimate after the MPT.