East Asian monsoon response to changes in Earth’s orbit: A new stable isotope modeling study

Understanding the timing, intensity, duration, and spatial extent of Asian monsoon rainfall is important for the large population across Asia. Meanwhile, a perspective from geological records of past climates can give insights into how the Asian monsoon will respond to anthropogenic forcing of future climate scenarios. Speleothems from caves had created a unique opportunity to study past climates because the oxygen isotopic ratios preserved in their minerals record environmental information when they were formed.

Oxygen isotope ratios have been shown to exhibit a close relationship with the amount of summer solar radiation in the northern hemisphere, which varies due to changes in Earth’s orbit. However, so far, there is no consensus on why the oxygen isotopic composition in speleothems follows the Earth’s orbital variation. This project will compare observed and modeled isotopic composition to inform a better understanding of the climate dynamics of the East Asian monsoon, thus improving our predictive ability of the East Asian monsoon.

Additionally, the researchers will work with the next generation of scientists, engineers, and citizens by (1) participating in Brown Earth Sciences curriculum design and teaching program to the local schools with a high percentage of under-represented students and (2) providing research opportunities in climate science to undergraduate researchers from minority-serving colleges and universities during the summer.

This research proposes incorporating stable water isotopes into the Geophysical Fluid Dynamics Laboratory (GFDL) Coupled Climate Model, allowing researchers to compare observed and modeled isotopes and disentangle what causes the variation of isotopes. Previous research from this research group supports the hypothesis that precipitation in the East Asian monsoon region is sensitive to summer insolation, emphasizing the importance of ocean dynamics in understanding the Asian monsoon system.

This research will validate the incorporated isotope model using present-day observations, perform past climate model simulations with a fully coupled ocean-atmosphere-land configuration, and assess the role of ocean circulation in the dynamics of the East Asian monsoon in response to the Earth’s orbit change.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.