Hadley cell in cold climate and its implication to the CO2 removal world

Seminar by Prof. Seok-Woo Son from Seoul National University

22 March 2023
KST 14:00 – 15:00

The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.

The Hadley Cell (HC) changes from Last Glacial Maximum (LGM) to preindustrial (PI) periods, and to the 23rd century under the extended concentration pathway 4.5 (ECP4.5) scenario are examined by comparing coupled model simulations archived for the Paleoclimate Modeling Intercomparison Project phase 3 and the Coupled Model Intercomparison Project phase 5. The result shows a systematic widening of the Southern-Hemisphere HC from the LGM to the PI and to the ECP4.5 conditions. Such widening is significantly correlated with global-mean surface air temperature change and the associated static stability change in the subtropics. However, this change was not coherent with the jet latitude change. While all models show a poleward jet shift from the PI to the ECP4.5 conditions, over one-half of the models exhibit no trend or even an equatorward shift from the LGM to the PI conditions in the Southern Hemisphere. This decoupling between the HC and jet latitude changes in the Southern Hemisphere is most pronounced in the austral winter when the Antarctic surface cooling in the LGM condition is comparable to or larger than the tropical upper-tropospheric cooling. This result, which indicates that polar amplification plays a crucial role in driving the decoupling of the tropical and midlatitude circulations in the Southern Hemisphere, is generalized by conducting a series of idealized dynamic core model experiments. 

The implication of the above result to the carbon neutrality is also investigated by performing CO2 removal experiments with CESM. It turns out that the Southern Hemisphere HC does not return to the present state when CO2 concentrations are reduced, because of the delayed cooling of the Southern Ocean.