Climate response to astronomical parameters, CO2 and ice sheets during past interglacials by Zhipeng WU

Louvain-La-Neuve

May 22, 2023

10h

Louvain-la-Neuve

Ocean room B002

This thesis aims to perform a comprehensive and systematic investigation of the climate response in the two hemispheres to astronomical parameters, CO2 and Northern Hemisphere (NH) ice sheets, as well as the half-precession cycles, during the interglacials of the past 800 ka mainly based on snapshot and transient simulations using the LOVECLIM model. The results show that the climate of the two hemispheres responds differently to astronomical parameters, CO2 and NH ice sheets. In terms of the effect of astronomical parameters, precession is more important in the Arctic sea ice and the SST at NH mid and high latitudes, as well as the SST at low latitudes of both hemispheres, while obliquity is more important in the Southern Ocean sea ice and SST at SH mid and high latitudes. The model results also show that the effect of CO2 on the SST in the mid-high latitudes is larger than in the low latitudes of both hemispheres, and CO2 plays a more important role on the SST at mid-high latitudes and sea ice in the SH than in the NH. As far as the effect of the NH ice sheets is considered, the changes in Southern Ocean sea ice are highly and positively correlated with the NH ice volume, but the effect of the NH ice sheets on Arctic sea ice appears nonlinear, which depends on the size and location of the ice sheets as well as the NH summer insolation. The response of the mid-high latitude SST to the NH ice sheets is similar to the sea ice response in the same hemisphere. The compilation of the published proxy records show that the half-precession cycles are mainly concentrated in the tropics and North Atlantic. Our model results show that the half-precession cycles can be resulted from the maximum equatorial insolation, like the simulated SST, surface air temperature (SAT) and precipitation near the Equator, and from the vegetation feedback, like the simulated grass fraction in the ‘Asian’ and ‘African’ monsoon regions.