828 / 2024-09-19 15:41:42

The latitudinal migration of intertropical convergence zone in response to precession across the Holocene

Intertropical convergence zone;,Latitudinal migration,Orbital precession,The Holocene,Climate simulation

Session 53 - Geological analogues for future warm ocean and climate

The intertropical convergence zone (ITCZ) is where the most intense rainfall occurs over the globe, locating near the tropics, dominating the hydroclimate of the tropics and regulates global water cycle through its latitudinal position. The north-south shift of the ITCZ is primarily controlled by the cross-equatorial energy transport, where it migrates into the warmer hemisphere in order to compensate the surplus of energy that’s been transported into that hemisphere. During the Holocene (current interglacial, 11.7 kyr BP to present), the orbital precession is one of the main external drivers that regulates the migration of the ITCZ. The Northern Hemisphere summers have gradually cooled since the Holocene thermal maximum (~ 8 kyr BP) in response to orbital precession, while the Southern Hemisphere summers gradually warmed. However, it’s still unclear how has the annual ITCZ migrated due to the Holocene precession, together with its driving mechanisms and the timing of its shift, either global or regional. Here we investigate how the ITCZ migrates in response to orbital precession during the Holocene utilizing water isotope-enabled climate model iCESM1.2, combined with available rainfall signal proxy records. We show that the annual mean position of ITCZ has migrated southward from the early Holocene (~ 8kyr BP), with boreal summer and autumn contributing most to its migration. This is largely following the declining trend of the boreal summer insolation, as the Northern Hemisphere cooled, more energy is transported from the Southern Hemisphere, thus migrating the ITCZ southward.