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Monsoonal response to mid-holocene orbital forcing in a high resolution GCM

Monsoonal response to mid-holocene orbital forcing in a high resolution GCM
Monsoonal response to mid-holocene orbital forcing in a high resolution GCM
In this study, we use a sophisticated high-resolution atmosphere-ocean coupled climate model, EC-Earth, to investigate the effect of Mid-Holocene orbital forcing on summer monsoons on both hemispheres. During the Mid-Holocene (6 ka), there was more summer insolation on the Northern Hemisphere than today, which intensified the meridional temperature and pressure gradients. Over North Africa, monsoonal precipitation is intensified through increased landward monsoon winds and moisture advection as well as decreased moisture convergence over the oceans and more convergence over land compared to the pre-industrial simulation. Precipitation also extends further north as the ITCZ shifts northward in response to the stronger poleward gradient of insolation. This increase and poleward extent is stronger than in most previous ocean-atmosphere GCM simulations. In north-westernmost Africa, precipitation extends up to 35° N. Over tropical Africa, internal feedbacks completely overcome the direct warming effect of increased insolation. We also find a weakened African Easterly Jet. Over Asia, monsoonal precipitation during the Mid-Holocene is increased as well, but the response is different than over North-Africa. There is more convection over land at the expense of convection over the ocean, but precipitation does not extend further northward, monsoon winds over the ocean are weaker and the surrounding ocean does not provide more moisture. On the Southern Hemisphere, summer insolation and the poleward insolation gradient were weaker during the Mid-Holocene, resulting in a reduced South American monsoon through decreased monsoon winds and less convection, as well as an equatorward shift in the ITCZ. This study corroborates the findings of paleodata research as well as previous model studies, while giving a more detailed account of Mid-Holocene monsoons.
1814-9332
723-740
Bosmans, J.H.C.
20249d98-78a4-49c4-9bc0-880cecef0662
Drijfhout, S.S.
a5c76079-179b-490c-93fe-fc0391aacf13
Tuenter, E.
33b282bc-c149-4ae1-92a9-cff714101d30
Lourens, L.J.
61c02597-1860-45e5-9b78-a1473c7c86dd
Hilgen, F.J.
a6acc962-bc4d-42b4-b8fa-a012f1301a11
Weber, S.L.
6d40758d-ce76-4faa-b8a9-727ca6189a10
Bosmans, J.H.C.
20249d98-78a4-49c4-9bc0-880cecef0662
Drijfhout, S.S.
a5c76079-179b-490c-93fe-fc0391aacf13
Tuenter, E.
33b282bc-c149-4ae1-92a9-cff714101d30
Lourens, L.J.
61c02597-1860-45e5-9b78-a1473c7c86dd
Hilgen, F.J.
a6acc962-bc4d-42b4-b8fa-a012f1301a11
Weber, S.L.
6d40758d-ce76-4faa-b8a9-727ca6189a10

Bosmans, J.H.C., Drijfhout, S.S., Tuenter, E., Lourens, L.J., Hilgen, F.J. and Weber, S.L. (2012) Monsoonal response to mid-holocene orbital forcing in a high resolution GCM. Climate of the Past, 8 (2), 723-740. (doi:10.5194/cp-8-723-2012).

Record type: Article

Abstract

In this study, we use a sophisticated high-resolution atmosphere-ocean coupled climate model, EC-Earth, to investigate the effect of Mid-Holocene orbital forcing on summer monsoons on both hemispheres. During the Mid-Holocene (6 ka), there was more summer insolation on the Northern Hemisphere than today, which intensified the meridional temperature and pressure gradients. Over North Africa, monsoonal precipitation is intensified through increased landward monsoon winds and moisture advection as well as decreased moisture convergence over the oceans and more convergence over land compared to the pre-industrial simulation. Precipitation also extends further north as the ITCZ shifts northward in response to the stronger poleward gradient of insolation. This increase and poleward extent is stronger than in most previous ocean-atmosphere GCM simulations. In north-westernmost Africa, precipitation extends up to 35° N. Over tropical Africa, internal feedbacks completely overcome the direct warming effect of increased insolation. We also find a weakened African Easterly Jet. Over Asia, monsoonal precipitation during the Mid-Holocene is increased as well, but the response is different than over North-Africa. There is more convection over land at the expense of convection over the ocean, but precipitation does not extend further northward, monsoon winds over the ocean are weaker and the surrounding ocean does not provide more moisture. On the Southern Hemisphere, summer insolation and the poleward insolation gradient were weaker during the Mid-Holocene, resulting in a reduced South American monsoon through decreased monsoon winds and less convection, as well as an equatorward shift in the ITCZ. This study corroborates the findings of paleodata research as well as previous model studies, while giving a more detailed account of Mid-Holocene monsoons.

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Published date: 2012
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 348335
URI: https://eprints.soton.ac.uk/id/eprint/348335
ISSN: 1814-9332
PURE UUID: c3d744b1-1cf9-45a7-b1f2-1c4b48dabfc0

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Date deposited: 12 Feb 2013 12:01
Last modified: 16 Jul 2019 21:43

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