Geochemically Defined Mean Position of the Intertropical Convergence Zone in the Central Pacific. Issue 19 (3rd October 2021)

• Record Type: Journal Article
• Authors: Seo, Inah; Kim, Mun Gi; Yoo, Chan Min; Hyeong, Kiseong
• Is Part Of: Geophysical research letters. Volume 48:Issue 19(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-03
• Subjects: Intertropical Convergence Zone -- eolian dust -- neodymium isotopes -- rare earth elements -- elemental composition -- sediment provenance; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL094432
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The Intertropical Convergence Zone (ITCZ) is a band of vigorous convection and high precipitation formed by the confluence of southeasterly and northeasterly trade winds, and acts as a barrier to cross‐equatorial dust transport. We investigate the provenance of dust in the surface sediments of 16 cores collected along a 131.5°W transect from the equator to 16°N in the central Pacific. The results reveal well‐defined Asian dust signals north of 7°N and mixed Asian–South American source signals south of 6°N. We propose the southernmost latitude with an intact Asian source signal (7°N) as the present‐day mean ITCZ position in terms of dust provenance in the central Pacific. This geochemically defined mean ITCZ position reflects differences in thermal and dust fluxes between hemispheres and can be used as a reference for quantitatively assessing ITCZ displacement in the sedimentary down‐core records back to ca. 14 Ma. Plain Language Summary: The Intertropical Convergence Zone (ITCZ), a band of heavy precipitation in the tropics, migrates latitudinally towards the warmer hemisphere on seasonal and longer timescales. The past and future latitudinal position of the ITCZ is of great interest to the scientific community as the ITCZ influences global temperature and precipitation patterns as well as the hydroclimate of the tropics. The position of the ITCZ can be identified by tracking changes in dust sources and fluxes between hemispheres, as the ITCZ acts as a barrier to cross‐equatorial dust transport. Here, we use geochemical analysis to investigate the regional sources of dust on the seafloor in various sites in the tropical central Pacific to define the mean present‐day position of the ITCZ. We find that dust deposited north of 7°N is predominantly from Asia and dust deposited south of 6°N is mostly from Asia and South America. We propose the southernmost latitude with an intact Asian source signal (7°N) as the present mean ITCZ position in the central Pacific. This geochemically defined mean ITCZ position can be used as a reference for the quantitative assessment of ITCZ displacement in the past using sedimentary down‐core records. Key Points: Dust originating from the Northern Hemisphere reaches at least 2°N in the central Pacific, traveled across the boreal winter Intertropical Convergence Zone (ITCZ) at 4°N 7°N, the southernmost latitude with an intact Asian source signal, is suggested as the geochemically defined present‐day mean ITCZ position The newly defined mean ITCZ position can be used as a reference for the quantitative assessment of ITCZ displacement in down‐core records