Disentangling abrupt deglacial hydrological changes in northern South America: Insolation versus oceanic forcing.

Hoffmann, J., Bahr, A., Voigt, S., Schönfeld, Joachim, Nürnberg, Dirk and Rethemeyer, J. (2014) Disentangling abrupt deglacial hydrological changes in northern South America: Insolation versus oceanic forcing. Geology, 42 (7). pp. 579-582. DOI 10.1130/G35562.1.

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Abstract

Paleoenvironmental studies and climate models demonstrate that fl uvial runoff and moisture
availability in the Caribbean hinterland react very sensitively to climatic variations.
Late Pleistocene and Holocene climate records document pronounced dry and wet periods
over tropical South America mainly caused by shifts of the Intertropical Convergence Zone
(ITCZ). However, forcing mechanisms for changes in the ITCZ position remain controversial.
Here we present high-resolution foraminiferal Ba/Ca and δ18Oseawater records from a core
located within the Orinoco River outfl ow documenting abrupt hydrological changes in the
Orinoco catchment area during the deglacial and Holocene. Our data, obtained from the
surface-dwelling foraminifera Globigerinoides ruber (pink), show an abrupt increase in Ba/
Ca ratios in the early Holocene, starting ~600 yr after the end of the Younger Dryas (YD) cold
interval at ca. 10.8 ka and suggesting a massive reorganization of moisture sources in northern
South America. In contrast, the salinity dependent δ18Oseawater from the same samples shows a
gradual decrease starting at the end of the YD. The offset of our Ba/Ca peak excludes meltwater
release in conjunction with the northern Andean glacier retreat well before the end of the
YD as a forcing mechanism. We suggest that the Ba/Ca record documents an abrupt increase
in Ba-rich waters of a northern Andean source caused by the insolation-driven shift of the
ITCZ and/or enhanced monsoon activity.

Document Type: Article
Additional Information: WOS:000339961400008
Keywords: South America; Caribbean; Orinoco; planktonic foraminifera; Barium; Younger Dryas
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1130/G35562.1
ISSN: 0091-7613
Expeditions/Models/Experiments:
Date Deposited: 23 Jul 2014 12:29
Last Modified: 17 May 2017 08:26
URI: http://oceanrep.geomar.de/id/eprint/25306

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