19 May 2022
19 May 2022
Status: a revised version of this preprint is currently under review for the journal CP.

Precessional pacing of tropical ocean carbon export during the Late Cretaceous

Ji-Eun Kim1, Thomas Westerhold2, Laia Alegret3, Anna Joy Drury4, Ursula Röhl2, and Elizabeth M. Griffith1 Ji-Eun Kim et al.
  • 1School of Earth Sciences, The Ohio State University, 43210 USA
  • 2Center for Marine Environmental Sciences (MARUM), University of Bremen, 28359 Germany
  • 3Department of Earth Sciences, University of Zaragoza, 50009 Spain
  • 4Department of Earth Sciences, University College London, WC1E 6BT UK

Abstract. The marine biological carbon pump, which exports organic carbon out of the surface ocean, plays an essential role in sequestering carbon from the atmosphere, thus impacting climate and affecting marine ecosystems. Orbital variations in solar insolation modulate these processes, but their influence on the tropical Pacific during the Late Cretaceous is unknown. Here we present a high-resolution composite record of elemental barium from deep sea sediments as a proxy for organic carbon export out of the surface oceans (i.e., export production) from Shatsky Rise in the tropical Pacific. Variations in export production in the Pacific during the Maastrichtian, from 71.5 to 66 million years ago, were dominated by precession and less so by eccentricity modulation or obliquity, confirming that tropical surface-ocean carbon dynamics were influenced by seasonal insolation in the tropics during this greenhouse period. We suggest that precession paced primary production in the tropical Pacific and recycling in the euphotic zone by changing water column stratification, upwelling intensity, and continental nutrient fluxes. Benthic foraminiferal accumulation rates covaried with export production providing evidence for bentho-pelagic coupling of the marine biological carbon pump across these high-frequency changes in a cool greenhouse planet.

Ji-Eun Kim et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2022-42', Anonymous Referee #1, 14 Jun 2022
    • AC1: 'Reply on RC1', Elizabeth M. Griffith, 10 Jul 2022
  • RC2: 'Comment on cp-2022-42', Mingsong Li, 26 Jun 2022
    • AC2: 'Reply on RC2', Elizabeth M. Griffith, 16 Jul 2022

Ji-Eun Kim et al.

Ji-Eun Kim et al.


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Short summary
This study attempts to get a better understanding of the marine biological carbon pump and ecosystem functioning under warmer than today conditions. Our records from marine sediments show the Pacific tropical marine biological carbon pump was driven by variations in seasonal insolation in the tropics during the late Cretaceous and may play a key role in modulating climate and the carbon cycle globally in the future.