Preprints
https://doi.org/10.5194/cp-2021-50
https://doi.org/10.5194/cp-2021-50

  12 May 2021

12 May 2021

Review status: this preprint is currently under review for the journal CP.

North Atlantic marine biogenic silica accumulation through the early-to-mid Paleogene: implications for ocean circulation and silicate weathering feedback

Jakub Witkowski1, Karolina Bryłka2, Steven M. Bohaty3, Elżbieta Mydłowska4, Donald E. Penman5, and Bridget S. Wade6 Jakub Witkowski et al.
  • 1Institute of Marine and Environmental Sciences, University of Szczecin, ul. Mickiewicza 18, 70-383 Szczecin, Poland
  • 2Department of Geology, Faculty of Science, Lund University, Sölvegatan 12, Lund, Sweden
  • 3Schoool of Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK
  • 4Institute of Spatial Management and Socio-Economic Geography, ul. Mickiewicza 18, 70-383 Szczecin, Poland
  • 5Department of Geosciences, Utah State University, 4505 Old Main Hill, Logan UT 84322, USA
  • 6Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK

Abstract. The Paleogene history of biogenic opal accumulation in the North Atlantic provides insight into both the evolution of deep-water circulation in the Atlantic basin, and weathering responses to major climate shifts. However, existing records are compromised by low temporal resolution and/or stratigraphic discontinuities. In order to address this problem, we present a multi-site, high-resolution record of biogenic silica (bioSiO2) accumulation from Blake Nose (ODP Leg 171B, western North Atlantic) spanning the early Paleocene through late Eocene time interval (~65‒34 Ma). This record represents the longest single-locality history of marine bioSiO2 burial compiled to date and offers a unique perspective into changes in bioSiO2 fluxes through the early-to-mid Paleogene extreme greenhouse interval and subsequent period of long-term cooling. Blake Nose bioSiO2 fluxes display prominent fluctuations that we attribute to variations in sub-thermocline nutrient supply via cyclonic eddies associated with the Gulf Stream. Whereas few constraints are available on the bioSiO2 flux pulses peaking in the early Paleocene and early Eocene, a middle Eocene interval of elevated bioSiO2 flux between ~46 and 42 Ma is proposed to reflect nutrient enrichment due to invigorated overturning circulation following an early onset of Northern Component Water export from the Norwegian-Greenland Sea at ~49 Ma. Comparison of our North Atlantic record against published Pacific bioSiO2 flux records indicates a diminished nutrient supply to the Atlantic between ~42 and 38 Ma, interpreted as a response to weakening of the overturning circulation. Subsequently, a deep-water circulation regime favoring limited bioSiO2 burial in Atlantic and enhanced bioSiO2 burial in the Pacific was established after ~38 Ma, likely in association with a further invigoration of deep-water export from the North Atlantic. We also observe that Blake Nose bioSiO2 fluxes through the middle Eocene cooling interval (~48 to 34 Ma) are consistently higher than background fluxes throughout the late Paleocene‒early Eocene interval of intense greenhouse warmth. This observation is consistent with a temporally variable rather than constant silicate weathering feedback strength model for the Paleogene, which would instead predict that marine bioSiO2 burial should peak during periods of extreme warming.

Jakub Witkowski et al.

Status: open (until 07 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-50', John Barron, 21 May 2021 reply
  • RC2: 'Comment on cp-2021-50', Louisa Bradtmiller, 10 Jun 2021 reply

Jakub Witkowski et al.

Jakub Witkowski et al.

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Short summary
We reconstruct the history of biogenic opal accumulation through the early-to-mid Paleogene in the western North Atlantic Ocean. Biogenic opal accumulation was controlled by deep-water temperatures, atmospheric greenhouse gas levels, and continental weathering intensity. Overturning circulation in the Atlantic was established at the end of the extreme early Eocene greenhouse warmth period. We also show that the strength of the link between climate and continental weathering varies through time.