Preprints
https://doi.org/10.5194/cp-2021-68
https://doi.org/10.5194/cp-2021-68

  18 Jun 2021

18 Jun 2021

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

Pliocene evolution of the tropical Atlantic thermocline depth

Carolien Maria Hendrina van der Weijst1, Josse Winkelhorst1, Wesley de Nooijer1, Anna von der Heydt2, Gert-Jan Reichart1,3, Francesca Sangiorgi1, and Appy Sluijs1 Carolien Maria Hendrina van der Weijst et al.
  • 1Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, the Netherlands
  • 2Department of Physics, Utrecht University, 3584CC Utrecht, the Netherlands
  • 3NIOZ Royal Netherlands Institute for Sea Research, 1797 SZ ‘t Horntje, the Netherlands

Abstract. It has been hypothesized that global temperature trends are tightly linked to tropical thermocline depth, and that thermocline shoaling played a crucial role in the intensification of late Pliocene northern hemisphere glaciation. The Pliocene thermocline evolution in the Pacific Ocean is well documented and supports this hypothesis, but thermocline records from the tropical Atlantic Ocean are limited. We present new planktonic foraminiferal Mg/Ca, δ18O and δ13C records from the late Pliocene interval at Ocean Drilling Program Site 959 in the eastern equatorial Atlantic (EEA), which we use to reconstruct ocean temperatures and relative changes in salinity and thermocline depth. Data were generated using surface-dwelling Globigerinoides ruber and subsurface-dwelling Neogloboquadrina dutertrei. Reduced gradients between the surface and subsurface records indicate deepening of the EEA thermocline at the end of the Mid-Piacenzian Warm Period (mPWP; ~3.3–3.0 Ma). We connect our late Pliocene records to previously published early Pliocene δ18O data from Site 959 and compare these to the Site 1000 in the Caribbean Sea. Over the course of the Pliocene, thermocline changes in the EEA and Caribbean Sea follow similar patterns, with prominent step-wise thermocline deepening between ~5.5 and 4.0 Ma, gradual shoaling up to the mPWP, followed by minor deepening at the end of the mPWP. The tropical thermocline depth evolution of the tropical Atlantic differs from the Pacific, which is characterized by gradual basin-wide shoaling across the Pliocene. These results potentially challenge the hypothesized link between tropical thermocline depth and global climate. The mechanisms behind the periodically divergent Pacific and Atlantic thermocline movements remain speculative. We suggest that they are related to basin geometry and heterogenous temperature evolutions in regions from where thermocline waters are sourced. A positive feedback loop between source region temperature and tropical cyclone activity may have amplified tropical thermocline adjustments.

Carolien Maria Hendrina van der Weijst 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-2021-68', Anonymous Referee #1, 16 Jul 2021
  • RC2: 'Comment on cp-2021-68', Anonymous Referee #2, 20 Aug 2021

Carolien Maria Hendrina van der Weijst et al.

Carolien Maria Hendrina van der Weijst et al.

Viewed

Total article views: 551 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
410 129 12 551 30 5 8
  • HTML: 410
  • PDF: 129
  • XML: 12
  • Total: 551
  • Supplement: 30
  • BibTeX: 5
  • EndNote: 8
Views and downloads (calculated since 18 Jun 2021)
Cumulative views and downloads (calculated since 18 Jun 2021)

Viewed (geographical distribution)

Total article views: 429 (including HTML, PDF, and XML) Thereof 429 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 18 Oct 2021
Download
Short summary
A hypothesized link between Pliocene (5.3–2.5 million years ago) global climate and tropical thermocline depth is currently only backed up by data from the Pacific Ocean. In our paper, we present temperature, salinity and thermocline records from the tropical Atlantic Ocean. Surprisingly, the Pliocene thermocline evolution was remarkably different in the Atlantic and Pacific. We need to reevaluate the mechanisms that drive thermocline depth, and how these are tied to global climate change.