Preprints
https://doi.org/10.5194/egusphere-2023-291
https://doi.org/10.5194/egusphere-2023-291
01 Mar 2023
 | 01 Mar 2023

Late Cenozoic Sea Surface Temperature evolution of the South Atlantic Ocean

Frida S. Hoem, Adrián López-Quirós, Suzanna van de Lagemaat, Johan Etourneau, Marie-Alexandrine Sicre, Carlota Escutia, Henk Brinkhuis, Francien Peterse, Francesca Sangiorgi, and Peter K. Bijl

Abstract. At present, a strong latitudinal sea surface temperature (SST) gradient of ~16 °C exists across the Southern Ocean, maintained by the Antarctic Circumpolar Current (ACC) and a set of complex frontal systems. Together with the Antarctic ice masses, this system has formed one of the most important global climate regulators. The timing of the onset of the ACC-system, its development towards modern-day strength, and the consequences for e.g., the latitudinal SST gradient around the southern Atlantic Ocean, are still uncertain. Here we present new TEX86-biomarker records, calibrated to SST, from two sites located east of Drake Passage (southern South Atlantic) to assist in better understanding two critical time intervals of prominent climate transitions during the Cenozoic: The Late Eocene–Early Oligocene (ODP Site 696) and Middle–Late Miocene (IODP Site U1536) transitions. Our results overall show rather temperate conditions (20–11 °C) during the Late Eocene to Early Oligocene interval, with a weaker latitudinal SST gradient (~8 °C) across the Atlantic sector of the Southern Ocean compared to present day (~16 °C). We ascribe the regional similarity in SSTs across the Late Eocene–Early Oligocene South Atlantic to a persistent, strong Subpolar Gyre circulation, connecting all sites, which can only exist in absence of a strong throughflow across the Drake Passage. Surprisingly, the southern South Atlantic records show comparable SSTs (~12–14 °C) during both the Earliest Oligocene Oxygen Isotope Step (EOIS, ~33.65 Ma) and the Miocene Climate Optimum (MCO, ~16.5 Ma). Apparently, maximum Oligocene Antarctic ice volume could coexist with warm ice-proximal surface ocean conditions, while at similar ocean temperatures, the Middle Miocene Antarctic ice sheet was strongly reduced. Southern South Atlantic SSTs cooled to ~5 °C at the onset of the Middle Miocene Climate Transition (MMCT, 14 Ma), making it the coldest oceanic region recorded around Antarctica and the likely main location for deep water formation. The already cold southern South Atlantic conditions at MMCT meant it experienced little cooling during the latter part of the Miocene, which contrasts the profound cooling due to northward expansion of the Southern Ocean frontal systems in the lower latitudes and other sectors of the Southern Ocean.

Journal article(s) based on this preprint

13 Oct 2023
| Highlight paper
Late Cenozoic sea-surface-temperature evolution of the South Atlantic Ocean
Frida S. Hoem, Adrián López-Quirós, Suzanna van de Lagemaat, Johan Etourneau, Marie-Alexandrine Sicre, Carlota Escutia, Henk Brinkhuis, Francien Peterse, Francesca Sangiorgi, and Peter K. Bijl
Clim. Past, 19, 1931–1949, https://doi.org/10.5194/cp-19-1931-2023,https://doi.org/10.5194/cp-19-1931-2023, 2023
Short summary Co-editor-in-chief

Frida S. Hoem et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-291', Anonymous Referee #1, 03 Apr 2023
    • AC1: 'Reply on RC1', Frida Hoem, 08 May 2023
  • RC2: 'Comment on egusphere-2023-291', Anonymous Referee #2, 06 Apr 2023
    • AC2: 'Reply on RC2', Frida Hoem, 08 May 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-291', Anonymous Referee #1, 03 Apr 2023
    • AC1: 'Reply on RC1', Frida Hoem, 08 May 2023
  • RC2: 'Comment on egusphere-2023-291', Anonymous Referee #2, 06 Apr 2023
    • AC2: 'Reply on RC2', Frida Hoem, 08 May 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
ED: Reconsider after major revisions (25 May 2023) by Ran Feng
AR by Frida Hoem on behalf of the Authors (30 Jun 2023)  Author's response   Author's tracked changes   Manuscript 
EF by Polina Shvedko (30 Jun 2023)  Supplement 
ED: Referee Nomination & Report Request started (08 Jul 2023) by Ran Feng
RR by Anonymous Referee #1 (04 Aug 2023)
ED: Publish subject to minor revisions (review by editor) (07 Aug 2023) by Ran Feng
AR by Frida Hoem on behalf of the Authors (17 Aug 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (23 Aug 2023) by Ran Feng
AR by Frida Hoem on behalf of the Authors (24 Aug 2023)  Manuscript 

Journal article(s) based on this preprint

13 Oct 2023
| Highlight paper
Late Cenozoic sea-surface-temperature evolution of the South Atlantic Ocean
Frida S. Hoem, Adrián López-Quirós, Suzanna van de Lagemaat, Johan Etourneau, Marie-Alexandrine Sicre, Carlota Escutia, Henk Brinkhuis, Francien Peterse, Francesca Sangiorgi, and Peter K. Bijl
Clim. Past, 19, 1931–1949, https://doi.org/10.5194/cp-19-1931-2023,https://doi.org/10.5194/cp-19-1931-2023, 2023
Short summary Co-editor-in-chief

Frida S. Hoem et al.

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

This paper presents two new long-term SST records from the south Atlantic Ocean. This region is marked by the strong ocean baroclinicity and associated SST gradient, and is key to understanding late Cenozoic Antarctic glaciation and deep ocean circulation. These records have the potential to significantly contribute to address those questions.
Short summary
We here present two new sea surface temperature (SST) records in comparison with availiable SST records to reconstruct the South Atlantic paleoceanographic evolution. Our results show low SST gradient in the Eocene-early Oligocene due to the persistent gyral circulation. Higher SST gradient in the Mid-Late Miocene infer a stronger circumpolar current. The southern South Atlantic was the coldest region in the Southern Ocean and likely the main deep water formation location in the Middle Miocene.