Preprints
https://doi.org/10.5194/cp-2022-79
https://doi.org/10.5194/cp-2022-79
 
04 Oct 2022
04 Oct 2022
Status: this preprint is currently under review for the journal CP.

Lipid biomarker-based sea (sub)surface temperature record offshore Tasmania over the last 23 million years

Suning Hou, Foteini Lamprou, Frida S. Hoem, Mohammad Rizky Nanda Hadju, Francesca Sangiorgi, Francien Peterse, and Peter K. Bijl Suning Hou et al.
  • Department of Earth Sciences, Utrecht University, Utrecht, 3584CB, the Netherlands

Abstract. The Neogene (23.04–2.58 Ma) is characterized by progressive buildup of Antarctic and Northern Hemisphere ice volume and climate cooling. Heat/moisture delivery to Antarctica is to a large extent regulated by the strength of meridional temperature gradients. However, the evolution of the Southern Ocean frontal systems remains scarcely studied in the Neogene. Here we present the first long-term continuous sea (sub)surface temperature (SST) record of the subtropical front area in the Southern Ocean at Ocean Drilling Program (ODP) Site 1168 off western Tasmania. This site is at present located near the subtropical front (STF), as it was during the Neogene, despite a 10 degree northward tectonic drift of Tasmania during the Neogene. We analyzed glycerol dialkyl glycerol tetraethers (GDGTs, on 433 samples) and alkenones (on 163 samples) and reconstructed the paleotemperature evolution using TEX86 and Uk’37 as two independent quantitative proxies. Both proxies indicate that Site 1168 experienced a temperate ~25 °C during early Miocene (23–17 Ma), reaching ~29 °C during the mid-Miocene Climatic Optimum. The stepwise ~10 °C cooling (20–10 °C) in the mid-to-late Miocene (12.5–5.0 Ma) is larger than observed in records from lower and higher latitudes. From the Pliocene to modern (5.3–0 Ma), STF SST first plateaus at ~15 °C (3 Ma), then decreases to ~6 °C (1.3 Ma), and eventually increases to the modern levels around ~16 °C (0 Ma), with a higher variability of 5 degrees compared to the Miocene. Our results imply that the latitudinal temperature gradient between the Pacific equator and STF during late Miocene cooling increased from 4 °C to 14 °C. Meanwhile, the SST gradient between the STF and the Antarctic margin decreased due to amplified STF cooling compared to the Antarctic Margin. This implies a narrowing SST gradient in the Neogene, with contraction of warm SSTs and northward expansion of subpolar conditions.

Suning Hou et al.

Status: open (until 08 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2022-79', Igor Obreht, 04 Nov 2022 reply

Suning Hou et al.

Data sets

sea-surface temperature proxy data (TEX86 and UK'37) from Ocean Drilling Program Site 1168 Bijl, P.K., Hoem, F.S., & Hou, S https://doi.org/10.5281/zenodo.7119904

Suning Hou et al.

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Short summary
Neogene climate cooling is thought to be accompanied by increased equator-to-pole temperature gradients, but mid-latitudes are poorly represented. We use biomarkers to reconstruct a 23 Myr continuous sea (sub)surface temperature record of the mid latitude Southern Ocean. We note a profound mid latitude cooling which narrowed the latitudinal temperature gradient with northward expansion of subpolar conditions. We surmise that this reflects the strengthening of the ACC and expansion of sea ice.