30 Jul 2021

30 Jul 2021

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

Last glacial millennial-scale hydro-climate and temperature changes in Puerto Rico constrained by speleothem fluid inclusion δ18O and δ2H values

Sophie F. Warken1,2, Therese Weissbach1,3, Tobias Kluge1,3,4, Hubert Vonhof5, Denis Scholz6, Rolf Vieten7, Martina Schmidt1, Amos Winter7,8, and Norbert Frank1 Sophie F. Warken et al.
  • 1Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
  • 2Institute of Earth Sciences, University of Heidelberg, Heidelberg, Germany
  • 3Heidelberg Graduate School of Fundamental Physics, Heidelberg University, Heidelberg, Germany
  • 4Institute of Applied Geosciences, Karlsruhe Institute of Technology, Karlsruhe, Germany
  • 5Max Planck Institute for Chemistry, Climate Geochemistry Department, Mainz, Germany
  • 6Institute for Geosciences, University of Mainz, Germany
  • 7Department of Marine Sciences, University of Puerto Rico, Mayagüez, Puerto Rico
  • 8Earth and Environmental Systems Department, Indiana State University, Terre Haute, Indiana, USA

Abstract. We present speleothem fluid inclusion δ18Of and δ2Hf values from Larga Cave, Puerto Rico, that covers the interval between 46.2 to 15.3 ka before present on millennial scale, including the Last Glacial Maximum (LGM) and several stadial and interstadial cycles. The dataset can be divided in two main clusters of stable isotope compositions of the fluid inclusion water with respect to the global meteoric water line which coincide with strong variations in the water content of the stalagmite. In particular, this clustering is found to be climate related, where the first cluster comprises samples from cold and dry periods, such as Heinrich and Greenland stadials, as well as parts of the LGM, which exhibit very high δ18Of and δ2Hf values. We interpret this enrichment as caused by evaporation inside the cave due to enhanced cave ventilation during these colder and drier times. In contrast, in most samples corresponding to warmer and wetter Greenland interstadials, but also for some from Heinrich Stadial 2 and 3, the δ18Of and δ2Hf values plot on the meteoric water line and modification of fluid inclusion water due to “in-cave” evaporation is found negligible.

Consequently, variations of last glacial hydro-climate and temperature in the western tropical Atlantic can be constrained. In general, δ18Of values from fluid inclusions are up to 3 ‰ higher than those of modern drip water, which is interpreted as a weaker atmospheric convective activity during the last glacial period. In addition, reconstructed temperatures suggest an average cooling of c. 3 °C during the LGM compared to modern cave temperature. During Heinrich Stadials 2 and 3, reconstructed cave temperatures yield an additional cooling of 2.9 ± 2.6 °C and 4.4 ± 0.6 °C, respectively. Higher δ18Of values of these samples further suggest that the drip water was dominated by orographic rainfall and/or cold fronts, along with weak or even absent convective activity. In contrast, during interstadial phases, reconstructed temperatures reached nearly modern values, and convective activity was comparable or only slightly weaker than today.

Sophie F. Warken et al.

Status: open (until 24 Sep 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-86', Anonymous Referee #1, 23 Aug 2021 reply
  • RC2: 'Comment on cp-2021-86', Anonymous Referee #2, 05 Sep 2021 reply

Sophie F. Warken et al.

Sophie F. Warken et al.


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Short summary
The analysis of fluid inclusions from a Puerto Rican speleothem provides quantitative information about past rainfall conditions and temperatures during the last glacial period, when climate was extremely variable. Our data show that the region experienced a climate that was generally colder and drier. However, we also reconstruct intervals when temperatures reached nearly modern values, and convective activity was comparable or only slightly weaker than today.