Last glacial millennial-scale hydro-climate and temperature changes in Puerto Rico constrained by speleothem fluid inclusion δ<sup>18</sup>O and δ<sup>2</sup>H values

Abstract

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.

Multi-proxy speleothem-based reconstruction of mid-MIS 3 climate in South Africa

“…4). Such departure from the LMWL has been observed earlier (Van Breukelen et al, 2008;Wainer et al, 2011;Warken et al, 2022) and could point either to analytical artefacts (e.g. Matthews et al, 2021) or to in-cave processes such as evaporation (Warken et al, 2022).…”

“…This information can now be gained from fluid inclusion water isotope (FIWI) measurements (e.g. Affolter et al, 2014;Fernandez et al, 2023;Matthews et al, 2021;Vonhof et al, 2006;Warken et al, 2022;Wassenburg et al, 2021;Wortham et al, 2022), which reveal the isotopic composition of former drip water preserved in microscopic inclusions in the speleothem calcite. Here we combine temperature estimates based on the difference in oxygen isotopic composition of fluid inclusions and calcite with another, independent temperature proxy, namely fluid inclusion microthermometry, which uses liquid-vapor homogenization temperatures to determine the density of the enclosed drip water (Krüger et al, 2011;Løland et al, 2022).…”

Analytical Artefacts Preclude Reliable Isotope Ratio Measurement of Internal Water in Coral Skeletons

“…With both instruments, mineral samples are crushed in a percussion device to release internal water for stable isotope measurement at a temperature of 115 °C (Vonhof et al 2006, De Graaf et al 2020a. Continuous-flow techniques have already been applied successfully to obtain isotope information on cave deposits (Van Breukelen et al 2008, Rowe et al 2012, Griffiths et al 2013, Labuhn et al 2015, Affolter et al 2019, Rogerson et al 2019, Matthews et al 2021, Wassenburg et al 2021, Warken et al 2022) and vein minerals (Bertotti et al 2017, De Graaf et al 2019, 2020b.…”

Hydroclimate variability in the Caribbean during North Atlantic Heinrich cooling events (H8 and H9)

“…For the late Holocene section, the δ 18 O and δ 13 C data are the least variable; these values are − 3.2 to − 5.7‰ and − 7.4 to − 13.1‰ respectively. Previous results in western Cuba revealed that the Caribbean region had a substantial change in temperature 37,38 , confirmed by a more recent speleothem paleoclimate evidence from Puerto Rico, which indicates a cooler last glacial maximum compared to the Holocene 39 . The analyses of drip water and speleothems from western Cuban caves showed that the δ 18 O values in this area are mainly dominated by the summer rainfall 1 .…”