Carbonate Clumped Isotope Reconstruction of Temperatures and Water 180/160 Ratios from Last Glacial Maximum and Holocene Climatic Optimum Age Calcic Paleosols in the Palouse Loess (Washington, USA)
Carbonate clumped isotope paleothermometry was applied to fill a critical knowledge gap about climate change from ~36,000 to 9,000 years ago by providing novel terrestrial paleoenvironmental data derived from two ancient soils from the Columbia Basin province in Washington, to reconstruct carbonate formation temperatures and water 18O/16O (δ18O) values. The Washtucna paleosol formed during Marine Isotope Stages 2 and 3. The Sand Hills Coulee paleosol is estimated age ranges from the Younger Dryas Stade to the Holocene Climatic Optimum (~13,000−7,000). Clumped isotope data indicate the coldest temperatures around the Last Glacial Maximum (LGM) were ~30−23 ka. Paleosol carbonate formed during the LGM at a temperature of ~18 oC with a calculated mean annual air temperature (MAAT) of ~0 oC and a warmest average monthly temperature (WAMT) of ~9 oC. The Sand Hills Coulee paleosol formed during the Holocene Climatic Optimum at a temperature of ~28 oC with a calculated MAAT of ~12 oC and a WAMT of ~21 oC. Carbonate minerals have enriched δ18O values (17 o/oo−18.7 o/oo) during the LGM than the Holocene soil carbonate (16.8 o/oo). Carbonate δ13C have relatively high values (-6.4 o/oo− -4.4 o/oo). Temperature results were compared to two types of climate model simulations, the Paleoclimate Intercomparison Modeling Project Phase 3 (PMIP3) ensemble of models, and the Transient Climate Evolution of the Last 21,000 Years simulation (TraCE-21ka). Clumped isotope MAT and WAMT are within error of the PMIP3 ensemble. The paleosol temperature data follows the same regional late Pleistocene temperature pattern depicted in the TraCE-21 ka model output, although the temperature changes are greater than what is observed in the data.