Paleoclimate Changes in the Pacific Northwest Over the Past 36,000 Years From Clumped Isotope Measurements and Model Analysis

Abstract

The Last Glacial Maximum (LGM; ∼23,000-19,000 years ago; ka) is the subject of extensive study and represents a global climate state dramatically different from that of today, characterized by reduced greenhouse gas concentrations and extensive ice sheets (Mix et al., 2001;Raynaud et al., 1993). Proxy records and climate models show that glacial-interglacial cycles are driven by orbital forcing and internal mechanisms such as variations in insolation, greenhouse gas levels, and distribution of ice sheets (

Clumped Isotopes Record a Glacial‐Interglacial Shift in Seasonality of Soil Carbonate Accumulation in the San Luis Valley, Southern Rocky Mountains, USA

“…Their stable isotopic composition (δ 18 O, δ 13 C) provides a useful indicator of paleoenvironmental conditions at the time of accumulation, and has been used to reconstruct changing paleo‐climate, vegetation, and elevation over a range of temporal and spatial scales in the geologic record (Cerling, 1984; Quade, 2014; Zamanian et al., 2016). Clumped isotope (∆ 47 ) thermometry has recently provided an additional novel paleotemperature indicator (Ghosh et al., 2006; Huntington & Petersen, 2023; Huntington et al., 2009), and has increasingly been applied to reconstructing late Pleistocene‐Holocene climate change from carbonate archives (e.g., mollusk shells, Eagle et al., 2013; lake tufas, Hudson et al., 2017; Santi et al., 2020; soil carbonates, Lechler et al., 2018; Lopez‐Maldonado et al., 2023). Recent work in the Rocky Mountains, comparing the magnitude of temperature shifts associated with the last glacial‐interglacial transition, highlights regional differences in temperature change reconstructed using numerical mass balance modeling of mountain glaciers at their glacial maximum extents, and disagreement between these glacial model‐based estimates and those from global and regional climate model simulations (Brugger et al., 2019, 2021; Leonard et al., 2017).…”