Quaternary Science Advances (Jan 2023)
Late Pleistocene glaciation in the southernmost Sangre de Cristo Mountains, New Mexico – Chronology and paleoclimate
Abstract
Surface-exposure dating of moraine boulders and numerical paleoglacier modeling yield the first numerical ages for the local Last Glacial Maximum (LGM) in the state of New Mexico and the southernmost Rocky Mountains, and the first glacier-based paleoclimate estimates for that region. Analysis of cosmogenic 10Be in samples from ten moraine boulders indicates that glaciers in the Winsor Creek drainage in the southern Sangre de Cristo Mountains occupied their LGM positions until ∼21.2 ± 2.0 ka, and likely remained near those positions until about 18.3 ± 1.3 ka. Application of a coupled energy/mass balance and ice-flow model to the reconstructed paleoglaciers indicates that temperature depressions of 8.6–9.0 °C from present temperatures would have been necessary to sustain glaciers in the drainage at their last glacial maximum extents, assuming precipitation amounts and seasonality were no different from modern. Model uncertainly in these estimates is approximately ±1.5 °C. Combining glacier-model output with climate-model output interpolated to the study region suggests that the LGM glaciers in the drainage were likely sustained by a temperature depression of ∼8 °C from modern conditions, coupled with an increase of ∼10–25% in precipitation, at least during the fall-through-spring seasons. Such an increase in accumulation season precipitation is consistent with previous suggestions of enhancement of Pacific-sourced cyclonic precipitation due to southward displacement of the LGM mean winter storm track across the western United States and/or of increased intensity and penetration of Pacific atmospheric rivers into the continent at the LGM.
