137 Joint SGD-SEPM-IAS Focus on the Sedimentary Record of Climate Change

Explore how sedimentary records reveal Earth's climatic history and processes driving environmental change. This session highlights proxies, stratigraphy, and emerging technologies, advancing understanding of past climates and informing predictions of future climate dynamics through interdisciplinary collaboration.

Monday, 20 October 2025
1:30 PM - 5:30 PM
HBGCC, 303C

An El Nino-like response during Heinrich Stadial 1 drives pluvial lake expansions in the Western North America

Paper number: 137-5
Program: Technical Sessions
Time: 2:40 PM – 2:55 PM

Authors

Abstract

The drought-prone southwestern US (SWUS) experienced exceptionally wet conditions during Heinrich Stadial 1 (HS1; 18-15 ka). Such a change has been hypothesized to be driven by deepening of the Aleutian Low, a southward shift of the jet stream, and increased atmospheric rivers in association with a slowdown of the Atlantic Meridional Overturning Circulation (AMOC). However, the pathways through which an AMOC-driven climate signal is propagated from the North Atlantic to the western US remain elusive. To address this question, we first establish the global hydroclimate response by comparing an ensemble of freshwater hosing simulations to a synthesis of global hydroclimate proxy data. The best-performing models exhibit an El Niño-like mean state change in the tropical Pacific, which is driven by a weakened meridional temperature gradient in the eastern tropical Pacific due to transmission of cooling from the tropical North Atlantic across the Isthmus of Panama. This El Niño-like response excites a northeastward-propagating rossby wave from the central Pacific, leading to a deepened Aleutian Low and enhanced southwesterly moisture transport to the SWUS. To further distinguish this mechanism, we run a set of sensitivity tests using an atmosphere-only model, which show that changes in tropical Pacific SST alone could account for the majority of precipitation increase observed in the SWUS. Our results demonstrate that a weaker AMOC influences SWUS hydroclimate via tropical teleconnection involving a zonally asymmetric change in the tropical Pacific. As the AMOC is projected to weaken in the future, the ability of models to correctly simulate the tropical Pacific response will be critical for accurately predicting future hydroclimate change in the western US.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413072

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.