Geological Society of America

10 Geochemistry and Mineralogy (Posters)

Sunday, 22 March 2026
8:00 AM - 12:00 PM
CCC, Ballroom C

Ecosystem-Specific Fire Responses to Abrupt Hydroclimate Change During Heinrich Stadial 1

Paper number: 10-4
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Zhao Wang Presenting Author
University of Connecticut , Storrs , Connecticut
Michael Hren
University of Connecticut , Storrs , Connecticut
Elizabeth Griffith
Ohio State University, Columbus, Ohio
Jonathan Smolen
Harvard University, Cambridge, Massachusetts
Sarah Pederzani
University of Utah, Salt Lake City, Utah
Clay Tabor
University of Connecticut , Storrs , Connecticut
Isabel Montañez
University of California, Davis, Davis, California
Jessica Oster
Vanderbilt University, Nashville, Tennessee
Yuval Burstyn
University of California, Davis, Davis, California
Cameron de Wet
Middlebury College, Middlebury, Vermont
Eliot Atekwana
University of California, Davis, Davis , California
Aida Zyba
Vanderbilt University, Nashville, Tennessee
Gabriel Bowen
University of Utah, Salt Lake City, Utah

Abstract

Understanding how fire regimes respond to abrupt hydroclimate change is essential for predicting ecosystem resilience under future climate instability. During Heinrich Stadial 1 (HS1; ~18.0–14.7 kyr BP), glacial meltwater discharge into the North Atlantic weakened the Atlantic Meridional Overturning Circulation (AMOC), driving pronounced shifts in moisture availability, seasonality, and fire activity across western North America. Here, we reconstruct fire–hydroclimate–vegetation interactions in California during HS1 using terrestrial ecosystem–derived molecular compounds preserved in speleothem carbonates from Lake Shasta Cavern (LSC; 40.804°N) and McLean’s Cave (ML1; 38.067°N). We quantify high–molecular–weight polycyclic aromatic hydrocarbons (HMW PAHs; 5- and 6-ring) as indicators of high-temperature biomass burning, alongside phytosterols and conifer-derived diterpenoids to trace vegetation productivity and fuel composition. At LSC, persistently elevated HMW PAH concentrations during early HS1 (~18.0–16.0 kyr BP) indicate frequent, high-intensity fires coincident with sustained terrestrial inputs from flowering plant–dominated ecosystems, suggesting that enhanced fuel production under wetter conditions promoted fire without long-term ecosystem collapse. In contrast, ML1 records show pronounced declines in diterpenoids (“resin oils”) during intervals of elevated PAHs toward the end of HS1 (~15.0 kyr BP), reflecting conifer forest loss under intensified fire stress linked to hydroclimate deterioration. These records demonstrate that HS1 fire regimes were governed by hydroclimate-driven fuel accumulation and vegetation-specific recovery capacity, rather than temperature or aridity alone. Our findings imply that future AMOC weakening could amplify fire risk in western North America by altering moisture seasonality and fuel dynamics, potentially pushing ecosystems toward critical fire-hydroclimate tipping points.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411261

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