Atmospheric Transmission of Temperature and Precipitation Change in Florida During North Atlantic Heinrich Events

Abstract Palynological analysis of a sediment core from Lake Tulane in south‐central Florida indicated major shifts in plant communities over the past 60,000 years which coincide with high‐latitude Dansgaard‐Oeschger cycles and the Heinrich Events (HE) that terminated them. To test the connection more directly between Heinrich Event and environmental change in Florida, we examined the distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) across an interval of the Lake Tulane core spanning Heinrich Stadials 2–4. These data are coupled with hydrological reconstructions based upon differences in δ 2 H values of terrestrial and aquatic n ‐alkanes. Our brGDGT and δ 2 H data are contextualized with simulations from the fully coupled iTRACE model representing Heinrich Stadial 1 and the succeeding interstadial (Dansgaard‐Oeschger 1). During Heinrich Stadials, brGDGT distributions indicate that subtropical Florida cooled, and based upon lower ε (C29‐C23) of terrestrial and aquatic n ‐alkanes, precipitation likely increased. This change is not correlated with the strength of the Atlantic Meridional Overturning Circulation as circulation was already reduced prior to HE. Instead, it likely reflects a southward displacement of the jet stream caused by a southward displacement of the strongest meridional temperature gradient during periods of high‐latitude cooling in the Northern Hemisphere. Spatially coherent patterns of jet stream displacement and velocity changes are apparent across the southern United States in iTRACE simulations and are mechanistically attributable to freshwater forcing in the North Atlantic. Together our proxy and modeling data support the interpretation that high‐latitude climate perturbations can be propagated to subtropical latitudes through primarily atmospheric, rather than oceanic, mechanisms.