EVIDENCE FOR THE YOUNGER DRYAS AND DANSGAARD-OESCHGER EVENTS FROM STALAGMITES IN THE MID-ATLANTIC REGION OF THE EASTERN UNITED STATES

Rapid climate change is a prominent feature of the last glacial interval. Large temperature changes in Greenland and the North Atlantic during the Younger Dryas Stadial and Dansgaard-Oeschger (D/O) and Heinrich events had impacts on European temperatures, the Asian summer monsoon, and South American precipitation. Very little is yet known about the extent of variability associated with these events in the eastern United States. Here, we present two precisely dated stalagmite records from Grand Caverns in Grottoes, Virginia, which provide strong evidence of the Younger Dryas and earlier D/O events impacting the Mid-Atlantic region of the eastern United States. The Younger Dryas event is U/Th-dated in both of the Grand Caverns stalagmites between 12,900-11,400 yr B.P., and characterized by a maximum negative excursion in δ¹⁸O values of speleothem calcite of ~1.3 ‰ across that time interval. Nineteen of the twenty most recent Dansgaard-Oeschger events show positive δ¹⁸O shifts concurrent with established events in the NGRIP ice core in nearly every instance of millennial-scale variability. While these events may be associated with persistent changes in mean annual temperature, the modern climate suggests that the stalagmite record reflects seasonal changes in temperature and/or precipitation, with high sensitivity to winter conditions. The expression of millennial events in δ¹⁸O from the Grand Caverns stalagmites contrasts with earlier results from Buckeye Creek Cave in West Virginia, which show minimal climate variability at millennial scales, but large changes associated with orbital forcing. The stronger expression of millennial events at Grand Caverns is likely due to its position on the eastern flank of the Appalachians, allowing a greater contribution of Atlantic moisture, particularly during winter months.