NSF Award
2402362
During the ice ages of the past few million years, ice sheets repeatedly grew southward from the Arctic. The ice sheet in North America advanced as far south as New York City during the most recent ice age, but little is known about its size before then. This project will determine if the ice sheet also reached New York during each of the past five ice ages using cave formations (speleothems) in the area. The findings will show how consistently (or not) ice sheets respond to drivers of climate change and improve estimates of how high sea levels rose during warm periods between ice ages. Given that ongoing ice sheet melt is projected to accelerate in our warming world, the real-world data generated in this research will provide timely information on how ice sheets and climate are linked. The most compelling findings will be delivered to the public through tours at a popular show cave and shared with the caving community through National Speleological Society print and online media. The scientists will participate in the NSS’s “Request a Speleoguest” program linking K-12 educators with cave experts, as well as develop an educational module, including caving trips, for a New York City charter school that serves primarily low-income students.<br/><br/>This project will apply a well-known but overlooked approach to constraining the Laurentide Ice Sheet’s (LIS) southern limit during glacial maxima of the past 500 kyr: developing a speleothem growth chronology within the ice sheet’s footprint. 150 uranium-thorium ages will be measured on a large collection of speleothems from 17 caves in east-central New York State, only 100-200 km inboard of its Last Glacial Maximum (LGM) margin. This chronology can provide a binary proxy of ice cover through time – speleothem growth typically occurs when ice-free conditions permit liquid water charged with soil CO2 to percolate into a well-ventilated cave, whereas growth usually halts when an area is glacier covered. Stable isotope profiles will also be measured along speleothems to develop a long climate reconstruction. The results will help address four longstanding problems in paleoclimate. (1) Did the LIS advance to near its LGM extent every glaciation? (2) How are interglacial sea level markers affected by the size and timing of prior ice loading? (3) Were abrupt glacial climate events related to rerouting of freshwater runoff by an oscillating LIS margin in eastern North America? (4) How were orbital and millennial-scale climate change expressed in the mid latitudes, near the LIS and upwind of the North Atlantic?<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
