Tropical paleoclimate reconstruction of Heinrich event 4 and Monsoon cycles using Peruvian speleothem isotope records

Paleoclimatology, the study of earth's past climate, is essential to our understanding of current climate and predicting what our future climate will look like. By investigating ancient climate records, we can compare historic patterns with the anthropogenic warming that has occurred since industrialization. Speleothems from tropical South America present us with the opportunity to extend paleoclimate records and uncover responses of low latitude to high latitude climate forcings (Sinon, 2021). South American Summer Monsoon (SASM) variability is recorded in the δ¹⁸O_calcite of speleothems, with the current record extending through the penultimate glacial period (MIS 6) (Sinon, 2021). We studied stalagmite 19-7, collected from Huagapo Cave in the Upper Amazon Basin of the Peruvian Andes Mountains, to identify trends of SASM strength in relation to Heinrich event 4. These events are pronounced cold intervals where large masses of ice break off from glaciers and cross the North Atlantic (Kanner, 2012). During Heinrich 4, the North Atlantic cooled and the SASM intensified, signifying a more southern position of the Intertropical Convergence Zone. This event, taking place around 41kya, is revealed in the stalagmite 19-7 isotope record through a 1‰ decrease in δ¹⁸O values over a period of 300 years. This decline represents an increase in precipitation, signifying a strong SASM. Our findings suggest that the reduced transport of heat to the north and increased heat buildup farther south— and resultant southward shift in the position of the ITCZ— have a significant influence on the intensity of the SASM, almost always which is recorded by tropical speleothems. 

Reference List

Sinon, H., 2021, Extending the Record: South American Summer Monsoon Variability During MIS 6 and a First Look into MIS 7 Using Stable Isotopes of Peruvian Speleothems, Undergraduate Thesis, Union College.

Kanner, L.C., Burns, S.J., Cheng, H., and Edwards, R.L., 2012, High-latitude forcing of the South American summer monsoon during the Last Glacial: Science (New York, N.Y.), v. 335, p. 570–573.