A Mountain Glacier Perspective on the Bipolar Seesaw

A global record of mountain glacier terminations during the last deglaciation dated by a large, uncurated dataset of cosmogenic-nuclide exposure ages highlights a statistically significant asynchrony in termination ages between the Northern and Southern Hemispheres. This interhemispheric temporal offset in glacier terminations is consistent with previously correlated ice core records that show a systematic, temporal interhemispheric lag of abrupt climate events, with the Southern Hemisphere leading the Northern Hemisphere by ~500-1000 years. Our analysis (i) aggregates cosmogenic-nuclide exposure ages from a global dataset of moraines to discern climatically driven peaks in moraine emplacement events, and (ii) utilizes a Monte Carlo simulation based on a null hypothesis that moraine emplacement is interhemispherically synchronous to estimate the statistical significance of the observed offset. The observed lag of Northern Hemisphere emplacement events compared to the Southern Hemisphere is statistically significant and supports the ‘bipolar seesaw’ pattern observed in ice core records.