Assessing the statistical uniqueness of the Younger Dryas: A robust multivariate analysis

Abstract

During the last glacial period (ca. 120-11kyrBP), dramatic temperature swings, known as Dansgaard-Oeschger (D-O) events, are clearly manifest in high-resolution oxygen isotope records from the Greenland Ice Sheet. Although variability in the Atlantic Meridional Overturning Circulation (AMOC) is often invoked, a unified explanation for what caused these "sawtooth-shaped"climate patterns has yet to be accepted. Of particular interest is the most recent D-O-shaped climate pattern that occurred from g1/414600 to 11500 years ago - the Bølling-Allerød (BA) warm interstadial and the subsequent Younger Dryas (YD) cold stadial. Unlike earlier D-O stadials, the YD is frequently considered a unique event, potentially resulting from a rerouting and/or flood of glacial meltwater into the North Atlantic or a meteorite impact. Yet, these mechanisms are less frequently considered as the cause of the earlier stadials. Using a robust multivariate outlier detection scheme - a novel approach for traditional paleoclimate research - we show that the pattern of climate change during the BA/YD is not statistically different from the other D-O events in the Greenland record and that it should not necessarily be considered unique when investigating the drivers of abrupt climate change. In so doing, our results present a novel statistical framework for paleoclimatic data analysis.