The magnitude of regional cooling across Southern Patagonia during the Antarctic Cold Reversal and Younger Dryas determined by glacier modelling

Determining the magnitude, timing and regional extent of past abrupt climate change events is crucial to resolve the spatial patterns and determine mechanism that drive rapid climate fluctuations. This thesis presents glacier model based quantitative paleotemperature reconstructions from two mountain glaciers in Southern Patagoniathat encompass the Late Glacial (c. 14.6–12.8 ka). Temperature anomalies resolved across a series of closely spaced Antarctic Cold Reversal (ACR; c. 14.5-12.9 ka) moraines were -3.0--2.6 °C at 47°S and -2.7--2.4 °C at 44°S. In both locations this was followed by either a precipitation reduction of 15-20 %, or a warming of +0.3°C from the Antarctic Cold Reversal moraines to moraines dated to the Younger Dryas (c. 12.9-11.7 ka). These anomalies show a shared, regional response across this latitude range in Patagonia, that follows the Antarctica temperature record. Further, the anomalies determined are a similar magnitude to glacier model based Antarctic Cold Reversal temperatures in New Zealand across the latitudes of 39-44 °S. This is evidence for a shared trans-Pacific climate response across the mid to high latitudes (47-39 °S) throughout the Late Glacial, that is best explained by a northward expansion of the southern westerly winds during the Antarctic Cold Reversal. These reconstructions were produced using globally available, remote sensing-based glacier datasets, and global reanalysis climate datasets.

The methodology applied presents an efficient paleoclimate reconstruction approach, which could be applied to the growing database of dated glacial moraines to produce a consistent, globally distributed, paleotemperature dataset.