A global perspective on Last Glacial Maximum to Holocene climate change

摘要

While the abrupt climate events of the last deglaciation are well defined in ice core records from the polar regions of both hemispheres, their manifestation elsewhere is less well constrained. Here we compile 104 high-resolution paleoclimate records to characterize the timing and spatial pattern of climate change during the last deglaciation. This compilation indicates relatively concurrent timing of the Last Glacial Maximum (LGM; peak glacial conditions) and the Altithermal (peak interglacial conditions) in the Northern (22.1 ± 4.3. ka and 8.0 ± 3.2. ka) and Southern (22.3 ± 3.6. ka and 7.4 ± 3.7. ka) Hemispheres, suggesting the hemispheres were synchronized by greenhouse gases, local insolation, and/or Northern Hemisphere induced ocean circulation changes. The magnitude of the glacial-interglacial temperature change increases with latitude, reflecting the polar amplification of climate change, with a likely minimum global mean cooling of ～-4.9 °C during the LGM relative to the Altithermal.Empirical orthogonal function (EOF) analysis of 71 records spanning 19-11ka indicates that two modes explain 72% of deglacial climate variability. EOF1 (61% of variance) shows a globally near-uniform pattern, with its principal component (PC1) strongly correlated with changes in atmospheric CO_2. EOF2 (11% of variance) exhibits a bipolar seesaw pattern between the hemispheres, with its principal component (PC2) resembling changes in Atlantic meridional overturning circulation strength. EOF analysis of 90 records from 15 to 11ka indicates that northern and southern modes of climate variability characterize the Younger Dryas-B?lling/Aller?d interval. These modes dominate at the higher latitudes of each hemisphere and exhibit a complex interaction in the tropics. The magnitude of the Younger Dryas climate anomaly (cooler/drier) increases with latitude in the Northern Hemisphere, with an opposite pattern (warmer/wetter) in the Southern Hemisphere reflecting a general bipolar seesaw climate response. Global mean temperature decreased by ～0.6°C during the Younger Dryas. Therefore, our analysis supports the paradigm that while the Younger Dryas was a period of global climate change, it was not a major global cooling event but rather a manifestation of the bipolar seesaw driven by a reduction in Atlantic meridional overturning circulation strength.