Extrapolar climate reversal during the last deglaciation

Yemane Asmerom,Victor J. Polyak,Matthew S. Lachniet

doi:10.1038/s41598-017-07721-8

Yemane Asmerom, Victor J. Polyak + Show 1 more

Open Access

https://doi.org/10.1038/s41598-017-07721-8

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Abstract

Large ocean-atmosphere and hydroclimate changes occurred during the last deglaciation, although the interplay between these changes remains ambiguous. Here, we present a speleothem-based high resolution record of Northern Hemisphere atmospheric temperature driven polar jet variability, which matches the Greenland ice core records for the most of the last glacial period, except during the last deglaciation. Our data, combined with data from across the globe, show a dramatic climate reversal during the last deglaciation, which we refer to as the Extrapolar Climate Reversal (ECR). This is the most prominent feature in most tropical and subtropical hydroclimate proxies. The initiation of the ECR coincides with the rapid rise in CO2, in part attributed to upwelling in the Southern Ocean and the near collapse of the Atlantic Meridional Overturning Circulation. We attribute the ECR to upwelling of cold deep waters from the Southern Ocean. This is supported by a variety of proxies showing the incursion of deep Southern Ocean waters into the tropics and subtropics. Regional climate variability across the extropolar regions during the interval previously referred to as the “Mystery Interval” can now be explained in the context of the ECR event.

Highlights

Large ocean-atmosphere and hydroclimate changes occurred during the last deglaciation, the interplay between these changes remains ambiguous
Stalagmite FS-AH1 was collected ~1.5 km into Fort Stanton Cave (Fig. S1), where current cave temperature is stable at 10 ± 0.55 °C and relative humidity is near 100% perennially
The imprint of millennial-scale climate variability over the last glacial period was documented in the southwestern United States by abrupt and large changes in stalagmite δ18O, which were previously shown to reflect, in part, changes in the ratio of winter to summer precipitation forced by meridional shifts in the polar jet stream[7, 16]

Summary

OPEN Extrapolar climate reversal during the last deglaciation

Large ocean-atmosphere and hydroclimate changes occurred during the last deglaciation, the interplay between these changes remains ambiguous. We suggest that the ECR and HS1 are two distinct events with different causes, the impact of these two events is similar across a range of tropical and subtropical regions and are most likely driven by changes in the long-term position of the ITCZ Both models and proxy data in general[29, 30] and for the western tropical Pacific in particular[31, 32] show a southward shift of the mean ITCZ position during cold events and drier than normal conditions[32], consistent with the patterns observed in western tropical Pacific rainfall (Fig. 6C). Our analysis of proxy data in the context of the global SST and hydroclimate data show that Southern Ocean upwelling had a profound influence across the globe, providing a coherent framework for understanding large changes in hydroclimate during a period previously dubbed as the mystery interval[33]

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