Extrapolar climate reversal during the last deglaciation

Area of Science:

• Paleoclimatology
• Oceanography
• Climate Science

Background:

• The last deglaciation saw significant ocean-atmosphere and hydroclimate shifts.
• The interplay between these changes, particularly during the last deglaciation, remains unclear.

Purpose of the Study:

• To reconstruct Northern Hemisphere polar jet variability using a high-resolution speleothem record.
• To investigate the causes and impacts of a major climate reversal during the last deglaciation.

Main Methods:

• Speleothem-based high-resolution paleoclimate reconstruction.
• Integration of global hydroclimate proxy data.
• Analysis of atmospheric CO2 levels and ocean circulation patterns.

Main Results:

• A speleothem record revealed polar jet variability largely consistent with Greenland ice cores, except during the last deglaciation.
• A dramatic climate reversal, termed the Extrapolar Climate Reversal (ECR), was identified in global tropical and subtropical hydroclimate proxies.
• ECR initiation correlated with rising CO2, Southern Ocean upwelling, and weakened Atlantic Meridional Overturning Circulation.

Conclusions:

• The ECR is attributed to the upwelling of cold Southern Ocean deep waters into the tropics and subtropics.
• This upwelling event explains regional climate variability previously termed the 'Mystery Interval'.
• The study clarifies the connection between oceanographic changes and hydroclimate shifts during the last deglaciation.