Major sea level fall during the Pliocene M2 glaciation

Area of Science:

• Paleoclimatology
• Oceanography
• Climate Science

Background:

• The extent of Pliocene M2 glaciation (~3.3 Ma) is debated, with oxygen isotopes suggesting cooling.
• Previous interpretations of benthic foraminiferal oxygen isotopes focused on temperature rather than ice volume.

Purpose of the Study:

• To refine the benthic foraminiferal Mg/Ca paleothermometer for precise bottom water temperature reconstruction.
• To reassess the ice volume and drivers of the Pliocene M2 glaciation.

Main Methods:

• Improved benthic foraminiferal Mg/Ca paleothermometry with ±0.2-0.3°C precision.
• Reconstruction of bottom water temperatures during the M2 glaciation.

Main Results:

• A significant ice volume increase (~55 m SLE) during M2 glaciation.
• Ice growth was more closely linked to a decrease in atmospheric CO2 than to ocean temperature changes.
• Reduced poleward heat transport in both hemispheres, exacerbated by Indonesian Seaway restriction, likely initiated and amplified glaciation.

Conclusions:

• Cryosphere expansion drove atmospheric CO2 decline, contributing to the magnitude of M2 ice growth.
• The Pliocene M2 glaciation demonstrates the cryosphere's sensitivity to ocean heat transport, with implications for modern climate.
• Reduced ocean heat transport is a key factor in glacial dynamics.