Glacial carbon cycle changes by Southern Ocean processes with sedimentary amplification

Area of Science:

• Paleoceanography
• Climate modeling
• Oceanography

Background:

• Paleo reconstructions suggest Southern Ocean carbon storage influenced glacial atmospheric carbon dioxide (pCO2).
• Quantifying this contribution in ocean general circulation models (OGCMs) is challenging.

Purpose of the Study:

• To quantify the Southern Ocean's contribution to low glacial atmospheric pCO2 using OGCMs.
• To improve model-data agreement for glacial deep water properties.

Main Methods:

• Utilized a 3D OGCM incorporating sedimentary processes.
• Simulated glacial periods with enhanced Southern Ocean salinity stratification and iron fertilization from glaciogenic dust.

Main Results:

• OGCM simulation improved agreement with paleo data for glacial deep water (isotopic carbon, oxygen, radiocarbon ages).
• Achieved a 77-ppm reduction in atmospheric pCO2, closely matching paleo records.
• Southern Ocean salinity stratification and iron fertilization amplified carbonate sedimentary feedback, increasing deep ocean carbon storage.

Conclusions:

• Southern Ocean salinity stratification and iron fertilization were key drivers of glacial carbon storage and pCO2 reduction.
• Accurate simulation of Southern Ocean properties is vital for understanding past ocean carbon cycle changes.