The marine biological pump is crucial for removing excess carbon dioxide from the atmosphere to the ocean interior and seafloor sediments, serving as a key mechanism for regulating Earth’s environmental changes through the carbon cycle. Investigating its geological evolution offers vital clues for understanding the formation of a habitable planet and predicting Earth’s future trends.

The late Miocene (11.6–5.33 Ma), with an atmospheric CO₂ concentration similar to the pre-industrial level, represents an ideal time window for understanding the relationship between anthropogenic climate, ocean circulation, and global carbon cycling. During this time interval, biogenic components in marine sediments have increased significantly, which is known as the Late Miocene Biogenic Bloom (LMBB). However, due to the limitations of traditional productivity proxies (e.g., biogenic calcium carbonate, biogenic silica), the temporal and spatial distributions of this event remain controversial.

Associate Professor Weiqi Yao’s research group from the Department of Ocean Science and Engineering at the Southern University of Science and Technology (SUSTech) has made important progress in understanding the marine biological carbon pump and its relationship to climate change. Their findings provide new insights into the LMBB.

Their work, titled “A Marine Barite Perspective of the Late Miocene Biogenic Bloom in the Equatorial Indian Ocean and Equatorial Western Atlantic Ocean”, has been published in Geophysical Research Letters, a journal listed in the Nature Index.

Figure 1. Oceanographic and productivity map of studied sites.

This study uses marine barite (BaSO₄) accumulation rate as a tracer of the LMBB, as marine barite precipitating from the water column is closely associated with export productivity and has very low solubility. Through comparing with multiple productivity proxies, including Ba_excess, bio-SiO₂ accumulation rate, and CaCO₃ accumulation rate records, the researchers reconstruct productivity changes from 12 to 5 Ma at ODP Site 758 in the equatorial Indian Ocean and ODP Site 926 in the equatorial western Atlantic.

Figure 2. Biogenic barium records and marine barite crystals.

The new barite records from two low-latitude sites inside and outside an upwelling regime suggest that the LMBB has commenced at ∼9 Ma in the equatorial Indian Ocean but has not occurred or sustained in the equatorial western Atlantic. The group’s work attributes the LMBB to intensified ocean overturning under global cooling by compiling sea-surface temperature and multi-proxy data. Enhanced biological productivity, driven by nutrient supply from upwelling, offered positive feedback to late-Miocene climate cooling.

Figure 3. Multi-proxy reconstructions between 12 and 5 Ma.

This study offers a new perspective on understanding the LMBB, deepening insights into how the marine biological carbon pump responds to climate change on geological timescales. It provides valuable references for addressing current global climate challenges and introduces innovative methods for reconstructing ocean productivity and carbon cycling in the future.

Master’s student Xinying Wu and Dr. Yue Hu are the co-first authors of the paper, with Associate Professor Yao Weiqi serving as the corresponding author. Dr. Jingbo Nan also made significant contributions to this work, with SUSTech recognized as the primary institution.

Paper link: https://doi.org/10.1029/2024GL111748

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