The Late Miocene, a geological period spanning 11.6 to 5.3 million years ago, was marked by significant transformations in global tectonics, biological communities, and climate systems. Previous studies have revealed that global cooling during this aera caused global temperatures to steadily between 7 and 5.4 million years ago, reaching levels comparable to modern ocean temperature.

During this period, the ocean temperatures in deep and shallow waters dropped significantly with the long-term cooling and reduction of atmospheric CO₂ since the Cenozoic. Therefore, the Late Miocene period is an important "time window" to study the interactions between ocean-land force and the global carbon cycle under warmer-than-modern conditions, offering valuable predictions into climate change and terrestrial ecosystem responses.

In the sedimentary records of many ocean basins, it was found that a long-lasting negative carbon isotope excursion occurred globally during the late Miocene period - the late Miocene carbon excursion. Existing studies have proposed three main hypotheses to explain this phenomenon, namely the terrigenous input hypothesis, the biological pump hypothesis, and the deep water and ocean current hypothesis. This series of changes in the composition of terrestrial and deep-sea carbon reservoirs is considered to be the main cause of the global cooling of the climate in the late Miocene.

To address these uncertainties, a recent study, using sedimentary records and model simulations, has uncovered that phosphate weathering processes during the Late Miocene played a crucial role in regulating the ocean carbon cycle and driving global cooling.

The researchers conducted environmental magnetic and geochemical analyses of Fe-Mn crust samples from the Magellan Seamount in the western Pacific. This provided significant evidence for a continuous increase in marine phosphate concentrations during the Late Miocene. Notably, the study identified a decoupling between phosphate and silicate weathering processes during this period. The researchers further proposed that enhanced phosphate weathering, driven by the uplift of the Qinghai-Tibet Plateau, likely contributed to a global decline in atmospheric CO₂ by boosting primary productivity and strengthening marine biological pumps.

This study underscores the pivotal role of phosphorus weathering on land during the Late Miocene and offers a novel perspective on the coupling between the marine carbon cycle and global climate change. The findings hold significant implications for advancing climate change predictions and understanding the responses of terrestrial ecosystems to long-term environmental shifts.