Global reorganization of deep-sea circulation and carbon storage after the last ice age

Using new and published marine fossil radiocarbon (14C/C) measurements, a tracer uniquely sensitive to circulation and air-sea gas exchange, we establish several benchmarks for Atlantic, Southern, and Pacific deep-sea circulation and ventilation since the last ice age. We find the most 14C-depleted water in glacial Pacific bottom depths, rather than the mid-depths as they are today, which is best explained by a slowdown in glacial deep-sea overturning in addition to a flipped glacial Pacific overturning configuration. These observations cannot be produced by changes in air-sea gas exchange alone, and they underscore the major role for changes in the overturning circulation for glacial deep-sea carbon storage in the vast Pacific abyss and the concomitant drawdown of atmospheric CO2.

Automated summary

This study provides several benchmarks for circulation and ventilation of the Atlantic, Southern, and Pacific deep-sea since the last ice age using measurements of marine fossil radiocarbon. The findings highlight the significant role of changes in overturning circulation in glacial deep-sea carbon storage and the simultaneous reduction of atmospheric CO2.