Mapping the evolution of marine carbon during the last deglaciation: δ13C perspectives on the deglacial ocean carbon cycle

초록

The changes in the ocean circulation and biological pump played crucial roles in the rise in atmospheric CO2 during the last deglaciation. However, our understanding remains limited regarding which processes-air-sea exchange, ocean circulation, and the biological pump-primarily influence the spatial dynamics of the oceanic carbon cycle. To address this knowledge gap, the present study compiles global stable carbon isotope (delta 13C) records from various sources, including shallow and deep planktic, along with epifaunal and infaunal benthic foraminifera. The synthesis reveals a total increase of 0.37 +/- 0.05 parts per thousand in marine delta 13 C values since the last glacial maximum. Of this increase, 68 +/- 5 % is attributed to the response of the oceans in the southern hemisphere, while 32 +/- 4 % is attributed to the northern hemisphere. By analyzing the difference between planktic and benthic foraminifera, a decreased vertical delta 13 C gradient ( delta 13 C sp-sb ) is observed during the last deglaciation, indicating rapid carbon exchange between surface and deep waters during deglaciation. Additionally, the offset between the epifaunal and infaunal delta 13 C ( delta 13 C sb-db ) provides insights into changes in productivity and bottom water oxygenation. Overall, the global synthesis suggests that the delta 13 C variation is largely controlled by ocean circulation in the northern hemisphere and at higher latitudes of the southern hemisphere, while primary production significantly influences subtropical regions. Furthermore, the delta 13 C confirms that the rise in atmospheric CO2 during the first phase of Heinrich Stadial 1 (HS1) resulted from reduced primary production in subtropical regions along with strong ventilation in the second phase of HS1. Interestingly, the delta 13 C variations during the Younger Dryas (YD) suggest strong ventilation without evident changes in primary production. This fourdimensional dataset provides valuable insights into the transient changes in the ocean carbon cycle during deglaciation.

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