Lower oceanic 𝛿¹³C during the Last Interglacial compared to the Holocene

Abstract. The last time in Earth’s history when the high latitudes were warmer than during pre-industrial times was the last interglacial (LIG, 129–116 ka BP). Since the LIG is the most recent and best documented warm time period, it can provide insights into climate processes in a warmer world. However, some key features of the LIG are not well constrained, notably the oceanic circulation and the global carbon cycle. Here, we use a new database of LIG benthic 𝛿¹³C to investigate these two aspects. We find that the oceanic mean 𝛿¹³C was ~ 0.2 ‰ lower during the LIG (here defined as 125–120 ka BP) when compared to the mid-Holocene (7–4 ka BP). As the LIG was slightly warmer than the Holocene, it is possible that terrestrial carbon was lower, which would have led to both a lower oceanic 𝛿¹³C and atmospheric 𝛿¹³CO₂ as observed in paleo-records. However, given the multi-millennial timescale, the lower oceanic 𝛿¹³C most likely reflects a long-term imbalance between weathering and burial of carbon. The 𝛿¹³C distribution in the Atlantic Ocean suggests no significant difference in the latitudinal and depth extent of North Atlantic Deep Water (NADW) between the LIG and the mid-Holocene. Furthermore, the data suggests that the multi-millennial mean NADW transport was similar between these two time periods.