Oceanic and climatic dynamics during the MIS 12–11 transition in the Gulf of Cádiz: Insights from coccolithophores

This study reconstructs environmental variability and surface-ocean dynamics across Termination V (MIS 12–11) in the Gulf of Cádiz using coccolithophore assemblages from International Ocean Discovery Program (IODP) Site U1386. Our data, combined with independent palaeoenvironmental proxies, including sea surface temperatures (SST), ice-rafted debris (IRD), benthic δ 18 O, and Mediterranean forest pollen assemblages, reveal a marked increase in coccolithophore productivity during MIS 11 compared to MIS 12. The end of the glacial period is characterised by higher abundances of Gephyrocapsa oceanica and reworked calcareous nannofossils, suggesting intensified Mediterranean Outflow Water (MOW). High abundances of the cold-water species Coccolithus pelagicus subsp. pelagicus , together with low SSTs and reduced Mediterranean forest pollen, reflect cold and dry conditions that were unfavourable for coccolithophore proliferation. These patterns suggest a weak westerly influence over southwestern Iberia, resulting in reduced precipitation and limited upwelling during the end of the MIS 12. In contrast, MIS 11 suggests stronger westerly influence, promoting wetter conditions and higher productivity. A sharp decline in productivity around 430 ka corresponds to a cooling event associated with increased IRD deposition, likely related to Heinrich-type event 4. These findings provide new insights into the coupling between atmospheric circulation, ocean dynamics, and primary productivity during the Mid-Brunhes Event. • High-resolution coccolithophore record across MIS 12–11 in the Gulf of Cádiz. • Productivity was lower in glacial MIS 12 and higher in interglacial MIS 11. • Small Gephyrocapsa group and G. caribbeanica are robust proxies for palaeoproductivity. • Coccolithophore and proxy data point to NAO-like atmospheric configurations. • Heinrich-type event 4 is identified around 430,000 years ago in multiproxy records.