Proxy reconstructions from the mid-Holocene (MH: 6,000 years ago) indicate an intensification of the West African Monsoon and a weakening of the South American Monsoon, primarily resulting from orbitally-driven insolation changes. However, model studies that account for MH orbital configurations and greenhouse gas concentrations can only partially reproduce these changes. Most model studies do not account for the remarkable vegetation changes that occurred during the MH, in particular over the Sahara, precluding realistic simulations of the period. Here, we study precipitation changes over northern Africa and South America using four fully coupled global climate models by accounting for the Saharan greening. Incorporating the Green Sahara amplifies orbitally-driven changes over both regions, and leads to an improvement in proxy-model agreement. Our work highlights the local and remote impacts of vegetation and the importance of considering vegetation changes in the Sahara when studying and modelling global climate.

Reconstructions of ocean primary productivity (PP) help to explain past and present biogeochemical cycles and climate changes in the oceans. We document PP variations over the last 50 kyr in a currently oligotrophic subtropical region, the Gulf of Cadiz (GoC). Data combine refined results from previous investigations on dinoflagellate cyst (dinocyst) assemblages, alkenones, and stable isotopes (18O, 13C) in planktonic (Globigerina bulloides) and endobenthic (Uvigerina mediterranea) foraminifera from cores MD04-2805 CQ and MD99-2339 with new isotopic measurements on epibenthic (Cibicidoides species) foraminifera and dinocyst-based estimates of PP using the new n = 1,968 modern database. We thus constrain paleoproductivity variations and export production by integrating qualitative information from micropaleontological bio-indicators with quantitative reconstructions of parameters such as dinocyst-based PP and seasonal sea-surface temperature (SST), as well as information about remineralization from the benthic Dd13C. We show that PP, carbon export, and remineralization were generally high in the NE subtropical Atlantic Ocean during the last glacial period and that the Last Glacial Maximum (LGM) had lower Dd13C than the Heinrich Stadials with sustained high PP, likely allowing enhanced carbon sequestration. This study also provides vital information on the dynamics PP regime changes, as the dataset includes alkenone-based SST and total organic carbon (TOC). We link these stimulated PP periods to seasonal intensification of upwelling, active almost year-round during stadials, but restricted to spring–summer during interstadials and LGM, like today. During interstadials, nutrient advection through freshwater inputs during autumn–winter rains need to be considered to fully understand PP regimes.