Three hundred thousand years of multi-millennial hydroclimate variability in Northern Africa based on speleothem records from Tunisia

Hydroclimate changes in Northern Africa reflect the interplay between mid-latitude westerlies and the West African monsoon, along with their intensity variations. The response of these atmospheric circulation systems to changing boundary conditions and their impacts on the precipitation during past episodes of climate change remain unconstrained, because of scarcity of well-dated terrestrial hydroclimate records from Northern Africa that reach beyond the Holocene interglacial. We present a 300,000-year hydroclimate record inferred from periods of speleothem formation from Tunisia, located in the northernmost Africa. This record captures the alternation of humid and arid phases during glacial and interglacial climate states, as well as the superimposed millennial-scale events. Humid conditions prevailed during the interglacial periods, while arid conditions were associated to glacial boundary conditions. Cave evidence suggests that these humid phases in northernmost Africa could mainly be attributed to the southward shift and strengthening of the mid-latitude westerlies and the Mediterranean storm track during interglacials, and vice versa in glacials. A comparison with palaeolake records from the Sahara suggests suggests that during interglacials winter westerlies and the summer West African Monsoon were crucial to bring moisture in Northern Africa, contributing to the development of wet conditions in the Sahara. Humid climate in Northern Africa prevailed during interglacial periods over the past 300,000 years and was mainly driven by southward shifts and intensification of mid-latitude westerlies and the Mediterranean storm track, based on speleothem records from Tunisia.