Plio-Pleistocene Southwest African Hydroclimate Modulated by Benguela and Indian Ocean Temperatures

Abstract

Future projections of southwestern African hydroclimate are highly uncertain. However, insights from past warm climates, like the Pliocene, can reveal mechanisms of future change and help benchmark models. Using leaf wax hydrogen isotopes to reconstruct precipitation (δDp) from Namibia over the past 5 million years, we find a long-term depletion trend (−50‰). Empirical mode decomposition indicates this trend is linked to sea surface temperatures (SSTs) within the Benguela Upwelling System, but modulated by Indian Ocean SSTs on shorter timescales. The influence of SSTs on reconstructed regional hydroclimate is similar to that observed during modern Benguela Ni (Figure presented.) o events, which bring extreme flooding to the region. Isotope-enabled simulations and PlioMIP2 results suggest that capturing a Benguela Ni (Figure presented.) o-like state is key to accurately simulating Pliocene, and future, regional hydroclimate. This has implications for future regional climate, since an increased frequency of Benguela Ni (Figure presented.) os poses risk to the ecosystems and industries in the region.