Enhanced Mediterranean Wetting in Response to Cold Indian Ocean SST during the Last Interglacial

Abstract

Abstract As a climate change hotspot, the Mediterranean is often thought to be directly influenced by the North Atlantic. However, growing evidence highlights remote effects of the tropical oceans on the North Atlantic, complicating our understanding of the mechanisms driving Mediterranean climate change. The Last Interglacial (~127 ka; LIG) and the mid-Holocene (~6 ka; MH), both characterized by higher boreal summer insolation and lower winter insolation compared to pre-industrial climate, provide valuable opportunities to investigate the Mediterranean climate’s response to global-scale forcings. Here, we show that multi-model simulations from the Paleoclimate Model Intercomparison Project Phase 4 (PMIP4), consistent with proxy data, reveal that the Mediterranean experienced wetter conditions during the LIG and MH compared to the pre-industrial period. The simulated wetting is most pronounced in late winter and early spring (February to April), with circulation anomalies resembling a negative phase of the North Atlantic Oscillation and the North Atlantic storm track shifts southward. Standalone atmospheric experiments reveal both local and teleconnected effects. A reduced meridional temperature gradient in the North Atlantic contributes about one-quarter of the increase in Mediterranean precipitation. More importantly, suppressed convection over the Indian Ocean forced by the local surface cooling induces roughly four-fifths of the simulated Mediterranean wetting. This physical link between Mediterranean wetting and Indian Ocean drying is consistently reproduced across the inter-model spread during the LIG. Our findings unravel the dominant role of Indian Ocean in Mediterranean wetting during interglacial intervals, with implications for the ongoing Mediterranean drying under global warming.

Affiliated Institutions

• Columbia University US
• Lamont-Doherty Earth Observatory US

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