IODP Expedition 401: Investigating Miocene Mediterranean-Atlantic Gateway Exchange (IMMAGE)

4th Deepwater Circulation Research Conference (4DWC), 24-26th May 2023, Edinburgh

Marine gateways play a critical role in the exchange of water, heat, salt and nutrients between oceans and seas. The advection of dense waters helps drive global thermohaline circulation and, since the ocean is the largest of the rapidly exchanging CO2 reservoirs, this advection also affects atmospheric carbon concentration. Changes in gateway geometry can therefore significantly alter both the pattern of global ocean circulation and associated heat transport and climate, as well as having a profound local impact. Today, the volume of dense water supplied by Atlantic-Mediterranean exchange through the Gibraltar Strait is amongst the largest in the global ocean. For the past 5 My, this overflow (the Mediterranean Overflow eater, MOW) has generated a saline plume at intermediate depths in the Atlantic that deposits distinctive contouritic sediments in the Gulf of Cadiz and contributes to the formation of North Atlantic Deep Water. This single gateway configuration only developed in the early Pliocene, however. During the Miocene, a wide, open seaway linking the Mediterranean and Atlantic evolved into two narrow corridors: one in northern Morocco; the other in southern Spain. Formation of these corridors permitted Mediterranean salinity to rise and a new, distinct, dense water mass to form and overspill into the Atlantic for the first time. Further restriction and closure of these connections resulted in extreme salinity fluctuations in the Mediterranean, leading to the formation of the Messinian Salinity Crisis salt giant. IMMAGE is an Land-2-Sea drilling proposal designed to recover a complete record of Atlantic-Mediterranean exchange from its Late Miocene inception to its current configuration. This will be achieved by targeting Miocene offshore sediments on either side of the Gibraltar Strait with IODP Expedition 401 and recovering Miocene core from the two precursor connections now exposed on land with ICDP. The scientific aims of IMMAGE are to constrain quantitatively the consequences for ocean circulation and global climate of the inception of Atlantic-Mediterranean exchange; to explore the mechanisms for high amplitude environmental change in marginal marine systems and to test physical oceanographic hypotheses for extreme high-density overflow dynamics that do not exist in the world today on this scale. Here we summarise the Late Miocene contourite depositional systems being targeted in the Gulf of Cadiz and West of Portugal, the drilling locations and the main objectives of IMMAGE and IODP Expedition 401. Further information about the IODP Expedition 401 at: https://iodp.tamu.edu/scienceops/expeditions/mediterranean_atlantic_gateway_exchange.html *IMMAGE team: Abdella Ait Salem, Alvaro Arnaiz, Nadia Bahoun, Asmae Benarchid, Guillermo Booth Rea, Domenico Chiarella, Damien Do Couto, Hajar el Talibi, Gemma Ercilla, Ferran Estrada, Marcus Gutjahr, Tim Herbert, Frits Hilgen, Francisco Jose Jiménez-Espejo, Wout Krijgsman, Santiago Ledesma-Mateo, Sonya Legg, Estefania Llave, Amine Manar, Pilar Mata, Hugo Matias, Paul Meijer, Cesar Rodriguez Ranero, Maria Isabel Reguera, Francisco J Rodríguez-Tovar, Michael Rogerson, Cristina Roque, Francisco Sierro, Duncan Wallace, Zakaria Yousfi