Evolution of Ocean Circulation in the North Atlantic Ocean During the Miocene: Impact of the Greenland Ice Sheet and the Eastern Tethys Seaway

Abstract

AbstractThe Modern Ocean is characterized by the formation of deep‐water in the North Atlantic Ocean (i.e., NADW). This feature has been attributed to the modern geography, in which the Atlantic Ocean is a large basin extending from northern polar latitudes to the Southern Ocean, the latter enabling the connection of the otherwise isolated Atlantic with the Pacific and Indian Oceans. Sedimentary data date the establishment of the NADW between the beginning of the Eocene (∼49 Ma) and the beginning of the Miocene (∼23 Ma). The objective of this study is to quantify the impact of Miocene geography (∼20 Ma) on NADW using new simulations performed with the Earth System Model IPSL‐CM5A2. We specifically focus on the closure of the Eastern Tethys Seaway (ETS), dated between 22 and 14 Ma, which allowed the connection between the Atlantic and Indian Oceans, and on the Greenland Ice Sheet, whose earliest onset remains open to discussion but for which evidence suggest a possible existence as early as the Eocene. Our results show that the closure of the ETS does not appear to impact the establishment of NADW, because waters from the Indian Ocean do not reach the NADW formation zone when the seaway is open. Conversely, the existence of an ice sheet over Greenland strengthens the formation of NADW owing to topography induced changes in wind patterns over the North Atlantic, which in turn, results in a salinification of the North Atlantic and Nordic Seas, and in an increase in deep‐water formation.