Tropical seaways played a more important role than high latitude seaways in Cenozoic cooling 1Bjerknes Centre for Climate Research, UniResearch, 5007, Bergen, Norway
26 Jul 2011
2Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, 100029, Beijing, China
Received: 15 March 2011 – Published in Clim. Past Discuss.: 21 March 2011 Abstract. Following the Early Eocene climatic optimum (EECO, ~55–50 Ma), climate deteriorated and gradually changed the earth
from a greenhouse into an icehouse, with major cooling events at the
Eocene-Oligocene boundary (∼34 Ma) and the Middle Miocene
(∼15 Ma). It is believed that the opening of the Drake Passage had a
marked impact on the cooling at the Eocene-Oligocene boundary.
Based on an Early Eocene simulation, we study the sensitivity of climate and
ocean circulation to tectonic events such as the closing of the West
Siberian Seaway, the deepening of the Arctic-Atlantic Seaway, the opening of
the Drake Passage, and the constriction of the Tethys and Central American
seaways. The opening of the Drake Passage, together with the closing of the
West Siberian Seaway and the deepening of the Arctic-Atlantic Seaway,
weakened the Southern Ocean Deep Water (SODW) dominated ocean circulation and
led to a weak cooling at high latitudes, thus contributing to the observed
Early Cenozoic cooling. However, the later constriction of the Tethys and
Central American Seaways is shown to give a strong cooling at southern high
latitudes. This cooling was related to the transition of ocean circulation
from a SODW-dominated mode to the modern-like ocean circulation dominated by
North Atlantic Deep Water (NADW).
Revised: 23 June 2011 – Accepted: 28 June 2011 – Published: 26 July 2011
Citation: Zhang, Z., Nisancioglu, K. H., Flatøy, F., Bentsen, M., Bethke, I., and Wang, H.: Tropical seaways played a more important role than high latitude seaways in Cenozoic cooling, Clim. Past, 7, 801-813, doi:10.5194/cp-7-801-2011, 2011.