Modelling global-scale climate impacts of the late Miocene Messinian Salinity Crisis

Abstract

Late Miocene tectonic changes in Mediterranean–Atlantic connectivity and climatic changes caused Mediterranean salinity to fluctuate dramatically, including a ten-fold increase and near-freshening. Recent proxy- and model-based evidence suggests that at times during this <i>Messinian Salinity Crisis</i> (MSC, 5.96–5.33 Ma), highly-saline and highly-fresh Mediterranean water flowed into the North Atlantic Ocean, whilst at others, no Mediterranean Outflow Water (MOW) reached the Atlantic. By running extreme, sensitivity-type experiments with a fully-coupled ocean–atmosphere general circulation model, we investigate the potential of these various MSC MOW scenarios to impact global-scale climate. <br><br> The simulations suggest that MOW had a greater influence on North Atlantic Ocean circulation and climate than it does today. We also find that depending on the presence, strength and salinity of MOW, the MSC could have been capable of cooling mid-high northern latitudes by more than 1.2 °C, with the greatest cooling taking place in the Labrador, Greenland–Iceland–Norwegian and Barents Seas. With <i>hyper</i>saline-MOW, a component of North Atlantic Deep Water formation shifts to the Mediterranean, strengthening the Atlantic Meridional Overturning Circulation (AMOC) south of 35&deg; N by 3–7 Sv. With <i>hypo</i>saline-MOW, AMOC completely shuts down, inducing a bipolar climate anomaly with strong cooling in the North (up to −10.5 °C) and weaker warming in the South (up to +2.5 °C). <br><br> These simulations identify key target regions and climate variables for future proxy-reconstructions to provide the best and most robust test cases for (a) assessing Messinian model performance, (b) evaluating Mediterranean–Atlantic connectivity during the MSC and (c) establishing whether or not the MSC could ever have affected global-scale climate

Pliocene oceanic seaways and global climate

“…This event appears synchronous to the Messinian Salinity Crisis. During this time the Mediterranean Sea was periodically blocked from and connected again with the North Atlantic18 with effects on the salinity of Mediterranean Outflow Water19. A recent modelling study19 suggested that a related change from more to less saline Mediterranean Outflow Water conditions would have caused a significant weakening of the AMOC in line with a typical bipolar temperature and salinity asymmetry.…”

“…The constriction of the Indonesian Seaway has been suggested to precondition the onset of Northern Hemisphere Glaciation1617. Other tectonic-induced closures and openings discussed here include the end of the Messinian Salinity Crisis during the latest Miocene (5.96–5.33 Ma) when the Mediterranean Sea was periodically blocked and connected again to the Atlantic Ocean with simulated effects on the AMOC1819. Also, we discuss possible climatic effects due to the opening of the Bering Strait that is assumed of having taken place during the Pliocene and proposed to be important for North Atlantic SST and the AMOC strength202122.…”

Orbital-driven environmental changes recorded at ODP Site 959 (eastern equatorial Atlantic) from the Late Miocene to the Early Pleistocene

“…Fluctuations in the amount and salinity of the Mediterranean Outflow Water between 6.0 and 5.5 Ma could have influenced the strength and position of the Atlantic Overturning Circulation. Modelling shows that this would have affected the meridional heat distribution, although the effects on climate outside the North Atlantic region are small (Ivanovic et al 2014). Model sensitivity experiments indicate changes in the rainfall pattern of northern Africa as the result of the desiccation and/or lower sea levels in the Mediterranean Basin (Murphy et al 2009;Schneck et al 2010).…”

A new stratigraphic position of some Early Pleistocene deposits in central Poland

“…This dras tic change in plant com mu ni ties in di cates a cli mate change that could be as so ci ated with a strong re gional cli mate fluc tu a tion. The likely cause of this change is the late Messinian Sa lin ity Cri sis (5.96-5.322 Ma), dur ing which the tem per a ture at mod er ate and higher lat i tudes prob a bly dropped by even a few de grees (Ivanovic et al, 2014).…”