The Messinian Salinity Crisis

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Modeling the Messinian Salinity Crisis:

Nearly 6 million years ago, the Messinian Salinity Crisis (MSC) began when the connection between the Atlantic Ocean and Mediterranean Sea was cut off.  This occurred due to a combination of lowered sea level of the global oceans and collision between the European and African plates that caused the land to lift.  Normally there is much more evaporation than precipitation over the Mediterranean Sea. This means that much more water is leaving than entering the sea.  Without a significant source of water from the Atlantic Ocean, this led to the evaporation much of the Mediterranean Sea.  A large underground canyon formed and rivers made deep incisions into the bottom of the basin.  This canyon was much larger than the Grand Canyon and had a depth of up to 2,000 meters (6562 feet).  We used the National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 3 (CAM3) to study how this event can affect the atmosphere and thus the weather during this time period.  Each simulation is run for 20 years and monthly averages over the last 10 years of each run were calculated. 

The control run simulates the present day Mediterranean Sea but we do not allow the Atlantic Ocean to transport any energy or heat into the Mediterranean Sea.  This was done because when the African and European continents collided it isolated the Mediterranean Sea from the Atlantic Ocean.  Therefore, no heat or energy was transported into the Sea when the MSC began. The Lowered Sea (LS) and Lowered Land (LL) are the two experiments where the sea level was reduced over the Mediterranean Sea.  In the LL case the surface of the basin was converted to land to simulate a completely dried up basin.  We also tested the sensitivity of creating land over the Mediterranean Sea in the model by running an Upper Land (UL) simulation.  In the UL case we changed the sea points in the model to land points and added some vegetation (mostly shrub and grassland), but the level of the surface was not reduced. 


Messinian Event




Horizonal heat transport through the strait is eliminated



Same as US but now the MS surface is converted to land to check the sensitivity of removing the MS



Simulates the Lago-Mare event, which occurred near the end of the MSC.  Water remains in the desiccated basin.


Deposition of Lower Evaporites

Simulates the middle of the MSC when all of the water is believed to have evaporated from the MS.

Table 1.  Describes each of the 4 cases and how they relate to the MSC. 

The Mediterranean Sea is located between between 30oN and 45oN and lies under the descending branch of the Hadley cell circulation. The Hadley cell circulation brings warm air from the tropics towards the poles.  Near the equator, warm air rises and is brought to the Earth's poles in the upper layers of the atmosphere.  The air cools and sinks near 30o latitude in the Northern Hemisphere.  As air sinks in the atmosphere its pressure increases.  When the pressure increases, the molecules in the air are squeezed tighter together and the molecules begin to collide.  Temperature is the measure of how fast the particles are hitting each other, and the faster they hit each other, the greater the temperature increases. As air sinks over the Mediterranean Sea it heats up.  Therefore there is high pressure and moderate temperatures over the Mediterranean Sea.  Its seasons range from rainy and cool in the winter to warm and dry in the summer.  When the Mediterranean Sea's water level dropped 2000 meters the surface pressure increased. (Fig. 1)


Figure 1:  The difference in Surface Pressure between the three cases (LS, LL, and UL) and the control (US).

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