Global Climate Model

About 6 million years ago the African and European continental plates collided and cut off the connection between the Atlantic Ocean and Mediterranean Sea. This event resulted in a drastic fall in the Mediterranean Sea level and is called the Messinian Desiccation. Desiccation means that the Mediterranean Sea was without water. Since the Mediterranean Sea covers an area of 1.5 million square miles this fall in sea level resulted in a canyon much larger than our own Grand Canyon! We're studying what the Earth would be like if the Mediterranean Sea completely dried up and left behind a large canyon. We used a computer model that simulates our atmosphere to study this event. Computer models of our atmosphere take all the physical and chemical relations that scientists can understand to model our climate.

Since there is much less precipitation over the Mediterranean Sea than evaporation there is what we call a negative water balance. This means that the Mediterranean Sea is losing water every year, just a slow pace. If the water flowing in from the Atlantic Ocean is restricted then over the course of thousands of years more and more water will evaporate and the Mediterranean Sea can eventually become completely dry. Sea water from our oceans contain salt and when sea water evaporates it leaves the salt behind. The Mediterranean Sea also contains salt because it is connected with the ocean. Scientists discovered the Messinian Desiccation because they found a layer of salt over thousand feet high at the bottom of the basin. When the Mediterranean Sea evaporated it deposited the salt on the bottom of the basin. There is also other evidence of the Messinian Desiccation. This is in the form of deep canyons in the bedrock around Egypt. Just like the Grand Canyon was cut when ice that used to cover the US retreated polewards and melted.

Mountain ranges have big effects on our climate, for example it's been shown that if North America didn't have mountains then western Europe would be much colder than it is today (Held, 1983; Seager et al., 2002). This is because when air flows over mountains it produces waves in our atmosphere. These waves move energy from one place to another. Therefore, mountain waves have the ability to influence climate in distant locations. Our North American mountains create atmospheric waves that transport energy in a way so that Western Europe is much warmer than eastern Canada, which is at the same latitude. In a computer model we were able to show that the effects of creating a big canyon over the Mediterranean Sea. When wind encounters the Mediterranean Canyon it leads to big temperature changes in and around the Mediterranean Sea as well as much more rain in the Alps. Atmospheric waves emanating from the Mediterranean region are believed to lead to significant temperature changes throughout the Northern Hemisphere.