Density+and+the+Ocean


 * Density and the Ocean**

Pour a bunch of salt into a cup of water. What do you notice?



If you let the salt and water sit out long enough, you will notice that the salt makes a layer at the bottom.

What do you think would happen if you add food coloring to cold water and mix it into hot water? Of course, after a while all the water will end up the same temperature- but at the start both of these demos will show you one thing:

If you do not have the chance to do these experiments at home, here is a video showing how cold and hot water mix, notice the interesting patterns that are made at the interface (where the two liquids meet) of the two temperatures. media type="youtube" key="Ak9CBB1bTcc" height="349" width="560" Salinity and temperature can determine water's density. Experiments in cups are one thing, but this phenominon takes place on a super large scale in our oceans! Since the Earth is tilted on its axis, not everywhere gets the same amount of solar heat from the sun...this leads to uneven heating of the world's water. Also, in areas where ice is being formed (like at the poles) the ocean water is saltier since the ice forms as fresh water. So basically since the world is not homogenous, we get areas of colder and hotter water and areas of saltier and less salty water. Just like we have seen differences in temperature and salinity cause mini currents in our cups, scientists have found the thermalhaline current flowing all around our planet, fueled by heat and salinity gradients (differences). Here is a video to explain it: media type="youtube" key="FuOX23yXhZ8" height="349" width="425"

Here is model of what is going on with the hot and cold water molecules to make the have different densities (please right click and click play to run the model): media type="file" key="hot_cold_water.swf" width="360" height="270"

One major questions scientists and concerned citizens have is how will the melting of the poles affect the global conveyer belt?