Re: what role does the ocean play in affecting the climate?

Stacy,

The oceans play a very large role in earth's global climate.

As you mentioned, water acts a kind of shock absorber for temperature changes. This occurs because water heats up and cools down more slowly than either air or land surface. So, during a single summer day the air temperature of a coastal town may fluctuate between say 80 degrees at mid day to 60 degrees at night, but the coastal water may only fluctuate between 70 degrees at mid day to 69 degrees at night. The water acts as a cooling force during the day and a warming force during the night. This explains why coastal cities have a much lower range of daily temperatures than interior cities. This process also works on a yearly scale. Coastal water temperature will be affected much less than air temperature by the changing seasons, so during summer the water is on average cooler than the air temperature and acts as a cooling force, and during the winter water is on average warmer than the air temperature and acts as a warming force. Again, coastal cities normally have a much smaller range of seasonal temperature variation than interior cities.

Another effect of waters ability to retain its energy can be witnessed where strong currents bring either warm or cold water to latitudes where you wouldn't normally expect it. For example, England is at the same latitude as Hudson Bay in Canada, but it has a much warmer average annual temperature because it is surrounded by the warm Gulf Stream current, carried up from the Gulf of Mexico.

Although the dramatic evidence for the ocean acting as a thermal shock absorber is best seen near the coast, in fact if the oceans did not exist the entire globe would experience much more dramatic temperature swings, both daily and with the seasons. To take it one step further you can look at the moon, which has neither water nor an atmosphere to buffer temperature, and so experiences temperataure shifts in the hundreds of degrees depending on whether it is lunar day or night.

Speaking of the atmosphere, the oceans and atmosphere are actually very closely linked. The ocean is the main source of moisture for the earth, so the amount of rainfall on land is largely controlled by its relationship to the ocean. The closer land is to the ocean and the warmer the temperature of the water is, the more rain you will have. How close you are to the ocean matters because the moisture must physically travel from its source (the ocean) in the form of clouds to the place where it rains or snows. The closer you are to the source, the more likely you are to get wet. Some places on earth, like the Gobi Desert in China, are so far from any large bodies of water that moisture physically can not get there very easily and as a result you get a desert. The temperature of the water matters because it is harder to evaporate cold water than warm water, so less moisture will be in the air in cold regions. This can be witnessed near the poles where very little snow falls each year, and more dramatically on the western coast of South America. Peru, although it is very near the equator, has a coast that is a desert even though it is directly next to the Pacific Ocean. The reason is that cold water currents upwell from the deep ocean to the surface near Peru, resulting in cold surface water that is difficult to evaporate. So western Peru, although it is has a warm climate and is near water, is very very dry.

Finally, the ocean also acts as a chemical shock absorber for the earth. Many elements are deposited in the ocean and stored in the form of sediments or rocks. A prime example is carbon dioxide. CO2 is a greenhouse gas that can raise global temperatures when in the atmosphere. A huge amount of CO2 is dissolved in ocean water, where much of it gets locked away in the form of carbonate sediment and limestone. If the ocean did not exist to store CO2, the atmosphere would contain much more and global temperatures would be significantly higher. Ozone is created within the upper atmosphere is not directly controlled by the ocean.

The effect the ocean has on climate is pervasive and complex. I hope I have given you some useful examples and explained the fundamental relationships.

Bill Raatz