|MadSci Network: Environment & Ecology|
Dear William! Now essentially what time are You referring to? I guess You are referring to the El Nino events, of the last years, aren't You? Well at first generally there are ocean currents. They do have a favourite direction due to main wind directions, the rotation of the earth and the tidal waves. In the Case of the American West Coast (South as well as North) the main current on the ocean surface goes west, i.e. away from th coast. This means waters from the depth of the ocean, which are nutrient rich come to the surface at the coastline. This means plankton finds good conditions to grow, an thus a rich food chain may start. The Nina effect means the currents are reversed for several months and the upwelling does not take place, thus the nutrients are much reduced and there is little food for macroorganims such as fish. This is what happens very drastically in the waters of Southern America and I think as well in waters of California. The effects in South America mean that in some years these waters are the among the fish richest in the world and in others among the poorest. In general terms this means the fishery on the West Coast is very much dependent on the currents of the ocean and thus the winds. Some people think there may be changes in the winds and ocean currents due to the greenhouse effect as ocean currents are very much dependent on temperature and temperature distribution on the globe. Anyway it seems the Nino effect, which is occuring naturally has been occuring more often in the last decades, possibly dues to the greenhouse effect. You will find more on the Nino and Nina effect on the following pages: (by the way effects are largest around christmas and the name refers to the spanish christmas scenery El Nino is the Jesus child) http://dir.yahoo.com/Science/Earth_Sciences/Meteorology/Weather_Phenomena/E l_Nino_and_La_Nina/
Try the links in the MadSci Library for more information on Environment & Ecology.