Oceanography Chapters 13 & 14

How the Ocean Moves Waves are a result of wind. As wind blows longer and harder, more waves will be produced. Surface currents move warm water toward the poles and cold water toward the equator. An example of a warm surface current would be the Gulf Stream. Tides are the daily rise and fall of sea level due to the gravitational attraction between the Moon, Sun, and Earth.

More on Tides… New and full moons create spring tides: highest high tide, lowest low tide First and third quarter moons create neap tides: lowest high tide, highest low tide High tides are found on whatever side of the Earth the Moon is on due to gravity. The exact opposite side of the Earth will also have high tide due to inertia. The tidal bulges follow the Moon where ever it goes. The difference between sea level at high tide and sea level at low tide is called the tidal range.

Coastal Upwelling High oceanic productivity occurs in areas of upwelling in the ocean, particularly along continental shelves The coastal upwelling in these regions is the result of deep oceanic currents colliding with sharp coastal shelves, forcing nutrient-rich cool water to the surface and pushing surface waters offshore.

Ocean and the Climate The ocean is the largest reservoir of heat at the Earth’s surface. The stored heat in the ocean drives much of the Earth’s weather. This stored heat also cases the climate near the ocean to be milder than the climate of the interior of continents. Since water absorbs and releases heat energy relatively slowly, water has a moderating effect on climate, and it also helps organisms regulate their body temperature. This high heat capacity causes a body of water to stay warmer or cooler longer than the surrounding earth and air.

Sea Breezes & Land Breezes Why are there land and sea breezes? Because land heats up and cools down much faster than the water, creating temperature and pressure differences. Warm air is less dense and rises over the land during the day, creating an onshore breeze from the sea. Cool air is more dense and sinks over the land at night, creating an offshore breeze from the land.

Topographic Features of the Ocean Floor The submerged extension of the continent below sea level is the continental margin. Mid-ocean ridges, trenches, volcanic island arcs, and seamounts are the result of tectonic activity. Chemosynthesis does not require sunlight. This occurs at hydrothermal vents near mid-ocean ridges. Photosynthesis is how plants and cyanobacteria (blue-green algae) near the ocean surface produce oxygen.

What is El Niño? El Niño is marked by warmer water in the Pacific off the coast of South America. It alters weather patterns in the United States and around the world. During La Niña conditions (normal) , the tradewinds blow toward the west across the tropical Pacific, away from South America. These winds pile up warm surface water in the west Pacific, so that the sea surface is about 1-2 feet (about 0.5 meter) higher at Indonesia than at Ecuador (in South America). The sea-surface temperature is about 8 degrees Celsius higher in the west, with cool temperatures off South America, due to an upwelling of cold water from deeper levels. This cold water is nutrient-rich, supporting high levels of primary productivity, diverse marine ecosystems, and major fisheries. During El Niño, the tradewinds relax in the central and western Pacific. Surface water temperatures off South America warm up, because there is less upwelling of the cold water from below to cool the surface. This cuts off the supply of nutrients, resulting in a drastic decline in the food chain, including commercial fisheries in this region.

Human Impact on the Ocean Evidence shows that human activities, including intense fishing around the world, are altering ocean ecosystems beyond their natural state. A recent study which has mapped the total human impact on the seas for the first time has revealed that the picture is far worse than the scientists imagined. 40% of the world's oceans have been heavily affected by human activities, including fishing, coastal development, and pollution from shipping.

Oceans Video