2000 EARTH SCIENCE VIDEOTAPES |
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Tape Title | Record ID | Date Produced | TRT: |
Synopsis |
| TOPEX/POSEIDON: REVEALING HIDDEN TIDAL ENERGY |
G00-058 | 06/14/00 | 00:06:37 | Surfers trying to stay ahead of a curling wave this summer might be relieved to know that a long-standing mystery has been solved. Until recently, the total energy imparted to the oceans from the Moon's gravitational pull has not been fully accounted for: about 30% had seemingly vanished without mathematical explanation. The total energy dissipating along the world's shallow areas and coasts don't add up to the expected total. But new research using data collected from the U.S./French satellite called Topex/Poseidon may have found the answer.
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TAPE CONTENTS: |
| ITEM (1): Dissipating Energy at the Bottom of the Ocean (Animation) - The Moon's gravity tugs at the Earth, causing ocean water to slosh back and forth in predictable waves called tides. But as you might expect, it's more complicated. As much as 30% of the total energy in the ocean may be scattered by rough topography found at the bottom of the sea. New research suggests that tidal swells break up and dissipate energy as they move past the rough terrain of undersea mountains and ridges in much the way that sound waves are scattered in a room with lots of obstructions.
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| ITEM (2): Dissipating Energy at the Bottom of the Ocean (Animation) Mapping the Tides from Space - Using six years of data from Topex/Poseidon, scientists derived a 16-day set of predictive data, showing a synthetic view of how the tides move around the world's oceans. In this animation, blue signifies places where the ocean level is lower than the average reference height, and red shows areas where it's higher. The difference is significant: between the darkest blue and the brightest red is a range of more than 15 meters, displaced by lunar tidal forces. White areas separating the blues and reds approximate the "zero" point, a reference sea level against which other areas are compared.
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| ITEM (3): Mapping Dissipation Zones - Research suggests that areas of pronounced topography on the floor of the ocean are likely to be where energy dissipates faster than elsewhere. On this world map, red areas show places where this proves to be true. In the Pacific around Hawaii, notice how the red is concentrated; craggy sub-surface ridges formed from young, active volcanoes act as dampers for tidal energy in that area. Other places that cause significant dissipation of energy include the area south of the Japanese archipelago, the area south of Madagascar, and the area surrounding the North Atlantic Ridge.
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| ITEM (4): Catching Waves - This map shows the patterns of tidal energy played out across the surface of the Earth as lines of force. The colors indicate where tides are strongest, with blues being weaker areas and reds being stronger. In almost a dozen places on this map the lines appear to converge, as if pulled together like a purse. Notice how at each of these places the surrounding color-the tidal force for that region-is blue. These convergent areas are called amphidromes, places where there is little or no apparent tide.
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| ITEM (5): How High the Sea: Topex/Poseidon at Work - Launched in 1992, Topex/Poseidon's primary mission is to measure global ocean circulation patterns by carefully plotting sea levels on a planetary scale. Data from the joint French and American project is valuable in the study of hurricanes, El Nino/La Nina behavior, marine life, climate forecasting, and more. The Jet Propulsion Laboratory manages the Topex/Poseidon mission for NASA's Office of Earth Science, Washington, DC.
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