2000 EARTH SCIENCE VIDEOTAPES |
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Tape Title | Record ID | Date Produced | TRT: |
Synopsis |
| THE RIVEN SKY: OZONE HOLE WIDENS, DEEPENS | G00-080A | 10/04/00 | 00:05:24 | This year's Antarctic ozone hole is the largest ever observed. Scientists continue to investigate the phenomenon, and are somewhat surprised by its scale. Using data from NASA's Total Ozone Mapping Spectrometer (TOMS) instrument onboard the Earth Probe satellite, researchers can evaluate and compare current conditions over the south pole to readings taken by other instruments in years past. Continued monitoring of polar ozone levels helps researchers gain a better understanding of how the planet's climate may be changing.
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TAPE CONTENTS: |
| ITEM (1): The Ozone Hole - This animation shows a huge section of the atmosphere around the south pole that's comparatively devoid of ozone. The gap reached a record size of 28.3 million kilometers squared on September 3, 2000. The previous record was 27.2 million square kilometers squared recorded on Sept. 19, 1998. Although current measurements of the ozone hole show that it's stabilized, low value points in the interior continue to decline. The lowest values are typically observed in the late September or early October.
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| ITEM (2): Bigger Than Last Year - The reasons behind the large size involve both low early spring ozone conditions, and an extremely large Antarctic vortex. The Antarctic vortex is a high altitude--or stratospheric--current of air that sweeps around the southernmost continent, forming a revetment of air that sequesters the ozone-depleted region from the rest of the Earth's atmosphere. In this animation we see what last year's ozone hole looked like. Although also considered a large gap, the hole appearing this September is not only larger, but also appears earlier than ever before.
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| ITEM (3): A Trend Towards Larger Losses - The following animation shows how ozone loss at the south pole has grown since the mid-80s. Early readings over Antarctica indicate little or no ozone depletion beyond naturally predicted levels. But as the 80s and 90s progress, a clear change in atmospheric chemistry takes place at the bottom of the world. The hole starts small in the late 80s and spreads as subsequent winter cycles break apart ozone molecules.
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| ITEM (4): What Causes Ozone Loss? - Ozone is produced by intense ultraviolet radiation in the upper stratosphere. This radiation breaks typical oxygen molecules (O2) into free oxygen atoms. Those free atoms of oxygen (O) then join with molecular oxygen (O2) and form molecules of ozone (O3). The ozone molecule generally absorbs ultra-violet radiation. But ozone is destroyed when it reacts with one of a variety of chemicals in the stratosphere such as chlorine, nitrogen, bromine or hydrogen. The hole showing up now over the south pole is the result of air patterns in the upper atmosphere working in concert with high concentrations of ozone destructive chemicals.
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