The Deep End Of The Ocean
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Her first reaction is panic, then anguish, and then as days turn into weeks and months enduring grief and guilt. Life goes on, but her pain goes so deep that she hardly dares trust her senses when she realizes she may have discovered the child a decade after his disappearance.
Active \"smoker\" hydrothermal vent chimneys about 9 meters tall are found deep in the Mariana Arc region in the Western Pacific Ocean. Credit: Pacific Ring of Fire 2004 Expedition. NOAA Office of Ocean Exploration; Dr. Bob Embley, NOAA PMEL, Chief Scientist.
The average depth of the ocean is about 3,688 meters (12,100 feet). The deepest part of the ocean is called the Challenger Deep and is located beneath the western Pacific Ocean in the southern end of the Mariana Trench, which runs several hundred kilometers southwest of the U.S. territorial island of Guam. Challenger Deep is approximately 10,935 meters (35,876 feet) deep. It is named after the HMS Challenger, whose crew first sounded the depths of the trench in 1875.
Students will experience the impact of bioluminescence on finding food and finding prey in the ocean. Students will be able to describe the positive and negative values of being able to produce light.
It is relatively straightforward to demonstrate the essential mechanism behind wind-driven ocean circulation in a laboratory experiment. The apparatus is shown in the figure below. A tank with a false sloping bottom is filled with water so that the water depth varies between 5cm at the shallow end and 15 cm at the deep end. A Perspex disc is rotated very slowly at the surface of the water in a (in the rotating frame) clockwise sense - a rate of 0.4 rpm works well. To minimize irregularities at the surface, the disc can be submerged so that its upper surface is a millimeter or so underneath the surface. The whole apparatus, disc and all, is then rotated in an anticlockwise sense at a speed of f = 2 ( 10 rpm).
The varying depth - in the direction parallel to the rotation vector - mimics the variation of the ocean depth measured in the direction parallel to the rotation vector on the sphere (see figure below). The shallow end of the tank is analogous to the poleward side of the ocean basin (why) and the deep end to the tropical side.
The stress applied by the lid to the water is analogous to the wind stress on the ocean surface. With clockwise differential rotation of the lid, fluid is drawn inwards in the Ekman layer just under the lid and pumped downwards into the interior, mimicking the pumping down of water in subtropical gyres by the action of the winds, as sketched below.
We see a clockwise (anticyclonic) gyre in the water with interior flow towards the deep end of the tank ('southwards'), as the Ekman pumping drives fluid columns to the deeper end of the tank. This flow (except near the lid) will be independent of depth. A strong ('northward') return flow forms at the ``western'' boundary; this is the tank's equivalent of the Gulf Stream.
CORVALLIS, Ore. - A new study has found evidence from the deep ocean that the Atlantic meridional overturning circulation - a system of currents that brings warm water from the tropics to the North Atlantic region and keeps its climate more moderate - declined at the end of the last ice age.
Some scientists have long suspected that was the case because the North Atlantic cooled at a time the rest of the planet was warming, but evidence to support the theory has been sparse or indirect. However, the new study, which utilized 25 deep ocean sediment cores and a corresponding computer model, determined that the AMOC not only declined - the process may have pumped more carbon dioxide into the atmosphere.
\"There has long been a feeling that if the deep ocean was changing at the end of the last ice age, there should be evidence from the deep ocean to document it - and that has been lacking,\" said Andreas Schmittner, a climate modeling scientist at Oregon State University and lead author on the study.
The isotopes show up in the shells of tiny organisms called foraminifera that are found in deep ocean sediment cores. When they were alive, their carbonate shells accumulated two carbon isotopes - C-12, a lighter isotope, and C-13, which is heavier. Scientists can tell by the ratio of the two isotopes how ocean circulation and biological productivity were changing and how that affected atmospheric carbon dioxide levels.
When productivity lessened with the decline of the Atlantic meridional overturning circulation, there was more C-13 in the ocean compared to C-12 - except in the North Atlantic, where C-13 decreased strongly in comparison to C-12. An abundance of C-12, on the other hand, indicates that the current system was strong and plankton blooms were plentiful.
\"You can divide the oceans of the world into small boxes and look at the physical processes like water velocity, salinity and nutrients to predict plankton growth, sinking rates after death, and how the carbon cycle is affected,\" he said.
Schmittner and Lund's model matched ice core data from Antarctica that show increasing levels of carbon dioxide in the atmosphere right after the end of the last glacial maximum (19,000 years before present) for several thousand years. Schmittner's model suggests that the Atlantic meridional overturning circulation decline pulled carbon dioxide from the deep ocean and gradually released it into the atmosphere.
\"The current affects the biological pump and if you turn the current off, you reduce the pump and you have less productivity,\" Schmittner said. \"The system then pulls carbon dioxide from the deep ocean and it winds up in the atmosphere.\" 59ce067264