- Branża: Education
- Number of terms: 34386
- Number of blossaries: 0
- Company Profile:
Founded in 1876, Texas A&M University is a U.S. public and comprehensive university offering a wide variety of academic programs far beyond its original label of agricultural and mechanical trainings. It is one of the few institutions holding triple federal designations as a land-, sea- and ...
A 1994-1998 program whose overall objective was to develop and design an acoustic system for long-term monitoring of the ocean temperature and ice thickness in the Arctic Ocean, including the Fram Strait, for climate variability studies and global warming detection. The specific objectives included:
* compilation and analysis of existing ocean and ice data from the Arctic ocean for use in climate and acoustic models;
* simulation of present and future ocean temperature, salinity and speed of sound fields, ice thickness concentration and extent in the Arctic Ocean caused by natural variability and global warming scenarios, as input to acoustic modeling;
* simulation of present and future basin-wide acoustic propagation using natural variability and global warming scenarios to investigate the sensitivity of acoustic methods for global warming detection;
* simulation of present and future acoustic propagation in the Fram Strait to investigate the sensitivity of acoustic methods for monitoring heat and volume fluxes in an area of strong mesoscale eddy activity; and
* design of an optimum acoustic monitoring system for climate change detection in the Arctic Ocean.
Industry:Earth science
The smallest and most poorly studied of the oceans on earth. It covers an area of 14 million square km that is divided by three submarine ridges, i.e. the Alpha Ridge, the Lomonosov Ridge, and an extension of the mid-Atlantic ridge. It is also nearly landlocked, covered year-round by pack ice, and one-third of its area is continental shelf containing marginal seas. The marginal seas of the Arctic are the Beaufort Sea, the Chukchi Sea, the East Siberian Sea, the Laptev Sea, the Kara Sea and the Barents Sea. An important climatic function of the Arctic and its adjacent seas is the production of the dense water than drives the global transports of heat and fresh water between the high latitude North Atlantic and the Pacific.
The physical processes that combine to produce the circulation in the Arctic and its marginal seas include:
* salt rejection from sea-ice growth forming dense water that continues surface buoyancy forcing after the freezing point is reached, preferentially where offshore winds maintain open waters for prolonged periods;
* advection of ice produced in marginal seas that exports fresh water from the basin, compensating for the freshening effect of precipitation and run-off from Arctic rivers; and
* drainage of dense shelf water from the Arctic shelves into the deep Eurasian basin, a process that affects the deep water properties in the convective gyres via exchanges through the Fram Strait.
Industry:Earth science
The main water transformations in the Arctic Mediterranean take place in a boundary current of Atlantic Water, which enters the Arctic across the Greenland-Scotland Ridge. After entering, it flows around the Arctic Ocean before exiting as the East Greenland Current, primarily via the Denmark Strait. On route, it experiences many branchings and mergings. The details of its journey around the Arctic are summarized by Rudels et al. (1999):
The circulation is dominated by the movement of warm Atlantic Water entering across the eastern part of the Greenland-Scotland Ridge into the Norwegian Sea. It flows along the Norwegian coast as the Norwegian Atlantic Current. When it reaches the latitude of the Bear Island Channel, its first major bifurcation occurs. A substantial fraction flows eastward and enters the Barents Sea, while the main part continues northward as the West Spitsbergen Current. Several branches are deflected westward from the current: north of the Greenland Sea basin, north of the Boreas basin and in Fram Strait. Only a smaller part of the West Spitsbergen Current eventually enters the Arctic Ocean and flows eastward along the Eurasian continental slope. North of the Kara Sea the boundary current meets the branch that turned east and entered the Barents Sea north of Norway. This branch reaches the Arctic Ocean by crossing the Barents Sea and the northern part of the Kara Sea. The combined boundary current continues eastward a short distance before it again splits. Branches leave the continental slope along bathymetric features, particularly along the Nansen-Gakkel Ridge, the Lomonosov Ridge and the Mendeleyev Ridge. However, a part of the boundary current follows the continental slope around the entire Arctic Ocean. As this part recrosses the Lomonosov Ridge into the Eurasian Basin it meets and mixes with the other branches as they converge east of the Morris Jesup Plateau. The waters exit the Arctic Ocean through Fram Strait, where they combine with the recirculating waters of the West Spitsbergen Current to continue southward along the Greenland continental slope as the East Greenland Current. The boundary current again diverges at bathymetric features, in this case the Greenland Fracture Zone and the Jan Mayen Fracture Zone, and branches from the boundary current enter the interior of the Boreas Basin and the Greenland Sea Basin. Exchanges in both directions occur, and the East Greenland Current is resupplied with water masses formed in the subpolar seas. The main part of the boundary current exits the Arctic Mediterranean through the 600 m deep Denmark Strait, but its denser fractions are deflected eastward along the Jan Mayen Fracture Zone and along the Iceland shelf slope and eventually enter the Norwegian Sea. The upper part of these waters then returns to the North Atlantic through the 850 m deep Faeroe-Shetland Channel.
Industry:Earth science
The region below the euphotic zone where no light is available for photosynthesis.
Industry:Earth science
In physical oceanography, a region of rapid transition located in the Antarctic Zone of Southern Ocean between the Continental Water Boundary to the south and the Polar Front to the north. It can be distinguished hydrographically by a salinity maximum below about 150 m caused by the upwelling of water of high salinity, i.e. North Atlantic Deep Water. Above this the maximum is blurred by high precipitation and the melting of ice. Its position corresponds reasonably well to the demarcation between the east and west wind drifts which, in the light of Ekman dynamics, at least partially explains its divergent nature.
Industry:Earth science
An instrument that can be programmed to cycle up and down through the water column at predetermined intervals to provide vertical profiles of temperature and salinity. ALACE floats have been used to track currents down to 1. 5 km. In operation, the float sinks to its neutral buoyancy depth, drifts with the current, and after a programmed time (5-30 days) increases its buoyancy by pumping oil into an external bladder to rise to the surface. It then transmits data to Service Argos satellites over a 24 hour period, returns the oil to the internal bladder, and sinks again to its neutral buoyancy depth. The cycling continues until the battery energy is depleted after around 100 cycles, or until the float fails for some other reason.
Industry:Earth science
An autonomous underwater vehicle (AUV), i.e. a robotic vehicle designed to carry a varying scientific payload which is changed to suit each mission.
Industry:Earth science
A vehicle that can roam the ocean and collect data on its own. They can wait for episodic, short-lived events and change course immediately to concentrate on the most interesting areas during an experiment. The MIT/WHOI program built the first prototype AUV, called the Sea Squirt, in 1988 which was used to take various measurements in rivers, harbors, lakes and ponds. The second prototype, called the Odyssey I, was first launched from an oceanographic research vessel in early 1993 in the Antarctic. It was capable of operating at depths of 6000 m. The third prototype, the Odyssey II, was designed to operate at full ocean depths. It was designed to be mass produced and to be configurable in a number of ways depending on mission requirements. An on-board computer executes navigation and control programs, and an acoustic modem is used for two-way digital communication. The first full-scale test of the Odyssey II took place in February 1998 in midwinter in the Labrador Sea. The plan of the experiment was to have the AUVs gather data about bottom water formation for three months, recharging and dumping data at an underwater docking station at regular intervals. A mechanical problem limited the experiment to two weeks, although much useful data was gained for the improvement of future experiments.
Industry:Earth science
A 1994 expedition in which two icebreakers - the USCGC Polar Sea and the CCGS Louis S. St. Laurent - sailed from Nome, Alaska to the North Pole across the entire Arctic basin, covering over 2000 nautical miles. The purpose of AOS was the increase understanding about the role of the Arctic in climate change and gather baseline data on contaminants in the region.
The significant science findings of the expedition were:
* the Atlantic layer of the Arctic Ocean was found to be 0. 5-1. 0°C warmer than prior to 1993;
* a large eddy of cold fresh water was found centered at 1000 m on the periphery of the Makarov Basin;
* biological productivity was estimated to be ten times greater than previous estimates;
* an active microbial community was found; and
* mesozooplankton biomass was found to increase with latitude.
Industry:Earth science
