- Industri: 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 technique for determining the unknown quantity of an element of known isotopic composition. A spike, i.e. a known quantity of the same element with a known different isotopic composition, is mixed with the sample and the composition assessed via the resulting isotopic composition of the mixture.
Industry:Earth science
Neither absolute abundances of minor isotopes nor absolute values of isotope ratios can be determined accurately enough for geochemical purposes. As such, differences in such absolute isotopic ratios between two substances are substituted. These comparisons are made between the laboratory samples and various internationally accepted standards known as isotope reference standards. Examples of these are SMOW (standard mean ocean water) and V-SMOW (a SMOW artificially prepared in Vienna) for oxygen and PDB (a Cretaceous belemnite) and V-PDB (the same prepared in Vienna) for oxygen in carbonates.
Industry:Earth science
A division of a deep-sea core on the basis of oxygen isotope ratios. There have been 19 isotope stages since the reversal of the Earth's magnetic field 700,000 years ago.
Industry:Earth science
Each of two or more varieties of a particular chemical element which have different numbers of neutrons in the nucleus, and therefore different relative atomic masses and different nuclear (but the same chemical) properties.
Industry:Earth science
The deep-sea expeditions that have taken place through the history of ocean sciences have been grouped into four eras:
* Era of Exploration (1873-1914)
* Era of National Systematic and Dynamic Ocean Surveys (1925-1940)
* Era of New Marine Geological, Geophysical, Biological and Physical Methods (1947-1956)
* Era of of International Research Cooperation (1957-Present)
The Era of Exploration is considered to have begun - along with modern oceanography - with the British Challenger expedition from 1873-1876. The era was characterized by widely-spaced stations alongs isolated profiles, and the combined results of several such expeditions provided a first overall picture of the bathymetry, stratification and circulation of the water masses and conditions for life in the deep oceans. Other significant expeditions in the era included the German Gazelle (1874-1876), National (1889), Valdivia (1898-1899), Gauss (1901-1903) and Deutschland (1911-1912) expeditions; the U.S. Blake (1877-1886) and Albatross (1887-1888) expeditions; the Russian Vitiaz (1886-1889) expedition; the Hirondelle and Pricesse Alice expeditions of Monaco (1888-1922); the Norwegian Fram (1893-1896), Michael Sars (1904-1913) and Armauer Hansen (1913-Onward) expeditions. These were single, long-term expeditions on large vessels until the Scandinavian school pioneered the use of smaller vessels for more systematic research, e.g. with the Armauer Hansen.
The Era of National Systematic and Dynamic Ocean Surveys was initiated in 1925-1927 by the German Atlantic Expedition on the RV Meteor. This expedition took closely spaced measurements at standard intervals all the way to the sea floor along fourteen latitudinal cross-sections of the Atlantic Ocean between 20 N and 65 S. This stimulated other nations to undertake similar expeditions, e.g. the Dutch Willebrord Snellius Expedition (1929-1930) in the East Indian seas, the British Discover Expeditions (since 1930) mostly in the Antarctic oceans, the American Atlantis Expeditions (since 1931) mostly in the North Atlantic, the Danish Dana II (1928-1930) around the world expedition, the Carnegie (1928) and Ryofu Maru and E. W. Scripps (since 1937) Pacific Ocean expeditions, the quasi-synoptic survey of the Gulf Stream northwest of the Azores by the Altair and Armauer Hansen in 1937, and the Russian icebreaker Sedov initiating research in the North Polar Sea in 1938.
Industry:Earth science
The lower layer of the ocean as defined by Defant in 1928. The stratosphere is a sluggish, cold layer which is homogeneous vertically and horizontally in its basic properties. It is a region of slow exchanges.
Industry:Earth science
In physical oceanography, the layer between the thermocline and the halocline. It is called this because of its effect on the mixed layer heat budget due to the temperature at the bottom of the barrier layer being zero, which excludes heat loss to the underlying water via mixing. It is defined as the difference between the thickness of the isothermal layer and the mixed layer (determined by a defined change in density), with the isothermal layer generally being greater than or equal to the mixed layer depth. In the Western Pacific, an area with a barrier layer, horizontal temperature gradients are also very small, leading to the conclusion that the net heat flux at the ocean surface must be close to zero.
Industry:Earth science
The measurement and charting of the spatial variation of the ocean depths.
Industry:Earth science
An inverse method for determining the oceanic velocity field where the motion is geostrophic and the potential vorticity locally balanced. This method provides a mechanism for determining the absolute geostrophic circulation field rather than just the relative field.
Industry:Earth science
The surface temperature of the ocean as measured by a bucket thermometer. This can also be the temperature measured by immersing a surface thermometer into a freshly drawn bucket of water.
Industry:Earth science
