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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 set of characteristics used to describe a sound signal. This may include sound echos from targets, radiated and ambient noise, with salient echo characteristics including target strength, spectral reflectivity versus frequency, doppler shift, doppler spread and target range extent.
Industry:Earth science
A process that significantly alters the sizes, characteristics and abundances of suspended particles in the ocean. There are two major mechanisms for aggregation:
* biologically mediated aggregation, which occurs when small particles are aggregated into fecal pellets through the feeding activities of animals; and
* aggregation via the largely physical processes of collision and sticking, i.e. coagulation.
The impacts of aggregation on marine ecosystems include:
* much of the particulate matter reaching the ocean interior and sea floor sinks as large, rapidly settling aggregates of detritus, mucous, algae and microorganisms in the visible size range, i.e. marine snow, so the export of carbon and nutrients from the surface ocean is directly linked to the mechanisms responsible for combining small particles into larger units capable of rapid settlement, i.e. aggregation;
* aggregation of small organisms and other organic particles affects the abilities of grazers to isolate their food from the aquatic environment and makes more food available to large-particle feeders;
* aggregation produces particles large enough to maintain unique internal chemical environments that can support unusual, microbial communities and potentially provide island-like refuges for protozoa and micorozooplankton; and
* aggregation affects the optical properties of seawater by altering the size distribution and abundance of particles available to absorb and scatter light.
Industry:Earth science
Also known as the U. S. Southern Ocean Joint Global Ocean Flux Study (JGOFS). AESOP involved studies of two different and distinct regions. The first was the Ross Sea continental shelf, where a series of six cruises (on the R. V. I. B. Nathaniel B. Palmer) collected data from October 1996 through February 1998. The second was the southwest Pacific sector of the Southern Ocean spanning the Antarctic Circumpolar Current (ACC) at 170°W, where data were collected during five cruises (on the R. V. Roger Revelle) from September 1996 through March 1998, as well as during selected transits between New Zealand and the Ross Sea.
The objectives of the project were to:
* better constrain the fluxes of carbon in the Southern Ocean,
* identify the factors and processes regulating the magnitude and variability of primary productivity, and
* gain a sufficient understanding of the Southern Ocean to model past and present carbon fluxes with sufficient accuracy to predict its response to future global changes.
The findings of AESOPS include:
* the Ross Sea continental shelf is among the most productive of all Antarctic systems, with a significant seasonal cycle;
* a seasonal bloom occurs in the region of the Polar Front;
* the annual production of the Ross Sea can be quantified by measuring deficits of nutrients and dissolved carbon dioxide;
* the phytoplankton blooms in the Ross Sea have essentially no losses due to microzooplankton herbivores;
* while iron did not stimulate phytoplankton growth in low silica waters north of the silica gradient, it substantially stimulated diatom growth in waters south of the gradient;
* the Polar Front region exhibits extreme mesoscale variability; and
* dissolved organic carbon concentrations increase seasonally by less than a third as much as particulate organic carbon levels.
Industry:Earth science
A water mass - also known as Adriatic Deep Water - formed in the southern Adriatic Sea that exits into the Ionian Sea via Otranto Strait. The temperature and salinity of ABW are 13°C and 38. 6 psu, respectively. There are a couple of competing conjectures as to the origin of the ABW:
* some postulate that North Adriatic Deep Water flowing into the canyon in the shelf of Bari mixes with Modified Levantine Intermediate Water (MLIW) to form ABW; and
* others think that contribution of NADW is minor and that the ABW is formed mainly by the mixing of the surface water in the center of the South Adriatic Pit with the underlying MLIW during periods of deep convection.
Either way, most studies confirm that ABW represents the most important component of the bottom water of the entire Eastern Mediterranean.
Industry:Earth science
A hydrographic division sometimes used in the North Atlantic Ocean to distinguish it from the polar domain to the north and the Atlantic domain to the south. In this region upper layer waters are relatively cold (0 to 4° C) and saline (34.6 to 34.9). The most significant indication that this domain is not just a smooth transition zone between the polar and Atlantic domains is that the waters are markedly denser than either of the surface source water masses (i.e. ''σt'' ranges from 27.5 to greater than 28).
Industry:Earth science
A part of the eastern basin of the Mediterranean Sea located between Italy and the Balkan Peninsula. It is landlocked on the north, east and west, and is linked with the Mediterranean through the Otranto Strait to the south. The Adriatic is a rectangular basin oriented in a NW-SE direction with a length of about 800 km and a width of about 200 km. It can be divided into three sub-basins:
* a northernmost shallow basin with the bottom sloping gently to the south and reaching at most 100 m;
* three pits located along the transversal line off Pescara (one of which is known as the Jabuka Pit), with a maximum depth of 280 m; and
* a southern basin called the South Adriatic Pit (separated from the middle basin by the 170 m deep Palagruza Sill) characterized by approximately circular isobaths, with a maximum depth of about 1200 m in the center.
The bottom rises toward the Strait of Otranto past the southern basin, with the strait having a maximum depth of 780 m, and average depth of 325 m, and a width of about 75 km.
The meteorological forcing has been summarized by Artegiani et al. (1993) as:
Mainly during the winter, the Adriatic Sea region is under a continuous influence of passing mid-latitude meteorological perturbations and of the wind systems associated with them. The two main wind systems are the bora and the scirocco. The bora is a dry and cold wind blowing in an offshore direction from the eastern coast. The scirocco blows from the southeast (i.e. along the longitudinal axis of the basin) bringing rather humid and relatively warm air into the region. In particular, the bora produces appreciable buoyancy fluxes through evaporative and sensible heat loss, induces both wind-driven and thermohaline circulation, and, most importantly, is responsible for deep water formation processes.
This is one of the two regions within the Mediterranean where freshwater input exceeds evaporation (the other being the Black Sea). This is due mostly to outflow from the Po River in the north, which accounts for 1700 m<sup>3</sup> s<sup>-1</sup> of the 4000 m<sup>3</sup> s<sup>-1</sup> total river discharge in the Adriatic.
The flow between the Adriatic and the greater Mediterranean through the Otranto Strait is that of a typical dilution basin wherein low salinity water exits near the surface and high salinity water enters at depth. The Mediterranean inflow is of surface Ionian water and, in a deeper layer from 200-300 m, of Modified Levantine Intermediate Water (MLIW). This inflow occurs over a wide area along the eastern shore of the strait, with near-surface outflow concentrated in a thin layer along the western coast. The latter consists of relatively fresh water originating mostly from the northern Adriatic. The remainder of the outflow consists of Adriatic Bottom Water (ABW), a water mass formed in the southern basin that flows over the sill of the Otranto Strait into the Ionian Sea.
The mean basin-wide circulation is generally a cyclonic pattern with several smaller, more or less permanent gyres embedded therein. A topographically controlled cyclonic gyre sitting over the South Adriatic Pit partially isolates the northern Adriatic from Mediterranean influence. This gyre causes a bifurcation of the incoming MLIW, with part of it entering the northern basins over the Palagruza Sill, while the rest is entrained into the South Adriatic cyclonic circulation cell. The circulation regime varies seasonally and interannually in response to changes in the heating and wind regimes. Seasonally, the winter circulation is characterized by a prevalence of warmer Mediterranean inflow reinforced by southerly winds. In summer, there is a stronger outflow of fresher and warmer Adriatic water along the western coast supported by the Etesian winds.
Industry:Earth science
A time scale characterizing the decay of an instantaneous input pulse into a reservoir. It is also used to characterize the adjustment of the mass of a reservoir following a change in the source strength.
Industry:Earth science
A marginal sea in the eastern Mediterranean Sea centered at approximately 25° E and 38° N. It is located between the Greek coast to the west, the Turkish coast to the east, and the islands of Crete and Rhodes to the south. It contains more than 2000 islands forming small basins and narrow passages with very irregular coastline and topography. The northern part of the Aegean is also known as the Thracian Sea, and the southern part between the Cretan Arc and the Kiklades Plateau (defined as the 400 m isobath) as the Cretan Sea. It contains an extended plateau (Thermaikos, Samothraki, Limnos and Kyklades) as well as the deep basins the North Aegean Trough (1600 m maximum depth), the Chios Basin (1160 m) and the Cretan Sea (two depressions in the east 2561 m and 2295 m deep). It covers an area of 20,105 km<sup>2</sup>, has a volume of 74,000 km<sup>3</sup>, and a maximum depth of 2500 m.
It is connected to the Levantine Sea to the southeast via the Cassos or Kasos Strait (67 km wide, 1000 m deep) between Crete and Karpathos, the Karpathos strait (43 km wide, 850 m deep) between Karpathos and Rhodes, and the Rodos or Rhodos Strait (17 km wide, 350 m deep) between Rhodes and Turkey. It joins the Ionian Sea and Cretan Sea to the southwest through the Antikithira Strait between Crete and Antikithira (32 km wide, 700 m deep), the Kithira Strait between Antikithira and Kithira (33 km wide, 160 m deep), and the Elafonissos Strait between Kithira and Peloponnese (11 km wide and 180 m deep). There is considerable and complicated interchange of water with the eastern Mediterranean through these passages. The Strait of Dardanelles (55 m deep, 0. 45-7. 4 km wide) provides a northern link to the Black Sea from which the Aegean receives around 190 km<sup>3</sup> per year of water.
The climate in the Aegean Sea area is characterized by the presence of two distinct periods, summer and winter, with spring and autumn relatively short and transitional. The topography and continual alternation of land and sea make the climate highly variable. Annual river runoff averages about 18,800 x 10<sup>6</sup>m<sup>3</sup>, and evaporation exceeds precipitation and river runoff. The most prominent wind pattern is the Etesian winds, which are persistent, northerly, cold and dry winds that often reach gale force in July and August. When this wind approaches the southern Aegean is bifurcates, becoming northeasterly over the Kitherian Straits and northwesterly-westerly over the southeastern Aegean. The Etesians vanish in late autumn to be replaced by violent cyclonic storms and highly variable prevailing winds.
The surface circulation is most affected by the summer Etesian winds and the low salinity inflow from the Black Sea. The winds cause upwelling along the western coasts of the islands in the eastern Aegean, and a accompanying cold surface zone with temperatures 2-3°C lower than in the northern and western Aegean. During the summer, this colder water is present in the eastern Aegean from Rodos Island up to the Limnos Plateau. In winter, the warmer waters of Levantine origin are found in the same area, while the cold waters arriving from the Strait of Dardanelles spread over the Samothraki Plateau and follow the general cyclonic circulation of the north Aegean. In addition to the overall cyclonic circulation, there is also a Samothraki anticyclonic gyre located in the northeastern part of the North Aegean, a semi-permanent feature that can be detected through most of the year, and an anticyclone near Athos.
The surface flow in the south is into the Aegean between Kithira and Crete, Crete and Karpathos, Karpathos and Rhodes, and Rhodes and Turkey, and into the Mediterranean between Kithira and the Peloponnese coast. There is systematic wind-driven upwelling along the northern coasts of the Patraikos and Korinthiakos Gulfs.
The main water masses found in the Aegean are (from shallowest to deepest):
* Black Sea Water (BSW);
* Levantine Intermediate Water (LIW);
* modified Atlantic Water (AW); and
* Eastern Mediterranean Deep Water (EMDW).
The BSW enters from the Strait of Dardanelles, producing a pronounced halocline in the norther Aegean with a maximum depth from 20-80 m. It moves southward and westward, following the general cyclonic circulation, and can be detected by a surface salinity minimum as far south as the Kithira Straits. LIW is the saltiest water mass of the eastern Mediterranean. It is generated in the Levantine and southern Aegean Seas in February and March. It flows eastwards and westwards from the Aegean, and also flows into the Aegean via the eastern straits of the Cretan Arc. It predominates in the subsurface layers of the Cretan Sea as well as in the eastern parts of the Aegean as far north as the southern boundary of the Limnos Plateau, and is easily identified by its salinity maximum. The modified AW enters the Aegean through the straits of the Cretan Arc and is identifed in several regions as a subsurface (30-200 m) salinity maximum. The Aegean deep water mass extends from about 400-500 m to the bottom, with temperatures ranging from 12-14. 5°C and salinities from 38. 68-38. 9.
Atmosphere/Ocean Chemistry Experiment (AEROCE) A multi-disciplinary and -institutional program focusing on a number of aspects of the atmospheric chemistry over the North Atlantic Ocean. The objectives of AEROCE are:
* to gauge the impact of anthropogenic sources on the chemical and physical properties of the atmosphere;
* to assess the consequences of the perturbuations on natural processes including climate; and
* to predict the longer term efforts via the use of models.
The program officially started in 1987 with coordinate measurements from four stations, i.e. Barbados, West Indies; Bermuda; Izaña, Tenerife, Canary Islands; and Mace Head Ireland. Five more stations were added in June 1995 to give greater geographical coverage of continuous measurements of bulk aerosol chemical composition and condensation nuclei.
Industry:Earth science
A collection of remote sensing experiments and projects being performed at the Institute of Marine Sciences at the University of Alaska Fairbanks. This seems to have been mothballed as of 2001. This is part of the larger SEA Project.
Industry:Earth science
