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An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis force, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun. Depth contours, shoreline configurations and interaction with other currents influence a current's direction and strength.
Ocean currents can flow for great distances, and together they create the great flow of the global conveyor belt which plays a dominant part in determining the climate of many of the Earthâ€™s regions. Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any other region at the same latitude. Another example is the Hawaiian Islands, where the climate is cooler (sub-tropical) than the tropical latitudes in which they are located, due to the effect of the California Current.
Surface ocean currents are generally wind driven and develop their typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in the southern hemisphere because of the imposed wind stresses. In wind driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. The areas of surface ocean currents move somewhat with the seasons; this is most notable in equatorial currents.
Ocean basins generally have a non-symmetric surface current, in that the eastern equatorward-flowing branch is broad and diffuse whereas the western poleward-flowing branch is very narrow. These western boundary currents (of which the gulf stream is an example) are a consequence of basic fluid dynamics.
Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation, also known as the ocean's conveyor belt, refers to the deep ocean density-driven ocean basin currents. These currents, which flow under the surface of the ocean and are thus hidden from immediate detection, are called submarine rivers. These are currently being researched using a fleet of underwater robots called Argo. Upwelling and downwelling areas in the oceans are areas where significant vertical movement of ocean water is observed.
Surface currents make up about 10% of all the water in the ocean. Surface currents are generally restricted to the upper 400|m|ft|abbr=on of the ocean. The movement of deep water in the ocean basins is by density driven forces and gravity. The density difference is a function of different temperatures and salinity. Deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase.
Ocean currents are measured in Sverdrup (Sv), where 1Sv is equivalent to a volume flow rate of 1000000|m3|ft3|abbr=on per second.
Knowledge of surface ocean currents is essential in reducing costs of shipping, since they reduce fuel costs. In the sail-ship era knowledge was even more essential. A good example of this is the Agulhas current, which long prevented Portuguese sailors from reaching India. Even today, the round-the-world sailing competitors employ surface currents to their benefit. Ocean currents are also very important in the dispersal of many life forms. An example is the life-cycle of the eel.
Ocean currents are important in the study of marine debris, and vice versa. These currents also affect temperatures throughout the world. For example, the current that brings warm water up the north Atlantic to northwest Europe stops ice from forming by the shores, which would block ships from entering and exiting ports.
Ocean acidification is the name given to the ongoing decrease in the pH of the Earth's oceans, caused by their uptake of anthropogeniccarbon dioxide from the atmosphere. Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.179 to 8.104, a change of âˆ’0.075 on the logarithmic pH scale which corresponds to an increase of 18.9% in H+ (acid) concentration. By the first decade of the 21st century however, the net change in ocean pH levels relative pre-industrial level was about -0.11, representing an increase of some 30% in "acidity" (ion concentration) in the world's oceans.
The carbon cycle describes the fluxes of carbon dioxide (CO|2) between the oceans, terrestrialbiosphere, lithosphere, and the atmosphere. Human activities such as land-use changes, the combustion of fossil fuels, and the production of cement have led to a new flux of CO|2 into the atmosphere. Some of this has remained there; some has been taken up by terrestrial plants, and some has been absorbed by the oceans.
The carbon cycle comes in two forms: the organic carbon cycle and the inorganic carbon cycle. The inorganic carbon cycle is particularly relevant when discussing ocean acidification for it includes the many forms of dissolved CO|2 present in the Earth's oceans.
When CO|2 dissolves, it reacts with water to form a balance of ionic and non-ionic chemical species: dissolved free carbon dioxide (CO|2|(aq)), carbonic acid (H|2|CO|3), bicarbonate (HCO|3|-) and carbonate (CO|3|2-). The ratio of these species depends on factors such as seawatertemperature and alkalinity (see the article on the ocean's solubility pump for more detail).
Dissolving CO|2 in seawater increases the hydrogen ion (H|+) concentration in the ocean, and thus decreases ocean pH. Caldeira and Wickett (2003) placed the rate and magnitude of modern ocean acidification changes in the context of probable historical changes during the last 300 million years.
Since the industrial revolution began, it is estimated that surface ocean pH has dropped by slightly more than 0.1 units on the logarithmic scale of pH, representing an approximately 29% increase in H|+|, and it is estimated that it will drop by a further 0.3 to 0.5 pH units (an additional doubling to tripling of today's post-industrial acid concentrations) by 2100 as the oceans absorb more anthropogenic CO|2. These changes are predicted to continue rapidly as the oceans take up more anthropogenic CO|2 from the atmosphere, the degree of change to ocean chemistry, for example ocean pH, will depend on the mitigation and emissions pathways society takes. Note that, although the ocean is acidifying, its pH is still greater than 7 (that of neutral water), so the ocean could also be described as becoming less basic.
Although the largest changes are expected in the future, a report from NOAA scientists found large quantities of water undersaturated in aragonite are already upwelling close to the Pacific continental shelf area of North America. Continental shelves play an important role in marine ecosystems since most marine organisms live or are spawned there, and though the study only dealt with the area from Vancouver to northern California, the authors suggest that other shelf areas may be experiencing similar effects.
Rate of Acidification
Similarly, one of the first detailed datasets examining temporal variations in pH at a temperatecoastal location found that acidification was occurring at a rate much higher than that previously predicted, with consequences for near-shore benthic ecosystems.
A December 2009 National Geographic report quoted Thomas Lovejoy, former chief biodiversity advisor to the World Bank on recent research suggesting "the acidity of the oceans will more than double in the next 40 years. This rate is 100 times faster than any changes in ocean acidity in the last 20 million years, making it unlikely that marine life can somehow adapt to the changes."
According to research, from the University of Bristol, published in the journal Nature Geoscience in February 2010, compared current rates of ocean acidification with the greenhouse event at the Paleocene-Eocene boundary, about 55 million years ago when surface ocean temperatures rose by 5-6 degrees Celsius, during which time no catastrophe is seen in surface ecosystems, yet bottom-dwelling organisms in the deep ocean experienced a major extinction. They concluded that the current acidification is on path to reach levels higher than any seen in the last 65 million years. The study also found that the current rate of acidification is "ten times the rate that preceded the mass extinction 55 million years ago," and Ridgwell commented that the present rate "is an almost unprecedented geological event." A National Research Council study released in April 2010 likewise concluded that "the level of acid in the oceans is increasing at an unprecedented rate."
A review by climate scientists at the RealClimate blog, of a 2005 report by the Royal Society of the UK similarly highlighted the centrality of the rates of change in the present anthropogenic acidification process, writing: "The natural pH of the ocean is determined by a need to balance the deposition and burial of CaCO|3 on the sea floor against the influx of Ca||2+ and CO|3|2- into the ocean from dissolving rocks on land, called weathering. These processes stabilize the pH of the ocean
In layman's terms, two events are mutually exclusive if they cannot occur at the same time (i.e., they have no common outcomes). An example is tossing a ...
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Answers:1 is commensalism because the fish is being protected by the anemone but the anemone is not being benefitted by the fish's presence. 2 is mutualism because both organisms are being benefitted. The bird gets a ride while the cattle get their pesty insects removed!
Answers:Your picture looks like dogfish, shark-type critters. I would say that ship-boring worms are decomposers as they breakdown cellulose in organic compounds.
Answers:Mutualism--clownfish and sea anemonae, termites and intestinal flagellates Commensalism-- Barnacles adhering to the skin of a whale or shell of a mollusk, tree frogs and various tropical plants Parasitism--lice, moquitoes, heartworms and hookworms, tapeworms
Answers:seagulls eat crabs on the beach... crabs don't really feed on algea or seaweed. try mollusks like the oyster or something that filter feeds. a lot of fish eats oysters....