ingranaggio della circolazione termoalina degli oceani. D’altra parte, l’upwel- ling costiero può indurre intensi flussi di calore nell’oceano, rendendo questo. Il picnoclino (dal greco πυκνός (puknòs), “denso”) è un sottile strato o una superficie che strati scorrono l’uno sull’altro dando luogo alla circolazione oceanica profonda (circolazione termoalina) con grande influenza sul clima globale. Anche gli oceani d’altra parte formano un tipo esclusivo di cella convettiva, ovvero la circolazione termoalina che è influenzata dal calore (termo) e dalla.
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Circolazione termoalina, profonda e delle alte latitudini. Result of the differential heating and cooling, and freshening and salting.
While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. The surface red, orange, yellow and deep violet, blue, green currents in the North Atlantic. The North Atlantic Current brings warm water northward where it cools. Some sinks and returns southward as a cold, deep, western-boundary current.
Some returns southward at the surface. From Woods Hole Oceanographic Institution. Periodic surges of icebergs during the last ice age appear to have modulated temperatures of the northern hemisphere by lowering the salinity of the far north Atlantic and reducing the meridional overturning circulation.
Data from cores through the Greenland ice sheet 1deep-sea sediments 2,3and alpine-lake sediments 4 indicate that: During recent times the circulation has been stable, and the polar front which separates warm and cold water masses has allowed warm water to penetrate beyond Norway. During the last ice age, periodic surges of icebergs reduced salinity and reduced the meridional overturning circulation, causing the polar front to move southward and keeping warm water south of Spain.
Similar fluctuations during the last interglacial appear to have caused rapid, large changes in climate. The Bottom plot is a rough indication of temperature in the region, but the scales are not the same. The switching on and off of the meridional overturning circulation has large hysteresis Figure The circulation has two stable states.
The first is the present circulation 1. In the second, 3 deep water is produced mostly near Antarctica, and upwelling occurs in the far north Pacific as it does today and in the far north Atlantic.
Once the circulation is shut off, the system switches to the second stable state. The return to normal salinity does not cause the circulation to turn on. Surface waters must become saltier than average for the first state to return.
V is the vertical integral of the northward velocity, and W0 is the velocity at the base of the thermocline. Sketch of the deep circulation resulting from deep convection in the Atlantic dark circles and upwelling through the thermocline elsewhere.
Note that the flow is constrained by the deep mid-ocean ridge system. Temperature and salinity measured at hydrographic stations on either side of the Gulf Stream. Data are from tables Temperature and salinity plotted as a function of depth. The same data, but salinity is plotted as a function of temperature in a T-S plot. Notice that temperature and salinity are uniquely related below the mixed layer.
A few depths termoaluna noted next to data points. Mixing of two rermoalina masses produces a line on a T-S plot. Mixing among three water masses produces intersecting lines on a T-S plot, and the apex at the intersection is rounded by further mixing.
Mixing of two water types of circolazoone same density L and G produces water that is denser M than either water type. T-S plot of data collected at various latitudes in the western basins of the south Atlantic.
Contour plot of salinity as a function of depth in the western basins of the Atlantic from the Arctic Ocean to Antarctica. The arrows mark the assumed direction of the flow in the cores. See also Figures Ter,oalina Lynn and Reid T-S plots of water in the various ocean basins. La corrente ha tre rami associati ai tre fronti ombreggiati verticalmente: Le stazioni idrologiche sono date in alto, ed i transporti sono relativi a 3, dbar.
Collect Leads new Upload Login. Loading SlideShow in 5 Seconds. Circolazione termoalina, profonda e termozlina alte latitudini PowerPoint Presentation. Email Presentation to Friend. By sibyl Follow User. Description Statistics Report Circolazione termoalina, profonda e delle alte latitudini.
Circolazione termoalina, profonda e delle alte latitudini 26 febbraio Thermohaline circulation Result of terjoalina differential heating and cooling, and freshening and salting i. Flows to the poles to replace sinking water. Cool water flows along the bottom and upwells towards low latitudes. Thermohaline circulation Most of northward, warm water flow is through the western boundary current because surface flow elsewhere wind-driven is southward.
Importance of Deep Circulation The contrast between the cold deep water and the warm surface waters determines the stratification of the oceans. Stratification strongly influences ocean dynamics. The volume of deep water is far larger than the volume of surface water. Although currents in the deep ocean are relatively weak, they have transports comparable to the surface transports.
The deep circulation influences Earth’s heat budget and climate. It varies on time scales from decades to centuries to millennia, and this variability is thought to modulate climate over such time intervals. The ocean may be the primary cause of variability over times ranging from years to decades, and it may have helped modulate ice-age climate. Oceanic Transport of Heat The oceans carry about half the heat from the tropics circklazione high tefmoalina required to maintain Earth’s temperature.
Heat carried by the Gulf Stream and the north Atlantic curcolazione warms Europe. Palm trees grow on the west coast of Ireland, but not in Newfoundland which is further south. There the surface water releases heat and water to the atmosphere and the water becomes sufficiently dense that it sinks to the bottom in the Norwegian and Greenland Seas.
The deep water later upwells in other regions and in other oceans, and eventually makes its way back to the Gulf Stream and the north Atlantic. Information contained in the Greenland and Antarctic ice sheets and in north Atlantic sediments provide important clues.
Temperatura superficiale marina
Theory for the Deep Circulation To describe the simplest aspects of the flow, we begin with the Sverdrup equation applied to a bottom current of thickness H in an ocean of constant depth: Integrating circolzione equation from the bottom of the ocean to the top of the abyssal circulation layer gives: Observations of Deep circulation Tefmoalina masses T-S plots are used to delineate water masses and their geographical distribution, to describe mixing among water masses, and to infer corcolazione of water in the deep ocean.
Heating, cooling, rain, and evaporation all contribute. Once the water sinks below the mixed layer, temperature and salinity can change only by mixing with adjacent water masses. Thus water from a particular region has a particular temperature associated with a particular salinity, and the relationship changes little as the water moves through the deep ocean.
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