OCEAN AND ATMOSPHERE
Changes to the climate, brought about by increasing levels of greenhouse gases in the atmosphere, will thus lead to changes in the oceans. Global Ocean-Atmosphere-Land System Panel, Climate Research Committee, Functional relationship between GOALS and the other components of the. NOAA's Ocean Service's Education Professional Development,Oceans, ocean, climate and weather connections based on the science literacy goals in the of different temperatures and densities in both the ocean and atmosphere. Describe the relationship between density of liquids and gases and their temperatures.
This would involve understanding the connections between global surface conditions SST, land-surface properties, snow, and ice and global atmospheric anomalies. The original prediction goals of TOGA in and around the tropical Pacific would be more fully accomplished by developing improved coupled models and by exploiting the data produced by the TOGA observing system, especially the TAO array.
As the domain of the GOALS program expands from the original TOGA focus on interannual variability in and over the tropical Pacific Ocean to include global interannual variability, the range of processes considered would also need to expand.
Expansion throughout the global tropics must involve consideration of interactions of the atmosphere with the land masses of India, Africa, and South America, as well as with the Indian and Atlantic oceans.
Expansion into higher latitudes brings new considerations of the interactions with land and with the higher-latitude oceans, as well as with ice and snow changes over the land masses and in the high latitude oceans.
Dynamics of ocean atmosphere exchange
Although GOALS would retain a focus on atmosphere—ocean interactions, the need to include land processes would also require close coordination and collaboration with other programs, especially with the Global Energy and Water Cycle Experiment GEWEXwhich is designed to improve the understanding of land-surface hydrology and other water-transport processes. The modulation of the ocean—atmosphere coupling also has important effects on ocean biology and the exchange of carbon across the air—sea interface.
The understanding of heat-flux fluctuations on seasonal-to-interannual time scales can provide useful input to ongoing programs such as the Joint Global Ocean Flux Study JGOFS and GEWEX for testing ideas about coupling among physical, chemical, and biological systems in the ocean, atmosphere, and on land.
Page 17 Share Cite Suggested Citation: Not only do short-term climate variations mask or enhance the effects of greenhouse changes, there is a distinct possibility that the slowly changing atmosphere and ocean may induce changes in the short-term climate variability that feed back on slow for example, decadal climate changes. Thus, the study of short-term climate variability is expected to make important contributions to the greenhouse problem.
As prediction models inevitably become more global in scope, a logical and needed extension of the TOGA prediction program is the investigation of the initialization and prediction of extratropical SST anomalies and their interaction with the global atmospheric flow.
Knowledge of extratropical SST anomalies is of interest in its own right and may be necessary for understanding and predicting seasonal-to-interannual climate variations in midlatitudes. Anomalies in soil moisture and snow cover have been shown to be important in the genesis and persistence of seasonal climate anomalies. Thus, to understand and predict climate variations, vegetation and land processes must also be considered, initially as boundary conditions and eventually as elements of a coupled system.
In summary, to understand and predict natural climate variations on time scales of seasons to several years, the state of the global upper ocean, atmosphere, and land system must be considered. Such a broad endeavor can be built from the current or anticipated TOGA prediction system in a sequence of measured and well-ordered steps. The study of the tropical Pacific Ocean should be expanded to include the tropical Atlantic, the Indian Ocean, and finally the global upper ocean. For time scales of less than several years, it is probable that only the upper few hundred meters of ocean and wind-driven ocean currents need be considered.
Land-surface processes involving soil moisture and albedo need to be considered for observing and predicting the state of the land surface and its interaction with the climate system. Since water also expands increases its volume when it is heated, global warming could also cause thermal expansion of sea water resulting in a rise in eustatic sea level. Oceanic Currents The surface of the oceans move in response to winds blowing over the surface.
The winds, in effect, drag the surface of oceans creating a current of water that is usually no more than about 50 meters deep. Thus, surface ocean currents tend to flow in patterns similar to the winds as discussed above, and are reinforced by the Coreolis Effect. But, unlike winds, the ocean currents are diverted when they encounter a continental land mass.
In the middle latitudes ocean currents run generally eastward, flowing clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. Such easterly flowing currents are deflected by the continents and thus flow circulates back toward the west at higher latitudes. Because of this deflection, most of the flow of water occurs generally parallel to the coasts along the margins of continents. Only in the southern oceans, between South America, Africa, Australia, and Antarctica are these surface currents unimpeded by continents, so the flow is generally in an easterly direction around the continent of Antarctica.
Ocean Waves Waves are generated by winds that blow over the surface of oceans.
In a wave, water travels in loops. But since the surface is the area affected, the diameter of the loops decreases with depth. The diameters of loops at the surface is equal to wave height h. This depth is called wave base. In the Pacific Ocean, wavelengths up to m have been observed, thus water deeper than m will not feel passage of wave. But outer parts of continental shelves average m depth, so considerable erosion can take place out to the edge of the continental shelf with such long wavelength waves.
When waves approach shore, the water depth decreases and the wave will start feeling bottom.
Dynamics of ocean atmosphere exchange | NIWA
Furthermore, as the wave "feels the bottom", the circular loops of water motion change to elliptical shapes, as loops are deformed by the bottom. As the wavelength L shortens, the wave height h increases. Eventually the steep front portion of wave cannot support the water as the rear part moves over, and the wave breaks.
This results in turbulent water of the surf, where incoming waves meet back flowing water. Rip currents form where water is channeled back into ocean. Wave Erosion - Rigorous erosion of sea floor takes place in the surf zone, i. Waves break at depths between 1 and 1. Thus for 6 m tall waves, rigorous erosion of sea floor can take place in up to 9 m of water. Waves can also erode by abrasion and flinging rock particles against one another or against rocks along the coastline.
Wave refraction - Waves generally do not approach shoreline parallel to shore. Instead some parts of waves feel the bottom before other parts, resulting in wave refraction or bending. Wave energy can thus be concentrated on headlands, to form cliffs. Headlands erode faster than bays because the wave energy gets concentrated at headlands.
Coastal Erosion and Sediment Transport Coastlines are zones along which water is continually making changes. Waves can both erode rock and deposit sediment. Because of the continuous nature of ocean currents and waves, energy is constantly being expended along coastlines and they are thus dynamically changing systems, even over short human time scales.
But, when the wave breaks as it approaches the shoreline, vigorous erosion is possible due to the sudden release of energy as the wave flings itself onto the shore. In the breaker zone rock particles carried in suspension by the waves are hurled at other rock particles.
As these particles collide, they are abraded and reduced in size. Smaller particles are carried more easily by the waves, and thus the depth to the bottom is increased as these smaller particles are carried away by the retreating surf. Furthermore, waves can undercut rocky coastlines resulting in mass wasting processes wherein material slides, falls, slumps, or flows into the water to be carried away by further wave action. Transport of Sediment by Waves and Currents Sediment that is created by the abrasive action of the waves or sediment brought to the shoreline by streams is then picked up by the waves and transported.
The finer grained sediment is carried offshore to be deposited on the continental shelf or in offshore bars, the coarser grained sediment can be transported by longshore currents and beach drift.
Longshore currents - Most waves arrive at the shoreline at an angle, even after refraction. Such waves have a velocity oriented in the direction perpendicular to the wave crests, but this velocity can be resolved into a component perpendicular to the shore Vp and a component parallel to the shore VL. The component parallel to the shore can move sediment and is called the longshore current.
Beach drift - is due to waves approaching at angles to beach, but retreating perpendicular to the shore line. This results in the swash of the incoming wave moving the sand up the beach in a direction perpendicular to the incoming wave crests and the backwash moving the sand down the beach perpendicular to the shoreline.
Thus, with successive waves, the sand will move along a zigzag path along the beach. Storms High winds blowing over the surface of the water during storms bring more energy to the coastline and can cause more rapid rates of erosion. Erosion rates are higher because: During storms wave velocities are higher and thus larger particles can be carried in suspension.
This causes sand on beaches to be picked up and moved offshore, leaving behind coarser grained particles like pebbles and cobbles, and reducing the width of the beach. During storms waves reach higher levels onto the shoreline and can thus remove structures and sediment from areas not normally reached by the incoming waves. Because wave heights increase during a storm, waves crash higher onto cliff faces and rocky coasts. Larger particles are flung against the rock causing rapid rates of erosion.
As the waves crash into rocks, air occupying fractures in the rock becomes compressed and thus the air pressure in the fractures is increased. Such pressure increases can cause further fracture of the rock. Types of Coasts The character and shape of coasts depends on such factors as tectonic activity, the ease of erosion of the rocks making up the coast, the input of sediments from rivers, the effects of eustatic changes in sea level, and the length of time these processes have been operating.
Rocky Coasts - In general, coastlines that have experienced recent tectonic uplift as a result of either active tectonic processes such as the west coast of the United States or isostatic adjustment after melting of glacial ice such as the northern part of the east coast of the United States form rocky coasts with cliffs along the shoreline.
Anywhere wave action has not had time to lower the coastline to sea level, a rocky coast may occur. Because of the resistance to erosion, a wave cut bench and wave cut cliff develops.
The cliff may retreat by undercutting and resulting mass-wasting processes. If subsequent uplift of the wave-cut bench occurs, it may be preserved above sea level as a marine terrace. Because cliffed shorelines are continually attacked by the erosive and undercutting action of waves, they are susceptible to frequent mass-wasting processes which make the tops of these cliffs unstable areas for construction Along coasts where streams entering the ocean have cut through the rocky cliffs, wave action is concentrated on the rocky headlands as a result of wave refraction Beaches - A beach is the wave washed sediment along a coast.
Beaches occur where sand is deposited along the shoreline. A beach can be divided into a foreshore zone, which is equivalent to the swash zone, and backshore zone, which is commonly separated from the foreshore by a distinct ridge, called a berm. Behind the backshore may be a zone of cliffs, marshes, or sand dunes.
Barrier Islands - A barrier island is a long narrow ridge of sand just offshore running parallel to the coast. Separating the island and coast is a narrow channel of water called a lagoon. Most barrier islands were built during after the last glaciation as a result of sea level rise. Barrier islands are constantly changing.
They grow parallel to the coast by beach drift and longshore drift, and they are eroded by storm surges that often cut them into smaller islands.
Since these organisms can only live in warm waters and need sunlight to survive, reefs only form in shallow tropical seas.
Fringing reefs form along coastlines close to the sea shore, whereas barrier reefs form offshore, separated from the land by a lagoon. Both types of reefs form shallow water and thus protect the coastline from waves. However, reefs are high susceptible to human activity and the high energy waves of storms. A submerged coast, and shows submerged valleys, barrier islands, and gentle shorelines, all due to rise of sea level since last glaciation age during glacial ages, seawater is tied up in ice, and sea level is lower; when the ice melts sea level rises.
Coastal Hazards Storms - great storms such as hurricanes or other winter storms can cause erosion of the coastline at much higher rate than normal. During such storms beaches can erode rapidly and heavy wave action can cause rapid undercutting and mass-wasting events of cliffs along the coast, as noted above.
Tsunamis - a tsunami is a giant sea wave generated by an earthquakes, volcanic eruptions, or landslides, as we have discussed before. Such waves can have wave heights up to 30 m, and have great potential to wipe out coastal cities.
Landslides - On coasts with cliffs, the main erosive force of the waves is concentrated at the base of the cliffs. As the waves undercut the cliffs, they may become unstable and mass-wasting processes like landslides will result.
Massive landslides can also generate tsunamis. Adapting to Coastal Erosion Seacliffs, since they are susceptible to landslides due to undercutting, and barrier islands and beaches, since they are made of unconsolidated sand and gravel, are difficult to protect from the action of the waves. Human construction can attempt to prevent erosion, but cannot always protect against abnormal conditions.
Furthermore, other problems are sometimes caused by these engineering feats. Protection of the Shoreline. Shoreline protection can be divided into two categories: Hard Stabilization - Two types of hard stabilization are often used. One type interrupts the force of the waves. Seawalls are built parallel to the coastline to protect structures on the beach. A seawall is usually built of concrete or piles of large rocks.
Waves crash against the seawall and are prevented from running up the beach. Breakwaters serve a similar purpose, but are built slightly offshore, again preventing the force of the waves from reaching the beach and any structures built on the beach. The other type interrupts the flow of sediment along the beach. These structures include groins and jetties, built at right angles to the beach to trap sand and widen the beach. While hard stabilization does usually work for its intended purpose, it does cause sediment to be redistributed along the shoreline.
Breakwaters, for example cause wave refraction, and alters the flow of the longshore current. Sediment is trapped by the breakwater, and the waves become focused on another part of the beach, not protected by the breakwater, where they can cause significant erosion.
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Similarly, because groins and jetties trap sediment, areas in the downdrift direction are not resupplied with sediment, and beaches become narrower in the downdrift direction. Soft stabilization is primarily accomplished by adding sediment to the coastline, usually by dredging sediment from offshore and pumping it onto the coastline.
Adding sediment is necessary when erosion removes too much sediment. But, because the erosive forces are still operating, such addition of sediment will need to be periodically repeated.
- Sea Surface Temperature
Coastal Erosion Controversies As noted above, hard stabilization usually affects areas in the downdrift direction of the longshore current. The net result being that some areas of a coastline are protected while other areas are destroyed. Nearly all human intervention with coastal processes interrupts natural processes and thus can have an adverse effect on coastlines.
Barrier Islands show a noticeable difference among the islands that have been built upon and those that have not. The undeveloped islands have beaches to meters wide, while the developed islands have beaches with widths less than 30 m.