Ocean Atmosphere System
So how does something in the ocean influence the atmosphere? We already saw how hurricanes depend on the sea for energy, but there's more. The sea and. Earth Processes, Structures and Extreme Weather study of Ocean,atmosphere and coastal systems. The Ocean-Atmosphere System. The oceans and the atmosphere are the two large reservoirs of water in the Earth's hydrologic cycle. The two.
This will result in release of CO2 and methane into the atmosphere and enhance the greenhouse effect. Breakdown of gas hydrates - This is basically solid water with gas molecules like methane locked into the crystal structure.
They occur in oceanic sediments and beneath frozen ground at the high latitudes. Warming of the oceans or warming of the soil at high lattitudes could cause melting of the gas hydrates which would release methane into the atmosphere.
Since methane is a greenhouse gas, this would cause further global warming. Climate Change Because human history is so short compared to the time scales on which global climate change occurs, we do not completely understand the causes. However, we can suggest a few reasons why climates fluctuate. Long term variations in climate tens of millions of years on a single continent are likely caused by drifting continents.
If a continent drifts toward the equator, the climate will become warmer. If the continent drifts toward the poles, glaciations can occur on that continent. Short-term variations in climate are likely controlled by the amount of solar radiation reaching the Earth.
Among these are astronomical factors and atmospheric factors. Astronomical Factors - Variation in the eccentricity of the Earth's orbit around the sun has periods of aboutyears andyears. Variation in the tilt of the Earth's axis has a period of about 41, years. Variation in the way the Earth wobbles on its axis, called precession, has a period of about 23, years. The combined effects of these astronomical variations results in periodicities similar to those observed for glacial - interglacial cycles.
Atmospheric Factors- the composition of the Earth's atmosphere can be gleaned from air bubbles trapped in ice in the polar ice sheets. Studying drill core samples of such glacial ice and their contained air bubbles reveals the following: During past glaciations, the amount of CO2 and methane, both greenhouse gasses that tend to cause global warming, were lower than during interglacial episodes. During past glaciations, the amount of dust in the atmosphere was higher than during interglacial periods, thus more heat was likely reflected from the Earth's atmosphere back into space.
The problem in unraveling what this means comes from not being able to understand if low greenhouse gas concentration and high dust content in the atmosphere caused the ice ages or if these conditions were caused by the ice ages.
Changes in Oceanic Circulation - small changes in ocean circulation can amplify small changes in temperature variation produced by astronomical factors. Other factors The energy output from the sun may fluctuate.
Large explosive volcanic eruptions can add significant quantities of dust to the atmosphere reflecting solar radiation and resulting in global cooling. Circulation in the Atmosphere The troposphere undergoes circulation because of convection.
Recall that convection is a mode of heat transfer. Convection in the atmosphere is mainly the result of the fact that more of the Sun's heat energy is received by parts of the Earth near the Equator than at the poles. Thus air at the equator is heated reducing its the density.
Lower density causes the air to rise. At the top of the troposphere this air spreads toward the poles. If the Earth were not rotating, this would result in a convection cell, with warm moist air rising at the equator, spreading toward the poles along the top of the troposphere, cooling as it moves poleward, then descending at the poles, as shown in the diagram above.
Once back at the surface of the Earth, the dry cold air would circulate back toward the equator to become warmed once again. Areas where warm air rises and cools are centers of low atmospheric pressure. In areas where cold air descends back to the surface, pressure is higher and these are centers of high atmospheric pressure.
The Coriolis Effect - Again, the diagram above would only apply to a non-rotating Earth. Since the Earth is in fact rotating, atmospheric circulation patterns are much more complex. The reason for this is the Coriolis Effect. The Coriolis Effect causes any body that moves on a rotating planet to turn to the right clockwise in the northern hemisphere and to the left counterclockwise in the southern hemisphere. The effect is negligible at the equator and increases both north and south toward the poles.
The Coriolis Effect occurs because the Earth rotates out from under all moving bodies like water, air, and even airplanes. Note that the Coriolis effect depends on the initial direction of motion and not on the compass direction.
If you look along the initial direction of motion the mass will be deflected toward the right in the northern hemisphere and toward the left in the southern hemisphere. Wind Systems High Pressure Centers - In zones where air descends back to the surface, the air is more dense than its surroundings and this creates a center of high atmospheric pressure.
Since winds blow from areas of high pressure to areas of low pressure, winds spiral outward away from the high pressure. But, because of the Coriolis Effect, such winds, again will be deflected toward the right in the northern hemisphere and create a general clockwise rotation around the high pressure center. In the southern hemisphere the effect is just the opposite, and winds circulate in a counterclockwise rotation about the high pressure center.
Such winds circulating around a high pressure center are called anticyclonic winds. Low Pressure Centers - In zones where air ascends, the air is less dense than its surroundings and this creates a center of low atmospheric pressure, or low pressure center. Winds blow from areas of high pressure to areas of low pressure, and so the surface winds would tend to blow toward a low pressure center.
But, because of the Coriolis Effect, these winds are deflected. In the northern hemisphere they are deflected to toward the right, and fail to arrive at the low pressure center, but instead circulate around it in a counter clockwise fashion as shown here.
In the southern hemisphere the circulation around a low pressure center would be clockwise. Such winds are called cyclonic winds.
Because of the Coriolis Effect, the pattern of atmospheric circulation is broken into belts as shown here. The rising moist air at the equator creates a series of low pressure zones along the equator. Water vapor in the moist air rising at the equator condenses as it rises and cools causing clouds to form and rain to fall.
After this air has lost its moisture, it spreads to the north and south, continuing to cool, where it then descends at the mid-latitudes about 30o North and South. Descending air creates zones of high pressure, known as subtropical high pressure areas. Because of the rotating Earth, these descending zones of high pressure veer in a clockwise direction in the northern hemisphere, creating winds that circulate clockwise about the high pressure areas, and giving rise to winds, called the trade winds, that blow from the northeast back towards the equator.
In the southern hemisphere the air circulating around a high pressure center is veered toward the left, causing circulation in a counterclockwise direction, and giving rise to the southeast trade winds blowing toward the equator. Air circulating north and south of the subtropical high pressure zones generally blows in a westerly direction in both hemispheres, giving rise to the prevailing westerly winds. These westerly moving air masses again become heated and start to rise creating belts of subpolar lows.
Meeting of the air mass circulating down from the poles and up from the subtropical highs creates a polar front which gives rise to storms where the two air masses meet. In general, the surface along which a cold air mass meets a warm air mass is called a front. The position of the polar fronts continually shifts slightly north and south, bringing different weather patterns across the land. In the summer months, the polar fronts shift northward, and warmer subtropical air circulates farther north.
The convection cells circulating upward from the equator and then back to surface at the mid-latitudes are called Hadley cells. Circulation upward at high latitudes with descending air at the poles are called Polar cells. In between are cells referred to as Ferrel cells. At high altitudes in the atmosphere narrow bands of high velocity winds flowing from west to east are called the jet streams.
The polar jet occurs above the rising air between the Polar cells and the Ferrel cells.
The subtropical jet occurs above the descending air between the Ferrel cells and the Hadley cells. These jet streams meander above the Earth's surface in narrow belts. In the northern hemisphere, where the jet streams meanders to the south it brings low pressure centers and associated storms further to the south.
Where it meanders to the north, the high pressure centers move to the north. Effect of Air Circulation on Climate Atmospheric circulation is further complicated by the distribution of land and water masses on the surface of the Earth and the topography of the land. If the Earth had no oceans and a flat land surface, the major climatic zones would all run in belts parallel to the equator.
But, since the oceans are the source of moisture and the elevation of the land surface helps control where moist air will rise, climatic zones depend not only on latitude, but also on the distribution and elevation of land masses. In general, however, most of the world's desert areas occur along the mid-latitudes where dry air descends along the mid-latitude high pressure zones.
Water and Heat Water has one of the highest heat capacities of all known substances. This means that it takes a lot of heat to raise the temperature of water by just one degree. Water thus absorbs a tremendous amount of heat from solar radiation, and furthermore, because solar radiation can penetrate water easily, large amounts of solar energy are stored in the world's oceans.
Further energy is absorbed by water vapor as the latent heat of vaporization, which is the heat required to evaporate water or change it from a liquid to a vapor. This latent heat of vaporization is given up to the atmosphere when water condenses to form liquid water as rain. If the rain changes to a solid in the form of snow or ice, it also releases a quantity of heat known as the latent heat of fusion.
Thus, both liquid water and water vapor are important in absorbing heat from solar radiation and transporting and redistributing this heat around the planet. As we will see throughout the next part of the course, this heat provides the energy to drive the convection system in the atmosphere and thus drives the water cycle and is responsible for such hazards as floods, thunderstorms, tornadoes, and tropical cyclones.
Air Masses Due to general atmospheric circulation patterns, air masses containing differing amounts of heat and moisture move into and across North America.
Polar air masses, containing little moisture and low temperatures move downward from the poles. Air masses that form over water are generally moist, and those that form over the tropical oceans are both moist and warm.
Climate change caused by ocean, not just atmosphere, study finds
Because of the Coriolis effect due to the Earth's rotation, air masses generally move across North America from west to east. But, because of the differences in moisture and heat, the collision of these air masses can cause instability in the atmosphere. Fronts and Mid-latitude Cyclones Different air masses with different temperatures and moisture content, in general, do not mix when they run into each other, but instead are separated from each other along boundaries called fronts.
When cold air moving down from the poles encounters warm moist air moving up from the Gulf of Mexico, Pacific Ocean, or Atlantic Ocean, a cold front develops and the warm moist air rises above the cold front. This rising moist air cools as it rises causing the condensation of water vapor to form rain or snow. Note that the cold air masses tend to circulate around a low pressure center in a counterclockwise fashion in the northern hemisphere.
Such circulation around a low pressure center is called a mid-latitude cyclone. When warm air moving northward meets the cooler air to the north, a warm front forms. During interglacial periods, the atmospheric levels doubled to perhaps parts per billion. Now we are at parts per billion and climbing. The sources for this rise include melting of tundra permafrost, biomass burning, leaks 36 - Q o z C: The dots indicate monthly average concentration.
Reprinted, by permission, from C. Copyright 3 by me American Geophysical Union. Atmospheric scientists try to decipher the workings of the physical climate system by constructing what are known as general circulation models. These computer models use math- ematical equations to express the basic physical principles that govern the global atmosphere and then use actual data to test whether the models adequately simulate reality.
The general circulation models, as they now exist, simu- late the physical climate and geographical features on a very coarse scale. A country the size of Japan, for example, does not appear on the computer-generated maps. Vast numbers of calculations and large amounts of computer time and money would be required to refine the scale. The current models clo not in- corporate other components of the earth system that are known to exert strong influences on the physical climate.
Scientists are attempting to incorporate the dynamics of the ocean, and its enormous abilities to absorb heat and carbon, into the climate models.
Cloud cover, too, has a strong moderating influence on the greenhouse effect, but it is difficult to characterize and incorporate into coarse-scale models. Even more clifficult to model, and perhaps more important, are the living parts of the world the forests, which store carbon and moisture, and the marine biota, which sequester carbon.
Scientists look longingly to the day when enough is understood about these processes to include them in the models. Perhaps such a grand mode! Just as atmospheric chemistry fluctuates, so does ocean chemistry, though not in the same ways. While much is known about ocean circulation and its coupling to at- mospheric currents and pressure, less is certain about its ability to store additional carbon or about how much heat it will store in response to rising surface temperatures.
The ocean is an immense reservoir of heat, holding the heat it absorbs from solar radiation longer than the land does. As the ocean water moves through its grand circulation scheme, heat is transferred vertically from the surface waters to the deep ocean and back, and horizontally from high latitude to Tow latitude and from longitude to longitude.
As heat is released by the ocean in a region remote from where it was absorbed, it interacts with the overlying atmo- sphere, moderating the daily and seasonal cycles and tempera- ture on the earth's surface areas. Kevin Trenberth, of the National Center for At- mospheric Research in Boulder, Colorado, and colleagues have shown that the hot and dry conditions in central North America in the summer of could have been triggered by unusual distributions in sea surface temperatures that occurred in the aftermath of the E!
A critical unanswered question is, what is the ocean's role in storing the carbon dioxide added to the atmosphere by hu- man activity? Preliminary calculations suggest that about half of the carbon dioxide added to the atmosphere by fossil fuel combustion and deforestation remains there. At least part of the carbon dioxide has been absorbed by the ocean, which holds 60 times as much carbon as there is In all of the atmospheric carbon dioxide.
The ocean's carbon largely resides at the bottom of the sea and has accumulated over billions of years. Photosynthetic plankton in the ocean's surface waters are consumed by other organisms; some of that carbon is returned to the atmosphere through respiration, and part goes into storage in the deep-sea sediment as detritus and shells or skeletons of marine organ- isms.
The free-fall of organisms from the surface to the ocean floor and the subsequent release of carbon as deep ocean waters are slowly recycled up to the surface waters have a profound effect on the way carbon is apportioned throughout the earth system. The movement of carbon through the earth system would be quite different if noting lived in the ocean. If one could con- sider the influence of physics and chemistry alone, carbon diox- ide in the surface waters would be evenly distributed. The food webs of organisms deter- mine to what degree the carbon that is fixed photosynthetically will go back into the water and to what degree it will go into the creep ocean.
In turn, the nature of the food web influences the partitioning of carbon dioxide. What is it, he asks, that determines the capacity of the ocean today to absorb carbon? Why is it not half that amount, or twice that amount? How might the capacity of the ocean to absorb the car- bon dioxide that is being released from fossil fuel combustion change in the future?
What are the implications of this for the ocean carbon cycle? What would happen if the surface ocean conditions were to change? Scientists have not yet answered these questions, but the record of the past provides some valuable clues in addressing them. The distinct correlation between the concentration of car- bon dioxide and the surface temperature of the planet during the glacial cycles over the lastyears must have involvecl the ocean.
Researchers believe the carbon cannot move through any other reservoirs in the earth system efficiently enough over those time periods to account for these changes in carbon diox- ide concentrations. While there are many questions in urgent need of answers, in the last decade the ocean science community has developed new and powerful techniques for addressing them.
Scientists have increased their understancting of the coupled nature of the atmosphere-ocean system, and of ocean physics and bio- geochemistry.
Until fairly recently, oceanographers based their studies of ocean processes on samples of ocean water gath- ered while aboard ships an extremely slow, labor-intensive process. Ships move at roughly 10 knots, but weather patterns can move across the surface of the earth much faster. Indeed, much of the data collected from the ocean surface is biased be- cause of problems of space and time scale. Now, satellites have made it possible to measure not only the ocean surface tem- perature but also how the surface currents are moving.
Surface winds can be tracked with instruments aboard satellites, anct the height of the ocean surface can be precisely gauged. These measurements reveal valuable information about ocean circu- lation. And, finally, the color of the ocean can be assessed to approximate the concentration of plankton pigment, and thus biological activity, at the ocean's surface.
LAND Nothing seems more solid than a tract of land, and yet the plants and animals, the soil, and the life-supporting nutrients provided by that land make up a single interdependent unit an ecosystem that is dynamic on time scales ranging from days to seasons to years to millennia. Over days and seasons, the earth's plant communities absorb and release carbon in a breath-like rhythm. Over years and decades, ecosystems respond to the natural patterns of plant succession and occasional events such as E1 Nino or drought.
At the far extreme, ecosystems on land change on time scales of tens to thousands of years according to the earth's glacial cycles. Ecosystems function metabolically, producing and consum- ing many of the gases that drive the earth system.
Plants capture energy from the sun and carbon dioxide from the atmosphere in their growth process. Terrestrial plants take up more than billion metric tons of carbon each year and return approx- imately as much to the atmosphere as plants die and decay. This cyclical exchange involves 20 times the amount of carbon released through combustion of fossil fuels. As is the case with carbon, the amount of nitrous oxide cycled through terrestrial ecosystems is much greater than the amount released through combustion of fossil fuels.
Atmosphere-Ocean Interaction | oculo-facial-surgery.info
Of the three main components of the earth system-atmo- sphere, oceans, and land the land is the most heterogeneous. The earth's surface is a mosaic of different types of ecosys- tems ranging from arid desert to tropical forests to tundra to the more familiar temperate forests.
Each harbors distinct plant and animal communities, and each uniquely contributes to the func- tioning of the earth system. Tropical rain forests, for example, with abundant moisture and high temperatures that facilitate ex- ceedingly rapid plant growth and decomposition of dead plant material, cover about 7 percent of the earth's land area but con- tribute a much larger share of the worId's annual turnover of biomass.
At the other end of the spectrum, the cold tempera- tures In the tundra inhibit decomposition of plant material, and so the carbon in the biomass is stored there for long periods.
Though change is a quality intrinsic to all ecosystems, changes to the plant cover from agriculture, clearing of forests, and other human activities are not just another sort of change imposed on the background of natural variation. Rather, they profoundly alter the amount of light reflected back to the atmo- sphere from the land, the roughness of the land surface, which influences wind patterns, and the cycling of materials through the earth system. For studies of the short-term dynamics of terrestrial ecosys- tems, biologists, like oceanographers and climatologists, have benefited from advances in satellite technology.
One of the most important short-term dynamic effects is the seasonal variation in vegetation, which can be seen from space and recorded in snapshots. Some of these images show where plants are active at any given time and are extremely useful because the informa- tion can be accumulated daily, summed annually, and compared with measurements of the atmosphere.
The ice age is of particular interest in light of projections for the planet in the next century. Even during glaciation and the retreat of glaciers, which occurred much more slowly than the rate of warming projected for the planet in the next years, the rate of change was so fast that only some species were able to adapt to the changes.
Associations between species were severed. Eventually those species that survived recolonized into new communities, often in unfamiliar areas and in different combinations of members. As a result, many ecosystems were composed of wholly different combinations of species than are found anywhere today.
During the ice age, the major vegetation zones shifted thou- sands of kilometers from their current positions, and so the frac- tion of the earth's surface covered by specific types of vegetation also was altered substantially. What is in store for ecosystems in the future, and how these changes will feed back to other parts of the earth system, are open questions.
Rain, a lake, dew, waves crashing along a shoreline, snow, fog, a freshwater spring sur- rounded by desert palms-water in these and many other fa- miliar forms means that life can be sustained. Nowhere else in the solar system does water currently exist in its liquid state; nowhere else has life taken root and flourished. Here water connects the various components of the biosphere, driving pro- cesses on land, sea, and air.
It resides temporarily in oceans, groundwater, lakes, ice, and clouds and flows between them through rainfall and snow, evaporation from surfaces and through plants, and runoff across the earth's surface. Nearly ev- ery process in the earth system requires it. It sculpts the earth's topography, pushing vast amounts of debris ahead of advanc- ing glaciers, compressing the land beneath mountains of ice.
Soil particles caught up in river flows traverse great distances to the oceans and lakes, where they settle to the bottom and eventually harden into sedimentary rock.
Climate change caused by ocean, not just atmosphere, study finds
Water also destroys rocks, acting as a solvent in the weathering process or splitting them mechanically, pushing into crevasses where it freezes and expands. Most aspects of the water cycle are poorly understood: There is simply too much of it in too many places for the many reservoirs, flows, and fluxes to be measured accurately.
We do know that oceans hold the lion's share, over 97 percent, of the earth's water, followed by glaciers and ice caps. Lakes, rivers, and other surface water hold a mere one or two ten-thousandths of the global water stock. People have affected the water cycle by constructing dams and reservoirs, which alter river flow and evaporation. Cities are built and paved, creating new patterns of runoff and pre- venting rainwater from entering the ground.