Changes in the distribution of heat within the belt are measured on time scales from tens to hundreds of years. While variations close to the ocean surface may induce relatively short-term climate changes, long-term changes in the deep ocean may not be detected for many generations. The ocean is the thermal memory of the climate system.
NASA satellite observations of the oceans of the past three decades have improved our understanding of global climate change by making global measurements needed for modeling the ocean-atmosphere climate system. Global data sets available on time scales of days to years and, looking ahead, to decades have been and will be a vital resource for scientists and policy makers in a wide range of fields.
Ocean surface topography and currents, vector winds both speed and direction , sea-surface temperature, and salinity are the critical variables for understanding the ocean-climate connection. Scatterometers are used to measure vector winds. The SeaWinds scatterometer has provided scientists with the most detailed, continuous global view of ocean-surface winds to date, including the detailed structure of hurricanes, wide-driven circulation, and changes in the polar sea-ice masses.
Scatterometer signals can penetrate through clouds and haze to measure conditions at the ocean surface, making them the only proven satellite instruments capable of measuring vector winds at sea level day and night, in nearly all weather conditions.
Bouncing radio waves off the ocean surface and timing their return with incredible accuracy, these instruments tell us the distance from the satellite to the sea surface within a few centimeters - the equivalent of sensing the thickness of a dime from a jet flying at 35, feet! At the same time, special tracking systems on the satellites give their position relative to the center of mass of Earth also with an accuracy of a few centimeters.
By subtracting the height of the satellite above the sea from the height of the satellite above the center of mass, scientists calculate maps of the sea-surface height and changes in the height due to tides, changing currents, heat stored in the ocean, and amount of water in the ocean. By mapping the topography of the ocean we can determine the speed and direction of ocean currents. Just as wind blows around high- and low-pressure centers in the atmosphere, water flows around the high and lows of the ocean surface.
Maps of sea-surface height are most useful when they are converted to topographic maps. To determine topography of the sea-surface, height maps are compared with a gravitational reference map that shows the hills and valleys of a motionless ocean due to variations in the pull of gravity. The GRACE Gravity Recovery and Climate Experiment mission will provide very accurate maps of gravity that will allow us to greatly improve our knowledge of ocean circulation.
GRACE has provided gravity measurements that are up to times more accurate than previous values. This improved accuracy will lead the way to break-throughs in our understanding of ocean circulation and heat transport. The increase in temperature and height in the equatorial region west of South America illustrates the El Nino event. Water is an enormously efficient heat-sink. Solar heat absorbed by bodies of water during the day, or in the summer, is released at night, or in winter. But the heat in the ocean is also circulating.
Such sinking is also a principal mechanism by which the oceans store and transport heat and carbon dioxide. Together, temperature and salinity differences drive a global circulation within the ocean sometimes called the Global Conveyor Belt.
The heat in the water is carried to higher latitudes by ocean currents where it is released into the atmosphere. Water chilled by colder temperatures at high latitudes contracts thus gets more dense.
In some regions where the water is also very salty, such as the far North Atlantic, the water becomes dense enough to sink to the bottom. Mixing in the deep ocean due to winds and tides brings the cold water back to the surface everywhere around the ocean.
Some reaches the surface via the global ocean water circulation conveyor belt to complete the cycle. During this circulation of cold and warm water, carbon dioxide is also transported. Cold water absorbs carbon dioxide from the atmosphere, and some sinks deep into the ocean. When deep water comes to the surface in the tropics, it is warmed, and the carbon dioxide is released back to the atmosphere.
Salinity can be as important as temperature in determining density of seawater in some regions such as the western tropical Pacific and the far North Atlantic. Rain reduces the salinity, especially in regions of very heavy rain. Some tropical areas get 3, to 5, millimeters of rain each year.
Evaporation increases salinity because as evaporation occurs, salt is left behind thus making surface water denser. Evaporation in the tropics averages 2, millimeters per year. Although you are putting the same amount of heat on both substances, the pot responds quicker than the water because water has a high heat capacity. Heat capacity is a measure of the heat required to raise the temperature of 1g of a substance by 1 Celsius.
In this example, water has a very high heat capacity, which means it requires a lot of heat or energy to change temperature compared to many other substances like the pot. Additionally to temperature, it takes a tremendous amount of energy to change the water molecules from one state to another.
In Earth, we have all three states of water - solid, liquid, and gas - and they're actually resistance from going back and forth from one state to another because of water's heat capacity. This relates to our ocean since the presence of the ocean moderates our daily lives and weather quite a bit in California through the amount of water molecules in the air.
Water has an especially high heat capacity at 4. This same concept can be expanded to a world-wide scale. The high heat capacity of water helps regulate global climate, as the oceans slowly absorb and release heat, preventing rapid swings in temperature see section 8. If water did not have such a high heat capacity, the temperature of Earth would change violently with the changing of day to night. The oceans would become frigid at night and boil during the day.
This world would be very difficult to survive in. A high specific heat of a substance means that a large amount of heat is required to raise the temperature of the substance. A relatively constant temperature without spikes and drops is essential to sustain life, as most organisms require temperatures to remain within a narrow range for their survival.
Thus, heat energy in the ocean can warm the planet for decades after it was absorbed.
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