The Role of Oceans |
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"Ocean water and currents affect climate. Because it takes
far more energy to change the temperature of water than land or air, water
warms up and cools off much more slowly than either. As a result, inland
climates are subject to more extreme temperature ranges than coastal
climates, which are insulated by nearby water.
Over half the heat that reaches the earth from the sun is absorbed by the ocean's surface layer, so surface currents move lots of heat. Currents that originate near the equator are warm; currents that flow from the poles are cold." (Smithsonian Ocean Planet) "The planetary water supply is dominated by the oceans (see Table 8b-1). Approximately 97 % of all the water on the Earth is in the oceans. The other 3 % is held as freshwater in glaciers and icecaps, groundwater, lakes, soil, the atmosphere, and within life." (Michael J. Pidwirny) Table 8b-1: Inventory of water at the Earth's surface.
"Water is continually cycled between its various reservoirs. This cycling occurs through the processes of evaporation, condensation, precipitation, deposition, runoff, infiltration, sublimation, transpiration, melting, and groundwater flow. Table 8b-2 describes the approximate residence times of water in the major reservoirs. On average water is renewed in rivers once every 16 days. Water in the atmosphere is completely replaced once every 8 days. Slower rates of replacement occur in large lakes, glaciers, ocean bodies and groundwater. Replacement in these reservoirs can take from hundreds to thousands of years. Some of these resources (especially groundwater) are being used by humans at rates that far exceed their renewal times. This type of resource use is making this type of water effectively nonrenewable." (Michael J. Pidwirny) Table 8b-2: Approximate residence time of water found in various reserviors.
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1.Area:
covers 70% of the Earths surface
Volume: 97% of
all the water on the Earth
Depth:
4 kilometers
3.Density:
1034-1035 kg/m3
(Pure water: 1000 kg/m3)
over 90% of the ocean. Depends on temperature and salinity.
cold
water
ā
high density
loss
of water by evaporation
ā
increase salinity
ā
high density
precipitation and river discharge
ā
decrease salinity
ā
low density
4.Heat
capacity: high compared to land
5.Temperature:
less variable than in the atmosphere
6.Freezing
point: 1.9°C,
not at 0°C
because of salinity
7.Surface
is not level
due to
currents, waves, atmospheric pressure differences, and variations in
gravity.
8.Two
main forms of circulation:
wind-driven circulation
(horizontal, surface waters, fast)
thermohaline circulation
(vertical, deep waters, slow)
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Additional Readings: | |||||||||||||||||||||||||||||||||||||||||||
El Nino / Southern Oscillation | |||||||||||||||||||||||||||||||||||||||||||
There has been a confusing range of uses for the terms El Niņo, La Niņa and ENSO by both the scientific community and the general public. I hope by taking this course students will have a better understanding of their meanings. | |||||||||||||||||||||||||||||||||||||||||||
What is the Southern Oscillation? What is the Southern Oscillation Index (SOI)? | |||||||||||||||||||||||||||||||||||||||||||
What is the Walker Circulation? | |||||||||||||||||||||||||||||||||||||||||||
What is El Nino? How often do El Nino events occur? | |||||||||||||||||||||||||||||||||||||||||||
What is La Nina? | |||||||||||||||||||||||||||||||||||||||||||
What is ENSO? Oceanic characteristics of ENSO and atmospheric characteristics of ENSO. Links between atmosphere-ocean in ENSO. | |||||||||||||||||||||||||||||||||||||||||||
How ENSO is developed? Nature and effects of oceanic Kelvin and Rossby waves in El Nino events. | |||||||||||||||||||||||||||||||||||||||||||
How does ENSO influence the world climate? | |||||||||||||||||||||||||||||||||||||||||||
Can ENSO be predicted? | |||||||||||||||||||||||||||||||||||||||||||
How ENSO is monitored? Range and nature of indices used to indicate the state of ENSO (El Nino or La Nina). | |||||||||||||||||||||||||||||||||||||||||||
Typical impacts of ENSO events (temperature and precipitation). ENSO and the climate in the USA in general, and in Texas in particular | |||||||||||||||||||||||||||||||||||||||||||
El Niņo. "El Niņo translates from Spanish as 'the
boy-child'. Peruvian anchovy fishermen traditionally used the term - a
reference to the Christ child - to describe the appearance, around
Christmas, of a warm ocean current off the South American coast, adjacent to
Ecuador and extending into Peruvian waters. El Niņo affects traditional
fisheries in Peru and Ecuador, In most years, colder nutrient-rich water
from the deeper ocean is drawn to the surface near the coast (upwelling),
producing abundant plankton, food source of the anchovy. However, when
upwelling weakens in El Niņo years, and warmer low-nutrient water spreads
along the coast, the anchovy harvest plummets. It was ruined in the four or
five most severe El Niņo events this century." (Bureau of Meteorology,
Australia) "The South American El Niņo current is caused by large-scale interactions between the ocean and atmosphere. Nowadays, the term El Niņo refers to a sequence of changes in circulations across the Pacific Ocean and Indonesian archipelago when warming is particularly strong (on average every three to eight years). Characteristic changes in the atmosphere accompany those in the ocean, resulting in altered weather patterns across the globe." (Bureau of Meteorology, Australia)
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Additional Readings | |||||||||||||||||||||||||||||||||||||||||||
El Nino and US Climate
Full-Text Resources
Cartoons |
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Last updated on 01/05/10 03:25 PM by Zong-Liang Yang |