Continuation of the notes
Light Transmission in Seawater -
Greenhouse Effect -
Oceanic Climatic Regions -
The sun radiated energy across the entire electromagnetic spectrum.
The most intense radiation radiated by the sun is in the visible region of the electromagnetic spectrum.
Within 1 m of the surface of the ocean, only 40% of the incident visible light remains, i.e. 60% is absorbed.
At a depth of 100 m, only 1-2% of incident visible light remains.
Differential absorption of visible light occurs in water.
The longer red wavelengths are absorbed rapidly, whereas the shorter blue-green wavelengths are transmitted to deeper depths.
The sun radiated across the electromagnetic spectrum.
The sun radiates most of its energy as visible light.
And most of the rest is slightly shorter, UV, and slightly longer, IR.
Most incoming solar radiation (approximately 70%) is absorbed by Earth's surface and lower atmosphere.
As Earth's temperature is relatively low, averaging 18oC, most absorbed radiation is reradiated as IR radiation.
Greenhouse gases in the atmosphere absorb IR radiation and hold this energy
in the atmosphere.
The primary greenhouse gases are H2O and CO2.
The concentration of CO2 in the atmosphere is increasing.
This increase results primarily from the burning of fossil fuels: coal, oil, gas, etc.
Increasing CO2 levels results in more IR radiation trapped in the
More energy trapped in the atmosphere should lead to higher atmospheric temperatures.
The phenomenon of increasing atmospheric temperatures is called global warming.
The many detrimental effects of rapid global warming include the melting of the polar ice caps and the flooding of the nearshore environment; significant changes in weather patterns; and increased rates of extinction due to habitat loss.
There are six open-ocean climatic regions that trend east-west:
Climatic regions have surface waters with different T and S that result from differing degrees of:
Changes in T and S result in surface waters of different densities.
The equatorial climatic region straddles the equator, 0o.
Earth's meteorological equator, the ITCZ, is located about 4o N.
It is a region of low atmospheric pressure, which results in ascending air.
It is a region of weak winds called the Doldrums.
The surface waters in the equatorial region are warm all year.
It is a region of heavy precipitation.
Throughout the year, precipitation > evaporation at the equator.
This results in lower than average salinity, <34.7 ppt.
This is the region of strong Trade Winds.
The strong winds cause strong equatorial currents.
Relatively warm surface water all year.
The subtropical regions straddle 30o north and 30o south.
It is a region of high atmospheric pressure, which results in descending air.
Cool, dry air descends from the upper atmosphere.
It is a region of weak winds called the Horse Latitudes.
Small changes in surface water temperature with the seasons are observed.
It is a region of high evaporation.
Throughout the year, evaporation > precipitation in the subtropical region.
This results in the highest salinity in the open ocean, as high as 37 ppt.
The boundary between the temperate and the subpolar climatic regions is 60o north and 60o south.
Near 60o is a region of low atmospheric pressure, which results in ascending air.
The temperate climatic region contains strong winds, the Westerlies.
The strong winds cause strong surface currents.
In this climatic region, the largest seasonal changes in surface water temperatures occur, the water is cold in the winter and warm in the summer.
Heavy precipitation occurs in the low pressure part of the temperate region near 60o.
Throughout the year, precipitation > evaporation.
This results in lower than average salinity in the surface waters, as low as 33 ppt.
This climatic region contains the Polar Easterlies.
Here the surface water is cold all year, > 5oC.
Ice forms in the winter, which creates the densest water in the open ocean.
This is the region of deep water formation.
The polar region is an area of high atmospheric pressure, which results in
The temperatures are near freezing all year.
However, the atmosphere is not in contact with the ocean in this climatic region.
The continent of Antarctica is at the south pole, and the Arctic Ocean at the north pole is covered with ice.
The notes continue in Currents