Causes Of Sea Level Rise

Rising Seas The causes

Sea levels have been rising since the peak of the last ice age. In the last 20,000 years, sea levels have climbed an estimated 100m. By 2100 global sea levels are expected to rise by a total of 9 to 88 cm over the levels in 1990.

Other Causes Vertical Landmass Movement is caused by Plate Tectonics. Oceanic Plates are being sub-ducted under the Continental Plates causing the Continental ones to rise and therefore experience little rise in sea level. The rift zones open as a plate tears in two creating both hills and valleys. Some of the Landmasses are Rebounding. During ice ages, massive glaciers push continents down into the lithosphere. When the weight is removed, the continents rise back slowly, relatively decreasing the rise in sea level Another cause is the Compaction of Underlying Sediments. Sediments (matter deposited by water, air or ice) are being compressed causing the rise in sea level to increase

Global Warming as a cause of Rising Sea Levels It can be done through Thermal Expansion. Water expands when heated without change in mass. Increasing the mass of the ocean can also cause a rise in sea levels. Adding water to the ocean by melting of the continental glaciers is responsible for that. All of these are direct causes of global increase in temperature, which takes place partially because off the emmition Measuring Sea-Level Sea levels were measured since the 17th century by Dip-stick like Tide Gauges affixed to a pier. However, there was no control over the relative movement of the pier or larger landmass. The purpose of those was strictly for navigational purposes and there was no strict data collection. Around 1850, Stilling wells were introduced. They were composed of a pipe with a small hole in the bottom to let the water in and a float, which moves a rod attached by wire to a recording device. The small hole at the bottom of the pipe can let in only a fixed amount of water at a time, making it possible to obtain measurement of sea levels that are relatively independent of wave activity. By 1990 a new method of Echolocation was introduced. It worked like stilling wells, but using sound waves, which bounce off the surface of the water to measure sea levels electronically.

In 1992 a Satellite Altimeter (TOPEX/Poseidon) was sent into space. It bounces radar beams off the surface of the ocean to determine sea level in relation to the center of the earth (accuracy of 3.1 mm). It shows an annual rate of rise in sea level of about 2.8mm

Tuvalu – a country to disappear

Tuvalu is made up of 9 atolls. Its combined area is about 23 000 square meters. With population of 4,000 and GNP of only about $11 million it is a society concentrated on family and community values. There is almost no tourism, but there is 100% literacy rate and virtually no violent crime. Most of Tuvalu is less than 1,5 m above sea level and since sea levels rose 20-30 cm in the last century and may rise 100 cm in the next, Tuvalu constantly experiences increase in flooding and higher rates of erosion. Salt water intrusion contaminates drinking water and makes agriculture harder. One day Tuvalu will disappear so its people have to choose to either stay and wait for death or emigrate and watch their culture disappear. So far, most chose to stay.