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Understanding sea level changes
| Name: | Description: | Size: | Format: | |
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| 126.58 MB | Adobe PDF |
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Abstract(s)
The dramatic sea level rise announced by the media and politicians, is, for the people, in general, the most known and dangerous consequence of climate change. However, talk about sea level changes without specifying the reference surface and in what the place of the Earth’s surface does not make sense. Measuring sea level is not easy. The tide gauge measurements are questionable. Altimetric measurements by satellites cover, only, the recent period and the interpretation of their results is not always consistent. In addition, as ww will see there are different types of sea level: (i) Absolute or Eustatic Sea Level ; (ii) Relative Sea Level ; (iii) Sea Surface Height. Saying that sea level will rise 4 cm (Al Gore in his book "An Inconvenient Truth" says: “6 meters”) until the end of the century without telling what sea level is taking into account is a lie by omission. On this subject, the opening remarks of President J. Chirac in the 6th conference of parties to Kyoto (Hague, November 2000): “Kyoto is the first component of an authentic global governance”, are highly significant. In this lecture, after a small introduction and a reminder of the basic conjectures, we will review the different sea level types, how we can measure them and with what precision, as well as, the main sea level changes drivers. Sea level and climate changes, implies a categorization. Taking into both the duration and magnitude of the sea level and climate drivers, Vigneau, J. P. (2005) in Climatologie textbook proposed the following hierarchization, which should always be taking into account when talking about climate or sea level changes : (i) Pulsations (4th order climate drivers), lasting a few years or a few decades and which are, perfectly, reversible (e.g., series of years of raining or drought) ; (ii) Oscillations, (3rd order) lasting from a few centuries to a few millennia, but are reversible (e.g., the Little Ice Age) ; (iii) Fluctuations, (2nd order) spreading out over tens, hundreds of thousands of years and have mark cyclic character (e.g., the evolution of the Quaternary) ; (iv) Mutations (1st order), lasted millions, tens or hundreds of millions of years that have a irreversible character (e.g., irreversible upheavals of the Earth’s surface).
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Keywords
Sea level Climate changes Geoid Earth ellipsoid Glacio-eustasy Tectono-eustasy Epeiro-eustasy Geoidal-eustasy Ocean thermal expansion Thermosteric sea level rise