Sea level

The sea level is the average height of the sea level (the surface of the sea), if all the variations that are the result of the tides to be averaged out. There are two ways to measure the height of the sea water: the absolute sea level relative to the center of the Earth relative to the sea level and with respect to the seabed.

The sea level is a result of the volume of liquid water on the Earth and of the average temperature which the average density influences on the water. Changes in absolute sea level (so-called eustatic changes) in the course of geological time scale and even in recorded history occurred. If a lot of ice in the polar caps andglaciers is stored declining sea level in glacial periods (ice ages) even many tens of meters.

The sea level is used as a reference plane to altitude to indicate locations in the country (such as airports and residences) and aircraft in the air.



Contents
*1 Changes in sea level  ==[Sea  level changes edit ]  == The change in the absolute sea level ( eustasie ) is determined by the size of the ice caps and the temperature of the sea water. Both depend on the average climate on Earth. If climate change occurs in the form of rising temperatures, the ice caps will melt and the sea water will be warmer. In both cases, increasing the absolute sea level. When temperatures drop also decreases the sea level.
 * 1.1 Effects of melting ice
 * 1.2 Developments in the 20th century
 * 2 See also
 * 3 External links
 * 4 Notes

The relative sea level depends not only on the eustasie also depend on the movement of the earth's crust and the flow of sediment to the seabed. If a lot of sediment remains on the bottom lie, the seabed will be higher and lower relative sea level. When the crust is moving down ( subsidence ) the relative sea level will actually increase. Sea levels may be altered locally while the absolute sea level remains the same. ===[Effects  of melting ice edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">]  === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Since 2.5 million years the Earth is in the Quaternary ice age, which means that there are ice caps on and around the polar regions. These ice sheets are not continuously Size: sometimes they grow (called glacial periods), sometimes they are smaller ( interglacial periods ). At this moment we are in an interglacial.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The melting of the ice sheets grow or weather greatly influences the volume of water is in the oceans. Especially in the ice sheets of Greenland and Antarctica are large amounts of water "saved".

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Until recently it was assumed that the melting of floating ice ( North Pole ) makes no difference ( Archimedes' principle ), and pack ice on land melts and lands in the sea ( Antarctica , Greenland ) sea level it raises. In a recent study by Peter Noerdlinger, however, claimed that the melting of floating zoetwaterijs indeed does the level of salt water to rise. <sup class="reference" id="cite_ref-1" style="line-height:1;unicode-bidi:-webkit-isolate;">[1] However, this effect is negligible compared to that of melting land ice.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Peter Noerdlinger arithmetic does not support its finding that the level may rise 4 cm. Assuming a capacity of about 23,000 km3 of fresh water and a North Pole sea surface of about 320,000,000 km2, sea levels would with 23000/320 000 000 * 2.5% * 1000 * 100 = 0.18 cm rise rather than as 4cm Peter indicates Noerdlinger. 2.5% is the ratio between fresh and salt water. ===<span class="mw-editsection-bracket" style="color:rgb(85,85,85);"><span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;">[Developments  in the 20th century <span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;">edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">]  === <p style="margin-top:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">During the 20th century, the sea level rose slightly, in the order of several tens of millimeters (195 millimeters between 1870 and 2004) <sup class="reference" id="cite_ref-2" style="line-height:1;unicode-bidi:-webkit-isolate;">[2] . About the absolute size of the rise in sea level is as yet not entirely agree: different methods give different results, and when measured at a place one can not distinguish between for example valleys of the country and rising from the sea. Probably the sea level increased by approximately 1.74 mm / yr in the 20th century, it should be noted that the increase in the second half of the century (1.45 mm / yr) was lower than in the first half (2 03 mm / yr). <sup class="reference" id="cite_ref-3" style="line-height:1;unicode-bidi:-webkit-isolate;">[3]

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">Also about the exact cause of the increase to date is still under discussion: this is due to melting of land ice or more of warming of the ocean water? Highly accurate satellite measurements make it easier today to follow the sea level altitude but systematic trends are sets of measurements needed to find cover those decades.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">The sea level rise has become topical due to the enhanced greenhouse effect and climate change . Scientists who are involved in this process there estimate that sea levels will rise up to 1 meter in 2100 and then will continue at the same pace. It may also lead to parts of Netherlands is exposed to a greater risk of flooding, or that one must make large investments in the seawall. Southeast of the line Breda - Amersfoort -Assen there is little danger, because that part is much higher. For poorer areas the danger is even greater than for the Netherlands, because there are few resources to keep out the sea. Many human activities are taking place on the coast and on land at sea level. Low-lying island groups like Tuvalu may eventually disappear under the sea.

<p style="margin-top:0.5em;margin-bottom:0.5em;line-height:22.3999996185303px;color:rgb(37,37,37);font-family:sans-serif;font-size:14px;">A recent international study <sup class="reference" id="cite_ref-4" style="line-height:1;unicode-bidi:-webkit-isolate;">[4] predicts rise up to 2 meters per century, so had predicted much more than the IPCC. The cause lies in the ice of Greenland that all would melt at a lower temperature rise. A significant number of scientists, however, doubt these conclusions. ==See also <span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;font-family:sans-serif;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] == ==External links <span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;font-family:sans-serif;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] == ==<span class="mw-editsection" style="-webkit-user-select:none;font-size:small;margin-left:1em;line-height:1em;display:inline-block;white-space:nowrap;unicode-bidi:-webkit-isolate;font-family:sans-serif;"><span class="mw-editsection-bracket" style="color:rgb(85,85,85);">[Notes  edit <span class="mw-editsection-bracket" style="color:rgb(85,85,85);">] ==
 * eustasie, the change in the absolute sea level
 * Normal Amsterdam Level, reference level in the Netherlands and Germany, known there as Normalnull
 * Second General Levelling, reference level in Belgium
 * Meter über Adria, reference level in Austria
 * altitude
 * water level, the interface between water and air
 * list of areas on land below sea level
 * British official website
 * Determination and interpretation
 * Environmentalists over the sea level
 * 1) ↑ The research of Peter Noerdlinger.
 * 2) ↑ John A. Church and Neil J. White (2006), A 20th century acceleration in global sea-level rise, in: GEOPHYSICAL RESEARCH LETTERS, VOL. 33.
 * 3) ↑ Holgate, SJ (2007), On the decadal rates of sea level change during the twentieth century, Geophys. Res. Lett, 34, L01602, doi:. 10.1029 / 2006GL028492.
 * 4) ↑ Article on Reuters.com