News24

Scientists pin down sea level rise

2012-03-29 16:10

London - The collapse of an ice sheet in Antarctica up to 14 650 years ago might have caused sea levels to rise between 14m and 18m, a study showed, data which could help make more accurate climate change predictions.

The melting of polar ice could contribute to long-term sea level rise, threatening the lives of millions, scientists say.

Sea levels have increased on average about 18cm since 1900 and rapid global warming will accelerate the pace of the increase, experts say, putting coastlines at risk and forcing low-lying cities to build costly sea defences.

Scientists in February said that thinning glaciers and ice caps were pushing up sea levels by 1.5mm a year, and experts forecast an increase of as much as 2m by 2100.

A very rapid sea level rise is thought to have occurred 14 650 years ago but details about the event have been unclear.

Coral

Some past sea level records have suggested glacier melt led to a 20m increase in less than 500 years.

But uncertainty lingered about the source of the melt, its force and its link to the changes in climate.

A team of scientists, including researchers from France's Aix-Marseille University and the University of Tokyo, claim to have solved the mystery which may shed light on climate change.

They reconstructed sea level changes by analysing samples of coral collected from reefs in Tahiti and dated them to determine the extent and timing of the sea level rise.

"Our results... reveal that the increase in sea level in Tahiti was between 12m and 22m, with a most probable value between 14m and 18m, establishing a significant melt water contribution from the southern hemisphere," said the authors of the study published in the journal Nature.

This implies the rate of sea level rise was more than 40mm a year, they said.

A UN climate panel on Wednesday said all nations will be vulnerable to the expected increase in heat waves, intense rains, floods and a probably rise in the intensity of droughts.

Comments
  • DuToitCoetzee - 2012-03-29 17:10

    Sjoe!!! I thought they caught me "piepie" in the sea, as usual.;)

  • John - 2012-03-30 07:12

    wow 2m by 2100. Wow you got me worried chaps!! Thanks for letting me know

  • jacques.buckle - 2012-03-30 07:55

    the southern African continent should be fine since its the highest above sea level

  • marius.dumas - 2012-04-01 23:42

    At the moment the sea level is the lowest (+/-a few meters) in 250 million years, 100 million years ago the sea level was 250m higher than now. For the last 100 million years the sea level has been coming down with a few bumps like during the last glaciered episode. If the water would rise with 250m it will be abnormal for planet earth any thing below that is still inside the natural range. If sea level would drop a few meters more it would officially be the lowest level in it entire existence. In this drop of sea level there have been many micro ups and downs as the trend is heading down. For the long term the trend is downward, meaning in terms of millions of years we might expect a further drop or a turning point as we are approaching the minima on the million year resolution. However the fact remains that sea level is dropping over the long term and doing so since it started at 250m higher than now over the last 100 million years. On the medium term, the sea level have been rising again since the last ice age due to a natural occurring global warming that bought an end to this icy period. However the last 8000 years the sea level was more stable than any ware during the 8000 to 18000 years ago period. From 18000 to 8000 years ago the water raised with about 120m while in the last 8000 years until now, it only raised with about 5 meters. In the last 8000 years, since the existence of humans we had the most stable sea level since 18 000 years ago.

      marius.dumas - 2012-04-01 23:47

      (The causes of sea level changes short term (fewer than 14months)) Diurnal and semidiurnal astronomical tides 12–24 h P = 0.2–10+ m Rotational variations (Chandler wobble) 14 month P Atmospheric pressure Hours to months= –0.7 to 1.3 m Winds (storm surges) 1–5 days < 5 m Evaporation and precipitation (may also follow long-term pattern) Days to weeks Ocean surface topography (changes in water density and currents) Days to weeks < 1 m El Niño/southern oscillation 6 mo every 5–10 yr < 0.6 m River runoff/floods 2 months =1 m Seasonal water density changes (temperature and salinity) 6 months 0.2 m Seiches (standing waves) Minutes to hours < 2 m (Long term effects) Plate tectonics and seafloor spreading (plate divergence/convergence) and change in seafloor elevation (mid-ocean volcanism) Eustatic 0.01 mm/yr Marine sedimentation Eustatic < 0.01 mm/yr Melting or accumulation of continental ice Eustatic 10 mm/yr (Climate changes during the 20th century) Antarctica (the results of increasing precipitation) Eustatic -0.2 to 0.0 mm/yr Greenland (from changes in both precipitation and runoff) Eustatic 0.0 to 0.1 mm/yr

      marius.dumas - 2012-04-01 23:49

      (Long-term adjustment to the end of the last ice age) Greenland and Antarctica contribution over 20th century Eustatic 0.0 to 0.5 mm/yr Release of water from earth's interior Eustatic Release or accumulation of continental hydrologic reservoirs Eustatic Thermal-isostasy (temperature/density changes in earth's interior) Glacio-isostasy (loading or unloading of ice) 10 mm/yr Hydro-isostasy (loading or unloading of water) Volcano-isostasy (magmatic extrusions) Sediment-isostasy (deposition and erosion of sediments) < 4 mm/yr Vertical and horizontal motions of crust (in response to fault motions) Local effect 1–3 mm/yr Sediment compression into denser matrix (particularly significant in and near river deltas) Loss of interstitial fluids (withdrawal of groundwater or oil) Local effect = 55 mm/yr Earthquake-induced vibration Shifts in hydrosphere, aesthenosphere, core-mantle interface Shifts in earth's rotation, axis of spin, and precession of equinox Eustatic External gravitational changes Eustatic Evaporation and precipitation (if due to a long-term pattern) For the few people who only know one scientific term in their vocablorary it might be hard to grasp this but so called “man made global warming” has a minority effect on water level changes. For the next thousands of years we will continue to experience slight increases in sea level.

      marius.dumas - 2012-04-01 23:49

      Consider some more facts: Surface area of Antarctica (14 million km2) Total Ocean surface 360×million km2 Water displayed for 18m rise = 360×million km2×0.018km = 6.48 million km3 ( 6.48 million km3)/( 14 million km2) = 462.8m thick The above calculation estimates that if a block of ice as big as the ENTIRE Antarctica must fall into the sea that it must be at least 462.8m (half a km thick) or in other simple words, the ice block must be much bigger than Antarctica it self to be able to displace that much water. What I try to say is that, I really doubt it is a part of Antarctica that collapse. Even if a block of ice the size of Antarctica will be dumped into the ocean will it not be able to cause that much rise in water on average. Climate change alarmist are at it again to use conditions that existed during chaotic times as we recovered from the last ice age as a propaganda tool for climate change hysteria. The Climate Gate Scandal already exposed the fraudulent tricks of the IPCC to deem them an unreliable contributor to climate science.

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