Sea Level History Refined

The huge rise in sea levels has been understood for some time though it isnot yet common knowledge.  These guyswent out and refined the curve as much as possible.  We are still left with averages, but the bigchanges are holding up.  Most importantthe first melt back began 19,000 years ago and I would guess that the secondmelt back began around 14,000 years ago, but was possibly masked by thecontinuation of the preceding melt back.

The unanswered question is why? There is ample support for a directed crustal shift for the second eventand I have posted extensively on this. It is reasonable that the first melt back was triggered naturally by aless than ideal first shift as has been suggested by other commentators.  This provided confirmation of the possibilityand showed what was possible if the crust was placed properly.

Otherwise we have no working theory for the ice ages that has ever stoodup unless you wish to have an hundred impossibilities before breakfast.

Like the original theory of plate tectonics, the theory of Hapwood andEinstein was dismissed because of no mechanism allowing a slippery crust.  I have overcome that omission in earlierposts and articles.  The weight ofoutright evidence forced acceptance of the first and ample evidence isavailable for the second.

In the meantime this polishes the sea level data but does not pick up thefast flood brought on by Lake Agassiz.  The resolution is not so good.

Global Sea-Level Rise At The End OfThe Last Ice Age
by StaffWriters

Southampton, UK (SPX) Dec 02, 2010

The researchers brought together about 400 high-quality sea-levelmarkers from study sites around the globe, concentrating on locations farremoved from the distorting effects of the past massive ice sheets.

Southampton researchers have estimated that sea-level rose by an average ofabout 1 metre per century at the end of the last Ice Age, interrupted by rapid'jumps' during which it rose by up to 2.5 metres per century. The findings,published in Global and Planetary Change, will help unravel the responses ofocean circulation and climate to large inputs of ice-sheet meltwater to theworld ocean.

Global sea level roseby a total of more than 120 metres as the vast ice sheets of the last Ice Agemelted back. This melt-back lasted from about 19,000 to about 6,000 years ago,meaning that the average rate of sea-level rise was roughly 1 metre percentury.

Previous studies ofsea-level change at individual locations have suggested that the gradual risemay have been marked by abrupt 'jumps' of sea-level rise at rates thatapproached 5 metres per century. These estimates were based on analyses of thedistribution of fossil corals around Barbadosand coastal drowning along the Sunda Shelf, an extension of the continental shelfof East Asia.

However, uncertaintiesin fossil dating, scarcity of sea-level markers, and the specificcharacteristics of individual sites can make it difficult to reconstruct globalsea level with a high degree of confidence using evidence from any one site.

"Rather thanrelying on individual sites that may not be representative, we have comparedlarge amounts of data from many different sites, taking into account allpotential sources of uncertainty," said Professor Eelco Rohling of theUniversity of Southampton's School of Ocean and Earth Science (SOES) based atthe National Oceanography Centre (NOC) in Southampton.

The researchersbrought together about 400 high-quality sea-level markers from study sitesaround the globe, concentrating on locations far removed from the distortingeffects of the past massive ice sheets.

Using an extensiveseries of sophisticated statistical tests, they then reconstructed sea-levelhistory of the last 21 thousand years with a high degree of statisticalconfidence.

Their analysesindicate that the gradual rise at an average rate of 1 metre per century wasinterrupted by two periods with rates of rise up to 2.5 metres per century,between 15 and 13 thousand years ago, and between 11 and 9 thousand years ago.

The first of thesejumps in the amount of ice-sheet meltwater entering the world ocean coincideswith the beginning of a period of global climate warming called the Bolling-Allerodperiod. The second jump appears to have happened shortly after the end the 'bigfreeze' called the Younger Dryas that brought the Bolling-Allerod period to anabrupt end.

"Our estimates ofrates of sea-level rise are lower than those estimated from individual studysites, but they are statistically robust and therefore greatly improve ourunderstanding of loss of ice volume due to the melting of the ice sheets at theend of the last Ice Age," said lead author Dr Jennifer Stanford of SOES.

"The new findingswill be used to refine models of the Earth climate system, and will thus helpto improve forecasts of future sea-level responses to global climate change," added Rohling.

The researchers areJenny Stanford, Rebecca Hemingway, Eelco Rohling and Martin Medina-Elizalde(SOES), Peter Challenor (NOC) and Adrian Lester (The Chamber of Shipping, London). Stanford, J. D.,Heminway, R., Rohling E. J., Challenor, P. G., Medina-Elizalde, M. and Lester,A. J. Sea-level probability for the last deglaciation: A statistical analysisof far-field records. Global and Planetary Change (Published online, November2010).

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