Dating of speleothems

This "basin effect" was exploited to build a sea level history in the Red Sea, because the extremely slow exchange of seawater within the basin means long local seawater residence times.

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Of particular interest is the finding that, during all periods of major global ice volume loss, rates of sea level rise reached at least 1.2 metres per century.

An arguably more important finding that the more finely resolved dating uncovered, was that major ice sheet reductions (as implied by sea level rise) followed polar warming much quicker than had previously been suspected.

The basin isolation effect of both sea level records, gave sufficient oxygen isotope signal similarity for accurate transfer.

The validity of this newly-dated sea level reconstruction was confirmed by comparison to other dated sea level benchmarks.

Many now seem to converge on 1-2 metres of sea level rise by 2100 - much higher than current rates. A recent paper, examining past ice sheet disintegrations, lends credence to these estimates.

A peer-reviewed paper, Grant (2012), outlines how the authors created a well- dated, and near-continuous, record of sea level over the last 150,000 years, a period which spans the last interglacial (the Eemian), and the last glacial maximum.

With some 60-70 metres worth of global sea level equivalent locked up in the vast ice sheets of Greenland and Antarctica, and with global warming well underway, it raises the question of how much sea level rise we are likely to see this century (and beyond), and just how fast this might happen.

Because the dynamics of ice sheet disintegration are only very crudely known, and ice sheet modelling is in its infancy, there is a large range of estimates of future sea level rise.

These consisted of long cool periods (glacials) where giant icesheets have grown on the continental land masses at, and near, the poles.

With the water evaporated off the oceans being locked up as ice on land, this ice sheet build-up substantially lowered global sea level.

Examination of oxygen-18 isotope ratios in the shells of forams, retrieved from Red Sea sediment cores, has revealed that they serve as a useful proxy for relative (i.e local) sea level in the Red Sea (see Siddall [2003] & Siddall [2004]).

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