Tuesday, November 18, 2014

New paper finds sea levels were 25 feet higher & partial collapse of Antarctic ice sheet during last interglacial

A paper published today in Quaternary Science Reviews finds sea levels during the last interglacial 125,000 years ago were ~7.6 meters or 25 feet higher than the present. According to the authors, melting of the polar ice sheets contributed ~5-8 meters to this peak and likely involved a partial collapse of the Antarctic Ice Sheet.

The paper adds to many others finding sea levels were ~20 - 66 feet higher than the present during the last interglacial, as well as during multiple other interglacials over the past 500,000 years to 5.3 million years. Thus, there is absolutely no evidence that the [decelerating] sea level rise over the past ~20,000 years during the present interglacial is unusual, unprecedented, or unnatural in comparison to prior interglacials, and thus, no evidence of a man-made influence on sea levels. 

Peak eustatic sea level (ESL) for MIS 5e estimated at ∼7.6 ± 1.7 m above present.
Polar ice sheets contributed ∼5–8 m of ice-equivalent sea level to this peak.
Partial collapse of Antarctic ice sheet may have occurred early in MIS 5e.
Gradual sea-level rise of ∼0.2 m ka−1 recorded between ∼129 and 125 ka.


In the search for a record of eustatic sea level change on glacial–interglacial timescales, the Seychelles ranks as one of the best places on the planet to study. Owing to its location with respect to the former margins of Northern Hemisphere ice sheets that wax and wane on orbital cycles, the local—or relative—sea level history is predicted to lie within a few meters of the globally averaged eustatic signal during the Last Interglacial period. We have surveyed and dated Last Interglacial fossil corals to ascertain peak sea level and hence infer maximum retreat of polar ice sheets during this time interval. We observe a pattern of gradually rising sea level in the Seychelles between ∼129 and 125 thousand years ago (ka), with peak eustatic sea level attained after 125 ka at 7.6 ± 1.7 m higher than present. After accounting for thermal expansion and loss of mountain glaciers, this sea-level budget would require ∼5–8 m of polar ice sheet contribution, relative to today's volume, of which only ∼2 m came from the Greenland ice sheet. This result clearly identifies the Antarctic ice sheet as a significant source of melt water, most likely derived from one of the unstable, marine-based sectors in the West and/or East Antarctic ice sheet. Furthermore, the establishment of a +5.9 ± 1.7 m eustatic sea level position by 128.6 ± 0.8 ka would require that partial AIS [Antarctic Ice Sheet] collapse was coincident with the onset of the sea level highstand.

New paper finds sea levels rose up to 8 times faster & to much higher levels during the last 5 interglacials

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