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New Study: Sea Level 1 Meter Higher, CO2 Lower 81,000 Years Ago
A new study has been published in the journal Science:
Sea-Level Highstand 81,000 Years Ago in Mallorca
Jeffrey A. Dorale,1,* Bogdan P. Onac,2,* Joan J. Fornós,3 Joaquin Ginés,3 Angel Ginés,3 Paola Tuccimei,4 David W. Peate1
Abstract:
Global sea level and Earth’s climate are closely linked. Using speleothem encrustations from coastal caves on the island of Mallorca, we determined that western Mediterranean relative sea level was ~1 meter above modern sea level ~81,000 years ago during marine isotope stage (MIS) 5a. Although our findings seemingly conflict with the eustatic sea-level curve of far-field sites, they corroborate an alternative view that MIS 5a was at least as ice-free as the present, and they challenge the prevailing view of MIS 5 sea-level history and certain facets of ice-age theory.
1 Department of Geoscience, University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242, USA.
2 Department of Geology, University of South Florida, 4202 East Fowler Avenue, SCA 528, Tampa, FL 33620, USA; and Department of Geology, Babes-Bolyai University, Emil Racovita Institute of Speleology Cluj, Romania.
3 Departament de Ciències de la Terra, Universitat de les Illes Balears, Carretera Valldemossa km 7.5, Palma de Mallorca, 07122, Spain.
4 Dipartimento di Scienze Geologiche, Università di Roma III, Largo St. Leonardo Murialdo, 1, 00146 Roma, Italy.
Excerpts:
Sea-level rises and falls as Earth’s giant ice sheets shrink and grow. It has been thought that sea level around 81,000 years ago—well into the last glacial period—was 15 to 20 meters below that of today and, thus, that the ice sheets were more extensive. Dorale et al. (p. 860; see the Perspective by Edwards) now challenge this view. A speleothem that has been intermittently submerged in a cave on the island of Mallorca was dated to show that, historically, sea level was more than a meter above its present height. This data implies that temperatures were as high as or higher than now, even though the concentration of CO2 in the atmosphere was much lower.
Because of its relation to continental ice volume, an accurate Quaternary sea-level curve has been a long-term goal of scientists interested in ice-age cycles and their causes. Ice-age theory has long assumed gradual ice buildup and more rapid ice melting in the generally accepted model of the ~100-ky cycle of glaciation. Instead, the emerging body of evidence suggests that both melting and accumulation can be very rapid during discrete intervals of time when specific conditions prevail. Furthermore, the 100-ky model of glaciation has always faced the problem that although the deep-sea 18O record is dominated by a 100-ky cycle, northern high-latitude summer insolation has negligible power in this band. Our data from Mallorca and data from other sites around the world indicate the possibility that eustatic sea level was near modern levels at ~80 ka. If this is true, the 100-ky cycle so universally accepted as the main rhythm of the Middle and Late Quaternary glaciations, in fact, applies rather poorly to ice growth and decay, but much better to carbon dioxide, methane, and temperatures recorded by polar ice.
CRN comment: The science isn’t settled!
February 22nd, 2010 at 7:54 pm
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