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Sci Tech
A warming climate can support glacial ice
A new study in the January 11 issue of the journal Science examines geochemical and sea level data retrieved from marine microfossils deposited on the ocean floor 91 million years ago during the Cretaceous Thermal Maximum. This extreme warming event in Earth’s history raised tropical ocean temperatures to 35-37°C (95-98.6°F), about 10°C (18°F) warmer than today, thus creating an intense greenhouse climate.
Using two independent isotopic techniques, researchers at Scripps Institution of Oceanography studied the microfossils to gather geochemical data on the growth and eventual melting of large Cretaceous ice sheets.
The researchers compared stable isotopes of oxygen molecules (d18O) in bottom-dwelling and near-surface marine microfossils, known as foraminifera, to show that changes in ocean chemistry were consistent with the growth of an ice sheet.
The second method in which an ocean surface temperature record was subtracted from the stable isotope record of surface ocean microfossils yielded the same conclusion.
Challenging beliefs
The new research challenges the generally accepted belief that substantial ice sheets could not have existed on Earth during past super-warm climate events.
The study by the researchers provides strong evidence that a glacial ice cap, about half the size of the modern day glacial ice sheet, existed 91 million years ago during a period of intense global warming.
This study offers valuable insight into current-day climate conditions and the environmental mechanisms for global sea level rise, according to a Scripps Institution of Oceanography press release.
The study found strong evidence that an ice sheet about 50-60 percent the size of the modern Antarctic ice cap existed for about 200,000 years.
The authors suggest that climate cycles may have favoured ice growth during a few times in the Cretaceous when natural climate variations produced unusually cool summers.
Likewise, high mountains under the modern Antarctic ice cap could have been potential sites for growth of large ice masses.
Ice sheets were much less common during the Cretaceous Thermal Maximum than during more recent ‘icehouse’ climates. Paradoxically, past greenhouse climates may have aided ice growth by increasing the amount of moisture in the atmosphere and creating more winter snowfall at high elevations and high latitudes, according to the paper’s authors.
— OUR BUREAU
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