Nirad Mudur/Newindpress
Bangalore, Jan 15: A new research connecting global warming with glacial melt and sea-level rise is set to stir a hornet's nest with its finding that glacial formation existed millions of years ago when global temperatures were much higher than at present.
A key discovery of glacial existence 90 million years ago (Cretaceous period), despite temperatures being 10 degrees Celsius warmer than today, has opened a whole new way for climate scientists to analyse the chemistry between warm temperatures, glacial melt and sea-level increase in today's perspective.
The study challenges the generally accepted belief that substantial ice sheets could not have existed on Earth during the Cretaceous Age about 90 million years ago, as temperatures were much higher than at present.
The study “Isotopic Evidence for Glaciation During the Cretaceous Supergreenhouse”, published in the January 11 issue of the journal `Science', is found consistent with other studies from Russia and New Jersey which showed that sea level actually fell by about 25-40 metres (82 to 131 feet) during the Cretaceous period when ice sheets were growing despite a warmer Earth.
Researchers Richard Norris, professor of paleobiology at Scripps Oceanography, and Andre Bornemann, post doctoral researcher, compared stable isotopes of oxygen molecules (d18O) from microfossils in the bottom and surface of the ocean to show that changes in ocean chemistry were consistent with the growth of an ice sheet.
The second independent method too confirmed that an ice sheet about 50-60 per cent the size of the modern Antarctic ice cap existed for about 200,000 years.
“This study demonstrates that even super-warm climates of the Cretaceous Thermal Maximum were not warm enough to prevent ice growth,” said Norris.
The study found that a glacial ice cap, about half the size of modern day glacial ice sheets, existed 91 million years ago during a period of intense global warming.
This extreme warming event then had raised tropical ocean temperatures during the Cretaceous period to 35-37 degrees C (95-98.6 degrees Fahrenheit) - - about 10 degrees C (18 degrees F) warmer than today -- creating an intense greenhouse climate.
The researchers suspect past greenhouse climates may have aided ice growth by increasing the amount of moisture in the atmosphere, creating more winter snowfall at high elevations and high latitudes to perpetuate glacier formations despite higher temperatures.
Could this recur is a question that climate scientists may have to focus on.