Scientists reconstructed the climatic development of the Arctic Ocean during the Cretaceous period, and determined a severe "cold snap" occurred.
The Cretaceous period, which took place 145 to 66 million years ago, was characterized by an extreme greenhouse climate and was one of the warmest periods in known history, Goethe University, Frankfurt reported. During this period, the poles were too warm to contain ice, and average ocean temperatures were at about 95 degrees Fahrenheit.
"A typical greenhouse climate; some even refer to it as a 'super greenhouse,'" said Professor Jens Herrle of the Goethe University and Senckenberg Biodiversity and Climate Research Centre. "We have now found indications in the Arctic that this warm era 112 to 118 million years ago was interrupted for a period of about [six] million years."
To make their findings, the researchers took samples from the Arctic Fjord Glacier and the Lost Hammer diapir locality on Axel Heiberg Island.
"In so doing, we also found so-called [mineral] glendonites," Herrle said. "These so-called pseudomorphs from calcite to ikaite are formed because ikaite is stable only below [eight] degrees Celsius and metamorphoses into calcite at warmer temperatures. Thus, our sedimentological analyses and age dating provide a concrete indication for the environmental conditions in the cretaceous Arctic and substantiate the assumption that there was an extended interruption of the interglacial period in the Arctic Ocean at that time."
The rocks were analyzed using geochemical and paleontological methods, allowing the researchers to look to the past for new insights into climate change and ocean circulation under extreme global temperatures. In order to gain this knowledge, researchers must determine what processes contribute to changes in climate under these temperatures. The researchers believe that in the case of the ancient cold snap, the opening of the Atlantic coupled with ocean circulation changes caused more carbon to be incorporated into sediments, resulting in a decrease in atmospheric carbon dioxide and subsequent global cooling.
The findings were published in a recent edition of the journal Geology.