Antarctic Ice Sheets Caused Ancient Mediterranean Sea To Dry Up

Scientists found, in a study, that the expansion of the Antarctic ice sheet caused the Mediterranean Sea to dry up 5.6 million years ago, according to a study at the University of Otago in New Zealand.

The drying of the Mediterranean was referred to as the Messinian Salinity Crisis (MSC), where the sea became a 1.5km deep basin for about 270,000 years. This was followed a deep layer of salt, after the seawater evaporated.

"We determined that the continent's ice was indeed growing in the lead up to the MSC, but the timings of key events did not precisely match," Dr. Christian Ohneiser, lead author of the study and geologist, said in a news release.

Scientists have debated and questioned the cause of the MSC for many years, however, Ohneiser and his team of researchers took a different angle in resolving the mystery.

The researchers studied 60 sedimentary drill cores from Antarctica. By using a computer model of the earth, they were able to evaluate the growth of the ice sheet in Antarctica and the environmental impacts. They found that as the Mediterranean Sea started to become dry, the earth's crust at the Strait of Gibraltar began to elevate, since the load from the water was removed. The Strait of Gibraltar is the entry point into the Mediterranean Sea from the Atlantic Ocean and it is nine miles (14 km) wide at its narrowest point.

"This kept the Mediterranean isolated from the Atlantic Ocean until the crust began to relax and sink. At the same time, Antarctica began to melt, raising sea levels again," said Ohneiser. "We found that the Antarctic ice sheet had an uneven effect on the global sea level because its growth resulted in a complex interplay between gravitational and rotational effects and the deformations to the Earth's crust caused by ice advance and retreat."

The rising sea levels 5.33 million years ago were adequate to flood over into the thin land bridge at Gibraltar, and the sea was then refilled by this flood, according to Ohneiser. In previous studies, researchers found that the Zanclean flooding refilled the Mediterranean in a few years.

"Future melting of the large Southern or Northern hemisphere ice masses will result in an uneven rise in sea-level around the world and this should be factored into future climate change scenarios," Ohneiser said.

The findings of this study were published in the journal Nature Communications.

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