Earth Survived an Ice Free Bering Sea: Life Improved on Earth

The earth goes through natural warming periods and natural cooling periods. Scientists who have been studying these cycles have taken core samples from the bottom of the Bering Sea and have discovered the Bering Sea went through a period where there was no ice in the sea that separates Russia from Alaska. Oh it's cold up there.

Guess what, life improved on earth because of this iceless period. That's what scientist Christina Ravelo, professor of ocean sciences at the University of California, Santa Cruz discovered and will report.

Deep sediment cores retrieved from the Bering Sea floor indicate that the region was ice-free all year and biological productivity was high during the last major warm period in Earth's climate history...

"Evidence from the Pliocene Warm Period is relevant to studies of current climate change because it was the last time in our Earth's history when global temperatures were higher than today," Ravelo said.

Carbon dioxide levels during the Pliocene Warm Period were also comparable to levels today, and average temperatures were a few degrees higher, she said. Climate scientists are interested in what this period may tell us about the effects of global warming, particularly in the polar regions. Current observations show more rapid warming in the Arctic compared to other places on Earth and compared to what was expected based on global climate models.

Ravelo's team found evidence of similar amplified warming at the poles during the Pliocene Warm Period. Analysis of the sediment samples indicated that average sea surface temperatures in the Bering Sea were at least 5 degrees Celsius warmer than today, while average global temperatures were only 3 degrees warmer than today.

Samples from the expedition showed evidence of consistently high biological productivity in the Bering Sea throughout the past five million years. The sediments contain fossils of plankton, such as diatoms, that suggest a robust ecology of organisms persisting from the start of the Pliocene Warm Period to the present. In addition, samples from the Pliocene Warm Period include deep-water organisms that require more oxygenated conditions than exist today, suggesting that the mixing of water layers in the Bering Sea was greater than it is now, Ravelo said.

"We usually think of the ocean as being more stratified during warm periods, with less vertical movement in the water column," she said. "If the ocean was actually overturning more during a period when it was warmer than today, then we may need to change our thinking about ocean circulation."