Imagine wanting to explore a rich pine forest during vacation --- in the Arctic. That's the way things were before, say scientists, and, with the way things are progressing with global warming, that's the way the Arctic could be again.
New research reveals the Arctic about 3.6 million years ago enjoyed a climate considerably warmer than it experiences now, according to a new study published in the journal Science.
An international team of scientists analyzed sediment cores collected in 2009 from Lake El'gygytgyn (pronounced El-Gee-Git-Kin), the oldest deep lake in the northeast Russian Arctic. The samples enabled the scientists to peer back into the Arctic's climate history dating from 2.2 million to 3.6 million years ago, during the middle Pliocene and early Pleistocene epochs, before the ice ages set in.
The researchers found that during that time, the Arctic had summer temperatures about 14 degrees Fahrenheit (8 degrees Celsius) warmer than they are in the region now, Julie Brigham-Grette, a professor in the department of geosciences at the University of Massachusetts Amherst and lead study author, told LiveScience.
"There was probably no sea ice, and the whole Arctic was pretty well forested, so it was a very different world..."to get Douglas fir and hemlock that far north of the Arctic Circle, you have to have pretty warm summers and warm winters in order for those trees to establish there," she said. "So, how did we go from that to the tundra that we have today, and what does this tell us about the future?"
Lake El'gygytgyn was formed 3.6 million years ago when a meteorite hit Earth and carved out a crater measuring 11 miles (18 kilometers) across. The lake is one of the few Arctic areas not eroded by continental ice sheets during the following ice ages, which means it has collected a continuous --- and undisturbed --- sediment record, the researchers said.
Lake E, as it's called by researchers, is currently covered in ice for most of the year and is so deep that if the Washington Monument, which stands 555 feet and 5â…› inches (169.294 m), were placed inside of it, the tip of the great marble obelisk would break the surface, Brigham-Grette said.
Previous research found the proportion of carbon dioxide in the atmosphere during the time of the meteor impact was similar to the levels recorded today.
Climate scientists this week saw the world's overall carbon dioxide level top 400 parts per million --- meaning 400 molecules of carbon dioxide in the atmosphere for every 1 million air molecules. That passes the previous high mark set 3 million years ago.
"We can see that the Arctic is quite sensitive to carbon dioxide changes and levels in the Pliocene were thought to be similar to today," Brigham-Grette said. "Some of the changes we see going on now - sea ice melting, tree lines migrating and glaciers with tremendous ablation rate - suggest that we're heading back to the Pliocene."
Brigham-Grette explained researchers are so focused on the weather of the past because "we want to know these mechanisms so we can understand better if the climate system has real, serious tipping points...As we get warmer, is there a tipping point where the climate would shift into a different kind of regime that we would be worried about? Understanding the past helps inform us of what the future might hold for us."