From: Andy Soos, ENN
Published December 29, 2009 10:41 AM

The Unfrozen North

There is increased evidence that the Arctic could face seasonally ice-free conditions and much warmer temperatures in the future. This has happened before.

Scientists have documented evidence that the Arctic Ocean and Nordic Seas were too warm to support summer sea ice during the mid-Pliocene warm period (3.3 to 3 million years ago). This period is characterized by warm temperatures similar to those projected for the end of this century, and is used to help understand future conditions


The US Geological Survey (USGS) has found that summer sea surface temperatures in the Arctic were between 10 to 18°C (50 to 64°F) during the mid-Pliocene, while current temperatures are around or below 0°C (32°F). The Pliocene is a time period 2.5 to 5 million years before the present year.

The Arctic Ocean is of particular interest because in this region climate models struggle to predict climate sensitivity and the response of sea ice. In order to provide the first quantitative climate data from this region during this period, sea surface temperatures were estimated from several ocean drilling sites. Evidence of much warmer than modern conditions in the Arctic Ocean during this time frame with temperatures as high as 18°C was found.

Examining past climate conditions will allow for a true understanding of how Earth’s climate system really functions.

Loss of sea ice could have varied and the consequences will have varied considerably. As examples rain fall patters would have been far different. Some deserts would have bloomed and some grasslands would have become deserts.

"In looking back 3 million years, we see a very different pattern of heat distribution than today with much warmer waters in the high latitudes,” said USGS scientist Marci Robinson. "The lack of summer sea ice during the mid Pliocene suggests that the record setting melting of Arctic sea ice over the past few years could be an early warning of more significant changes to come."

Global average surface temperatures during the mid-Pliocene were about 3°C (5.5°F) greater than today and within the range projected for the 21st century. So our present global temperatures are not as hot as they once were. The world has been here before.

Scientists have also studied conditions during the mid-Pliocene by analyzing fossils dated back to this time period. A knowledge of past animal and plant life will help understand and confirm how climate has changed in particular global locations. This plus continued scientific investigation will help a greater understanding of how climate has already changed over millions of years.

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