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| Current issues in Climate Science: Focus on the Poles |
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| Written by Robert Ferguson | ||||||||||||
| Friday, 13 July 2007 | ||||||||||||
Page 5 of 10
The early Holocene wasn’t the only period of extended warmth and greatly reduced sea ice that the polar bears managed to survive through. Another long much-warmer-than-present period occurred during the warm period in between the last two ice ages (known as the last interglacial). A recent project was created to pull together available data on past environments in the Arctic. The Circum-Arctic Paleo Environments (CAPE) is an activity within the International Geosphere-Biosphere Program that aims to facilitate international syntheses of Arctic records. The 25-member CAPE-Last Interglacial Project Members team recently published an article characterizing the Arctic warmth during the time of the last interglacial (LIG). The work “Last interglacial Arctic warmth confirms polar amplification of climate change” was published early in 2007 in the scientific journal Quaternary Science Reviews. Many previous works indicate that Earth was warmer during the LIG than for any other period within the past 250,000 years. However, few detailed quantitative reconstructions of the period exist. The CAPE research group quantitatively estimated circum-Arctic summer air and sea surface temperatures for the LIG as reconstructed from terrestrial- and marine-based proxy records detailed in previous research conducted by a large body of scientists. The group emphasized temperatures in summer because they “exert the dominant control on glacier mass balance” and summer temperature is “the most effective predictor for most biological processes.” The group found evidence that the LIG persisted for 10,000 to 12,000 years and that Arctic summer air temperatures during the LIG were 4 to 5ºC above present for much of the region. The warming seems to have occurred rapidly, peaking in the early portion of the LIG. The group contends that Arctic summer temperatures were warm enough “to melt all glaciers below 5 km elevation, except the Greenland ice sheet, which was reduced by ca 20-50%.” In regard to Arctic Ocean sea ice, the group states that the margins of the permanent ice “retracted well into the Arctic Ocean basin” and the ice was of an extent that was smaller than during the highly publicized ice retreat of the Holocene. When examining evidence of vegetation changes, the group concluded that “boreal forests advanced to the Arctic Ocean Coast across vast regions of the Arctic currently occupied by tundra.” In fact, across most of northern Russia, they report that forests were displaced northward by as much as 400 to 1000 km.
 Regional maximum LIG summer Arctic temperature anomalies (ºC) relative to present. (taken from Cape Project Members report, 2006). Temperature across large portions of the Arctic were several degrees above present day values.
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