Climate Number: 1,450 Years
The September/October Arctic sea ice annual minimum this year was the second lowest minimum on record for the 33 year period of satellite observations. The lowest minimum was recorded in 2007. But how do these ice extents relate to what the sea ice has done over the past several hundred or thousand years? Known relationships between interannual variability of Arctic sea ice and weather in other areas of the Arctic exist – weather influences things like ice accumulation, tree growth and lake sediment deposition. Analysis of ice cores (particularly from the Greenland Ice Sheet), tree rings and core samples taken from lake bottoms can be used to reconstruct the weather in the Arctic and the historical extent of Arctic sea ice. Through this analysis, researchers have pieced together the past 1,450 years of Arctic sea ice, with a record extending back to 561 A.D. The analysis shows that the extent of the Arctic sea ice does not necessarily fluctuate with global temperature trends inferred from other proxy records. For example, sea ice was at a lower extent near the beginning of the Dark Ages Cold Period from 600 to 900 A.D. than it was during the Medieval Warm Period. This suggests that changes in the transport of warm waters from the North Atlantic into the Arctic Ocean have been the primary driver of variability in Arctic Sea Ice extent over the past 1,450 years. The analysis also suggests that shrinking of Arctic Sea Ice over the past few decades and the recent satellite records for minimum extent have no precedent during this 1,450 year period.
Seasons: Winter, Spring, Summer, Fall
Source: Kinnard, C et al. “Reconstructed changes in Arctic sea ice over the past 1,450 years.” Nature 479 (2011): 509-512.