Using ice cores, tree-ring records, and log books of mariners who plied Arctic waters hundreds of years ago, researchers have discovered that the extent of sea ice between Greenland and Svalbard is lower today than it has been in 800 years.
Writing in the journal Climate Dynamics, the researchers also found that the 20th century saw the lowest sustained maximum extent of sea ice in the region since the year 1200.
By combining ice core and tree ring “proxy records” with data from logbooks of whalers and fishermen who travelled to the boundary of the sea ice, the researchers were able to reconstruct many ups and downs over time, according to Aslak Grinstead, a geophysicist at the University of Copenhagen. They found that even though the 13th century was very warm and sea ice sparse, it could not compete with declines seen during the 2oth century.
That finding is significant because global warming skeptics claim the warming we are experiencing today was rivaled by that of the Medieval Warm Period. Their reasoning is that since the warming of that period was perfectly natural, so could the warming of the present period. Now, the reconstruction of sea ice conditions dating back to the Medieval Warm Period shows that what at least one region of the Arctic has been experiencing is indeed unprecedented.
Meanwhile, a daily update of Arctic sea ice conditions by the National Snow and Ice Data Center shows that the extent right now is well below the 1979 to 2000 average: