Long Term Perspectives For Arctic Sea Ice
By Paul Homewood
Map showing maximum (April) sea ice extension in the Atlantic sector of the Arctic (Norwegian Polar Institute 2000). The map is based on a database on sea ice extension in the area shown during the past 400 years, to a high degree based on written records found in ships logbooks.
While we get excited about short term changes in Arctic sea ice extent, it is worth looking at some of the movements back and forth over the last 300 years. The above map is courtesy of
the sea ice database established at the Norwegian Polar Institute by Torgny Vinje.
Note how far sea ice expanded between 1769 and 1866. Unfortunately, nothing is shown for the warm period in the 1930s and 40s, but HH Lamb records, in Climate, History and the Modern World, how sea ice greatly expanded in what the Icelanders call the Sea Ice Years, beginning in 1965:
The cooling of the Arctic since 1950-60 [bear in mind the book was published in 1982] has been most marked in the very same regions which experienced the strongest warming in the earlier decades of the 20thC, namely the central Arctic and northernmost parts of the two great continents remote from the world’s oceans, but also in the Norwegian-East Greenland Sea….
A greatly increased flow of the cold East Greenland Current has in several years (especially 1968 and 1969, but also 1965, 1975 and 1979) brought more Arctic sea ice to the coasts of Iceland than for fifty years. In April-May 1968 and 1969, the island was half surrounded by ice, as had not occurred since 1888.
Such sea ice years have always been dreaded in Iceland’s history because of the depression of summer temperatures and the effects on farm production….. The 1960’s also saw the abandonment of attempts at grain growing in Iceland, which had been resumed in the warmer decades of this century after a lapse of some hundreds of years…
Clearly there is nothing “normal” about the period when satellite measurements of Arctic ice began.
Neven points out that there is some confusion about the 1769 line on the map. Whilst the Norwegian Polar Institute state it is for April, another paper by Isaakson et al label it as August.
I have just posted further clarification on this matter here.