In the photo: An unusual sight: the melted water flows down a waterfall from one of the studied icebergs.
As a result of the record melting of ice in the Arctic Ocean last summer, the thickness of the ice cover in winter decreased by an average of 26 cm, which is about 10% of the average. In some large regions, the ice thickness has decreased by almost a fifth - by about half a meter.
Despite a gradual reduction in the minimum summer ice-covered area, winter ice thickness has remained approximately constant over the past five years. However, this changed last winter, say the authors of the paper accepted for publication in Geophysical Research Letters.
Scientists used data from altimeters on the European satellites Envisat and CryoSat-2, which from October last year to March this year collected a lot of data on the height of the ice surface in the region. Since the density of water and ice in Arctic conditions is practically constant, about 10% of the total volume of the ice floe usually floats above the surface. This allows you to immediately estimate the volume of the ice floe itself.
The individual accuracy of the RA-2 radar-altimeter readings, which was used to measure the height, is about 4.5 cm, which is broadcast 45 cm across the ice thickness, but the abundance of points and the random nature of instrumental errors make it possible to calculate the mean values with much greater accuracy. This is exactly what Katarina Giles, Seymour Laxon and Andy Reeda of University College London have done.
This year, the minimum area of the Arctic ice did not reach last year's record, although it dropped below all other indicators over the past decades, during which satellite observations continue. At the same time, scientists note that the Arctic summer of 2007 was abnormally warm, while this year was more or less cold in the Arctic.
In this regard, many scientists fear that the “critical point” beyond which natural regulatory mechanisms stop working - for example, the thermal inertia of old, thick ice - has already been passed, and a further reduction in the ice area will only provoke its further reduction. Therefore, the complete melting of the Arctic ice in the summer, which was previously predicted for the end of the 21st century, we can expect in the first half of the century.