Ocean temperatures are also rising briskly. In the period from January to October 2014, the oceans were almost half a degree warmer than the average of the reference period 1961-90 and therefore warmer than in any other year in recorded history. Sea levels are also rising with the rising temperatures, partly due to the thermal expansion of the water and partly due to the melting glaciers.
Ice and glaciers
The extent of sea ice in the Arctic fell in summer to its 6th lowest level since measurements began and the trend towards shrinkage observed in recent years continued. The linear trend from 1979 to 2014 shows a decline of 13.3% ice area per decade for the month of September (when the annual minimum is reached) compared to the middle of the period 1981-2010.
In the Antarctic, on the other hand, a new September high was reached and a slightly positive trend (1.3% per decade) continues. It is not clear where this increase comes from. Possible explanations include a strengthening of the westward drift around Antarctica and/or the fact that the salinity of the sea is decreasing due to the influx of fresh water (produced by melting ice shelves), which promotes freezing.
For the Alpine glaciers, the hydrological year (October 1 to September 30 of the following year) was different in 2014. While low-lying glaciers lost mass again, some smaller, high glaciers, whose tongues had already retreated from the valleys, were able to gain mass in some cases. The mass balance of a glacier indicates how much mass disappears or is added per year averaged over the glacier area. Some small Tauern glaciers recorded slightly positive balances in 2014, such as the Stubacher Sonnblickkees, the Kleinfließkees and the Mullwitzkees. The Vernagtferner in the Ötztal Alps is more or less balanced for the first time in 30 years, while the directly neighboring Kesselwandferner is clearly positive. The Kesselwandferner has already retreated further upwards and is smaller and therefore more responsive.
It may have been a warm year, but the Alpine summer was also quite rainy and summer snowfalls at high altitudes slowed down the ice melt on the glaciers considerably. The positive balances, or rather the less negative balances compared to previous years, are the result of heavy winter snowfall, at least in the south, and the wet summer, with the latter probably being the decisive factor.
