Warmer Gulf Stream waters melt fjord ice on Svalbard
Top image: Fieldwork on the sea ice during the recent AGF-211/AGF-212 cruise with RV Lance. Photo: Anna Sjöblom/UNIS.
For the first time the warm West-Spitsbergen current is appearing near the surface at 79° N. This means that the fjord ice on Svalbard is disappearing at great speed. The observations were made at a recent UNIS geophysics cruise.
11 May 2007
Text: Tor Gammelsrød, UNIS Adjunct Professor in Oceanography
The Arctic Geophysics courses AGF-211 (Air-Ice-Sea Interaction I) and AGF-212 (Snow and Ice Processes) spent almost two weeks on a cruise with the ice-breaker “Lance” around Svalbard. One of the purposes of the cruise was to investigate the reason why the Arctic fjord ice is melting. This issue is one of the central questions in the bipolar IPY project BIAC, which is lead from Norway.
New ice measurement method
The Arctic ice has become 35 percent thinner since the 1960’s, but to measure the ice thickness is an expensive and time consuming affair if the measurements are to be carried out from a ship.
A new instrument is being developed at the German polar research organization; Alfred Wegener Institut (AWI) in Bremerhaven. The instrument will hopefully be used to measure ice thickness by using an air plane.
Therefore, the UNIS students measured ice thickness by drilling through the ice every five meters along a 250 m long line. A plane from AWI flew over the line in 30 m height several times to test the instrument.
The results from this experiment, which was conducted in the Wahlenberg fjord on Nordaustlandet, are not yet available.
Walrus put a “bent” in measurements
The UNIS students also established an observation platform on an ice sheet north of Svalbard. The aim was to study how the ice floe moved according to currents and wind, and to conduct a series of measurements in and under the ice to study the melting processes. The turbulence under the ice is of central interest, and a series of advanced and expensive instruments were placed just below the ice. These measurements had to be cancelled unfortunately, due to an amorous walrus who tried to mate with one of the instruments. The result was a bent steel rod and aborted measurements!
On the way westwards towards Greenland, measurements were conducted on an ice floe that had survived at least one summer in the Arctic, i.e. multi-year ice. According to recent climate models, the multi-year ice will disappear by the middle of this century. This ice floe was therefore thoroughly investigated to determine the ice structure.
Warm water appearing in Kongsfjorden
On the way to and from Greenland, the West-Spitsbergen current was measured twice, at 80° and 79° N. This current consists of warm (+2 – 4 C°) Atlantic water and is an extension of the Gulf Stream system. Usually the West-Spitsbergen current disappears down to a 100 m below the surface before it reaches 79° N.
However, this year the current was active all the way to the sea surface, an observation never made before. The satellite images showed that Kongsfjorden is ice-free, so “Lance” set course towards Ny-Ålesund so we could find the reason for an open fjord. Usually there is sea ice in Kongsfjorden at this time of year, at least from the Kongsvegen glacier front and out to Ny-Ålesund. The Kongsfjorden experiences ocean swells from the northwest, which breaks up the ice; and strong winds from southeast that brings the broken ice out of the fjord. However, this year we found that the entire Kongsfjorden was filled with warm Atlantic water, so the ice had melted completely.
In the Arctic the Atlantic Ocean water appear at 100 m depth or more, and is thus isolated from the sea ice. If the Atlantic Ocean water now is starting to rise up towards the surface, the future of the spreading of sea ice is indeed in peril!