The Mystery of the Vanishing Ice Pack
Published on 28.05.2007 - The Arctic Arc
Following the rapid dislocation of the sea ice in the Lincoln Sea, around the mouth of the Robeson Channel, from the 8th of May to the 19th of May, the expedition was forced to change its route. The question lying in most peoples' minds was "Is this a bad thing? What's going to happen next?"
To avoid the rapidly disintegrating pack ice to the west which was blocking the entrance to the Victoria Fjord, it was urgent that the Arctic Arc Expedition change direction on approaching the Greenland coast. Would the team be able to safely cross the safe ice "bridge" which lies over the older ice towards Greenland, or would they be in danger due to the combination of the shattering ice to the west and of the rapid drift and developing leads to the east? If things went for the worse, how much time would we have to go and get them before they were lost in the Fram Straits?
It became urgent to get rapid answers to these questions. If the phenomenon underhand in the Lincoln Sea were an anual and natural event, then it would probably follow a more or less recognisable pattern, and we would have certain clues as to the outcome.
- So was this event normal?
- If, however, it turned out to be an anomaly, what caused it?
- Was there any way of predicting from previous years' ice behaviour what might have happened next?
The Ice Man
With all these questions running through my mind, I took the plane to Copenhagen last week to see the Ice Man himself. The Ice Man, Leif Toudal Pedersen, is something of a legend in Polar circles. Based at the Danish Technical University campus at Lyngby, he works for the recently merged entity called the Danish National Space Centre.
The one defining feature of Leif is that he never seems to sleep, and anytime, day and night, if you ever need a sea ice chart of the Arctic or Antarctic, just name it, send out a message to Leif. He will magically and in no time bring together all that you need and he will walk you through all the dangers on sea, like a modern wizzard.
Leif Toudal Pedersen is a member of the PolarView team, and acts as a user friendly interface between the European Space Agency, and its client groups, collecting data on demand and making it useable in practical "field" situations.
Leif takes the enormous data files ceaselessy churned out ("acquired") by the satellites, extracts the useful information, compresses it down until it is small enough to squeeze through the narrow-bandwidth connections of the roving satellite data links, and then delivers it to the very ends of the Earth. Leif was also on hand during the last Antarctic season to provide the Norwegian and Belgian Antarctic Research Expeditions (BELARE and NARE), aboard the ice class ship the Ivan Papanin, with the means to safely navigate through the pack ice on their approach to 5° East and to Breid Bay to unload their cargo.
My questions to Leif were very simple. Firstly, "Was the opening of the Robeson Channel in May a normal yearly occurrence?"
Leif was totally clear. Without a doubt, in no way was this a normal event. Not only was the Robeson Channel already open in May, months before schedule, but it appeared that the channel had not closed up at all during the winter, something which was again highly unusual.
The next step was to find out if satellite information could be found to support that view. Satellite observation techniques, while becoming increasingly more sophisticated, are still a relatively young science in historical terms. Available data does not go back very far, meaning that any conclusion based on this method should be carefully interpreted. In addition, archived data is often patchy and incomplete. It is difficult to find everything you need to build up a complete picture based on only one set of data. Several sets from different sensor instruments have to be lined up in order to build up a complete picture.
Satellites hover over the Earth, like giant bugs, "sensing" different sections of the electromagnetic spectrum which is irradiated from the surface of the Earth. Much as a bee can see UV radiation which is invisible to humans, satellites can "see" radar and infrared parts of the spectrum. The MODIS and MERIS sensors can provide easy to understand images using the visible spectrum. In parallel with the radar images available, it quickly emerged that archived images dating back to 2001 mainly confirmed what Leif had said: the Robeson Channel is not usually open in May.
The anomaly can be seen most clearly in comparing the satellite images from 2002 and 2007 for the month of May. In 2007 the channel is open all the way south west through the Kane Basin to the Smith Sound exit on Baffin Bay.
Is this bad?
The burning question is "What's most likely to happen next?". Once more, as this is an unusual event, it will be difficult to predict the future. The last break up of this kind in the Lincoln Sea was recorded in 2004. In comparing images from May and July 2004, another surprise emerges. The ice does not evacuate to Baffin Bay the way it does this year. The plug in the Robeson Channel is persevering, and the lead refreezes.
As this year's situation is not comparable to any other for which we have data, we have no choice but to wait and see what happens next. It is too early to say at present how the combination of global warming and cyclonic activity are responsible for this situation. But as data begins to come in, first explanations will not be too far behind.
There are some favorable conditions on the expedition's side.
- First of all, the drift is not too rapid, southerly for the most part. Leif has calculated that it can bring a positive contribution of up to 4km a day.
- Second of all, the route covers multi-year ice which is less likely to break unless there is powerful cyclonic activity.
- And, finally, the team is getting lighter as they use up the food reserves and their approach to Greenland is picking up in pace despite the awful terrain conditions and the deep drifts resulting from the daily heavy snow fall ...
Everything seems to be set for the final dash to the coast.
Gigi Johnson, IPF