8. Field report
Alert, 17 April, 2006
Receiver on the ice which was not covered with snow. Under these conditions it is easy to locate the instruments. The cooler is keeping the batteries and recorders warm. The cooler is connected to a seismometer standing on the ice recording the waves from the blastings. Enlarge
Trine Dahl-Jensen from GEUS starting up the hunt for receivers on the ice. Enlarge
Fueling of helicopter on the ice. Enlarge
Received from Ron Verral and Trine Dahl-Jensen
Edited by Henrik HÝjmark Thomsen, GEUS
The hunt for instruments with new data
13 April, 2006
Weather in Alert: -22, light wind, sunny. Warmer in the afternoon.
Finally we got flying weather and we started out to recover the 43 receivers we had left on the ice 9 April (Read 6. Field report). We were up against two things. First the ice had moved during our weather days in Alert and second we have got a lot of new snow, which could cover up the receivers. The Twin Otter left first and went to the fuel cache on the southern part of the inner line and radioed back the new coordinates. They left a satellite tracker at the location and continued north along the predicted line, and rapidly spotted several receivers. They radioed the receiver positions back to the two helicopter teams who should recover the instruments. We found all the receivers except two. We hunted a long time for the two lost boxes, and we eventually came to the conclusion, that the snow had drifted right over them. At least five of the boxes that we did find were showing only an inch or two of their orange lid; they were almost buried, too. The garbage bags that had been left with these ones were, in fact, completely invisible under all that snow. We think that we were very lucky to lose only two after the recent high winds. More good news is that all the boxes we recovered contained good data. Finally, in the good-news department, the recording wizards discovered that even after a prolonged period on the ice, the equipment inside the box was still no colder than zero degrees. This says a great deal for the design of the insulated boxes - the "coolers". More to the point, this gives us greater flexibility in our next two lines. The boxes can be left on the ice quite a few days before there is any worry of the recorders freezing.
After the successful recovery of the receivers we should find the five unexploded shots at positions IS7-11, which we also left on the ice at 9 April (Read 6. Field report). They can be used on our continued work on the outer line, which stretches further north out in the Arctic Ocean in continuation of the inner line. We had a good idea where they were since each shot had a beacon associated with it - a beacon that sends its position to Alert via satellite. By checking a web site, John Shimeld, our ice-motion watcher, can keep tabs on where they are. They were 30 km apart, so this involved quite a bit of flying. The first three were easy. There they were - just as we had left them - a little bit snow-covered, perhaps, but easily seen and in good shape. We stopped at each location, checked everything, fluffed up the garbage bags and left. When we got to location IS10, it just wasn't there. We circled and circled but found nothing. 'How can this be?', we said. 'The beacon is still sending its position.' Eventually, we gave up and went on to IS11. We found it easily. We still were not done. Site IS10 was still out there toying with us. It was sending out its location, but it was not visible. By this time we were getting low on fuel, so we went to the ice camp for gas. There we double checked the coordinates with Shimeld in Alert. The consensus was that the shot holes should be right where we were looking. So, off we went again. We went to the exact location given by the coordinates, and instead of looking over a fairly large region for something quite visible, the pilot, Gerard Hartery, turned very tight circles around the 'spot'. After a couple of turns he said, 'There it is!' What he had seen was a half-inch aluminium pipe sticking out of the snow, with a very small antenna attached to its top. Everything else was covered. These pilots seem to have the eyes of eagles. Once we landed we found a loop of primacord sticking up through the snow. This enabled us to find the roll of primacord, and, presto, number 10 site was again useful. It was a good day. All five shots were found and they are now ready to be used as some of the southernmost shots on the outer line, where we will start working the next days. We have therefore renamed the shots from IS7-11 to OS3-7, which in the local LORITA-slang means: O for outer line, S for shot and the number of the blasting position.
During the day the Twin Otter went up north along the outer line to find a suitable location to establish a northern cache for fuel and explosives. They succeeded to find at good location, which will help us during the coming days operations in this part of the line.
The BG-team, who is going to measure water depths and gravity, had their first real measurements on the southern inner line. They managed to measure at 27 positions. The work went fine, but they were slowed down by all the new snow. It was necessary for them to dig down through the snow to the solid ice to find a stable foundation for the sensitive gravimeter. In practice this meant, that they had to remove up to 60 cm of snow before they could start the measurements.
Receiver nearly covered with snow. Only the orange lid of the cooler is visible. Enlarge
John Boserup from GEUS picking up a cooler from the ice.Enlarge
John Boserup wedged into the back seat of the helicopter with seventeen coolers like a sardine in a can. And, more amazingly, he managed to have a cup of tea out of that thermos on the way back with the instruments. Enlarge
Visit at shot IS11. To the right you see the read beacon, which is sending its position to Alert. We had to dig in the snow to find the role with primacord. It connects the explosives hanging 100 m down in the ocean with the surface. We only need access to the primacord to do the blasting. Enlarge
Measurements of water depths and gravity on the ice. It was necessary to dig down through the snow to the solid ice to find a stable foundation for the sensitive gravimeter.Enlarge
A typical view from the helicopter during a flight over the ice. The large ridge in the background is pressed up by movements in the ice. Enlarge
14 April, 2006
VHF repeater on Merv's Peak. The view is out of this world. It was a perfect calm day on this location. You look down 2000 ft to the Arctic Ocean below.
Photo: Kelly Bentham.
Weather in Alert: -26,9, light wind, sunny. Warmer in the afternoon
The plan for the day was to load the northernmost shots on the outer line, but already in the morning we had to change the plan, as a large cloud system was moving in over the northern end of the line. Instead we went out to load the two southernmost shots on the outer line OS1-2. We just managed to load OS1 and drilled the hole for OS2, but we did not manage to load the shot in the last hole, due to incoming fog and low clouds making the work impossible. The helicopters returned to Alert and waited to see if this fairly small area of low clouds would move off. It did not. Instead it changed direction to move along the line.
That freed helicopter time to establish a VHF repeater on top of a near by mountain. It shall help us getting a better communication with the helicopters, when they are far out on the ice. During the earlier days we have had problems with reaching the helicopter by radio, especially when they are sitting on the ice surface. The mountain that rises about 200ft right out of the sea is located about 25 miles north of Alert. Officially, it is unnamed but local it is called Merv's Peak after Merv Black who suggested many years ago that it would make a good location for a repeater.
15 April, 2006
Map of the outer line. Green lenses show the planned shots. 17 April we have loaded shots OS1-7, and we still need to load the four northermost shots. The green squares with an aircraft symbol - Cache IS and Cache OS show the southern cache, we used during the operations along the inner line and the northern cache, we will be using during the coming operations respectively. The white square with a cross is the manned ice camp, which is also used as a cache for fuel and explosives. All the small red dots along the lines are positions where we shall deploy receivers on the ice. Here 17 April we have deployed 70. Enlarge
Weather in Alert: -24, calm, overcast morning, later sunny.
The departure from Alert was delayed until 11:30 due to cloud cover and fog over the southern part of the outer line. The Twin Otter went to the ice camp with fuel and a load of receivers to be deployed later on the day, and the helicopters went out on the outer line. The first job was to load the shot at location OS2 at the southern end of the line. Finally we succeeded to load this shot, and the rest of the day the helicopters were busy deploying receivers along the line. We would jump out of the helicopter, shovel a bare spot on the ice 10 metres, or so, away from the helicopter and place the receiver on the ice. We then shovelled snow into a couple of garbage bags and set them upside-down and off to the side. The black bags will help us find the boxes later. We then hopped back into the helicopter and headed off to the next spot, which was only 30 or 40 seconds ahead. After a long day, where we succeeded to deploy 70 instruments, we returned to Alert 23:00.
16 April, 2006
Weather in Alert: -27, calm, overcast morning, evening sunny.
It was half a weather day in Alert. The Twin Otter were busy flying fuel and explosives to the northern cache at the outer line. We had hoped to finish the deployment to day of instruments and loading of shots on the line, but the helicopters could not fly due to low clouds over most of the outer line.
17 April, 2006
Weather in Alert: -27, calm, overcast morning, evening sunny.
Another day with far from perfect weather over the outer line. No helicopter flying in the morning due to low clouds and fog. The Twin Otter was again busy flying out fuel to the northern cache, so that the helicopters can get fuel here during the coming days operations in this part of the line. At the same time the pilots reported weather conditions back to Alert along line. At 13:00 the report seemed to improve and the helicopters took off at 14:00, only to return about 200 km out due to increasing fog and bad flying conditions.