10. Field report
Alert, 21 April, 2006
Isa Asudeh has just checked the six receivers left out in the cold at the ice camp. With a big smile and thumb´s up Isa signalled to us, that they were still working. This meant that we could start the shooting and after that start to deploy the receivers. Enlarge
Loading of explosives at shot location OS8 to the north at the outer line. The explosives were detonated short after. Enlarge
Flag parade at the ice camp. From left to right we have the Danish, the Canadian and the Greenland flag. We apologize that we did not have a Nunavut flag handy. Enlarge
Picture showing one of the long open leads in the sea ice, taken from a height of about 2000 ft. Along such leads shear motion can take place, when the ice is drifting. Enlarge
Received from Ron Verral and Trine Dahl-Jensen
Edited by Henrik Højmark Thomsen, GEUS
Finally - the first data from the outer line is retrieved
19 April, 2006
Weather in Alert: -24, overcast, fog.
This morning, the weather was back to its annoyingly poor state. At the morning weather briefing, we believe that the official term for the flying conditions was, "Poo-poo-kaka". It became a weather day in Alert - with no flying. The ice camp was in zero visibility all day, and here in Alert we had low clouds and fog offshore. We were waiting and used the time to discuss the plans.
20 April, 2006
Weather in Alert: -19, overcast, fog, clearing in the evening.
Another weather day in Alert - still no flying. The weather at ice camp was good in the morning, but bad in the late afternoon. In Alert we have had low visibility and fog all day. Another day of waiting. We are sure the pilots worried a bit about their helicopters, which were left at the ice camp 18. April, although they did not say anything.
The weather has far from been smiling on us during the work on the outer line. Although we succeeded to detonate three shots two days ago on 18 April (read 9. Field report), we still have 110 receivers standing on the seismic line, which hopefully contain data from the three shots. Moreover we have six shots on the ice, that are loaded but not exploded and two locations that have to be loaded and detonated. With just a little luck with the weather, we should be able to get a lot more data, if we succeed to detonate the last eight shots. However, the shooting will only be successful, if the receivers do not run out of battery. We are worried about the 70 receivers that were set out on the ice on 15 April. They have now been standing out in cold for five days. Their battery life is finite and the batteries become very sluggish below about -20 degrees. We know from tests performed in Ottawa that the recording boxes will work happily for about five days at a temperature of minus forty. Since the temperature here has been warmer than that, they should last a few days more than five. Exactly how many more is a subject of debate. If they are left out too long, they won't work, and they won't provide us with any data. It is therefor important for us to know if the receivers are working before we start to detonate the explosives. If they do not work we have to collect them from the ice and bring them in, warm them up, give them new batteries and set them out again. It is very time consuming, so we want to avoid that if possible.
We hope for a helping hand from the ice camp. During deployment of the 70 instruments on 15 April, we had left six receivers at the ice camp, which we did not manage to deploy due to the weather. They have been standing out in the cold under the same conditions as all the receivers on the line, and by checking if they are still living we will have a very good idea about the state of line receivers before we hopefully can start shooting tomorrow.
21 April, 2006
Weather in Alert: -19, sunny.
Today, for a welcome change, the weather maps looked good both here in Alert and out along the outer line. A very full Twin Otter with 12 passengers - helicopter pilots, engineers and scientists got off to the ice camp at 8:30. On arrival at the camp Isa Asudeh quickly checked the six receivers, which have been standing there out in the cold. With a big smile and thumb´s up Isa signalled to us, that they were still working. This meant that we could start the shooting and after that start to deploy the receivers.
Despite the good weather at the ice camp we could still not reach the northernmost shot location OS11 due to fog and low clouds in the area. So the first two teams went to shot location OS8 to load and detonate the explosives, and during the following hours two teams visited the other shot sites to detonate. At 15:50 in the afternoon we had succeeded to detonate the shots at locations OS1, 2, 3, 4, 6, 7, and 8, and soon after we started to pick-up the receivers. All three helicopter-teams were busy the rest of the day picking-up receivers and flying the instruments to the ice camp and from here they were ferried to Alert by the Twin Otter. We recovered all the 110 receivers except the five northernmost ones, which we could not find. However we know they are out there some place and we will look for them tomorrow, if the weather permits. For the same reason we left the satellite beacon at the now detonated shot site OS7 to help finding the missing receivers.
Trine Dahl-Jensen and Søren Bredvig Nielsen were collecting the instruments along the southern part of the line. At first they had no trouble at all finding the receivers, but under their way north along the line they crossed a wide lead of open water. After this crossing the receivers seem to vanish. They searched up and down and back and forth - but no instruments. Eventually, they called back to Alert to get the latest coordinates of the satellite beacon, which had been standing at the nearby shot site OS3. From Alert they were told to fly 16 km to the west to find the continuation of the line on the northern side of the wide lead. "Strange", they thought. But due to the ice shear along the lead, the line had, during the last days, been offset by this distance to the west. They were amazed, when they found the continuation of the line and again could start picking-up receivers. We have enclosed a satellite picture showing the offset of the line along the wide lead of open water.
After a long day on the ice, we left one of the helicopters at the ice camp, while to two others where heading back to Alert. The Twin Otter picked up the rest of the people from the operations and took them in to Alert from the ice camp. All were back between 22:30 and midnight.
Once the receivers were opened in Alert, they were emptied for data. Isa Asudeh examined a fairly large sample of them, and all of those had good data. So again we have succeeded to get important data up from the bottom of the Arctic Ocean. Despite we were tired after a long day of work, everybody were smiling, when we heard the news about the data quality.
During the day the Twinn Otter took Søren Rysgaard and Martin Blicher from Greenland Institute of Natural Resources out to the ice camp. They are working on a separate research project concerning the importance of sea ice in transporting carbon dioxide from the atmosphere to the ocean. The work is made in connection with the LORITA-activities, but they are also bringing along a CTD-equipment, which can measure the variations in temperature and salinity in the ocean below the sea ice. The temperature and the amount of salt in the water influences the speed of sound in the water, so the CTD-measurements will be used to translate the echo sounder measurements, which are collected by the LORITA BG team, to exact water depths. Søren and Martin succeeded to measure the salinity and temperature in the whole water column below the ice camp and collected water and ice samples for chemical analysis.
Satellite picture from 21 April showing the working area in the Arctic Ocean. Northern coast of Canada is seen in the lower left corner and the coast of Greenland is seen lower right. Position of the ice camp is shown by a green square. Black features on the ice looking like rivers are leads in the sea ice. The points called IS1, IS2, etc. are the inner line shot locations. Those called OS3, OS4, etc. are the outer line shot locations. The map shows where these shots were detonated - not where they were set out in the first place. The shots OS5, OS9 and OS10 were detonated at 18 April. And OS3, OS4, etc. were detonated 21 April. Correspondingly the white line shows the positions of receivers at 18 April and the red line the positions of the instruments 21 April. The most interesting part of the line is just north of IS6, where you can see a 16 km offset of the line to the west. It was here Trine Dahl-Jensen and Søren Bredvig Nielsen for a short while lost track of the line of instruments. The offset of the line is due to shear motion along the lead of open water, which can be clearly seen on the picture. The yellow crosses show the location of the east-west running cross line our third and final seismic run.