2008 report
Progress: 60%
Partner 1: UPMC
Reported under WP8
Partner 2: AWI
AWI's activities in 2007 centred on continuing ice thickness measurements in the Trans Polar drift stream and the region between the North Pole and Ellesmere Island, using the helicopter-borne electromagnetic induction (HEM) instrument. The 2007 campaign had intended to use Russian Mi-8 helicopters, which would have allowed long transects between the Tara, the North Pole, the ITP deployment sites and 87oN. One successful transect was completed, from the North Pole for 350 km to the southwest, to 87oN, 58oW, north of Ellesmere Island. Severe technical difficulties were then encountered, relating to the wireless network card used to transfer data between the bird and the computer inside the helicopter, which prevented further data acquisition.
The long transect revealed the presence of predominantly second-year ice with a mean total (snow+ice) thickness of 3.31± 1.51m and a modal thickness of 2.35 m. There was almost no open water and very little thin ice. There was no strong thickness trend between the Pole and the coast of Ellesmere Island. Ground-based EM measurements were also performed at the Pole, giving a bi-modal thickness distribution, with 5 cm of snow on first year ice and 20-40 cm of snow on the second year ice. Comparing the results with those obtained in 2001 in the same region indicates continued thinning of between 30-70 cm over the period.
Following the North Pole campaign, a chartered Canadian helicopter was operated from Alert ( Ellesmere Island) to deploy four GPS drifting buoys in the Lincoln Sea. Snow thickness profiles were also performed.
Full details of the field measurements can be found in the 2007 Campaigns Field Report, Deliverable No. D1.1-3.
In August and September of 2007, extensive thickness surveys were performed during the Polarstern cruise ARK 22/2 in major parts of the Transpolar Drift. However, due to the special conditions with a record minimum ice coverage, only regions of first-year ice were visited. Overall, modal ice thicknesses were on 0.9 m, which is much less than during measurements previously performed in similar conditions in the same ice regime in 1995.
Partner 13: UCAM-DAMTP
DAMTP activities in the reporting period were divided between autonomous underwater vehicle (AUV) operations, and a serendipitous cruise of the UK Royal Navy submarine HMS Tireless. Though the latter was not funded directly by DAMOCLES, the ice draft data will be used in support of our DAMOCLES activities.
Tireless was fitted with a Kongsberg-Simrad EM-3002 multi-beam sonar for the cruise, which represents the first such data from Arctic submarine voyages. Data were acquired continuously under the ice, during the submarine's passage to the U.S. APLIS ice camp in the Beaufort Sea. Detailed surveys were performed along the way, and also at the ice camp itself. These surveys were over-flown by the DNSC laser profilometer, and we intend to merge and compare these datasets in the near future.
Some technical problems were encountered with the EM-3002 unit, due to seawater penetration of the cable connecting the sonar head with the processing unit, and significant data dropouts occurred as a result. The large volume of data acquired is currently being processed and we hope to release these shortly to the appropriate public databases.
The Gavia AUV was deployed on two occasions. The first was a technical development exercise, performed in a frozen lake in Canada during February 2007, using a Gavia owned by the University of British Columbia. The exercise examined the navigational capabilities of the AUV - whether it could reliably return to a small hole in the ice – and under-ice launch and recovery techniques. Unfortunately, navigational reliability was insufficient to allow easy recovery from a small hole in the ice, and the intended deployment from the Tara was postponed until this could be improved.
The AUV was subsequently deployed at the U.S. APLIS ice camp in the Beaufort Sea, in April 2007, though the vehicle was operated on a 400m kevlar tether, enabling it to be quickly pulled back to the ice hole at the end of each mission. This severely limited the radius of operations, confining the data gathering to the immediate area of the put-in hole, but the exercise was nonetheless very successful. Both the AWI HEM bird and the DNSC laser profilometer were present at the same ice camp, and co-incident runs by all three instruments were achieved, for the first time. Analysis is currently focussing on the merging of these three datasets for a complete description of the ice volume in the region. Results were published in Geophysical Research Letters ( 1/1/08) and presented at the American Geophysical Union Fall Meeting ( 11/12/07).
The APLIS deployment was largely funded by the US National Science Foundation, enabling the DAMOCLES funds to be reserved for an un-tethered deployment in 2008. This is planned from Alert on Ellesmere Island, in May 2008.
Deviation from plan: DAMOCLES deployment moved to 2008 due to technical difficulties.
Partner 15: UCL
Work at UCL continued on the sea ice retrievals explicitly on the cross calibration between ERS and Envisat during 2003. Additionally investigations were carried out into the capability of radar/laser data to estimate snow depth by differencing ICESat and Envisat freeboards during the ICESat periods of operation. Whilst the results show some promise further work, particularly using in-situ validation data, are required to interpret the results. Finally near real time estimates of ice freeboard from Envisat were transmitted to two separate field campaigns in btoh the Arctic and Antarctic where UCL teams were measuring snow properties and for the Antarctic, radar penetration. Work on Envisat is now continuing through national funding and co-operation with DAMOCLES will primarily involve comparisons with in-situ data once they become available.
Partner 29: DNSC
The DNSC laser profilometer was fitted to a Ken Borek Twin Otter for the 2007 campaign, from April 8 – May 8 2007. Profiles were flown around the Tara, at the US APLIS ice camp, and from Alert station. In addition, lines north of Greenland, in the Fram Strait and north of Alert were flown to repeat previous years' surveys.
At Tara, a complete ‘mow-the-lawn' survey was flown, including the drilling and snow-pit areas. The Twin Otter also performed the air-dropping of 16 MetOcean CALIB buoys in the area, in support of the University of Hamburg's (partner 14) atmospheric programme. Two tiltmeter buoys (SAMS, partner 35) and a POPS profiling buoy (UPMC, partner 1) were also deployed by the aircraft, landing on sea ice for the purpose. The deployment of a second POPS and an ice mass balance buoy (IMB) was cancelled due to the break-up of the runway. The planned co-incident flight with the EM bird was cancelled due to the technical problems encountered with that instrument. Laser data are currently being processed and this is expected to be completed soon, when comparisons with AUV and HEM data will be made.
Full details of the field measurements can be found in the 2007 Campaigns Field Report, Deliverable No. D1.1-3.
Partner 35: SAMS
Five tiltmeter buoys were deployed in the period; two at the U.S. APLIS ice camp, in the Beaufort Sea; one at the North Pole Barneo station; one east of the Pole and one between the Pole and Greenland. The tiltmeter at Tara, deployed in September 2006, continued to operate. Good coverage of the Arctic Ocean was therefore achieved, with at least three buoys lined up in the direction of swell-wave propogation, along a deep-water path, as intended. The APLIS buoys give the attenuation undergone by the waves traversing the whole Arctic pack ice, though these stopped transmissions during the summer, when the unprecedented ice retreat left them in open water (they do not float). Tilt data are continuing to be processed.
Partner 48: NIERSC 25%
Historical sea ice and snow measurements from the Russian Sever expeditons from 1928 to 1989 are used in combination with other ice thickness data for studies of trend and variability over seven decades. An overview of data are presented in report D.1.1-09, first version. The report presents annual and regional coverage of the data. Further work will include merging the Sever data with data from other expedition and new data from recent expedition.
