Petermann Ice Island 'A' survey results, offshore labrador

In August 2010 a 265 km2 ice island calved from the Petermann Glacier in northern Greenland. Soon after the initial calving event the mass broke into several pieces, some of which exited Baffin Bay and drifted south toward the Labrador coast. By June 2011 PII-A, a large fragment of the initial Petermann Ice Island, was situated offshore Labrador and in one week it had moved 225 km down the coast. Concern arose that if PII-A continued its trajectory it could reach the Grand Banks by August 2011, posing a potential risk for existing infrastructure in the offshore region of Newfoundland. To properly assess the potential risk a realistic estimate of ice mass was necessary. This in turn required field measurements of the ice islands thickness. A three-day field program was carried out on the Petermann Ice Islands, PII-A and PII-A-a, from June 17-19, 2011. At this time PII-A and PII-A-a were situated offshore Labrador, Canada, approximately 100 km northeast of the town of Rigolet. Geophysical survey methods, including Ground Penetrating Radar (GPR) and Seismic Reflection, were used to identify the base of the islands and obtain ice thickness measurements at various locations. Eight satellite tracking beacons were deployed on PII-A and one was deployed on PII-A-a. Ablation data, photographs and video footage were also obtained during the program. On July 22, 2011, PII-A was revisited while it was situated off the southern Labrador coast. GPR measurements were acquired at the pre-existing stations; the measurements allowed for deterioration rates due to surface and basal melting to be calculated for PII-A. Results of the field measurements indicate that ice thickness varied between 50 to 80 m on PII-A; the thickness of PII-A-a was 30 m at a single survey location. Surface melt rates of 2.7-6.3 cm day"1 were observed over a 1-day period in June. For the 35-day period between June and July visits, average surface and basal melt of 5.0 cm day"1 and 3.4 cm day"1, respectively, were calculated. Copyright 2012, Offshore Technology Conference