Petermann Ice Island 'A' Survey Results, Offshore Labrador

Abstract

In August 2010 a 265 km2 ice island calved from the Petermann Glacier innorthern Greenland. Soon after the initial calving event the mass broke intoseveral pieces, some of which exited Baffin Bay and drifted south toward theLabrador coast. By June 2011 PII-A, a large fragment of the initial PetermannIce Island, was situated offshore Labrador and in one week it had moved 225 kmdown the coast. Concern arose that if PII-A continued its trajectory it couldreach the Grand Banks by August 2011, posing a potential risk for existinginfrastructure in the offshore region of Newfoundland. To properly assess thepotential risk a realistic estimate of ice mass was necessary. This in turnrequired 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 weresituated offshore Labrador, Canada, approximately 100 km northeast of the townof Rigolet. Geophysical survey methods, including Ground Penetrating Radar(GPR) and Seismic Reflection, were used to identify the base of the islands andobtain ice thickness measurements at various locations. Eight satellitetracking beacons were deployed on PII-A and one was deployed on PII-A-a. Ablation data, photographs and video footage were also obtained during theprogram. On July 22, 2011, PII-A was revisited while it was situated off thesouthern Labrador coast. GPR measurements were acquired at the pre-existingstations; the measurements allowed for deterioration rates due to surface andbasal melting to be calculated for PII-A. Results of the field measurementsindicate that ice thickness varied between 50 to 80 m on PII-A; the thicknessof PII-A-a was 30 m at a single survey location. Surface melt rates of 2.7–6.3cm day-1 were observed over a 1-day period in June. For the 35-day periodbetween June and July visits, average surface and basal melt of 5.0 cm day-1and 3.4 cm day-1, respectively, were calculated.

Wind‐driven upwelling around grounded tabular icebergs

“…The recent decline in Arctic summer sea ice extent has led to an increased usage of the Arctic for commercial shipping, as well as renewed efforts in hydrocarbon exploration in the region [Smith and Stephenson, 2013;Hossain and Rao, 2014]. The threat that icebergs still pose to ships and offshore structures continues to fuel interest in iceberg trajectories and decay mechanisms [Halliday et al, 2012;Peterson et al, 2012;Turnbull et al, 2015]. Similiarly, recent efforts to couple numerical ocean models to land-ice models have led to an increased interest in Arctic and Antarctic icebergs [Martin and Adcroft, 2010;Hunke and Comeau, 2011;Coogle, 2013].…”

Surface ablation model evaluation on a drifting ice island in the Canadian Arctic

“…The TIM was run with GEM model data (TIM GEM ) and the same DDFs as TIM AWS-Val and TIM AWS-Fit for operational validation. The TIM model and 'optimal' DDF calculated for the entire Berghaus dataset were validated by running the TIM on another ice island located in the Eastern Canadian Arctic in 2011, PII-A, using GEM model T a data and surface ablation records reported by Halliday et al (2012). This model run is referred to as TIM-PIIA GEM .…”

“…This increases to approximately 30% for an ice island with a 10 km waterline (Ballicater Consulting Ltd., 2012). An example of the mass loss by surface ablation for an ice island is provided by Halliday et al (2012) who document the surface ablation observed for PII-A, a product of the 2010 Petermann Glacier calving event (Johannessen et al, 2011). This ice island was visited twice between June and July 2011 when adrift off the coast of Labrador.…”

“…This ice island was visited twice between June and July 2011 when adrift off the coast of Labrador. The average surface ablation (n = 4) was 1.7 m over 35 days resulting in an average daily surface ablation of 4.9 cm d −1 (Halliday et al, 2012). Based on an estimated extent of 62 km 2 (Halliday et al, 2012), this equates to a mass loss through surface ablation of 9.6 × 10 4 tons over the 1-month period.…”

“…The average surface ablation (n = 4) was 1.7 m over 35 days resulting in an average daily surface ablation of 4.9 cm d −1 (Halliday et al, 2012). Based on an estimated extent of 62 km 2 (Halliday et al, 2012), this equates to a mass loss through surface ablation of 9.6 × 10 4 tons over the 1-month period. This is 60% of the total mass loss due to thickness change (surface and basal ablation), which was equal to 16 × 10 4 tons.…”