Ice island thinning: rates and model calibration with in situ observations from Baffin Bay, Nunavut

• Published in: The Cryosphere
• Main Authors: A. J. Crawford, D. Mueller, G. Crocker, L. Mingo, L. Desjardins, D. Dumont, M. Babin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Baffin Bay; Greenland; Nares; Nunavut; Baffin; glacier; Nares strait; North Atlantic; Petermann glacier; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-14-1067-2020; https://doaj.org/article/d6b24e2c1881443097f06329e62a9dba

A 130 km 2 tabular iceberg calved from Petermann Glacier in northwestern Greenland on 5 August 2012. Subsequent fracturing generated many individual large “ice islands”, including Petermann ice island (PII)-A-1-f, which drifted between Nares Strait and the North Atlantic. Thinning caused by basal and surface ablation increases the likelihood that these ice islands will fracture and disperse further, thereby increasing the risk to marine transport and infrastructure as well as affecting the distribution of freshwater from the polar ice sheets. We use a unique stationary and mobile ice-penetrating radar dataset collected over four campaigns to PII-A-1-f to quantify and contextualize ice island surface and basal ablation rates and calibrate a forced convection basal ablation model. The ice island thinned by 4.7 m over 11 months. The majority of thinning (73 %) resulted from basal ablation, but the volume loss associated with basal ablation was ∼12 times less than that caused by areal reduction (e.g. wave erosion, calving, and fracture). However, localized thinning may have influenced a large fracture event that occurred along a section of ice that was ∼40 m thinner than the remainder of the ice island. The calibration of the basal ablation model, the first known to be conducted with field data, supports assigning the theoretically derived value of 1.2×10 −5 m 2∕5 s <math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><msup><mi/><mrow><mo>-</mo><mn mathvariant="normal">1</mn><mo>/</mo><mn mathvariant="normal">5</mn></mrow></msup></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="21pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="dc3a2b0c77aa6bbfb7ca38686ad27960"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-14-1067-2020-ie00001.svg" width="21pt" height="11pt" src="tc-14-1067-2020-ie00001.png"/></svg:svg> ...