Meighen Ice Cap: changes in geometry, mass, and climatic response since 1959

Remote sensing (satellite and airborne) and in situ monitoring measurements indicate that the Meighen Ice Cap has thinned by 10 ± 3 m between 1960 and 2016, resulting in areal shrinkage by 32 km 2 (38%) and total mass loss of 0.71 ± 0.2 gigatonnes. Retreat of the ice margin along the North basin by up to 2.5 km accounted for 50% of the total area loss over the 56-year period of this study. A strong inverse relationship between atmospheric summer temperature anomalies, and in situ mass balance measurements (r = −0.74) indicates that accelerated rates of mass loss from the Meighen Ice Cap are largely driven by regional scale summer warming. Increases in summer temperature anomalies by 1.9 °C from 1960–2004 to 2005–2016 coincided with a five-fold increase in surface melt across the Meighen Ice Cap. Since the 1990s, the Equilibrium Line Altitude has been positioned above the summit of the Meighen Ice Cap, resulting in loss of the accumulation zone that persisted for the first three decades of this study. Since the early 2000s, the ice cap summit has thinned by more than 4 m, which is unprecedented in the period of record. Response time calculations based on 2006–2016 average mass balance data indicate that the Meighen Ice Cap, which has been in existence for ∼3500 years, will completely disappear in ∼175 years.