Decadal slowdown of a land-terminating sector of the Greenland Ice Sheet despite warming

• Published in: Nature
• Main Authors: Tedstone, Andrew J., Nienow, Peter W., Gourmelen, Noel, Dehecq, Amaury, Goldberg, Daniel, Hanna, Edward
• Other Authors: School of Geosciences Edinburgh, University of Edinburgh, Laboratoire d'Informatique, Systèmes, Traitement de l'Information et de la Connaissance (LISTIC), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry ), Department of Geography Sheffield, University of Sheffield Sheffield
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: geo; envir; Greenland; Ice Sheet
• Online Access: https://doi.org/10.1038/nature15722; https://hal.archives-ouvertes.fr/hal-01230099

International audience Ice flow along land-terminating margins of the Greenland Ice Sheet (GIS) varies considerably in response to fluctuating inputs of surface meltwater to the bed of the ice sheet. Such inputs lubricate the ice–bed interface, transiently speeding up the flow of ice1, 2. Greater melting results in faster ice motion during summer, but slower motion over the subsequent winter, owing to the evolution of an efficient drainage system that enables water to drain from regions of the ice-sheet bed that have a high basal water pressure2, 3. However, the impact of hydrodynamic coupling on ice motion over decadal timescales remains poorly constrained. Here we show that annual ice motion across an 8,000-km2 land-terminating region of the west GIS margin, extending to 1,100 m above sea level, was 12% slower in 2007–14 compared with 1985–94, despite a 50% increase in surface meltwater production. Our findings suggest that, over these three decades, hydrodynamic coupling in this section of the ablation zone resulted in a net slowdown of ice motion (not a speed-up, as previously postulated1). Increases in meltwater production from projected climate warming may therefore further reduce the motion of land-terminating margins of the GIS. Our findings suggest that these sectors of the ice sheet are more resilient to the dynamic impacts of enhanced meltwater production than previously thought.