Impact of the melt–albedo feedback on the future evolution of the Greenland Ice Sheet with PISM-dEBM-simple

• Published in: The Cryosphere
• Main Authors: Zeitz, M., Reese, R., Beckmann, J., Krebs-Kanzow, U., Winkelmann, R.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2021
• Subjects: Greenland; Ice Sheet; The Cryosphere
• Online Access: https://publications.pik-potsdam.de/pubman/item/item_26432; https://publications.pik-potsdam.de/pubman/item/item_26432_1/component/file_26482/26432oa.pdf

Surface melting of the Greenland Ice Sheet contributes a large amount to current and future sea level rise. Increased surface melt may lower the reflectivity of the ice sheet surface and thereby increase melt rates: the so-called melt–albedo feedback describes this self-sustaining increase in surface melting. In order to test the effect of the melt– albedo feedback in a prognostic ice sheet model, we imple- ment dEBM-simple, a simplified version of the diurnal En- ergy Balance Model dEBM, in the Parallel Ice Sheet Model (PISM). The implementation includes a simple representation of the melt–albedo feedback and can thereby replace the positive-degree-day melt scheme. Using PISM-dEBM- simple, we find that this feedback increases ice loss through surface warming by 60 % until 2300 for the high-emission scenario RCP8.5 when compared to a scenario in which the albedo remains constant at its present-day values. With an increase of 90 % compared to a fixed-albedo scenario, the effect is more pronounced for lower surface warming under RCP2.6. Furthermore, assuming an immediate darkening of the ice surface over all summer months, we estimate an up- per bound for this effect to be 70 % in the RCP8.5 scenario and a more than 4-fold increase under RCP2.6. With dEBM- simple implemented in PISM, we find that the melt–albedo feedback is an essential contributor to mass loss in dynamic simulations of the Greenland Ice Sheet under future warming.