title: A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps.
abstract: Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36±16 Gt-1, or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.
authors.affiliation: Institute for Marine and Atmospheric Research Utrecht, Utrecht University, 3584 CC Utrecht, The Netherlands.
authors.forename: B
authors.initials: B
authors.lastname: Noël
authors.affiliation: Institute for Marine and Atmospheric Research Utrecht, Utrecht University, 3584 CC Utrecht, The Netherlands.
authors.forename: W J
authors.initials: WJ
authors.lastname: van de Berg
authors.affiliation: Department of Geoscience and Remote Sensing, Delft University of Technology, 2600 AA Delft, The Netherlands.
authors.forename: S
authors.identifier: 0000-0002-1622-0177
authors.initials: S
authors.lastname: Lhermitte
authors.affiliation: Institute for Marine and Atmospheric Research Utrecht, Utrecht University, 3584 CC Utrecht, The Netherlands.
authors.forename: B
authors.initials: B
authors.lastname: Wouters
authors.affiliation: Department of Geography, University of Zürich, CH-8006 Zürich, Switzerland.|Department of Geosciences, University of Fribourg, CH-1700 Fribourg, Switzerland.|Geological Survey of Denmark and Greenland GEUS, 1350 København K, Denmark.
authors.forename: H
authors.initials: H
authors.lastname: Machguth
authors.affiliation: Byrd Polar Research Center and School of Earth Sciences and Department of Geography, Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: I
authors.identifier: 0000-0002-8072-6260
authors.initials: I
authors.lastname: Howat
authors.affiliation: Geological Survey of Denmark and Greenland GEUS, 1350 København K, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Citterio
authors.affiliation: Norwegian Polar Institute, Fram Centre, NO-9296 Tromsø, Norway.
authors.forename: G
authors.initials: G
authors.lastname: Moholdt
authors.affiliation: Institute for Marine and Atmospheric Research Utrecht, Utrecht University, 3584 CC Utrecht, The Netherlands.
authors.forename: J T M
authors.initials: JT
authors.lastname: Lenaerts
authors.affiliation: Institute for Marine and Atmospheric Research Utrecht, Utrecht University, 3584 CC Utrecht, The Netherlands.
authors.forename: M R
authors.initials: MR
authors.lastname: van den Broeke