5. Greenland Ice Sheet and Arctic Mountain Glaciers

This chapter provides a review and update of meltwater and Arctic hydrology, and the impact of glacier and ice sheet mass balance contributions to sea-level rise and ocean circulation. It highlights the recent work and results of large-scale modeling of Greenland climate, glaciers, and ice caps and Greenland Ice Sheet (GrIS) mass balances, and Greenland spatiotemporal freshwater runoff to the surrounding oceans and seas (spatiotemporal runoff simulations based on SnowModel/HydroFlow generated individual drainage catchments for Greenland (n = 3,150), each with an individual flow network). The mass balance for the GrIS was close to equilibrium during the relatively cold 1970s and 1980s and lost mass rapidly as the climate warmed in the 1990s and 2000s. Since 2003, the average annual GrIS mass loss rate was 250–300 km³ yr⁻¹ (equal to 250–300 Gt yr⁻¹). This represents a GrIS loss rate equivalent to a eustatic sea-level rise contribution of 1.1 mm SLE yr⁻¹, compared to a mean estimated global sea-level rise of 3.3 ± 0.4 mm SLE yr⁻¹ from 1993 to 2009, and an average 4.8 mm SLE yr⁻¹ for 2013–2018. Not only has the GrIS lost mass, the land- and marine-terminating outlet glaciers on the periphery of the GrIS have undergone rapid mass and area changes over the recent decades. For example, for the last decade (2000–2010) the average simulated Greenland runoff was 572 ± 53 km³ yr⁻¹ (1.6 ± 0.2 mm SLE yr⁻¹), where the simulations indicated that 69% of the runoff to the surrounding seas originated from the GrIS and 31% came from the land area.