Greenland ice sheet

The Greenland ice sheet (GrIS) sits atop the largest island in the world and contains the equiva-lent of 7.4 m of global mean sea level rise (Morlighem et al. 2017). While the GrIS was likely in balance (i.e., ice mass gain was balancing ice mass loss) during the 1970s, 1980s, and early 1990s, it began to lose mass in earnest in the mid- to late-1990s (Mouginot et al. 2019). As Greenland loses ice, cold, fresh meltwater is added to the ocean, which increases sea levels and also impacts ocean properties and circulation (e.g., Luo et al. 2016); alters nutrient and sediment fluxes (e.g., Cape et al. 2018; Overeem et al. 2017); and influences local ecosystems (e.g., Hopwood et al. 2018). Observations of the GrIS over the “balance year” of accumulation and loss, from September 2018 through August 2019, reveal another year of dramatic ice melt. The extent and magnitude of ice loss in 2019 rivaled 2012, the previous record year of ice loss