Brief communication: Firn data compilation reveals the evolution ofthe firn air content on the Greenland ice sheet

Abstract. The firn covering the Greenland ice sheet interior can retain part of the surface melt, buffering the ice sheet’s contribution to sea level, but its characteristics are still little known. Using remote-sensing observations from 2000–2017, we estimate that firn covers 1,405,500 ± 17,250 km 2 of the ice sheet. We present 344 firn-core-derived observations of the top 10 m firn air content (FAC 10 ), indicative of the firn’s meltwater retention capacity. FAC 10 remained stable in the coldest 74 % of the firn area during 1953–2017, while FAC 10 decreased in the warmest and driest 12 % of the firn area between 1997–2008 and 2011–2017, resulting in a loss of 180 ± 78 km 3 (−26 ± 11 %) of air from the near-surface firn.