Shallow firn cores 1989–2019 in southwest Greenland's percolation zone reveal decreasing density and ice layer thickness after 2012

Abstract Refreezing of meltwater in firn is a major component Greenland ice-sheet's mass budget, but situ observations are rare. Here, we compare the density and total ice layer thickness upper 15 m 19 new 27 previously published cores drilled at locations southwest (1850–2360 a.s.l.) between 1989 2019. At all sites, covaries with over time space. two sites earliest (1989 1998), bulk increased by 15–18%, top 28 21 years, respectively. However, following extreme melt 2012, elevation-detrended using 30 from decreased kg ?3 ?1 3.75 2013 In contrast, lowest elevation site's shows no trend. Thus, temporary build-up pore space infiltration capacity possible despite long-term increase ice-sheet melting.