An improved mass budget for the Greenland ice sheet

TLDR

NASA’s Operation IceBridge ice‑thickness surveys provide high‑precision, decade‑long discharge data for most Greenland marine‑terminating outlet glaciers, prompting a reassessment of their temporal and spatial change. Annual measurements of 178 outlet glaciers show that only 15 glaciers account for 77 % of the 739 ± 29 Gt of ice lost since 2000, with four glaciers contributing ~50 %; the share of ice‑discharge loss fell from 58 % before 2005 to 32 % between 2009–2012, and 84 % of the post‑2009 mass‑loss increase is due to surface runoff, supporting model projections that surface mass balance will dominate Greenland’s 21st‑century sea‑level rise.

Abstract

Abstract Extensive ice thickness surveys by NASA's Operation IceBridge enable over a decade of ice discharge measurements at high precision for the majority of Greenland's marine‐terminating outlet glaciers, prompting a reassessment of the temporal and spatial distribution of glacier change. Annual measurements for 178 outlet glaciers reveal that, despite widespread acceleration, only 15 glaciers accounted for 77% of the 739 ± 29 Gt of ice lost due to acceleration since 2000 and four accounted for ~50%. Among the top sources of loss are several glaciers that have received little scientific attention. The relative contribution of ice discharge to total loss decreased from 58% before 2005 to 32% between 2009 and 2012. As such, 84% of the increase in mass loss after 2009 was due to increased surface runoff. These observations support recent model projections that surface mass balance, rather than ice dynamics, will dominate the ice sheet's contribution to 21st century sea level rise.