A glacier whose terminus is increasingly retreating upvalley compared to its previous position due to a higher level of ablation compared to accumulation
https://nsidc.org/cryosphere/glossary-terms/glaciers?page=2
By Mauri Pelto (talk · contribs) - Own work by the original uploader, Public Domain, https://commons.wikimedia.org/w/index.php?curid=507879