Committed retreat: controls on glacier disequilibrium in a warming climate

• DOI: 10.1017/jog.2018.57
• Publication Date: 2018-07-23T05:08:07Z
• Authors: JOHN ERICH CHRISTIAN; MICHELLE KOUTNIK; GERARD ROE
• Keywords: Disequilibrium; Glacier mass balance; Forcing (mathematics); Cirque glacier

ABSTRACT The widespread retreat of mountain glaciers is a striking emblem recent climate change. Yet mass-balance observations indicate that many are out equilibrium with current climate, meaning observed retreats do not show the full response to warming. This fundamental consequence glacier dynamics: typically have multidecadal timescales, and so their lags centennial-scale trends. A substantial difference between transient length persists throughout warming period; we refer this as ‘disequilibrium’. Forcing idealized geometries gradual shows timescale fundamentally governs evolution disequilibrium. Comparing hierarchy different models suggests accurate estimates ice thickness climatology, which control timescale, more important than higher order dynamics for capturing Current disequilibrium has previously been estimated selection individual glaciers; our modeling sustained dynamics, robust across range geometries. implies committed additional, kilometer-scale retreats, even without further Disequilibrium must also be addressed when calibrating used reconstructions projections in future