Abstract
The rapid acceleration of Greenland Ice Sheet mass loss over,
particularly the last two decades, is well documented.However, limits in
early remote sensing restricted the details with which we could examine
local changes on an ice-sheet-wide scale, particularly in areas of slow
motion, along shear margins and complex coastal terrain. We explore the
localcharacter of rapid contemporary change marine-terminating glaciers
using satellite-derived ice sheet surface velocities,glacier terminus
advance/retreat history, and surface elevation-change data from the
1980s to the present. Widespread glacierterminus retreat is a strong and
more consistent climate response indicator than velocity change, but
local changes in velocityare critical indicators of rapid ice sheet
reconfiguration. Ice thickness changes related to changing ice dynamics
often providethe first evidence of processes that initiate outlet
glacier retreats and mass loss, such as the development of sub-ice
shelfcavities and subglacial hydrology changes. Reconfiguration is
observed locally as narrowing zones of fast-flow, ice flowrerouting,
shear margin migration, and likely glacier outlet abandonment. These
patterns are apparent in all ice sheet sectorsand observable from
space-borne instruments. The rapid reconfiguration now well underway in
Greenland has wide-rangingimplications, including expected changes in
subglacial hydrology, ice discharge, freshwater flux to the ocean, and
transport ofnutrients and sediment. Lacking detailed observations of
earlier deglaciations and current limits on ice-sheet modelcapabilities,
the expanding details of these combined observational records may
provide a valuable analog for studying pastice sheet dynamics and
projecting future ice loss.