1. Scientists studied sets of small ridges running parallel

to the coast at the grounding line, where the base of

the ice sheet meets the ocean. The ridges are formed by

the tidal motion lifting the ice sheet twice a day

Ice shelf

Ice flow

Ocean

Grounding line

Tidal motion

2. Sediments at the grounding line are pushed up into

the ridges leaving a set of parallel lines.

The speed of the ice sheet collapse can be calculated

by measuring the distance between them

Retreated

ice shelf

Retreating

grounding line

Parallel lines

of sediment

Distance between ridges used to

calculate speed of ice sheet collapse