Parts of ice sheets that flow into the oceans and affect sea level can flow unusually fast by slipping over their beds. We use Elmer/Ice to solve for the first time in three dimensions the equations that describe the flow of ice as it slips over a bumpy rock bed. We include the important tendency for glaciers to separate from rock and form water‐filled cavities down‐glacier from bumps. These calculations indicate that resistance to slip depends sensitively on the bump shape and spacing. Cavities can cause the bed to become more slippery the faster the ice slides, with this destabilizing effect being more severe for bumps that are laterally narrow and widely spaced. However, bumps with steeply sloping up‐glacier sides can reverse this effect and cause resistance to slip to increase over a wide range of increasing slip velocity. This diverse behavior highlights the need for estimates of glacier slip velocity to incorporate the actual topography of glacier beds.
Read more: Helanow C., N. R. Iverson, L. K. Zoet and O. Gagliardini, 2019. Sliding relations for glacier slip with cavities over three‐dimensional beds, Geophysical Research Letters, doi:10.1029/2019GL084924.