Abstract
A time‐dependent numerical model has been constructed that simulates retreat of a West Antarctic ice stream from the edge of the continental shelf during the Holocene period of rising sea level. This paper describes a method for computing the deformation of the solid earth caused by changes in ice and water loading during retreat of the ice stream. The relative sea level changes caused by earth deformation are incorporated as a feedback mechanism in the ice stream model. Elastic and viscous uplift of the earth, caused by thinning of the ice stream and its catchment area, is found to delay retreat of the grounding line relative to computed retreat when the ice stream was assumed to be resting on a rigid earth. Computed retreat of the grounding line began very slowly, at 15,000 B.P., because of rising eustatic sea level. Retreat accelerated after about 30 km, at 13,000 B.P., because of increasing water depth and a seabed sloping down toward the ice sheet interior. By 8000 B.P. the feedback effects of earth deformation caused retreat of the grounding line to be delayed by about 1000 years, relative to computed retreat on a rigid earth. The elastic and viscous earth response exerted a moderating influence on the computed retreat rate because uplift at the grounding line partially counteracted the effect of increasing water depth. Computed retreat of the grounding line slowed, and gradually stopped, near the present position of the ice stream grounding line. Uplift of the seafloor caused the total retreat distance to be reduced by 80 km relative to retreat computed on a rigid earth. A readvance of 20 km of the grounding line occurred between 3000 B.P. and the present because continuing viscous uplift caused sea depth to decrease. Resistance from the Ross Ice Shelf was found to be of primary importance in bringing retreat of the grounding line to a stop in the Ross Embayment, as suggested by earlier investigators. Within the context of a given ice shelf retreat history the feedback effects of earth deformation caused a reduction of the grounding‐line retreat rate, a reduction of the total computed retreat distance, and a readvance of the grounding line after eustatic sea level stopped rising.
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