Antarctic ice sheet volume at 18,000 years B.P. and Holocene sea - level changes at the West Antarctic margin. (waisworkshop.org)
The latter is almost linearly related to changes in ice sheet volume; the former, however, is influenced by a range of factors, including atmosphere / ocean dynamics and changes in Earth's gravitational field, rotation, and crustal and the mantle deformation associated with the redistribution of mass between land ice and the ocean. (bobkopp.net)
Independently, Greenland and Antarctic ice sheet volumes were estimated by observations from adjacent ocean sediment records and by ice sheet models. (sciencedaily.com)