The idea here is to use measurements of vertical velocity to define the local mass balance at selected sites in Antarctica. We install special markers in holes drilled into firn and measure changes in their position using very precise GPS surveys. Vertical velocities are compared with accumulation rates obtained from the same sites.
Mass balance is the difference between the two quantities.
We currently have markers installed at several sites in Antarctica and have been conducting measurements since 1992. A new method for determining ice thickness changes at remote locations. Annals of Glaciology , vol 20, 263-268. Hamilton, G.S. and I.M. Whillans, 1996. Hamilton, G.S., I.M. Whillans and P.J. Morgan.