Present-day glacial isostatic adjustment of Antarctica
Changes in mass balance (or the amount of ice that has melted) can be measured using space-geodetic techniques that detect variations in the Earth's gravity field and changes in ice height. Both satellite altimetry (used to measure ice topography heights) and GRACE (measures changes in potential) are sensitive to ongoing changes in continental lithosphere from glacial isostatic adjustment, the visco-elastic response of the Earth to the removal of a load after significant ice sheet melting over the past 10,000 years.
The rate of present-day uplift can be estimated using data from permanent GPS installations in Antarctica and can provide constraints on the modelling of the timing and amount of ice that has melted. Since 1998, RSES has installed and operated a network of remote GPS sites in East Antarctica specifically to estimate the isostatic adjustment pattern in the region. Uplift rates are significantly lower than anticipated, implying that either less ice has melted than is incorporated in the glaciology models or that the melting process ended earlier than expected.
Cosmogenic exposure dating utilises the amount of bombardment of cosmic particles that rocks have undergone to calculate when the rocks were exposed to the atmosphere. This provides constraints on the retreat of ice sheets. Coupled with dating of raised marine platforms, lake sediments and biological samples, past ice histories can be reconstructed to generate predicted present-day uplift scenarios that can be compared to observed uplift rates from GPS.