Improving Ice Sheet Mass Balance Estimates Using Laser Ranging Interferometer (LRI) GRACE-FO and GRACE Data

The ice mass balance of the Antarctic and Greenland Ice Sheets and the World's Glaciers and Ice Caps (GIC) is of considerable importance to assessments of sea level change and projections of sea level rise by models. Since 2002, the GRACE/GRACE-FO missions have produced monthly estimates of changes in glaciers and ice sheet mass.

We present the GRACE/GRACE-FO record from 2002 to present for Greenland, Antarctica, and the GIC with the total loss of ice on Earth for the entire period, using observation of the earth time variable gravity in the form of spherical harmonics In the last few years, we note a pause in the acceleration in mass loss of Antarctica and of Greenland. Similarly, the total mass loss of GIC is has proceeded at a nearly constant rate despite important year to year variability and regional variability. We introduce work using LRI for GRACE-FO that allows us to examine sub-monthly changes of key regions of Greenland and Antarctica and also mass balance at the basin scale, e.g. in the important Amundsen Sea Embayment sector of West Antarctica. We use synthetic data to quantify error sources and independent data (RACMO, MERRA-2, Mass Budget, ICESat-2) to evaluate the GRACE-FO products and fill in data gaps. Initial LRI results using a point mass, a spherical cap, a line mass, and basin-wide mass changes are very encouraging.

We will also present sub-monthly results in zones of intense summer melt in Greenland and abrupt precipitation in East Antarctica to illustrate the enhanced capability of LRI at examining rapid meteorological events in polar regions.