Long-term (1979-2010) ice mass balance in Antarctica and Greenland estimated from the Earth's rotational pole variations.

Detail variations of polar ice mass balance during the last decade have been revealed from the satellite geodetic observation. However, it is still uncertain the continent-wide Antarctic and Greenland ice mass balance before the satellite gravimetry and altimetry missions. In this study, we estimate long-term (1979-2010) polar ice mass variations by comparing observed and modeled polar motion excitations (χ1,χ2). Excitations of polar motion associated with wind and current are estimated with ECMWF and GECCO2, respectively, and they are corrected from observed excitations. Residual excitations are mainly due to fluid mass redistribution on the Earth's envelope, and they are compared with modeled excitations associated with atmospheric pressure (ECMWF), ocean bottom pressure (GECCO2), terrestrial water storage (GLDAS), mountain glaciers (GLIMS) and polar ice sheets. Ice mass variations in polar ice sheets during 1979-2010 are estimated based on surface mass balance from numerical models (ECMWF and RACMO2) and ice dynamic observations. Observed and modeled excitations agree very well over seasonal and inter-annual time scale. In addition, both χ1 show similar quadratic variations indicating that polar ice mass balance used here is reasonable. However, there exist significant difference for the quadratic trend in χ2, and it is not certain to explain it yet. This study shows that long-term geodetic observations are potentially useful to understand history of polar ice mass balance and to project future sea level rise.