Using GRACE/GRACE-FO and Swarm to estimate ice-sheets mass loss in Antarctica and Greenland during 2002-2020

The Intergovernmental Panel on Climate Change's (IPCC) Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) concluded that the Antarctica and Greenland ice sheets were major contributors to global sea-level rise. Satellite gravimetry, e. g. the Gravity Recovery and Climate Experiment (GRACE) and the GRACE Follow-on (GRACE-FO) missions, provides the direct observations of large-scale ice mass loss. However, there is a one-year data gap spanning from July 2017 to May 2018 between GRACE and GRACE-FO. Fortunately, operating from November 2013, the Swarm mission with a constellation of three LEO (Low Earth Orbit) satellites can be used to recover global large-scale temporal gravity fields. Meanwhile, the ARIMA-MC (Autoregressive Integrated Moving Average Model-Monte Carlo) method also makes forecasting the missing time-varied gravity possible. The main objective of this study is to determine ice mass variations in Antarctica and Greenland during the one-year gap between GRACE and GRACE-FO. Our results indicated that Swarm's results were comparable to the forecast from the ARIMA-MC method in space-time. From April 2002 to March 2020, the rates of ice mass loss were -119 +/- 23 Gt.a(-1) and -259 +/- 20 Gt.a(-1) over Antarctica and Greenland, respectively, which was equivalent to the global sea level rise at the rate of similar to 0. 33 mm.a(-1) and similar to 0. 72 mm.a(-1), respectively. The ice loss rate of Wilkes Land in Antarctica during 2010-2020 was accelerated by 10 times comparing to the period of 2002-2009. The major abrupt ablation of Greenland in the summer of 2019 was connected to the NAO (North Atlantic Oscillation) event.

Automated summary

The IPCC's SROCC report identifies Antarctica and Greenland ice sheets as major contributors to global sea-level rise. This study fills the data gap between GRACE and GRACE-FO missions using the Swarm satellite mission and ARIMA-MC method, and determines the ice mass variations in Antarctica and Greenland during this gap. The results show significant ice mass loss rates in both regions, with some areas experiencing accelerated loss rate in different periods.