Return to rapid ice loss in Greenland and record loss in 2019 detected by the GRACE-FO satellites

Mass loss from the Greenland ice sheet returned to record levels in 2019, following unusually small loss in 2017-18, according to an analysis of satellite data from GRACE and its follow-on mission GRACE-FO. Between 2003-2016, the Greenland ice sheet (GrIS) was one of the largest contributors to sea level rise, as it lost about 255 Gt of ice per year. This mass loss slowed in 2017 and 2018 to about 100 Gt yr(-1). Here we examine further changes in rate of GrIS mass loss, by analyzing data from the GRACE-FO (Gravity Recovery and Climate Experiment - Follow On) satellite mission, launched in May 2018. Using simulations with regional climate models we show that the mass losses observed in 2017 and 2018 by the GRACE and GRACE-FO missions are lower than in any other two year period between 2003 and 2019, the combined period of the two missions. We find that this reduced ice loss results from two anomalous cold summers in western Greenland, compounded by snow-rich autumn and winter conditions in the east. For 2019, GRACE-FO reveals a return to high melt rates leading to a mass loss of 223 +/- 12 Gt month(-1) during the month of July alone, and a record annual mass loss of 532 +/- 58 Gt yr(-1).