GRACE and mass budget method reveal decelerated ice loss in east Greenland in the past decade

Excellent progress has been made in characterizing and understanding ice loss in Greenland, but most existing studies used a constant model to describe the long-term trend, preventing a detailed and rigorous understanding of change in the trend. Moreover, the impacts of atmospheric forcing on the trend of ice mass change are not clear. To address these limitations, we propose a piecewise trajectory model to detect the breaking points in the trend of ice mass change and estimate the optimal segmented trends. A breaking point located around 2012.6 was detected in the CW, SW, NE, SE, and the whole Greenland based on Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-on (FO) data and the mass budget method (MBM). Piecewise trend estimates from both methods suggest that the ice loss decelerated dramatically in east Greenland in 2012.6–2021 compared to 2002–2012.6. The GRACE results indicate that the mass loss rate decelerated by 70% (22.1 ± 0.8 to 6.6 ± 1.0 Gt/yr) in the NE and 38% (89.0 ± 1.5 to 55.4 ± 0.7 Gt/yr) in the SE. Though the rates slightly increased in some regions, the Greenland ice loss rate overall decreased from 269.9 ± 1.8 Gt/yr to 217.0 ± 3.3 Gt/yr. Mass budget analysis suggests that this deceleration was mainly caused by increased precipitation in east Greenland, which was associated with persistent positive North Atlantic Oscillation (NAO) phase in 2013–2021. During this positive NAO period, the enhanced westerlies and low-pressure anomaly off southeast Greenland advected more wet warm air to east Greenland and thus caused more precipitation. As the NAO exhibited a strong positive trend in this century, if it persists into the future, precipitation will have a high chance to increase in east Greenland, benefitting Greenland retaining ice.