Climatic controls on interannual mass balance of Arctic glaciers and ice caps

Abstract. Interannual variability in glacier and ice cap (GIC) mass balance can be large amplitude, masking the underlying decadal trends associated with external forcing. Here we apply Independent Component Analysis (ICA) to global GIC mass anomalies derived from the Gravity Recovery and Climate Experiment (GRACE) mission and GRACE Follow-On (GRACE-FO) satellite gravimetry missions over 2002–2024. We show that Arctic glacier regions dominate the leading interannual variability in the global gravimetry record, and account for more than two-thirds of recent global GIC mass loss. Two leading Arctic ICA modes explain ~75 % of interannual variance and are associated with North Atlantic Oscillation (NAO)- and Pacific Decadal Oscillation (PDO)-related multi-year climate variability. Multiple linear regression further shows that variability linked to these climate modes explains much of the interannual glacier-mass variability in Arctic glacier regions and significantly affects trend estimates. This effect is most pronounced in Alaska, where the uncorrected trend is about 25 % less negative than the value after accounting for this variability (−69 ± 21 Gt yr⁻¹ versus −92 ± 16 Gt yr⁻¹). These results suggest that persistent North Atlantic and Pacific circulation variability can substantially change regional glacier mass loss, with direct implications for interpreting recent Arctic glacier change and their secular trends driven by external forcing.