Comparative analysis of mass balance estimates since 1959 at Mittivakkat Gletsjer (SE Greenland)

Mittivakkat Gletsjer (MIT) has the longest glaciological surface mass balance (SMB) record of any peripheral glacier in Greenland. In this study, we utilize the glaciological SMB record, calibrate SMB from the Regional Atmospheric Climate Model (RACMO), and calculate geodetic mass balance (MB) to provide a multi-methodic assessment of trends in SMB. Glaciological SMB and modelled SMB correlate well (r = 0.80, p < 0.01) and all three methods agree on an accelerating mass loss. The modelled output shows that mass loss more than tripled from -0.26 ± 0.40 m w.e. a-1 on average in 1959-92 to -0.91 ± 0.40 m w.e. a-1 in 1993-2024, coinciding with an annual mean temperature increase from -1.6°C to -0.1°C for the respective periods. The modelled SMB extending back to 1959 shows that mass loss is linked to increasing air temperatures and decreasing winter precipitation. Our findings highlight: (I) Calibrating SMB from RACMO allows for reconstructing mass changes on the scale of individual glaciers. (II) MIT is out of balance with the current climate and experienced a change in mass balance during the 1990s, similar to that observed in the Greenland periphery.