Mass Variations in the Siberian Permafrost Region from GRACE

After 7 years in orbit, the GRACE satellite mission now facilitates the detection of smaller secular trends of mass variations as well as long-periodic signals. In this study, we focus on changes of the permafrost regime in Siberia, Russia, using GRACE monthly solutions from the three main analysis centres GFZ, CSR and JPL. The results show that observed positive trends of mass changes are related to large Siberian rivers such as Ob, Lena and Yenisei. Two major trends of about 0.7 μGal/a can be clearly identified. The first concerns the upper Ob River. It includes, depending on the specific GRACE solution centre, the Angara River drainage basin, which is part of the Yenisei River system. The second trend is centred on the upper Lena River north-east of Lake Baikal and is also clearly determined, but with different solution-dependent values. All these significant trends seem to be caused by long-term hydrological changes, especially since no other reasonable geophysical explanation is found yet. Similar features can be found in the trend of the GLDAS hydrology model. Removing the hydrological contribution positive mass changes of about 0.8 μGal/a appear in the Central Siberian Plateau and the Kolyma River drainage basin, which may be related to changes in permafrost. However, further investigations are needed to really understand such mass changes and attribute them to the related physical processes.