Based on glacio-meteorological records, 7 years of in-situ mass balance data, and a temperature-index model, the long-term annual and seasonal mass balances of Shiyi Glacier in the northeast Tibetan Plateau (TP) were reconstructed from 1963/64 to 2016/17. Variations were then linked to local climatic and macroscale circulation changes. The model was calibrated based on in-situ mass balance data and was driven by daily air temperature and precipitation data recorded at nearby alpine meteorological stations. The results show that the reconstructed annual mass balance experienced an overall downward trend over the past 54 years, with a remarkably high mass loss rate during 1990/91-2016/17. Analysis of mass balance sensitivity and local climatic changes shows that the pronounced mass loss since the 1990s can be mainly attributed to cumulative positive temperature increases caused by air temperature increases and prolongation of the ablation season. From the perspective of macroscale circulation, the reconstructed annual mass balance values correlate well with zonal wind speeds (June to September) in the glacierized region. For the positive/negative phase of the annual mass balance, an inverse spatial pattern in relation to geopotential height change (low/high-pressure centres) and corresponding conversion of cyclonic/anti-cyclonic circulation were present in northern hemisphere mid-latitudes. Comparative analysis of existing long-term mass balance series over the TP indicates that asynchronous climatic changes in the different glacierized regions led to inconsistent interannual fluctuations in glacier mass balance.

InSAR time series of surface deformation from 16 yr of Envisat (2003-2011) and Sentinel-1 (2014-2019) ESA satellite radar measurements have been constructed to characterise spatial and temporal dynamics of ground deformation over an 80,000 km(2) area in the permafrost of the northeastern Tibetan Plateau. The regional deformation maps encompass various types of periglacial landforms and show that seasonal thaw effects are controlled by the sediment type and local topography. High seasonal ground movements are concentrated on shallow slopes and poor-drainage areas in unconsolidated, frost-susceptible and fine-grained sediments within glacier outwash plains, braided stream plains, alluvial deposits or floodplains. Fast subsidence due to thaw settlement takes place during June/July while frost heave is intense during December/January when two-sided freezing of pore water under pressure causes prolonged ice segregation near the permafrost table. The analysis reveals pervasive subsidence of the ground of up to similar to 2 cm/yr, and increasing by a factor of 2 to 5 from 2003 to today, in high-relief and well-drained areas. The findings suggest that seasonal thaw increasingly affects ice-rich layers at the permafrost table, as well as high-rates of widespread mass movements of non-consolidated sediments, the latter amplified by an increase of effects from frost heave/thaw settlement. (C) 2020 Elsevier B.V. All rights reserved.