Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology 1 , raising global sea-level 2 and elevating natural hazards 3 . Yet, due to the scarcity of constrained mass loss observations, glacier evolution during the satellite era is only known as a geographic and temporal patchwork 4,5 . Here we reveal the accelerated, albeit contrasted, patterns of glacier mass loss during the early twenty-first century. By leveraging largely untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth's glaciers. We extensively validate our estimates against independent, high-precision measurements and present the first globally complete and consistent estimate of glacier mass change. We show that, during 2000-2019, glaciers lost 267 ± 16 Gt yr -1 , equivalent to 21 ± 3% of observed sea-level rise 6 . We identify a mass loss acceleration of 48 ± 16 Gt yr -1 per decade, explaining 6-19% of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the last two decades. Glaciers presently lose more mass, and at similar or larger accelerated rates, than the Greenland or Antarctic ice sheets taken separately [7][8][9] . Uncovering the patterns of mass change in many regions, we find contrasted glacier fluctuations that agree with decadal variability in precipitation and temperature. Those include a newly-identified North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from Northwestern American glaciers and the apparent end of the Karakoram anomaly of mass gain 10 . We anticipate our highly-resolved estimates to foster the understanding of drivers that govern the distribution of glacier change, and to extend our capabilities of predicting these changes at all scales. Predictions robustly benchmarked against observations are critically needed to design adaptive policies for the management of local water resources and cryospheric risks as well as for regional-to-global sea-level rise.About 200 million people live on land predicted to fall below the high-tide lines of rising sea levels by the end of the century 11 , while more than one billion could face water shortage and food insecurity within the next three decades 4 . Glaciers distinct from the ice sheets play a prominent role in these repercussions as the largest estimated contributor to twenty-first century sea-level rise after thermal expansion 2 , and as one of the most climate-sensitive constituents of the world's natural water towers 12,13 . Current glacier retreat temporarily mitigates water stress on populations reliant on ice reserves by increasing river runoff 1 , but this short-lived effect will eventually decline 14 . Understanding present-day and future glacier mass change is thus crucial to avoid water scarcity-induced socio-political instability 15 , to predict the alteration of coastal areas due to sea-level rise 4 , and to assess the impacts on ecosystems 16 as w...

Abstract. We present glacier thickness changes over the entire Pamir–Karakoram–Himalaya arc based on ICESat satellite altimetry data for 2003–2008. We highlight the importance of C-band penetration for studies based on the SRTM elevation model. This penetration seems to be of potentially larger magnitude and variability than previously assumed. The most negative rate of region-wide glacier elevation change (

The response of the Greenland Ice Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of ice mass changes before 1992, when Greenland-wide observations first became available. The only previous estimates of change during the twentieth century are based on empirical modelling and energy balance modelling. Consequently, no observation-based estimates of the contribution from the GIS to the global-mean sea level budget before 1990 are included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Here we calculate spatial ice mass loss around the entire GIS from 1900 to the present using aerial imagery from the 1980s. This allows accurate high-resolution mapping of geomorphic features related to the maximum extent of the GIS during the Little Ice Age at the end of the nineteenth century. We estimate the total ice mass loss and its spatial distribution for three periods: 1900-1983 (75.1 ± 29.4 gigatonnes per year), 1983-2003 (73.8 ± 40.5 gigatonnes per year), and 2003-2010 (186.4 ± 18.9 gigatonnes per year). Furthermore, using two surface mass balance models we partition the mass balance into a term for surface mass balance (that is, total precipitation minus total sublimation minus runoff) and a dynamic term. We find that many areas currently undergoing change are identical to those that experienced considerable thinning throughout the twentieth century. We also reveal that the surface mass balance term shows a considerable decrease since 2003, whereas the dynamic term is constant over the past 110 years. Overall, our observation-based findings show that during the twentieth century the GIS contributed at least 25.0 ± 9.4 millimetres of global-mean sea level rise. Our result will help to close the twentieth-century sea level budget, which remains crucial for evaluating the reliability of models used to predict global sea level rise.

No abstract

Abstract:With its temporal resolution of 10 days (five days with two satellites, and significantly more at high latitudes), its swath width of 290 km, and its 10 m and 20 m spatial resolution bands from the visible to the shortwave infrared, the European Sentinel-2 satellites have significant potential for glacier remote sensing, in particular mapping of glacier outlines and facies, and velocity measurements. Testing Level 1C commissioning and ramp-up phase data for initial sensor quality experiences, we find a high radiometric performance, but with slight striping effects under certain conditions. Through co-registration of repeat Sentinal-2 data we also find lateral offset patterns and noise on the order of a few metres. Neither of these issues will complicate most typical glaciological applications. Absolute geo-location of the data investigated was on the order of one pixel at the time of writing. The most severe geometric problem stems from vertical errors of the DEM used for ortho-rectifying Sentinel-2 data. These errors propagate into locally varying lateral offsets in the images, up to several pixels with respect to other georeferenced data, or between Sentinel-2 data from different orbits. Finally, we characterize the potential and limitations of tracking glacier flow from repeat Sentinel-2 data using a set of typical glaciers in different environments: Aletsch Glacier, Swiss Alps; Fox Glacier, New Zealand; Jakobshavn Isbree, Greenland; Antarctic Peninsula at the Larsen C ice shelf.

This is a repository copy of Error sources and guidelines for quality assessment of glacier area, elevation change, and velocity products derived from satellite data in the Glaciers_cci project.

Digital Elevation Models (DEMs) play a prominent role in glaciological studies for the mass balance of glaciers and ice sheets. By providing a time snapshot of glacier geometry, DEMs are crucial for most glacier evolution modelling studies, but are also important for cryospheric modelling in general. We present a historical medium-resolution DEM and orthophotographs that consistently cover the entire surroundings and margins of the Greenland Ice Sheet 1978–1987. About 3,500 aerial photographs of Greenland are combined with field surveyed geodetic ground control to produce a 25 m gridded DEM and a 2 m black-and-white digital orthophotograph. Supporting data consist of a reliability mask and a photo footprint coverage with recording dates. Through one internal and two external validation tests, this DEM shows an accuracy better than 10 m horizontally and 6 m vertically while the precision is better than 4 m. This dataset proved successful for topographical mapping and geodetic mass balance. Other uses include control and calibration of remotely sensed data such as imagery or InSAR velocity maps.

This study independently quantifies geodetic elevation change and models surface mass balance to solve the continuity equation. The approach is tested on two dynamically different glaciers, Kongsvegen and Kronebreen in northwest Svalbard, through two time epochs, 1966-1990/95 (I) and 1990/95-2007 (II). On Kongsvegen, a dynamically inactive glacier, the residual term represents an error associated with determining elevation changes and surface mass balance. It is apparent that centerline mass-balance estimates are not representative of the entire glacier, which we relate to center-line accumulation being larger than the elevation bin average. On Kronebreen, a fast-flowing and actively calving glacier, a significant part of the residual is identified with the long-term calving flux. For both glaciers, the cumulative surface mass balance remained close to zero during the first epoch but became increasingly negative in the second epoch. The long-term calving flux of Kronebreen is estimated to be -0.14 ± 0.03 km3 w.e.a-1 during epoch I and-0.20 ± 0.05 km3 w.e.a-1 in epoch II.