Changes of the tropical glaciers throughout Peru between 2000 and 2016 – mass balance and area fluctuations

Glaciers in tropical regions are very sensitive to climatic variations and thus strongly affected by climate change. The majority of the tropical glaciers worldwide are located in the Peruvian Andes, which have shown significant ice loss in the last century. Here, we present the first multi-temporal, region-wide survey of geodetic mass balances and glacier area fluctuations throughout Peru covering the period 2000–2016. Glacier extents are derived from Landsat imagery by performing automatic glacier delineation based on a combination of the NDSI and band ratio method and final manual inspection and correction. The mapping of debris-covered glacier extents is supported by synthetic aperture radar (SAR) coherence information. A total glacier area loss of  km2 (−29 %, −34.3 km2 a−1) is obtained for the study period. Using interferometric satellite SAR acquisitions, bi-temporal geodetic mass balances are derived. An average specific mass balance of  kg m−2 a−1 is found throughout Peru for the period 2000–2016. However, there are strong regional and temporal differences in the mass budgets ranging from 45±97 to  kg m−2 a−1. The ice loss increased towards the end of the observation period. Between 2013 and 2016, a retreat of the glacierized area of  km2 (−16 %, −101.9 km2 a−1) is mapped and the average mass budget amounts to  kg m−2 a−1. The glacier changes revealed can be attributed to changes in the climatic settings in the study region, derived from ERA-Interim reanalysis data and the Oceanic Nino Index. The intense El Niño activities in 2015/16 are most likely the trigger for the increased change rates in the time interval 2013–2016. Our observations provide fundamental information on the current dramatic glacier changes for local authorities and for the calibration and validation of glacier change projections

Mass balance and area changes of glaciers in the Cordillera Real and Tres Cruces, Bolivia, between 2000 and 2016

Climate change has led to a significant shrinkage of glaciers in the Tropical Andes during the last decades. Recent multi-temporal quantifications of ice mass loss at mountain range to regional scale are missing. However, this is fundamental information for future water resource planning and glacier change projections. In this study, we measure temporally consistent glacier area changes and geodetic mass balances throughout the Bolivian Cordillera Real and Tres Cruces based on multi-sensor remote-sensing data. By analyzing multi-spectral satellite images and interferometric SAR data, a glacier recession of 81 ± 18 km2 (29%; 5.1 ± 1.1 km2 a−1), a geodetic mass balance of −403 ± 78 kg m−2 a−1 and a total ice mass loss of 1.8 ± 0.5 Gt is derived for 2000–2016. In the period 2013–2016, ice mass loss was 21% above the average rate. A retreat rate of 15 ± 5 km2 a−1 and a mass budget of −487 ± 349 kg m−2 a−1 are found in this more recent period. These higher change rates can be attributed to the strong El Niño event in 2015/16. The analyses of individual glacier changes and topographic variables confirmed the dependency of the mass budget and glacier recession on glacier aspect and median elevation

Detailed quantification of glacier elevation and mass changes in South Georgia

Most glaciers in South America and on the Antarctic Peninsula are retreating and thinning. They are considered strong contributors to global sea level rise. However, there is a lack of glacier mass balance studies in other areas of the Southern Hemisphere, such as the surrounding Antarctic Islands. Here, we present a detailed quantification of the 21st century glacier elevation and mass changes for the entire South Georgia Island using bi-static synthetic aperture radar interferometry between 2000 and 2013. The results suggest a significant mass loss since the beginning of the present century. We calculate an average glacier mass balance of -1.04 0.09 m w.e.a(-1) and a mass loss rate of 2.28 0.19 Gt a(-1) (2000-2013), contributing 0.006 0.001 mm a(-1) to sea-level rise. Additionally, we calculate a subaqueous mass loss of 0.77 0.04 Gt a(-1) (2003-2016), with an area change at the marine and lake-terminating glacier fronts of -6.58 0.33 km(2) a(-1), corresponding to similar to 4% of the total glacier area. Overall, we observe negative mass balance rates in South Georgia, with the highest thinning and retreat rates at the large outlet glaciers located at the north-east coast. Although the spaceborne remote sensing dataset analysed in this research is a key contribution to better understanding of the glacier changes in South Georgia, more detailed field measurements, glacier dynamics studies or further long-term analysis with high-resolution regional climate models are required to precisely identify the forcing factors

Rapid glacier retreat and downwasting throughout the European Alps in the early 21st century

Mountain glaciers are known to be strongly affected by global climate change. Here we compute temporally consistent changes in glacier area, surface elevation and ice mass over the entire European Alps between 2000 and 2014. We apply remote sensing techniques on an extensive database of optical and radar imagery covering 93% of the total Alpine glacier volume. Our results reveal rapid glacier retreat across the Alps (−39 km² a−1) with regionally variable ice thickness changes (−0.5 to −0.9 m a−1). The strongest downwasting is observed in the Swiss Glarus and Lepontine Alps with specific mass change rates up to −1.03 m.w.e. a−1. For the entire Alps a mass loss of 1.3 ± 0.2 Gt a−1 (2000–2014) is estimated. Compared to previous studies, our estimated mass changes are similar for the central Alps, but less negative for the lower mountain ranges. These observations provide important information for future research on various socio-economic impacts like water resource management, risk assessments and tourism

Surface elevation changes of glaciers in the Cordillera Real and Tres Cruces, Bolivia, between 2000 and 2016

During the last decades, climate change has led to a significant shrinkage of glaciers in the Tropical Andes. However, there is a lack of recent multi-temporal quantifications of ice mass loss at mountain range to regional scales. We measure temporally consistent glacier area changes and geodetic mass balances throughout the Bolivian Cordillera Real and Tres Cruces based on multi-sensor remote sensing data in the period 2000-2016. By analyzing interferometric SAR data a geodetic mass balance of -399±98 kg m-2 a-1 and a total ice mass loss of 1.84±0.46 Gt is derived for 2000-2016. In more recent years, ice loss was above the average rate. A mass budget of -467±358 kg m-2 a-1 is found after 2013. These higher change rates can be attributed to the strong El Niño event in 2015/16. The data set consists of elevation change maps for each subregion (R1, R2, R3; see associated article) for the periods 2000-2013, 2000-2016 and 2013-2016. The glacier outlines used to delineate the glacier areas are available via the Global Land Ice Measurements from Space (GLIMS) database. Each elevation change map is a mosaic of several dh/dt GeoTiff data sets. The product is derived from differencing of TanDEM-X and SRTM Digital Elevation Models. See the associated article for further information regarding the generation of the data sets. Please note: The here provided elevation change maps are unfiltered (i.e. no outliers were removed) The "date_merge....." data sets provide information on the observation period (measured in years relative to the date of the start of the observation period). Data sets with observation periods starting in 2000: The mean data of the SRTM mission (2000-02-16) is used as the data reference. Data sets with observation periods starting in 2013: The date of the individual TanDEM-X DEM tiles is used as data reference (date of TanDEM-X tiles in 2013 can be derived from the data sets covering the period 2000-2013; "SRTM mean date" + "date_merge_......2000-2013...."

Surface elevation changes of the tropical glaciers throughout Peru between 2000 and 2016

Glaciers in tropical regions are very sensitive to climatic variations and thus strongly affected by climate change. The majority of the tropical glaciers worldwide are located in the Peruvian Andes, which have shown significant ice loss in the last century. Here, we present the first multi-temporal, region-wide survey of geodetic mass balances throughout Peru covering the period 2000-2016. Using interferometric satellite SAR acquisitions, bi-temporal geodetic mass balances are derived. An average specific mass balance of -296±41 kg m-2 a-1 is found throughout Peru for the period 2000-2016. However, there are strong regional and temporal differences in the mass budgets ranging from 45±97 kg m-2 a-1 to -752±452 kg m-2 a-1. The ice loss increased towards the end of the observation period. Between 2013 and 2016, the average mass budget amounts to -660±178 kg m-2 a-1. The glacier changes revealed can be attributed to changes in the climatic settings in the study region, derived from ERA-Interim reanalysis data and the Oceanic Niño Index. The intense El Niño activities in 2015/16 are most likely the trigger for the increased change rates in the time interval 2013-2016. Our observations provide fundamental information on the current dramatic glacier changes for local authorities and for the calibration and validation of glacier change projections. The data set consists of elevation change maps for each subregion (R1, R2, R3; see associated article) for the periods 2000-2013, 2000-2016 and 2013-2016. The glacier outlines used to delineate the glacier areas are available via the Global Land Ice Measurements from Space (GLIMS) database. Each elevation change map is a mosaic of several dh/dt GeoTiff data sets. The product is derived from differencing of TanDEM-X and SRTM Digital Elevation Models. See the associated article for further information regarding the generation of the data sets. Please note: The here provided elevation change maps are unfiltered (i.e. no outliers were removed). The "date_merge....." data sets provide information on the observation period (measured in years relative to the date of the start of the observation period). Data sets with observation periods starting in 2000: The mean data of the SRTM mission (2000-02-16) is used as the data reference. Data sets with observation periods starting in 2013: The date of the individual TanDEM-X DEM tiles is used as data reference (date of TanDEM-X tiles in 2013 can be derived from the data sets covering the period 2000-2013; "SRTM mean date" + "date_merge_......2000-2013...."

Surface elevation changes of glaciers in the European Alps between 2000 and 2014

Glaciers in the European Alps are known to be strongly affected by global climate change. Here we provide temporally consistent changes in glacier area, surface elevation and ice mass over the entire European Alps between 2000 and 2014. Our measurements show strong glacier surface lowering throughout the European Alps with regional variability in average ice thickness changes (-0.5 to -0.9 ma-1). For the entire Alps we estimate a mass loss of 1.3±0.2 Gta-1 (2000-2014). Our results provide important information for future socio-economic research, such as water resource management, tourism and risk assessment, and for the calibration and validation of glacier change projections. The dataset includes glacier elevation change maps (GeoTiffs) of the entire European Alps for the periods 2000-2012 and 2000-2014. Elevation changes are derived from differencing Digital Elevation Models (DEMs) of the SRTM and TanDEM-X satellite missions. Average surface elevation change rates (ma-1) were calculated based on specifically generated glacier outlines (2000, 2011 & 2014) and outlines of the Randolph Glacier Inventory (V6.0 Central Europe). Elevation change maps are cropped to Randolph Glacier Inventory outlines and the spatial union of specific glacier outlines from 2000 and 2011 (for elevation change 2000-2012) and 2000 and 2014 (for elevation change 2000-2014), respectively. See the associated publication for further details regarding the datasets and calculation of surface elevation change and geodetic mass change with a temporal mean area. All elevation change maps are provided as GeoTiffs with a spatial resolution of approximately 30m. Please note that the provided elevation change measurements are not filtered (no outlier removal applied). The observation period of each raster cell is measured in years between the respective TanDEM-X DEM and the SRTM reference DEM. As reference date the mean date of the SRTM mission (2000-02-16) is used

Elevation and Mass Changes of the Southern Patagonia Icefield Derived from TanDEM-X and SRTM Data

The contribution to sea level rise from Patagonian icefields is one of the largest mass losses outside the large ice sheets of Antarctica and Greenland. However, only a few studies have provided large-scale assessments in a spatially detailed way to address the reaction of individual glaciers in Patagonia and hence to better understand and explain the underlying processes. In this work, we use repeat radar interferometric measurements of the German TerraSAR-X-Add-on for Digital Elevation Measurements (TanDEM-X) satellite constellation between 2011/12 and 2016 together with the digital elevation model from the Shuttle Radar Topography Mission (SRTM) in 2000 in order to derive surface elevation and mass changes of the Southern Patagonia Icefield (SPI). Our results reveal a mass loss rate of −11.84 ± 3.3 Gt·a−1 (corresponding to 0.033 ± 0.009 mm·a−1 sea level rise) for an area of 12573 km2 in the period 2000–2015/16. This equals a specific glacier mass balance of −0.941 ± 0.19 m w.e.·a−1 for the whole SPI. These values are comparable with previous estimates since the 1970s, but a magnitude larger than mass change rates reported since the Little Ice Age. The spatial pattern reveals that not all glaciers respond similarly to changes and that various factors need to be considered in order to explain the observed changes. Our multi-temporal coverage of the southern part of the SPI (south of 50.3° S) shows that the mean elevation change rates do not vary significantly over time below the equilibrium line. However, we see indications for more positive mass balances due to possible precipitation increase in 2014 and 2015. We conclude that bi-static radar interferometry is a suitable tool to accurately measure glacier volume and mass changes in frequently cloudy regions. We recommend regular repeat TanDEM-X acquisitions to be scheduled for the maximum summer melt extent in order to minimize the effects of radar signal penetration and to increase product quality

Rapid glacier retreat and downwasting throughout the European Alps in the early 21st century

Glaciers in the European Alps are strongly affected by global warming, yet there is no methodologically consistent alpine-wide analysis on glacier changes. Here the authors show significant glacier retreat and an ice mass loss of 1.3 ± 0.2 Gt a−1, derived from contemporaneous measurements of glacier areas and elevations

Annual glacier elevation change rate raster dataset, Southern Patagonia Ice Field, 2000 and 2015 (unfiltered)

The contribution to sea level rise from Patagonian icefields is one of the largest mass losses outside the large ice sheets of Antarctica and Greenland. However, only a few studies have provided large-scale assessments in a spatially detailed way to address the reaction of individual glaciers in Patagonia and hence to better understand and explain the underlying processes. In this work, we use repeat radar interferometric measurements of the German TerraSAR-X-Add-on for Digital Elevation Measurements (TanDEM-X) satellite constellation between 2011/12 and 2016 together with the digital elevation model from the Shuttle Radar Topography Mission (SRTM) in 2000 in order to derive surface elevation and mass changes of the Southern Patagonia Icefield (SPI). Our results reveal a mass loss rate of −11.84 ± 3.3 Gt- a−1 (corresponding to 0.033 ± 0.009 mm- a−1 sea level rise) for an area of 12573 km2 in the period 2000-2015/16. This equals a specific glacier mass balance of −0.941 ± 0.19 m w.e.- a−1 for the whole SPI. These values are comparable with previous estimates since the 1970s, but a magnitude larger than mass change rates reported since the Little Ice Age. The spatial pattern reveals that not all glaciers respond similarly to changes and that various factors need to be considered in order to explain the observed changes. Our multi-temporal coverage of the southern part of the SPI (south of 50.3° S) shows that the mean elevation change rates do not vary significantly over time below the equilibrium line. However, we see indications for more positive mass balances due to possible precipitation increase in 2014 and 2015. We conclude that bi-static radar interferometry is a suitable tool to accurately measure glacier volume and mass changes in frequently cloudy regions. We recommend regular repeat TanDEM-X acquisitions to be scheduled for the maximum summer melt extent in order to minimize the effects of radar signal penetration and to increase product quality