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In recent years, satellite remote sensing has revolutionized observations of glacier dynamics enabling for the first time the generation of detailed ice-velocity fields at regular intervals for Icelandic glaciers. We generated dense time series of ice-velocity fields from 2014 to 2020 exploiting the continuous acquisition of Sentinel-1 SAR using the offset-tracking technique. The fastest ice flow, with velocities up to 400–800 metres per year, is observed in the middle and lower part of the main outlet glaciers of the ice caps that span a large elevation range in the areas of high precipitation in the South and Southeast of Iceland. Several outlet glaciers of Vatnajökull, such as Skeiðarárjökull and Breiðamerkurjökull, draining towards the South and Southeast, show high-ice-speed channels with pronounced shearing zones where the ice speed increases by an order of magnitude within a distance of only a few ice thicknesses. Velocities on the order of a few tens of metres per year, and up to 50–100 metres per year, are observed on the large surge-type outlet glaciers of N- and W-Vatnajökull and generally on glaciers in the central Icelandic highland and in the northern and western part of the country. Slow-moving ice is observed along the main ice divides and near the glacier margins. The velocity data set is affected by gaps due to decorrelation, particularly during summer, because of temporal variations in the radar-image texture. The ice-velocity fields derived in this study from Sentinel-1 data agree well with other data sets, although these are affected by a larger number of outliers and data gaps, particularly in the accumulation areas. The generated velocity time series can be used for monitoring long-term dynamic trends, seasonal variations and for studying glaciological events such as surges or jökulhlaups.

Ice flow of the Antarctic Ice Sheet has experienced multi-annual acceleration in response to increased rates of ice thinning and retreat. Despite the well-documented seasonality of ice flow in Arctic and Alpine regions, little to no observations exist of seasonal ice-flow variability in Antarctica, due largely to a lack of systematic, high temporal-resolution satellite imagery. Accordingly, the mechanisms driving any such seasonality remain similarly undetermined. Such information is critical for understanding, modelling, and ultimately refining projections of the ongoing and future contribution of Antarctica to global sea-levels.Here, we use high spatial- and temporal- (6/12-daily) resolution Copernicus Sentinel-1a/b synthetic aperture radar (SAR) observations spanning 2014 to 2020 to provide evidence for seasonal flow variability of land ice feeding George VI Ice Shelf (GVIIS), Antarctic Peninsula. Between 2014 and 2020, the flow of glaciers draining to GVIIS from Palmer Land and Alexander Island increased during the austral summertime (December – February) by ~15% relative to baseline rates of flow. This speedup is corroborated by independent observations of ice flow as imaged by the Landsat 8 Operational Land Imager.To identify the likely drivers of this seasonality, we carry out statistical time-series analyses on an array of remotely sensed and reanalysis datasets of potential environmental forcing mechanisms. We find that both surface and oceanic forcing act as statistically significant precursors to summertime ice-flow acceleration. Ultimately, these findings imply that seasonality may be present elsewhere in Antarctica where comparable forcing mechanisms exist.

The limited availability of Synthetic Aperture Radar (SAR) data over glaciers and ice sheets in the past, which formed a major obstacle for obtaining consistent climate data records, has been overcome by the Copernicus Sentinel-1 (S-1) mission, launched in 2014. S-1 SAR data in Greenland, Antarctica and other polar regions have since been regularly acquired every 6 to 12 days, allowing for the operational monitoring and time series analysis of key climate variables at a high spatial and temporal resolution. Exploiting the extensive archive of S-1 acquisitions, we have developed algorithms for retrieving dense time series of glacier and ice sheet velocities, ice discharge and surface melt processes, facilitated by the ESA Climate Change Initiative (ESA CCI), ESA Polar Science Cluster (ESA POLAR+) and EU Copernicus Climate Change Service (C3S) programs. In order to improve existing ice velocity products, we have implemented an InSAR processing line for generation of high-resolution velocity fields from crossing orbits and included a tide correction module to the offset-tracking processing line which accounts for the vertical motion of floating ice shelves and ice tongues due to ocean tides and pressure differences. We present synergistic InSAR and offset tracking ice velocity products, derived from repeat pass S-1 Interferometric Wide (IW mode) swath data, for the Greenland Ice Sheet and report on the performance of the products using in-situ GPS data. Additionally, we show velocity variations of major outlet glaciers in Greenland and Antarctica and other polar ice bodies. The generated ice velocity maps, complemented with ice thickness and other Earth observation datasets, form the basis for deriving ice flow and discharge fluctuations and trends at sub-monthly to multi-annual time scales. To evaluate snowmelt dynamics in Greenland and Antarctica, we have also developed an algorithm for generating maps of snowmelt extent based on multitemporal S-1 SAR and Advanced Scatterometer (ASCAT) data. The dense backscatter time series yields a unique temporal signature that is used to identify the different stages of the melt/freeze cycle and to estimate the melting intensity of the surface snowpack. The high-resolution melt maps form the main input for deriving value-added products on annual melt onset, ending and duration. Intercomparisons with in-situ weather station data and melt products derived from regional climate models (RCMs) and passive microwave radiometers confirm the ability of the algorithm to detect short-lived and longer melt events. Our results demonstrate the excellent capability of the S-1 mission in combination with other sensors for comprehensive monitoring of key climate variables on glaciers and ice sheets, providing essential input for various applications such as ice dynamic and climate modelling.

The subglacial lake Grímsvötn, beneath Vatnajökull ice cap, has been an important study area since the first attempts to explain the physics of jökulhlaups. The lake, covered by an up to 300 m thick ice shelf, is situated within a caldera of an active central volcano. It collects meltwater produced by geothermal and volcanic activity, in addition to meltwater from the glacier surface. During most of the 20th century the period of water accumulation was typically 4-6 years, collecting 1-3 km3 of water. The jökulhlaups, as observed in the river at the glacier terminus ~50 km south of the lake, typically reached peak discharge of 2,000-10,000 m3s-1 after approximately exponential increase over 2-3 weeks. In October 1996, 3.2 km3 of meltwater from an eruption north of Grímsvötn were collected in the lake. This resulted in hydrostatic uplift of the lake ice dam and sudden release of the accumulated water, reaching a peak flow of ~50,000 m3s-1 at the glacier terminus in less than a day. Due to damage to the lake ice dam during the 1996 jökulhlaup and further undermining from geothermal activity near the dam, the water accumulation and release has been different after this event. Between 1996 and 2018, smaller jökulhlaups typically occurred at 1-2 year intervals with the largest volume of ~0.6 km3 in 2004 and 2010. The jökulhlaup discharge still resembled an exponentially rising discharge, but faster, reaching a peak discharge at the glacier front in 3-5 days after detection of flood water in the river. In 2004 and 2010 the peak discharge was ~3,000 m3s-1. From autumn 2018 until November 2021, ~1 km3 of water accumulated in Grímsvötn. The lake level has been monitored since the 1990s, but now with increased accuracy using online GNSS stations located on the floating ice shelf and repeated glacier surface mapping using Pléiades stereo images. Around mid-November 2021 the GNSS instruments started subsiding, revealing that the lake had started draining. In 3 weeks, the discharge from the lake, estimated from the subsidence rate and the lake hypsometry, gradually increased from a few m3s-1 to a peak discharge of ~3500 m3s-1 on 4 December. A few days later, the lake had drained completely. We present the data showing the development at the lake prior to and during the jökulhlaup, and we report on: a) discharge measurements near the glacier front, which combined with the lake discharge allows for an estimate of the temporal subglacial floodwater storage, b) horizontal and vertical ice motion in the vicinity and above the subglacial flood route during the jökulhlaup, from ICEYE and Sentinel-1 radar images obtained with InSAR (24 hour repeat) analysis and amplitude offset tracking, showing the distribution of flood water and the widespread effect of the jökulhlaup on the horizontal ice motion, c) ice surface motion measured by a GNSS station located half-way between the lake and the glacier margin, spanning the entire jökulhlaup. All this provides new insight into the physical processes occurring during a slow, exponentially rising jökulhlaup from Grímsvötn.

Ice shelves play a crucial role in controlling rates of ice discharge across Antarctica’s grounding lines. Mass loss from ice shelves, predominately due to basal melting and calving, can reduce the buttressing force provided by ice shelves, leading to increased grounded ice discharge. Despite the importance of ice shelves, existing estimates of calving and freshwater fluxes from ice shelves have utilised disparate datasets valid for inconsistent time periods or have relied on simplifying assumptions, resulting in a limited account of the health of many ice shelves and little indication of processes driving ice shelf mass imbalance.Here, we quantify calving and basal melt fluxes at annual temporal resolution during 2010 to 2019. Our annual measurements account for annual variations in ice velocity and basal melt rate for 183 ice shelves, and annual variations calving front position for 34 major ice shelves (accounting for ~90% of the ice shelf area). On average during the study period, a calving flux of 1283±109 Gt yr-1 is roughly equal to a melt flux of 1247±149 Gt yr-1. Inter-annual variations in the fluxes of both basal meltwater and calving mean that the melt contribution to ice shelf mass loss varies between 35% and 62%, with the lowest contributions in years with large calving events. These large (>100 Gt) calving events are rare (8 events during 2010-2019), yet account for 35% of the total ice shelf calving flux, highlighting the importance of large calving events for ice shelf mass balance over short time scales. Eighty percent of ice shelves, including many in East Antarctica, are melting at or faster than their balance rates, indicating that ocean-driven erosion of ice shelf grounding lines is widespread around Antarctica. Furthermore, we find a significant and strong positive correlation (R=0.68) between basal melt flux and grounding line discharge, implying that ocean-driven melt may pace grounded ice loss from Antarctica.

Recent satellite-remote sensing studies have documented the multi-decadal acceleration of the Antarctic Ice Sheet in response to rapid rates of concurrent ice-sheet retreat and thinning. Unlike the Greenland Ice Sheet, where historical, high temporal resolution satellite and in situ observations have revealed distinct changes in land ice flow across intra-annual timescales, similar seasonal signals have not previously been observed in Antarctica. Here, we use high spatial and temporal resolution Copernicus Sentinel-1A/B synthetic aperture radar observations acquired between 2014 and 2020 to provide the first evidence for seasonal flow variability of the land ice feeding George VI Ice Shelf (GVIIS), Antarctic Peninsula. Our observations reveal a distinct austral summertime (December – February) speedup of ~0.06 ± 0.005 m d-1 (~22 ± 1.8 m yr-1) at, and immediately inland of, the grounding line of the glaciers nourishing the ice shelf, which constitutes a mean acceleration of ~15 % relative to baseline (timeseries-averaged) rates of flow. These findings are corroborated by independent, optically derived velocity observations. Regional contrasts in the onset of ice-flow acceleration and the overall timing of the speedup events across GVIIS fingerprint oceanic forcing as the primary control of this seasonality. Our findings imply that analogous ice-ocean interactions may be ongoing at the grounding lines of other ocean-vulnerable outlet glaciers around Antarctica. Assessing the degree of seasonal ice-flow variability at such locations is important for quantifying Antarctica’s future contribution to global sea-level rise.

Monitoring the evolution of ice shelf damage such as crevasses and rifts is important for a better understanding of the mechanisms controlling the breakup of ice shelves and for improving predictions about iceberg calving and ice shelf disintegration. Nowadays, the previously existing observational gap has been reduced by the Copernicus Sentinel-1 Synthetic Aperture Radar (SAR) mission that provides a continuous coverage of the Antarctic margins with a 6 or 12-day repeat period. These unprecedented coverage and temporal sampling enable for the first time a year-round systematic monitoring of ice shelf fracturing and iceberg calving, as well as the detection of precursor signs of calving events. In this paper, a novel method based on SAR interferometry is presented for an automatic detection and delineation of active cracks on ice shelves. Active cracks cause phase discontinuities in an interferogram that are extracted automatically by applying a Canny edge detection procedure to the spatial phase gradient derived from a SAR interferogram. The potential of the proposed method is demonstrated in the case of Brunt Ice Shelf, Antarctica, using a stack of 6-day repeat Sentinel-1 interferograms acquired between September 2020 and March 2021. The full life cycle of the North Rift is monitored, including the rift detection, its propagation at rates varying between 0.35 km d−1 and 1.29 km d−1, and the final calving event that gave birth to the iceberg A74 on 26 February 2021. The automatically delineated cracks agree well with the eventual location of the ice shelf edge after the iceberg broke off. The stress field variations observed in the interferograms are attributed to a rigid-body rotation of the ice about the expanding tip of the North Rift in response to the rifting activity. The extent of the North Rift is captured by SAR interferometry well before it becomes visible in SAR backscatter images, hence highlighting the high sensitivity of SAR interferometry to small variations in the ice shelf stress field and its potential for detecting early signs of natural calving events, as well as ice shelf fracturing and damage development in response to atmospheric and oceanic warming caused by climate change.

The understanding of permafrost distribution in Iceland is still limited and current knowledge is mainly based on small scale observations and regional modelling using temperature data. In the Alps Perennial Snow Patches have been considered to protect permafrost from solar radiation and are used as an indicator for the occurrence of local permafrost. In this study perennial snow fields are detected and classified based on aerial and satellite images. Effects of climatic and topographic factors on the snow field occurrence are investigated aiming to provide insight into the distribution of local permafrost in northern Iceland. Multi-temporal optical satellite images (Landsat-5/-7/-8 and Sentinel-2, 1984–2017) have revealed a time-variable distribution of perennial snow patches as possible permafrost indicators on the Tröllaskagi Peninsula in northern Iceland. Calculated normalized difference snow index in combination with different threshold values at the end of summer season within six selected study areas show that several snow patches are present in a time period of over 30 years. Perennial snow patches in the study areas exhibit strong fluctuations in extent due to different local characteristics, e.g. elevation, aspect or topography (plateau/open slopes vs. valleys/cirques). In three of the six study areas snow patches have a high probability of occurrence and the pattern of the distribution is very similar in each time period. Comparison with climate data from nearby weather stations indicates that perennial snow patches can be used in combination with mean annual air temperatures as indicators for local permafrost distributions.

Despite the potentially detrimental impact of large-scale calving events on the geometry and ice flow of the Antarctic Ice Sheet, little is known about the processes that drive rift formation prior to calving, or what controls the timing of these events. The Brunt Ice Shelf in East Antarctica presents a rare natural laboratory to study these processes, following the recent formation of two rifts, each now exceeding 50 km in length. Here we use a unique 50-years' time series of in-situ and remote sensing observations, together with numerical modelling, to reveal how slow changes in ice shelf geometry over time caused build-up of mechanical tension far upstream of the ice front, and culminated in rift formation and a significant speed-up of the ice shelf. These internal feedbacks, whereby ice shelves generate the very conditions that lead to their own (partial) disintegration are currently missing from ice flow models, which severely limits their ability to accurately predict future sea level rise.

The Sentinel-1 acquisition planning for polar regions provides almost uninterrupted observations of the Greenland Ice Sheet margin, key regions in Antarctica and other polar ice masses. The satellite constellation has thereby changed the landscape for satellite Earth observation (EO) in the polar regions, providing excellent opportunities for operational monitoring of key climate variables including ice velocity and glacier discharge. Based on Sentinel-1 SAR imagery, an archive of ice velocity maps covering the polar regions has been generated, encompassing the entire mission duration. The ice velocity maps, complemented with ice thickness and other EO datasets, form the basis for deriving ice flow, discharge fluctuations and trends at sub-monthly to multi-annual time scales, providing key input for ice dynamic and climate modelling. Our results underscore the value of long-term comprehensive monitoring of the polar ice masses, which is vital to gain insight for predicting their response to ongoing climate and ocean warming.

Active subglacial lakes have been identified throughout Antarctica, offering a window into subglacial environments and their impact on ice sheet mass balance. We use high-resolution altimetry measurements over the Thwaites Glacier to show that a lake system underwent a second episode of drainage activity in 2017, only four years after another substantial drainage event. Our observations suggest significant modifications of the drainage system between the two events, with 2017 experiencing greater upstream discharge, faster lake-to-lake connectivity, and the transfer of water within a closed system. Measured rates of lake recharge during the inter-drainage period are significantly larger than modelled estimates, suggesting processes which drive subglacial melt production are currently underestimated. Our study highlights new methods of exploring subglacial environments through the application of altimetry, with potential applications for studying subglacial lakes across Antarctica

Active subglacial lakes have been identified throughout Antarctica, offering a window into subglacial environments and into controls on ice dynamics. Between June 2013 and January 2014 a system of connected subglacial lakes drained in unison under the Thwaites glacier in the West Antarctic ice sheet, the first time that such a system has been observed in the Amundsen Sea Sector. Estimates based on catchment scale melt production suggested that lake drainages of this type should occur every 20 to 80 years. We collected elevations from January 2011 to December 2019 over the Thwaites lake region using the CryoSat-2 swath interferometric mode and ICEsat-2 land ice elevations, as well as ice velocity from the Sentinel-1 SAR mission since 2014. Using various elevation time series approaches, we obtain time dependent elevations over each lake. Results indicate that the upstream lakes undertake a second episode of drainage during mid-2017, only 3 years after the previous event, and that a new lake drained. Unlike the 2013-2014 episode, this new drainage episode contributed to filling one of the downstream lake with no evidence of further downstream activity. This new sub-glacial lake activity under Thwaites offer the possibility to explore lake connectivity, subglacial melt production and the interaction with ice dynamics.

Recent years have seen major advancements in satellite Earth observation of polar land ice. Among the most notable are the developments enabled by the Copernicus Sentinel program, including the Sentinel-1 SAR mission. The Sentinel-1 constellation, with its dedicated polar acquisition scheme, has provided the opportunity to derive ice flow velocity of the Greenland and Antarctic ice sheets at an unprecedented scale and temporal sampling. A continuous observational record of the ice sheet margins since October 2014, augmented by dedicated ice sheet wide mapping campaigns, enabled the operational monitoring of key climate variables like ice velocity and glacier discharge. In 2019 additional tracks have been added to the regular acquisition scheme, covering the slow-moving interior of the Greenland Ice Sheet, opening up new opportunities for interferometric applications and permitting to derive monthly ice sheet wide velocity maps. Based on repeat pass Sentinel-1 SAR data, acquired in Interferometric Wide (IW) swath mode, we have generated a dense archive of ice velocity maps covering the polar regions and encompassing the entire mission duration, now spanning well over 5 years. Including the latest observational data, we present ice velocity maps of Greenland, Antarctica and other major ice caps, focusing on time series of ice flow fluctuations of major outlet glaciers. The ice velocity maps, complemented by high resolution DEMs and ice thickness data, form the basis for studying ice dynamics and discharge fluctuations and trends at sub-monthly to multi-annual time scales. Our results underscore the value of long-term comprehensive monitoring of the polar ice masses, which is vital for to gain insight for predicting their response to ongoing climate warming.This poster highlights some of the main achievements and latest developments of 5 years of Sentinel-1 ice flow mapping in the Polar regions facilitated by the ESA Climate Change Initiative (CCI), EU Copernicus Climate Change Service (C3S) and Austrian Space Applications Programme (ASAP).

The Getz region is a marine-terminating sector of West Antarctica, characterised by a ~650 km long ice shelf that buttresses the inland ice sheet. The majority of the Getz drainage basin is grounded well below sea level, and while the ice shelf has thinned, its calving front has remained relatively stable since the early ’90s. Satellite observations have shown strong thinning of both the ice sheet and ice shelf over the past 25-years, and mass balance studies have shown that the sector is negatively imbalanced (−16.4 ± 4.0 Gt/year). In this study, we use satellite data to measure ice speed in the Getz region, over a 25-year period from 1994 to 2019. We use Synthetic Aperture Radar (SAR) data from historical missions including ERS-1, 2 and ALOS PALSAR, in combination with newer data from the Sentinel-1a & b satellite constellation, to generate annual velocity maps. The Sentinel-1 data extend the historical velocity record and provides a new high temporal resolution record, 6-day averaged solutions, of velocity change since 2017. We used satellite observations in combination with the BISICLES ice sheet model to fill gaps in the observational record, and to measure ice discharge and from the region. We find there are 14 distinct flow units that drain the Getz coastline, with average speeds ranging from 153 ± 7 to 1053 ± 194 m/yr around the grounding line. Our results show that all of these flow units have sped up during the study period, since 1994. At the grounding line, we measure an average speed increase of ~5 m/yr2, with some flow units accelerating by over 11 m/yr2. We find that the spatial pattern of change in ice speed is consistent with the regions of strongest surface lowering, which on some flow units occurs at rates of up to -2.4 m/yr. Our observations show that ice speedup is greatest where the ice is thickest (>700 m), and grounded most deeply. This long 25-year record of change also shows that on some ice streams, the rate of change in ice speed has not been constant throughout the study period. In some regions where ocean temperature measurements are also available, we find that increases in ice speed coincide with the periodic presence of circumpolar deep water, which may therefore be responsible for driving this change. In summary, this study provides a new record of change in ice speed for a rapidly evolving region of Antarctica. In the future, it will be important to use both ocean models and observations to improve our understanding of how ocean forcing is driving dynamic imbalance in the region. This will improve our understanding of the physical mechanisms driving change in Antarctica, helping us to better constrain the ice sheets future contribution to global sea level rise.

The northern and southern Patagonian ice fields (NPI and SPI) have been subject to accelerated retreat during the last decades, with considerable variability in magnitude and timing among individual glaciers. We derive spatially detailed maps of surface elevation change (SEC) of NPI and SPI from bistatic synthetic aperture radar (SAR) interferometry data of the Shuttle Radar Topography Mission (SRTM) and TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X) for two epochs, 2000–2012 and 2012–2016, and provide data on changes in surface elevation and ice volume for the individual glaciers and the ice fields at large. We apply advanced TanDEM-X processing techniques allowing us to cover 90 % and 95 % of the area of NPI and 97 % and 98 % of SPI for the two epochs, respectively. Particular attention is paid to precisely co-registering the digital elevation models (DEMs), accounting for possible effects of radar signal penetration through backscatter analysis and correcting for seasonality biases in case of deviations in repeat DEM coverage from full annual time spans. The results show a different temporal trend between the two ice fields and reveal a heterogeneous spatial pattern of SEC and mass balance caused by different sensitivities with respect to direct climatic forcing and ice flow dynamics of individual glaciers. The estimated volume change rates for NPI are -4.26±0.20 km3 a−1 for epoch 1 and -5.60±0.74 km3 a−1 for epoch 2, while for SPI these are -14.87±0.52 km3 a−1 for epoch 1 and -11.86±1.99 km3 a−1 for epoch 2. This corresponds for both ice fields to an eustatic sea level rise of 0.048±0.002 mm a−1 for epoch 1 and 0.043±0.005 mm a−1 for epoch 2. On SPI the spatial pattern of surface elevation change is more complex than on NPI and the temporal trend is less uniform. On terminus sections of the main calving glaciers of SPI, temporal variations in flow velocities are a main factor for differences in SEC between the two epochs. Striking differences are observed even on adjoining glaciers, such as Upsala Glacier, with decreasing mass losses associated with slowdown of flow velocity, contrasting with acceleration and increase in mass losses on Viedma Glacier.

Through both atmospheric and oceanic circulation, heat is transferred between the equator and the poles. Possible ways in which the Arctic ecological systems can be affected by warmer temperatures include: changes in amount and duration of snow and ice cover; frequency and extent of spring floods; changes in the ratio of precipitation minus evapotranspiration; amounts of water transport from lakes and rivers from snow and permafrost melting; and a decrease in frozen precipitation. A key component in transferring heat is through freshwater exchange in and out of the Arctic. Hence, accurate mapping freshwater fluxes and potentially its changes with time is vital to describe the heat transfer and its possible temporal changes.

The Greenland ice sheet is a major contributor to sea level rise, adding an estimated 0.47 +/− 0.23 mm/yr to global mean sea level between 1991 and 2015 (van den Broeke et al., 2016). Making sea level rise projections for the future and understanding the processes controlling current observed rates of sea level rise are crucially dependent on understanding the present-day state of the ice sheet. Here, we provide an overview of the current state of the mass budget of Greenland based on satellite gravimetry and remote sensing observations of surface elevation change, ice sheet velocity and calving front positions. We also combine these essential climate variables with a regional climate model (RCM) output from an ice sheet model (ISM) to gain insight into poorly understood ice sheet dynamical and surface mass processes. On average from 1992 to 2017 the ice sheet in some locations has lost up −2.65 m/yr in elevation based on ESA Radar altimetry analysis. Calving fronts have retreated all around Greenland since the 1990s and in only two out of 28 study locations have they remained stable. The locations of grounding lines at 5 key glaciers with floating ice tongues have remained stable over the observation period. However a detailed case study at Petermann glacier with an ice fracture model shows the sensitivity of these floating ice shelves to future climate change. GRACE gravimetric mass balance (GMB) data allows us to tie together disparate lines of evidence showing that Greenland has lost about 265 +/− 25 Gt/yr of ice over the period 2002 to 2015. RCM and ISM simulations show that surface mass processes dominate the overall Greenland ice sheet mass budget except for areas of fast ice sheet flow but marked differences between models and between models and observations indicate that not all processes are captured accurately, indicating areas of greater uncertainty and directions of future research for future sea level rise projections.

We evaluate modelled Antarctic ice sheet (AIS) near-surface climate, surface mass balance (SMB) and surface energy balance (SEB) from the updated polar version of the regional atmospheric climate model RACMO2 (1979–2016). The updated model, referred to as RACMO2.3p2, incorporates upper-air relaxation, a revised topography, tuned parameters in the cloud scheme to generate more precipitation towards the AIS interior, and modified snow properties reducing drifting snow sublimation and increasing surface snowmelt. Comparisons of RACMO2 model output with several independent observational data show that the existing biases in AIS temperature, radiative fluxes and SMB components are further reduced with respect to the previous model version. The model integrated annual average SMB for the ice sheet including ice shelves (minus the Antarctic Peninsula (AP)) now amounts to 2229 Gt y-1, with an interannual variability of 109 Gt y-1. The largest improvement is found in modelled surface snowmelt, that now compares well with satellite and weather station observations. For the high-resolution (~ 5.5 km) AP simulation, results remain comparable to earlier studies. The updated model provides a new, high-resolution dataset of the contemporary near-surface climate and SMB of the AIS; this model version will be used for future climate scenario projections in a forthcoming study.

We analyzed volume change and mass balance of outlet glaciers of the northern Antarctic Peninsula over the period 2011 to 2013, using topographic data of high vertical accuracy and great spatial detail, acquired by bistatic radar interferometry of the TanDEM-X/TerraSAR-X satellite formation. The study area includes glaciers draining into the Larsen-A, Larsen Inlet, and Prince-Gustav-Channel embayments. After collapse of buttressing ice shelves in 1995 the glaciers became tidewater calving glaciers and accelerated, resulting in increased ice export. Downwasting of most glaciers is going on, but at reduced rates compared to previous years in accordance with deceleration of ice flow. The rate of mass depletion is 4.2 ± 0.4 Gt a−1, with the largest contribution by Drygalski Glacier amounting to 2.2 ± 0.2 Gt a−1. On the technological side, the investigations demonstrate the capability of satellite-borne single-pass radar interferometry as a new tool for accurate and detailed monitoring of glacier volume change.

Ocean bottom pressure (OBP) changes are caused by a redistribution of the ocean’s internal mass that are driven by atmospheric circulation, a change in the mass entering or leaving the ocean, and/or a change in the integrated atmospheric mass over the ocean areas. The only previous global analysis investigating the magnitude of OBP surface displacements used older OBP data sets (van Dam et al. in J Geophys Res 129:507–517, 1997). Since then significant improvements in meteorological forcing models used to predict OBP have been made, augmented by observations from satellite altimetry and expendable bathythermograph profiles. Using more recent OBP estimates from the Estimating the Circulation and Climate of the Ocean (ECCO) project, we reassess the amplitude of the predicted effect of OBP on the height coordinate time series from a global distribution of GPS stations. OBP-predicted loading effects display an RMS scatter in the height of between 0.2 and 3.7 mm, larger than previously reported but still much smaller (by a factor of 2) than the scatter observed due to atmospheric pressure loading. Given the improvement in GPS hardware and data analysis techniques, the OBP signal is similar to the precision of weekly GPS height coordinates. We estimate the effect of OBP on GPS height coordinate time series using the MIT reprocessed solution, mi1. When we compare the predicted OBP height time series with mi1, we find that the scatter is reduced over all stations by 0.1 mm on average with reductions as high as 0.7 mm at some stations. More importantly we are able to reduce the scatter on 65 % of the stations investigated. The annual component of the OBP signal is responsible for 80 % of the reduction in scatter on average. We find that stations located close to semi-enclosed bays or seas are affected by OBP loading to a greater extent than other stations.

We analyze spatial and temporal variability of the surface velocity field of David Glacier and its floating seaward extension Drygalski Ice Tongue. We obtain velocity measurements by combinations of automated feature tracking, interferometry and speckle tracking using 1997 Antarctic Mapping Mission-1 and 2000 Modified Antarctic Mapping Mission RADARSAT-1 data. We compare short-term velocities, three-year averaged velocities, and earlier studies to investigate whether any significant changes have occurred. Drygalski Ice Tongue advanced 2200 m over the three-year time interval, increasing its area by almost 45 km2 (an area three times that size calved off in early 2005). Our comparison suggests that the velocity field remained relatively constant from about 1991 to 2000. The yearly advance rate is similar to the long-term rate derived from a 1960 map and earlier studies, suggesting long-term steady flow. The new velocity estimates are used in combination with isostatically derived ice thickness fro...

This paper presents a newly derived velocity field of the Brunt Ice Shelf and Stancomb-Wills Ice Tongue in East Antarctica. Velocity is derived using automated feature-tracking techniques on RADARSAT-1 imagery from the 1997 Antarctic Mapping Mission-1 (AMM-1) and 2000 Modified Antarctic Mapping Mission (MAMM). We measure velocities up to 1350 m a−1 at the ice front. Closer investigation of the velocity field and radar images reveals an obvious divergence of contemporary flowlines from relict flow stripes along a portion of Stancomb-Wills Ice Tongue. Analysis of relict flow stripes can reveal glacial events in the past. Assuming relatively steady flow since the event occurred, we utilize the current velocity field to reconstruct former stripe configuration. We believe the flowline deviation points to a change in dynamics that occurred approximately 140 years ago, perhaps due to thinning and an associated shift in grounding-line position. This seems to be supported by historic observations and bottom topography data.

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.

The TanDEM-X/TerraSAR-X satellite formation, applying bistatic radar interferometry, delivers precise, spatially detailed topographic data, an excellent basis for mapping glacier volume change. Repeat pass data of these satellites are used for mapping glacier motion, key information for investigating the dynamic response of glaciers to changing boundary conditions. The synergistic analysis of these data sets provides main glacier parameters: the total net mass balance at annual and multi-annual intervals, the surface mass balance providing the link to atmospheric forcing, and ice export due to calving which is sensitive to changes in ice dynamics and ocean properties. The methods and capabilities of the TanDEM-X mission for delivering these parameters are described. The application is demonstrated for outlet glaciers of the Antarctic Peninsula that have been subject to major dynamic instability in recent years after collapse of buttressing ice shelves.

We use repeat-pass SAR data to produce detailed maps of surface motion covering the glaciers draining into the former Larsen B ice shelf, Antarctic Peninsula, for different epochs between 1995 and 2013. We combine the velocity maps with estimates of ice thickness to analyze fluctuations of ice discharge. The collapse of the central and northern sections of the ice shelf in 2002 led to a near-immediate acceleration of tributary glaciers as well as of the remnant ice shelf in Scar Inlet. Velocities of the glaciers discharging directly into the ocean remain to date well above the velocities of the pre-collapse period. The response of individual glaciers differs and velocities show significant temporal fluctuations, implying major variations in ice discharge and mass balance as well. Due to reduced velocity and ice thickness the ice discharge of Crane Glacier decreased from 5.02 Gt a−1 in 2007 to 1.72 Gt a−1 in 2013, whereas Hektoria and Green glaciers continue to show large temporal fluctuations in response to successive stages of frontal retreat. The velocity on Scar Inlet ice shelf increased two- to three fold since 1995, with the largest increase in the first years after the break-up of the main section of Larsen B. Flask and Leppard glaciers, the largest tributaries to Scar Inlet ice shelf, accelerated. In 2013 their discharge was 38%, respectively 45%, higher than in 1995.

Background Current treatment modalities for chronic leg ulcers are time consuming, expensive, and only moderately successful. Recent data suggest that creating a subatmospheric pressure by vacuum-assisted closure (V.A.C., KCI Concepts, San Antonio, Texas) therapy supports the wound healing process. Methods The efficacy of vacuum-assisted closure in the treatment of chronic leg ulcers was prospectively studied in a randomized controlled trial in which 60 hospitalized patients with chronic leg ulcers were randomly assigned to either treatment by V.A.C. or therapy with conventional wound care techniques. The primary outcome measure was the time to complete healing (days). Statistical analysis was performed on the intention-to-treat basis. Results The median time to complete healing was 29 days (95% confidence interval [CI], 25.5 to 32.5) in the V.A.C. group compared with 45 days (95% CI, 36.2 to 53.8) in the control group (P = .0001). Further, wound bed preparation during V.A.C. therapy was also significantly shorter at 7 days (95% CI 5.7 to 8.3) than during conventional wound care at 17 days (95% CI, 10 to 24, P = .005). The costs of conventional wound care were higher than those of V.A.C. Both groups showed a significant increase in quality of life at the end of therapy and a significant decrease in pain scores at the end of follow-up. Conclusions V.A.C. therapy should be considered as the treatment of choice for chronic leg ulcers owing to its significant advantages in the time to complete healing and wound bed preparation time compared with conventional wound care. Particularly during the preparation stage, V.A.C. therapy appears to be superior to conventional wound care techniques.

Between 1978 and 1982 an experiment on group treatment for and by psoriasis sufferers was conducted, based on a pyramid of previous investigations since 1968. Each group was facilitated by a duo consisting of a fellow sufferer and a physician, both having trained together. The subjects practiced the procedure described, directed toward self-care and mutual aid facilitated and supported by the duo, in a series of ten 2-hour weekly sessions. A pretest/ posttest control group design was used. Comparing the results of the quantitative analysis of the experimental groups with those of the control groups, the experimental groups showed significant change. The results of the qualitative analysis showed that decrease of anxiety correlated with mastering of the skills involved. The key element affecting outcome was the balance in cooperation within the duo, the expertise of the patient lying in his personal experience of the condition, and the expertise of the physician in his knowledge and skills. One of the method's main characteristics was the intrinsic complementarity of the duo partners.

Pseudomonic acid, a new wide-spectrum antimicrobial agent, was evaluated as a 2% formulation in a cream. Animal studies showed that this formulation was just capable of penetrating the skin. When administered parenterally to animals, pseudomonic acid was converted to inactive metabolites that were quickly eliminated from the body. When pseudomonic acid was applied as a cream to human skin, no sensitization was observed. In an open clinical study, sixty-eight patients with skin infections (mostly superficial conditions such as impetigo, infected eczema, folliculitis, or balanitis) applied pseudomonic acid cream three times a day for 5 days. In fifty patients the infections completely cleared within 2 days of the end of therapy, and considerable clinical improvement was noted in sixteen more. One patient stopped the treatment prematurely due to local burning pain, and one patient could not be evaluated clinically.

Satellite data provide a large range of information on glacier dynamics and changes. Results are often reported, provided and used without consideration of measurement accuracy (difference to a true value) and precision (variability of independent assessments). Whereas accuracy might be difficult to determine due to the limited availability of appropriate reference data and the complimentary nature of satellite measurements, precision can be obtained from a large range of measures with a variable effort for determination. This study provides a systematic overview on the factors influencing accuracy and precision of glacier area, elevation change (from altimetry and DEM differencing), and velocity products derived from satellite data, along with measures for calculating them. A tiered list of recommendations is provided (sorted for effort from Level 0 to 3) as a guide for analysts to apply what is possible given the datasets used and available to them. The more simple measures to describe product quality (Levels 0 and 1) can often easily be applied and should thus always be reported. Medium efforts (Level 2) require additional work but provide a more realistic assessment of product precision. Real accuracy assessment (Level 3) requires independent and coincidently acquired reference data with high accuracy. However, these are rarely available and their transformation into an unbiased source of information is challenging. This overview is based on the experiences and lessons learned in the ESA project Glaciers_cci rather than a review of the literature.

ArticlePublished: 10 December 2019This is an unedited manuscript that has been accepted for publication. Nature Research are providing this early version of the manuscript as a service to our customers. The manuscript will undergo copyediting, typesetting and a proof review before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers apply.Mass balance of the Greenland Ice Sheet from 1992 to 2018The IMBIE TeamNature (2019)Cite this article6914 Accesses1410 AltmetricMetricsdetailsAbstractIn recent decades, the Greenland Ice Sheet has been a major contributor to global sea-level rise1,2, and it is expected to be so in the future3. Although increases in glacier flow4–6 and surface melting7–9 have been driven by oceanic10–12 and atmospheric13,14 warming, the degree and trajectory of today’s imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet’s volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. Although the ice sheet was close to a state of balance in the 1990s, annual losses have risen since then, peaking at 335 ± 62 billion tonnes per year in 2011. In all, Greenland lost 3,800 ± 339 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.6 ± 0.9 millimetres. Using three regional climate models, we show that reduced surface mass balance has driven 1,971 ± 555 billion tonnes (52%) of the ice loss owing to increased meltwater runoff. The remaining 1,827 ± 538 billion tonnes (48%) of ice loss was due to increased glacier discharge, which rose from 41 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. Between 2013 and 2017, the total rate of ice loss slowed to 217 ± 32 billion tonnes per year, on average, as atmospheric circulation favoured cooler conditions15 and as ocean temperatures fell at the terminus of Jakobshavn Isbræ16. Cumulative ice losses from Greenland as a whole have been close to the IPCC’s predicted rates for their high-end climate warming scenario17, which forecast an additional 50 to 120 millimetres of global sea-level rise by 2100 when compared to their central estimate.