Description: The firn density, temperature and liquid water content of the Greenland ice sheet have been modelled with the IMAU-FDM firn model. IMAU-FDM is forced at the surface with the latest output of the regional climate model RACMO2.3p2. The data is on a horizontal grid of 11x11 km and covers 1960-2016 with a 10-day temporal resolution. Here, time series of the firn air content (vertically integrated difference between firn and ice density (= 917 kg m-3)) and 10-m firn temperature are provided. All other IMAU-FDM output is available from the authors without conditions.

Description: The Canadian Arctic Archipelago (CAA) comprises multiple small glaciers and ice caps mostly concentrated on Ellesmere and Baffin Islands in the northern (NCAA) and southern parts (SCAA) of the archipelago, respectively. Because these glaciers are small and show complex geometries, current regional climate models, using 5 to 20 km horizontal resolution, do not properly resolve surface mass balance (SMB) patterns. Here, we present a 58-year (1958-2015) reconstruction of daily SMB of the CAA, statistically downscaled to 1 km from the output of the regional climate model RACMO2.3 at 11 km. By correcting for biases in elevation and ice albedo, the downscaling method significantly improves runoff estimates over narrow outlet glaciers and isolated ice fields. Since the last two decades, NCAA and SCAA glaciers have experienced warmer conditions (+1.1°C) resulting in continued mass loss of 28.2 ± 11.5 Gt yr-1 and 22.0 ± 4.5 Gt yr-1 respectively, more than doubling (11.9 Gt yr-1) and doubling (11.9 Gt yr-1) the pre-1996 average. While the interior of NCAA ice caps can still buffer most of the additional melt, the lack of a perennial firn area over low-lying SCAA glaciers caused uninterrupted mass loss since the 1980s. In the absence of significant refreezing capacity, this indicates inevitable disappearance of these highly sensitive glaciers.

Description: This dataset contains Greenland Ice Sheet snowfall climatologies derived from Release 5, Version P1 of the CloudSat snowfall product (2C-SNOW-PROFILE: http://www.cloudsat.cira.colostate.edu/data-products/level-2c/2c-snow-profile). Before gridding, we applied a filter to the 2C-SNOW-PROFILE product which excluded all snowfall rates that were greater than two standard deviations from a 50 km running median. Snowfall climatologies were produced by (1) averaging all valid CloudSat snowfall rate observations within 45 km of the grid cell center, (2) averaging these snowfall rates for each month, and (3) averaging all months to produce a snowfall climatology for the 2006-2016 study period. We also produced seasonal snowfall climatologies by averaging monthly snowfall rates from the following periods (e.g. Spring [MAM], Summer [JJA], Autumn [SON], and Winter [DJF]). The snowfall climatologies have a WGS84 / NSIDC Sea Ice Polar Stereographic North projection (EPSG:3413) with a spatial resolution of 15 x 15 km. Snowfall rate units are in meters per year. This dataset also contains a Greenland Ice Sheet summer precipitation phase climatology for the 2006-2016 study period which was produced from Release 5, Version P1 of the CloudSat precipitation product (2C-PRECIP-COLUMN: http://www.cloudsat.cira.colostate.edu/data-products/level-2c/2c-precip-column). This climatology was derived using the same sampling strategy as the snowfall climatologies but was produced by dividing the number of events classified as rain by the total number of precipitation events.

Description: The dataset contains model output presented in the manuscript 'A long-term dataset of climatic mass balance, snow conditions and runoff in Svalbard (1957-2018)', which is considered for publication in The Cryosphere. The data are structured in 3-D arrays containing spatially distributed and annual mean values of the variables specified below. The spatial resolution is 1x1-km. Variables included in the dataset: ----------------------------- - Climatic mass balance - Air temperature - Precipitation - Runoff - Refreezing - Pore space (down to 14 m) - Subsurface temperature (at 14 m depth) - Snow disappearance date - Snow onset date

Description: Since the early 1990s, the Greenland ice sheet (GrIS) has been losing mass at an accelerating rate, primarily due to enhanced meltwater runoff following an atmospheric warming of ~1ºC. Here we show that a pronounced latitudinal contrast exists in the GrIS response to recent warming. The ablation area in north Greenland expanded by 46%, almost twice as much as in the south (+25%), significantly increasing the relative contribution of the north to total GrIS mass loss. This latitudinal contrast originates from a different response to the recent change in large-scale Arctic summertime atmospheric circulation, promoting southwesterly advection of warm air towards the GrIS. In the southwest, persistent high atmospheric pressure reduced cloudiness, increasing runoff through enhanced absorption of solar radiation; in contrast, increased early-summer cloudiness in north Greenland enhanced atmospheric warming through decreased longwave heat loss. This triggered a rapid snowline retreat, causing early bare ice exposure, amplifying northern runoff. The data set includes: 5.5 km data: annual mean summertime (June-July-August) shortwave down/upward radiation (swsd/swsu; W m-2), longwave down/upward radiation (lwsd/lwsu; W m-2), surface albedo (alb; unitless) and cloud content (qci; kg m-2) modelled by RACMO2.3p2 at 5.5 km spatial resolution for the period 1958-2017. 1 km data: annual cumulative meltwater runoff (kg m-2 or mm w.e.) modelled by RACMO2.3p2 at 5.5 km resolution and further statistically downscaled to 1 km for the period 1958-2017. Annual maximum bare ice extent (unitless) remotely sensed by MODIS at 1 km spatial resolution for the period 2000-2018. Mask file at 1 km resolution including longitude/latitude coordinates and outlines of the seven Greenland ice sheet sectors investigated in the study. Additional RACMO2.3p2 data, including daily downscaled surface mass balance (SMB) components at 1 km and modelled climate variables at 5.5 km resolution, are freely available from the authors upon request and without conditions. To submit a request, please contact Brice Noël: mailto:b.p.y.noel@uu.nl.

Description: Compared to other Arctic ice masses, Svalbard glaciers are low-elevated with flat interior accumulation areas, resulting in a marked peak in their current hypsometry (area-elevation distribution) at ~450 m above sea level. Since summer melt consistently exceeds winter snowfall, these low-lying glaciers can only survive by refreezing a considerable fraction of surface melt and rain in the porous firn layer covering their accumulation zones. We use a high-resolution climate model to show that modest atmospheric warming in the mid-1980s forced the firn zone to retreat upward by ~100 m to coincide with the hypsometry peak. This led to a rapid areal reduction of firn cover available for refreezing, and strongly increased runoff from dark, bare ice areas, amplifying mass loss from all elevations. As the firn line fluctuates around the hypsometry peak in the current climate, Svalbard glaciers will continue to lose mass and show high sensitivity to temperature perturbations. The data set includes annual cumulative SMB and components statistically downscaled from the output of the Regional Atmospheric Climate Model RACMO2.3 to 500 m spatial resolution (1958-2018). SMB components include total precipitation (snowfall and rainfall), snowfall, runoff, melt, refreezing and retention (mm w.e. per year), as well as summer (June-July-August) 2 m air temperature (K). The data set also includes modelled (RACMO2.3; 1958-2018) and observed (MODIS; 2000-2018) bare ice area, and modelled ablation zone area (1958-2018; km2). The mask file includes longitude/latitude (ºN/ºW), land-sea, ice and sector masks from the Randolph Glacier Inventory version 6, and surface topography (m above sea level) from the S0 Terreng Digital Elevation Model (Norwegian Polar Institute) on the 500 m grid. Daily downscaled SMB and components are available from the authors upon request and without conditions (b.p.y.noel@uu.nl).

Description: The Greenland Ice Sheet has been a major contributor to global sea-level rise in recent decades1,2, and it is expected to continue to be so3. Although increases in glacier flow4–6 and surface melting7–9 have been driven by oceanic10–12 and atmospheric13,14 warming, the magnitude and trajectory of the ice sheet’s mass 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. The ice sheet was close to a state of balance in the 1990s, but annual losses have risen since then, peaking at 345 ± 66 billion tonnes per year in 2011. In all, Greenland lost 3,902 ± 342 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.8 ± 0.9 millimetres. Using three regional climate models, we show that the reduced surface mass balance has driven 1,964 ± 565 billion tonnes (50.3 per cent) of the ice loss owing to increased meltwater runoff. The remaining 1,938 ± 541 billion tonnes (49.7 per cent) of ice loss was due to increased glacier dynamical imbalance, which rose from 46 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. The total rate of ice loss slowed to 222 ± 30 billion tonnes per year between 2013 and 2017, on average, as atmospheric circulation favoured cooler conditions15 and ocean temperatures fell at the terminus of Jakobshavn Isbræ16. Cumulative ice losses from Greenland as a whole have been close to the rates predicted by the Intergovernmental Panel on Climate Change for their high-end climate warming scenario17, which forecast an additional 70 to 130 millimetres of global sea-level rise by 2100 compared with their central estimate.

Description: We use satellite and airborne altimetry to estimate annual mass changes of the Greenland Ice Sheet. We estimate ice loss corresponding to a sea-level rise of 6.9 ± 0.4 mm from April 2011 to April 2020, with a highest annual ice loss rate of 1.4 mm/yr sea-level equivalent from April 2019 to April 2020. On a regional scale, our annual mass loss timeseries reveals 10–15 m/yr dynamic thickening at the terminus of Jakobshavn Isbræ from April 2016 to April 2018, followed by a return to dynamic thinning. We observe contrasting patterns of mass loss acceleration in different basins across the ice sheet and suggest that these spatiotemporal trends could be useful for calibrating and validating prognostic ice sheet models. In addition to resolving the spatial and temporal fingerprint of Greenland's recent ice loss, these mass loss grids are key for partitioning contemporary elastic vertical land motion from longer-term glacial isostatic adjustment (GIA) trends at GPS stations around the ice sheet. Our ice-loss product results in a significantly different GIA interpretation from a previous ice-loss product.

Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in The Cryosphere 9 (2015): 2009-2025, doi:10.5194/tc-9-2009-2015.

Description: Observed changes in the surface elevation of the Greenland Ice Sheet are caused by ice dynamics, basal elevation change, basal melt, surface mass balance (SMB) variability, and by compaction of the overlying firn. The last two contributions are quantified here using a firn model that includes compaction, meltwater percolation, and refreezing. The model is forced with surface mass fluxes and temperature from a regional climate model for the period 1960–2014. The model results agree with observations of surface density, density profiles from 62 firn cores, and altimetric observations from regions where ice-dynamical surface height changes are likely small. In areas with strong surface melt, the firn model overestimates density. We find that the firn layer in the high interior is generally thickening slowly (1–5 cm yr−1). In the percolation and ablation areas, firn and SMB processes account for a surface elevation lowering of up to 20–50 cm yr−1. Most of this firn-induced marginal thinning is caused by an increase in melt since the mid-1990s and partly compensated by an increase in the accumulation of fresh snow around most of the ice sheet. The total firn and ice volume change between 1980 and 2014 is estimated at −3295 ± 1030 km3 due to firn and SMB changes, corresponding to an ice-sheet average thinning of 1.96 ± 0.61 m. Most of this volume decrease occurred after 1995. The computed changes in surface elevation can be used to partition altimetrically observed volume change into surface mass balance and ice-dynamically related mass changes.

Description: P. Kuipers Munneke received financial support from the Netherlands Polar Programme (NPP) of the Netherlands Institute for Scientific Research (NWO). ECMWF at Reading (UK) is acknowledged for use of the Cray supercomputing system. The J. E. Box contribution is supported by Det Frie Forskningsråd grant 4002-00234 and Geocenter Denmark.