Climate sensitivity studies of the Greenland ice sheet using satellite AVHRR, SMMR, SSM/I and in situ data

Physical geographer Konrad “Koni” Steffen, lost 8 August 2020 in a crevasse on the Greenland ice sheet, was a pioneer in satellite remote sensing and field observations of the Greenland ice sheet. This Classics Revisited piece honors the memory of Koni Steffen and examines the impact of a work which laid the foundation for numerous studies that made the Greenland ice sheet and the man global icons of climate change.

Download Full-text

Greenland ice sheet surface mass balance 1991–2000: Application of Polar MM5 mesoscale model and in situ data

Journal of Geophysical Research Atmospheres ◽

10.1029/2003jd004451 ◽

2004 ◽

Vol 109 (D16) ◽

Cited By ~ 126

Author(s):

Jason E. Box

Keyword(s):

Mass Balance ◽

Mesoscale Model ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Mass Balance ◽

Surface Mass ◽

Sheet Surface ◽

In Situ Data

Download Full-text

Validation of airborne and satellite altimetry data by Arctic Truck citizen science

Geological Survey of Denmark and Greenland Bulletin ◽

10.34194/geusb.v47.5369 ◽

2021 ◽

Vol 47 ◽

Author(s):

Andreas Stokholm ◽

Sine M. Hvidegaard ◽

Rene Forsberg ◽

Sebastian B. Simonsen

Keyword(s):

Citizen Science ◽

Satellite Altimetry ◽

Ice Sheets ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Gps Data ◽

Kinematic Gps ◽

In Situ Data ◽

Cost Efficient

The elevation of ice sheets response dynamically to climate change and satellite altimetry is the preferred tool for evaluating the ice sheet-wide changes. In-situ validation are needed to ensure the quality of the observed elevation changes, but the coast is most often the limiting factor for the amount of in-situ data available. As more and more tourists are accessing the ice sheets, citizen science might provide the needed in-situ data in an environmental and cost-efficient way. Here, we investigate opportunistic kinematic-GPS profiles across the Greenland ice sheet, collected the American-Icelandic Expedition on the Greenlandic icecap 2018. First, the collected GPS-data are tested against widely used NASA Operation IceBridge airborne lidar-scannings, and shows good agreement, with an accuracy of 11 cm. The main difference is attributed to changes in the compaction of the snow as encountered while driving, as well as changing tire pressures. The kinematic-GPS data is then used for satellite validation by inter-comparing it with data from ESA's CryoSat-2 mission. Here, a bias in the two records of 89 cm is observed, with the Cryosat-2 observation originating from the subsurface of the ice sheet. This points to surface penetration of Ku-band radar on the Greenland ice sheet, and the observed magnitude is in accordance with the literature. Finally, we assess the long-term durability of citizen science kinematic-GPS data, when compared to a profile obtained in 2005 near Kangerlussuaq, West Greenland. Here, the records show an average ice elevation decreased of 9 meters and with peaks at 25.7 meters. This result show how kinematic-GPS data can be used to see the full impact of climate change by repeat measurements. Thereby are citizen science kinematic-GPS data shown to be a highly versatile approach to acquire high-resolution validation data for satellite altimetry, with the added benefit of potentially direct sampling properties of the surface and firn, when applying traditional airborne platforms. Thereby linking up with citizen-science expeditions is truly a beneficial way of providing cost-efficient satellite validations and may also have a societal impact by involving more in the climate monitoring of ice sheets.

Download Full-text

Mapping the aerodynamic roughness of the Greenland ice sheet surface using ICESat-2

10.5194/egusphere-egu21-2136 ◽

2021 ◽

Author(s):

Maurice van Tiggelen ◽

Paul C.J.P. Smeets ◽

Carleen H. Reijmer ◽

Bert Wouters ◽

Jakob F. Steiner ◽

...

Keyword(s):

Eddy Covariance ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Surface Elevation ◽

Spatiotemporal Variability ◽

Atmospheric Models ◽

Laser Altimeter ◽

Eddy Covariance Measurements ◽

Aerodynamic Roughness

The roughness of a natural surface is an important parameter in atmospheric models, as it determines the intensity of turbulent transfer between the atmosphere and the surface. Unfortunately, this parameter is often poorly known, especially in remote areas where neither high-resolution elevation models nor eddy-covariance measurements are available.In this study, we take advantage of the measurements of the ICESat-2 satellite laser altimeter. We use the geolocated photons product (ATL03) to retrieve a 1-m resolution surface elevation product over the K-transect (West Greenland ice sheet). In combination with a bulk drag partitioning model, the retrieved surface elevation is used to estimate the aerodynamic roughness length (z0m) of the surface.We demonstrate the high precision of the retrieved ICESat-2 elevation using co-located UAV photogrammetry, and then evaluate the modelled aerodynamic roughness against multiple in situ eddy-covariance observations. The results point out the importance to use a bulk drag model over a more empirical formulation.The currently available ATL03 geolocated photons are used to map the aerodynamic roughness along the K-transect (2018-2020). We find a considerable spatiotemporal variability in z0m, ranging between 10&#8722;4 m for a smooth snow surface to more than 10&#8722;1 m for rough crevassed areas, which confirms the need to incorporate a variable aerodynamic roughness in atmospheric models over ice sheets.

Download Full-text

The darkening of the Greenland ice sheet: trends, drivers, and projections (1981–2100)

The Cryosphere ◽

10.5194/tc-10-477-2016 ◽

2016 ◽

Vol 10 (2) ◽

pp. 477-496 ◽

Cited By ~ 81

Author(s):

Marco Tedesco ◽

Sarah Doherty ◽

Xavier Fettweis ◽

Patrick Alexander ◽

Jeyavinoth Jeyaratnam ◽

...

Keyword(s):

Ice Sheet ◽

Greenland Ice Sheet ◽

Aerosol Deposition ◽

Near Surface ◽

Multispectral Data ◽

Warming Climate ◽

Air Temperatures ◽

Increasing Trends ◽

Snow And Ice

Abstract. The surface energy balance and meltwater production of the Greenland ice sheet (GrIS) are modulated by snow and ice albedo through the amount of absorbed solar radiation. Here we show, using space-borne multispectral data collected during the 3 decades from 1981 to 2012, that summertime surface albedo over the GrIS decreased at a statistically significant (99 %) rate of 0.02 decade−1 between 1996 and 2012. Over the same period, albedo modelled by the Modèle Atmosphérique Régionale (MAR) also shows a decrease, though at a lower rate ( ∼ −0.01 decade−1) than that obtained from space-borne data. We suggest that the discrepancy between modelled and measured albedo trends can be explained by the absence in the model of processes associated with the presence of light-absorbing impurities. The negative trend in observed albedo is confined to the regions of the GrIS that undergo melting in summer, with the dry-snow zone showing no trend. The period 1981–1996 also showed no statistically significant trend over the whole GrIS. Analysis of MAR outputs indicates that the observed albedo decrease is attributable to the combined effects of increased near-surface air temperatures, which enhanced melt and promoted growth in snow grain size and the expansion of bare ice areas, and to trends in light-absorbing impurities (LAI) on the snow and ice surfaces. Neither aerosol models nor in situ and remote sensing observations indicate increasing trends in LAI in the atmosphere over Greenland. Similarly, an analysis of the number of fires and BC emissions from fires points to the absence of trends for such quantities. This suggests that the apparent increase of LAI in snow and ice might be related to the exposure of a "dark band" of dirty ice and to increased consolidation of LAI at the surface with melt, not to increased aerosol deposition. Albedo projections through to the end of the century under different warming scenarios consistently point to continued darkening, with albedo anomalies averaged over the whole ice sheet lower by 0.08 in 2100 than in 2000, driven solely by a warming climate. Future darkening is likely underestimated because of known underestimates in modelled melting (as seen in hindcasts) and because the model albedo scheme does not currently include the effects of LAI, which have a positive feedback on albedo decline through increased melting, grain growth, and darkening.

Download Full-text

The surface albedo of the Greenland ice sheet: satellite-derived and in situ measurements in the Søndre Strømfjord area during the 1991 melt season

Journal of Glaciology ◽

10.1017/s0022143000004214 ◽

1996 ◽

Vol 42 (141) ◽

pp. 364-374 ◽

Cited By ~ 67

Author(s):

Wouter H. Knap ◽

Johannes Oerlemans

Keyword(s):

Surface Albedo ◽

Near Infrared ◽

Broad Band ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Zone Ii ◽

High Degree ◽

Pixel Scale ◽

Very High

AbstractThe temporal and spatial variation in the surface albedo of the Greenland ice sheet during the ablation season of 1991 is investigated. The study focuses on an area east of Søndre Strømfjord measuring 200 km by 200 km and centred at 67°5′ N, 48° 13′W. The analysis is based on satellite radiance measurements carried out by the Advanced Very High Resolution Radiometer (AVHRR). The broad-band albedo is estimated from the albedos in channel 1 (visible) and channel 2 (near-infrared). The results are calibrated with the surface albedo of sea and dry snow.Satellite-derived albedos are compared with GIMEX ground measurements at three stations. There is a high degree of consistency in temporal variation at two of the three stations. Large systematic differences are attributed to albedo variations on sub-pixel scale.In the course of the ablation season four zones appear, each parallel to the ice edge. It is proposed that these are, in order of increasing altitude: (I) clean and dry ice, (II) ice with surface water, (III) superimposed ice, and (IV) snow. An extensive description of these zones is given on the basis of the situation on 25 July 1991. Zones I, III and IV reveal fairly constant albedos (0.46, 0.65 and 0.75 on average), whereas zone II is characterised by an albedo minimum (0.34). Survey of the western margin of the Greenland ice sheet (up to 71° N) shows that the zonation occurs between 66° and 70° N.

Download Full-text

Multi-modal albedo distributions in the ablation area of the southwestern Greenland Ice Sheet

The Cryosphere ◽

10.5194/tc-9-905-2015 ◽

2015 ◽

Vol 9 (3) ◽

pp. 905-923 ◽

Cited By ~ 13

Author(s):

S. E. Moustafa ◽

A. K. Rennermalm ◽

L. C. Smith ◽

M. A. Miller ◽

J. R. Mioduszewski ◽

...

Keyword(s):

Surface Albedo ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Arctic Region ◽

Bimodal Distribution ◽

The Arctic ◽

Remotely Sensed Data ◽

Data Set ◽

Ablation Area

Abstract. Surface albedo is a key variable controlling solar radiation absorbed at the Greenland Ice Sheet (GrIS) surface and, thus, meltwater production. Recent decline in surface albedo over the GrIS has been linked to enhanced snow grain metamorphic rates, earlier snowmelt, and amplified melt–albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation area albedo and meltwater production is still relatively unknown. In this study, we analyze albedo and ablation rates using in situ and remotely sensed data. Observations include (1) a new high-quality in situ spectral albedo data set collected with an Analytical Spectral Devices Inc. spectroradiometer measuring at 325–1075 nm along a 1.25 km transect during 3 days in June 2013; (2) broadband albedo at two automatic weather stations; and (3) daily MODerate Resolution Imaging Spectroradiometer (MODIS) albedo (MOD10A1) between 31 May and 30 August 2012 and 2013. We find that seasonal ablation area albedos in 2013 have a bimodal distribution, with snow and ice facies characterizing the two peaks. Our results show that a shift from a distribution dominated by high to low albedos corresponds to an observed melt rate increase of 51.5% (between 10–14 July and 20–24 July 2013). In contrast, melt rate variability caused by albedo changes before and after this shift was much lower and varied between ~10 and 30% in the melting season. Ablation area albedos in 2012 exhibited a more complex multimodal distribution, reflecting a transition from light to dark-dominated surface, as well as sensitivity to the so called "dark-band" region in southwest Greenland. In addition to a darkening surface from ice crystal growth, our findings demonstrate that seasonal changes in GrIS ablation area albedos are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. Thus, seasonal variability in ablation area albedos appears to be regulated primarily as a function of bare ice expansion at the expense of snow, surface meltwater ponding, and melting of outcropped ice layers enriched with mineral materials, enabling dust and impurities to accumulate. As climate change continues in the Arctic region, understanding the seasonal evolution of ice sheet surface types in Greenland's ablation area is critical to improve projections of mass loss contributions to sea level rise.

Download Full-text

The surface albedo of the Greenland ice sheet: satellite-derived and in situ measurements in the Søndre Strømfjord area during the 1991 melt season

Journal of Glaciology ◽

10.3189/s0022143000004214 ◽

1996 ◽

Vol 42 (141) ◽

pp. 364-374 ◽

Cited By ~ 4

Author(s):

Wouter H. Knap ◽

Johannes Oerlemans

Keyword(s):

Surface Albedo ◽

Near Infrared ◽

Broad Band ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Zone Ii ◽

High Degree ◽

Pixel Scale ◽

Very High

AbstractThe temporal and spatial variation in the surface albedo of the Greenland ice sheet during the ablation season of 1991 is investigated. The study focuses on an area east of Søndre Strømfjord measuring 200 km by 200 km and centred at 67°5′ N, 48° 13′W. The analysis is based on satellite radiance measurements carried out by the Advanced Very High Resolution Radiometer (AVHRR). The broad-band albedo is estimated from the albedos in channel 1 (visible) and channel 2 (near-infrared). The results are calibrated with the surface albedo of sea and dry snow.Satellite-derived albedos are compared with GIMEX ground measurements at three stations. There is a high degree of consistency in temporal variation at two of the three stations. Large systematic differences are attributed to albedo variations on sub-pixel scale.In the course of the ablation season four zones appear, each parallel to the ice edge. It is proposed that these are, in order of increasing altitude: (I) clean and dry ice, (II) ice with surface water, (III) superimposed ice, and (IV) snow. An extensive description of these zones is given on the basis of the situation on 25 July 1991. Zones I, III and IV reveal fairly constant albedos (0.46, 0.65 and 0.75 on average), whereas zone II is characterised by an albedo minimum (0.34). Survey of the western margin of the Greenland ice sheet (up to 71° N) shows that the zonation occurs between 66° and 70° N.

Download Full-text

Basal Drainage System Response to Increasing Surface Melt on the Greenland Ice Sheet

Science ◽

10.1126/science.1235905 ◽

2013 ◽

Vol 341 (6147) ◽

pp. 777-779 ◽

Cited By ~ 102

Author(s):

T. Meierbachtol ◽

J. Harper ◽

N. Humphrey

Keyword(s):

Conceptual Models ◽

Ice Sheet ◽

Drainage System ◽

Greenland Ice Sheet ◽

System Response ◽

Mountain Glaciers ◽

In Situ Observations ◽

Key Aspects ◽

Conduit Development

Surface meltwater reaching the bed of the Greenland ice sheet imparts a fundamental control on basal motion. Sliding speed depends on ice/bed coupling, dictated by the configuration and pressure of the hydrologic drainage system. In situ observations in a four-site transect containing 23 boreholes drilled to Greenland’s bed reveal basal water pressures unfavorable to water-draining conduit development extending inland beneath deep ice. This finding is supported by numerical analysis based on realistic ice sheet geometry. Slow meltback of ice walls limits conduit growth, inhibiting their capacity to transport increased discharge. Key aspects of current conceptual models for Greenland basal hydrology, derived primarily from the study of mountain glaciers, appear to be limited to a portion of the ablation zone near the ice sheet margin.

Download Full-text

Evaluation of a new snow albedo scheme in RACMO2 for the Greenland ice sheet

10.5194/egusphere-egu2020-15261 ◽

2020 ◽

Author(s):

Christiaan van Dalum ◽

Willem Jan van de Berg ◽

Stef Lhermitte ◽

Michiel van den Broeke

Keyword(s):

Climate Models ◽

Climate Model ◽

Regional Climate ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Atmospheric Conditions ◽

Surface Mass ◽

Snow Albedo ◽

In Situ Data ◽

Snow And Ice

Snow and ice albedo schemes in present day climate models often lack a sophisticated radiation penetration scheme and are limited to a broadband albedo. In this study, we evaluate a new snow albedo scheme in the regional climate model RACMO2 that uses the two-stream radiative transfer in snow model TARTES and the spectral-to-narrowband albedo module SNOWBAL for the Greenland ice sheet. Additionally, the bare ice albedo parameterization has been updated. The snow and ice albedo output of the updated version of RACMO2, referred to as RACMO2.3p3, is evaluated using PROMICE and K-transect in-situ data and MODIS remote-sensing observations. Generally, the RACMO2.3p3 albedo is in very good agreement with satellite observations, leading to a domain-averaged bias of only -0.012. Some discrepancies are, however, observed for regions close to the ice margin. Compared to the previous iteration RACMO2.3p2, the albedo of RACMO2.3p3 is considerably higher in the bare ice zone during the ablation season, as atmospheric conditions now alter the bare ice albedo. For most other regions, however, the albedo of RACMO2.3p3 is lower due to spectral effects, radiation penetration, snow metamorphism or a delayed firn-ice transition. Furthermore, a white-out effect during cloudy conditions is captured and the snow albedo shows a low sensitivity to low soot concentrations. The surface mass balance of RACMO2.3p3 compares well with observations. Subsurface heating, however, now leads to increased melt and refreezing in south Greenland, changing the snow structure.

Download Full-text