scholarly journals PROMICE automatic weather station data

2021 ◽  
Author(s):  
Robert S. Fausto ◽  
Dirk van As ◽  
Kenneth D. Mankoff ◽  
Baptiste Vandecrux ◽  
Michele Citterio ◽  
...  
Keyword(s):  
Surface Energy Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Weather Station ◽  
Automatic Weather Station ◽  
Atmospheric Conditions ◽  
Production Chain ◽  
Near Surface ◽  
Surface Mass ◽  
Future Assessment

Abstract. The Programme for Monitoring of the Greenland Ice Sheet (PROMICE) has been measuring climate and ice sheetproperties since 2007. Currently the PROMICE automatic weather station network includes 25 instrumented sites in Greenland.Accurate measurements of the surface and near-surface atmospheric conditions in a changing climate is important for reliablepresent and future assessment of changes to the Greenland ice sheet. Here we present the PROMICE vision, methodology,and each link in the production chain for obtaining and sharing quality-checked data. In this paper we mainly focus on thecritical components for calculating the surface energy balance and surface mass balance. A user-contributable dynamic webbaseddatabase of known data quality issues is associated with the data products at (https://github.com/GEUS-PROMICE/PROMICE-AWS-data-issues/). As part of the living data option, the datasets presented and described here are available atDOI: 10.22008/promice/data/aws, https://doi.org/10.22008/promice/data/aws (Fausto and van As, 2019).

scholarly journals Programme for Monitoring of the Greenland Ice Sheet (PROMICE) automatic weather station data

2021 ◽  
Vol 13 (8) ◽  
pp. 3819-3845
Author(s):  
Robert S. Fausto ◽  
Dirk van As ◽  
Kenneth D. Mankoff ◽  
Baptiste Vandecrux ◽  
Michele Citterio ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Weather Station ◽  
Automatic Weather Station ◽  
Atmospheric Conditions ◽  
Production Chain ◽  
Near Surface ◽  
Surface Mass ◽  
Future Assessment ◽  
Critical Components

Abstract. The Programme for Monitoring of the Greenland Ice Sheet (PROMICE) has been measuring climate and ice sheet properties since 2007. Currently, the PROMICE automatic weather station network includes 25 instrumented sites in Greenland. Accurate measurements of the surface and near-surface atmospheric conditions in a changing climate are important for reliable present and future assessment of changes in the Greenland Ice Sheet. Here, we present the PROMICE vision, methodology, and each link in the production chain for obtaining and sharing quality-checked data. In this paper, we mainly focus on the critical components for calculating the surface energy balance and surface mass balance. A user-contributable dynamic web-based database of known data quality issues is associated with the data products at https://github.com/GEUS-Glaciology-and-Climate/PROMICE-AWS-data-issues/ (last access: 7 April 2021). As part of the living data option, the datasets presented and described here are available at https://doi.org/10.22008/promice/data/aws (Fausto et al., 2019).

scholarly journals Climatology and ablation at the South Greenland ice sheet margin from automatic weather station observations

2009 ◽  
Vol 3 (1) ◽  
pp. 117-158 ◽  
Author(s):  
D. van As ◽  
C. E. Bøggild ◽  
S. Nielsen ◽  
A. P. Ahlstrøm ◽  
R. S. Fausto ◽  
...  
Keyword(s):  
Surface Albedo ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Katabatic Wind ◽  
Weather Station ◽  
Automatic Weather Station ◽  
The South ◽  
Near Surface ◽  
Highly Sensitive ◽  
Wind Events

Abstract. We describe the climatology from a meteorological dataset acquired from automatic weather station observations done in the ablation zone of the Greenland Ice Sheet between 2001 and 2007. Stations were placed in three regions below the polar circle: on the southern tip of the ice sheet, on a calving glacier in the Nuuk fjord, and on the south-eastern ice margin near Tasiilaq. The yearly cycles in temperature, relative humidity and wind speed reveal the largest variability in wintertime, causing annual values to depend largely on winter values. Adding to wintertime variability are extremely strong and cold katabatic wind events in the southeast ("piteraqs"). During summer no pronounced daily cycle in near-surface atmospheric parameters is recorded in the three regions, in spite of a large cycle in solar radiation, dominantly regulating surface melt. Net ablation is largest at the southernmost station due to low surface albedo, and can be up to six metres per year, but is highly sensitive to the timing of the start of the ice ablation season. Illustrative of this is that similar ablation amounts are found in the Nuuk fjord region where little or no snow accumulates in winter.

scholarly journals Assessing the accuracy of Greenland ice sheet ice ablation measurements by pressure transducer

2012 ◽  
Vol 58 (212) ◽  
pp. 1144-1150 ◽  
Author(s):  
Robert S. Fausto ◽  
Dirk Van As ◽  
Andreas P. Ahlstrøm ◽  
Michele Citterio
Keyword(s):  
Time Series ◽  
Pressure Transducer ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ablation Rate ◽  
Absolute Pressure ◽  
Weather Station ◽  
Automatic Weather Station ◽  
Vertical Column ◽  
Physically Based

AbstractWe present a method of measuring ice ablation using an absolute pressure transducer as part of an automatic weather station (AWS) system, which we have installed in 17 locations on the Greenland ice sheet. The pressure transducer assembly is drilled into the ice, enclosed in a hose filled with antifreeze liquid. The pressure signal registered by the transducer is that of the vertical column of liquid over the sensor, which can be translated to depth, and ice ablation rate, knowing the density of the liquid. Measuring at sub-daily timescales, this assembly is well suited to monitoring ice ablation in remote regions, with clear advantages over other, well-established methods. The pressure transducer system has the potential to monitor ice ablation for several years without re-drilling, and the system is suitable for high-ablation areas (>5ma-1). A routine to transform raw measurements into ablation values is presented, including a physically based method to remove air-pressure variability from the signal. The pressure transducer time series is compared to that recorded by a sonic ranger for the climatically hostile setting on the Greenland ice sheet.

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

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

<p>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.</p>

scholarly journals Partitioning of melt energy and meltwater fluxes in the ablation zone of the west Greenland ice sheet

2008 ◽  
Vol 2 (2) ◽  
pp. 179-189 ◽  
Author(s):  
M. van den Broeke ◽  
P. Smeets ◽  
J. Ettema ◽  
C. van der Veen ◽  
R. van de Wal ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Ablation Zone ◽  
The West ◽  
Near Surface ◽  
Surface Mass ◽  
West Greenland ◽  
Ice Melt ◽  
June July

Abstract. We present four years (August 2003–August 2007) of surface mass balance data from the ablation zone of the west Greenland ice sheet along the 67° N latitude circle. Sonic height rangers and automatic weather stations continuously measured accumulation/ablation and near-surface climate at distances of 6, 38 and 88 km from the ice sheet margin at elevations of 490, 1020 and 1520 m a.s.l. Using a melt model and reasonable assumptions about snow density and percolation characteristics, these data are used to quantify the partitioning of energy and mass fluxes during melt episodes. The lowest site receives very little winter accumulation, and ice melting is nearly continuous in June, July and August. Due to the lack of snow accumulation, little refreezing occurs and virtually all melt energy is invested in runoff. Higher up the ice sheet, the ice sheet surface freezes up during the night, making summer melting intermittent. At the intermediate site, refreezing in snow consumes about 10% of the melt energy, increasing to 40% at the highest site. The sum of these effects is that total melt and runoff increase exponentially towards the ice sheet margin, each time doubling between the stations. At the two lower sites, we estimate that radiation penetration causes 20–30% of the ice melt to occur below the surface.

scholarly journals The modelled liquid water balance of the Greenland Ice Sheet

2017 ◽  
Author(s):  
Christian R. Steger ◽  
Carleen H. Reijmer ◽  
Michiel R. van den Broeke
Keyword(s):  
Water Balance ◽  
Liquid Water ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Special Focus ◽  
Southeastern Part ◽  
Upward Migration ◽  
Near Surface ◽  
Surface Mass ◽  
Surface Melt

Abstract. Recent studies indicate that the surface mass balance will dominate the Greenland Ice Sheet's (GrIS) contribution to 21st century sea level rise. Consequently, it is crucial to understand the liquid water balance (LWB) of the ice sheet and its response to increasing surface melt. We therefore analyse a firn simulation conducted with SNOWPACK for the GrIS and over the period 1960–2014 with a special focus on the LWB and refreezing. An indirect evaluation of the simulated refreezing climate with GRACE and firn temperature observations indicate a good model performance. Results of the LWB analysis reveal a spatially uniform increase in surface melt during 1990–2014. As a response, refreezing and runoff also indicate positive trends for this period, where refreezing increases with only half the rate of runoff, which implies that the majority of the additional liquid input runs off the ice sheet. However, this pattern is spatially variable as e.g. in the southeastern part of the GrIS, most of the additional liquid input is buffered in the firn layer due to relatively high snowfall rates. The increase in modelled refreezing leads to a general decrease in firn air content and to a substantial increase in near-surface firn temperature in some regions. On the western side of the ice sheet, modelled firn temperature increases are highest in the lower accumulation zone and are primarily caused by the exceptional melt season of 2012. On the eastern side, simulated firn temperature increases more gradually and with an associated upward migration of firn aquifers.

scholarly journals Unprecedented atmospheric conditions (1948–2019) drive the 2019 exceptional melting season over the Greenland ice sheet

2020 ◽  
Vol 14 (4) ◽  
pp. 1209-1223 ◽  
Author(s):  
Marco Tedesco ◽  
Xavier Fettweis
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Mass Balance ◽  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Atmospheric Conditions ◽  
Surface Mass ◽  
Artificial Neural

Abstract. Understanding the role of atmospheric circulation anomalies on the surface mass balance of the Greenland ice sheet (GrIS) is fundamental for improving estimates of its current and future contributions to sea level rise. Here, we show, using a combination of remote sensing observations, regional climate model outputs, reanalysis data, and artificial neural networks, that unprecedented atmospheric conditions (1948–2019) occurring in the summer of 2019 over Greenland promoted new record or close-to-record values of surface mass balance (SMB), runoff, and snowfall. Specifically, runoff in 2019 ranked second within the 1948–2019 period (after 2012) and first in terms of surface mass balance negative anomaly for the hydrological year 1 September 2018–31 August 2019. The summer of 2019 was characterized by an exceptional persistence of anticyclonic conditions that, in conjunction with low albedo associated with reduced snowfall in summer, enhanced the melt–albedo feedback by promoting the absorption of solar radiation and favored advection of warm, moist air along the western portion of the ice sheet towards the north, where the surface melt has been the highest since 1948. The analysis of the frequency of daily 500 hPa geopotential heights obtained from artificial neural networks shows that the total number of days with the five most frequent atmospheric patterns that characterized the summer of 2019 was 5 standard deviations above the 1981–2010 mean, confirming the exceptional nature of the 2019 season over Greenland.

Time-Domain Reflectometry Observations of Meltwater Percolation and Retention in the Firn Layer of the Greenland Ice Sheet

2020 ◽  
Author(s):  
Samira Samimi ◽  
Shawn Marshall ◽  
Michael McFerrin
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Time Domain ◽  
Liquid Water ◽  
Surface Energy Balance ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Time Domain Reflectometry ◽  
Latent Heat Release ◽  
Near Surface

<p>Mass loss from the Greenland Ice Sheet has increased in recent decades due to significant increases in surface melt and runoff. The fraction of summer melt retains as a liquid water or refreezes as it percolates into the underlying cold firn, acting as a buffer to the summer runoff. There are challenges to quantifying both infiltration and refreezing of meltwater in this complex heterogeneous cold firn and to understand the spatial variability of these processes. In this study we present continuous in situ measurements of near-surface temperature and dielectric permittivity, a proxy for volumetric water content, using TDR (Time Domain Reflectometry) methods in the percolation zone of the southern Greenland Ice Sheet. We established two observation sites near Dye 2 in April, 2016, excavating firn pits to depths of 2.2 and 5.3 m. The two sites are 650 m apart to quantify the percolation and refreezing of meltwater and to observe the spatial variability of these processes through summer 2016. Thermistor arrays were used to track the thermal signature of meltwater penetration in firn, through the effects of latent heat release when meltwater refreezes. Through the addition of TDR probes, we attempt to directly quantify meltwater volume as well as hydraulic conductivity of the near-surface snow and firn. An automatic weather station (AWS) configured for surface energy balance monitoring was also installed. AWS data were used to calculate the surface energy balance and model meltwater production. The melting front, characterized by 0°C conditions and direct evidence of liquid water, penetrated to a depth of between 1.8 and 2.1 m in summer 2016; at depths of 2.1 m and greater, temperatures remained below 0°C, there was no evidence of abrupt warming (i.e. latent heat release), and dielectric permittivities remained at their background levels. Meltwater penetrated several thick ice layers, but not until temperatures reached the melting point at these depths, implying that ice layers may transition to a permeable ‘slush’ layer, given enough conductive and latent heating, permitting progressive penetration of meltwater to depth. Firn temperatures (sub-zero conditions below ~2 m) appear to have been the main barrier to deep penetration of meltwater during summer 2016.</p>

scholarly journals Estimating the Greenland ice sheet surface mass balance contribution to future sea level rise using the regional atmospheric climate model MAR

2013 ◽  
Vol 7 (2) ◽  
pp. 469-489 ◽  
Author(s):  
X. Fettweis ◽  
B. Franco ◽  
M. Tedesco ◽  
J. H. van Angelen ◽  
J. T. M. Lenaerts ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Model ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Mass Balance ◽  
Near Surface ◽  
Surface Mass

Abstract. To estimate the sea level rise (SLR) originating from changes in surface mass balance (SMB) of the Greenland ice sheet (GrIS), we present 21st century climate projections obtained with the regional climate model MAR (Modèle Atmosphérique Régional), forced by output of three CMIP5 (Coupled Model Intercomparison Project Phase 5) general circulation models (GCMs). Our results indicate that in a warmer climate, mass gain from increased winter snowfall over the GrIS does not compensate mass loss through increased meltwater run-off in summer. Despite the large spread in the projected near-surface warming, all the MAR projections show similar non-linear increase of GrIS surface melt volume because no change is projected in the general atmospheric circulation over Greenland. By coarsely estimating the GrIS SMB changes from GCM output, we show that the uncertainty from the GCM-based forcing represents about half of the projected SMB changes. In 2100, the CMIP5 ensemble mean projects a GrIS SMB decrease equivalent to a mean SLR of +4 ± 2 cm and +9 ± 4 cm for the RCP (Representative Concentration Pathways) 4.5 and RCP 8.5 scenarios respectively. These estimates do not consider the positive melt–elevation feedback, although sensitivity experiments using perturbed ice sheet topographies consistent with the projected SMB changes demonstrate that this is a significant feedback, and highlight the importance of coupling regional climate models to an ice sheet model. Such a coupling will allow the assessment of future response of both surface processes and ice-dynamic changes to rising temperatures, as well as their mutual feedbacks.

scholarly journals Reconstructions of the 1900–2015 Greenland ice sheet surface mass balance using the regional climate MAR model

2016 ◽  
Author(s):  
Xavier Fettweis ◽  
Jason E. Box ◽  
Cécile Agosta ◽  
Charles Amory ◽  
Christoph Kittel ◽  
...  
Keyword(s):  
Mass Balance ◽  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Surface Mass Balance ◽  
Reference Period ◽  
Ice Dynamics ◽  
Near Surface ◽  
Surface Mass

Abstract. With the aim of studying the recent Greenland Ice Sheet (GrIS) Surface Mass Balance (SMB) decrease with respect to the last century, we have forced the regional climate MAR model (version 3.5.2) with the ERA-Interim (1979–2015), ERA-40 (1958–2001), NCEP-NCARv1 (1948–2015), NCEP-NCARv2 (1979–2015), JRA-55 (1958–2014), 20CRv2(c) (1900–2014) and ERA-20C (1900–2010) reanalysis. While all of these forcing products are reanalyses assumed to represent the same climate, they produce significant differences in the MAR simulated SMB over their common period. A temperature adjustment of +1 °C (respectively −1 °C) improved the accuracy of MAR boundary conditions from both ERA-20C and 20CRv2 reanalyses given that ERA-20C (resp. 20CRv2) is 1 °C colder (resp. warmer) over Greenland than ERA-Interim over 1980–2010. Comparisons with daily PROMICE near-surface observations validated these adjustments. Comparisons with SMB measurements from PROMICE, ice cores and satellite derived melt extent reveal the most accurate forcing data sets for simulating the GrIS SMB to be ERA-Interim and NCEP-NCARv1. However, some biases remain in MAR suggesting that some improvements need still to be done in its cloudiness and radiative scheme as well as in the representation of the bare ice albedo. Results from all forcing simulations indicate: (i) the period 1961–1990 commonly chosen as a stable reference period for Greenland SMB and ice dynamics is actually a period when the SMB was anomalously positive (~ +10 %) compared to the last 120 years; (ii) SMB has decreased significantly after this reference period due to increasing and unprecedented melt reaching the highest rates in the 120 year common period; (iii) before 1960, both ERA-20C and 20CRv2 forced MAR simulations suggest a significant precipitation increase over 1900–1950 although this increase could be the result of an artefact in reanalysis not enough constrained by observations during this period. These MAR-based SMB and accumulation reconstructions are however quite similar to those from Box (2013) after 1930, which confirms the Box (2013)'s stationarity assumption of SMB over the last century. Finally, the ERA-20C forced simulation only suggests that SMB during the 1920–1930 warm period over Greenland was comparable to the SMB of the 2000's due to both higher melt and lower precipitation than normal.

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