Accumulation over the Greenland Ice Sheet as represented in reanalysis data

2011 ◽  
Vol 28 (5) ◽  
pp. 1030-1038 ◽  
Author(s):  
Linling Chen ◽  
Ola M. Johannessen ◽  
Huijun Wang ◽  
Atsumu Ohmura
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Reanalysis Data

scholarly journals High resolution (1 km) positive degree-day modelling of Greenland ice sheet surface mass balance, 1870–2012 using reanalysis data

2016 ◽  
Vol 63 (237) ◽  
pp. 176-193 ◽  
Author(s):  
DAVID J. WILTON ◽  
AMY JOWETT ◽  
EDWARD HANNA ◽  
GRANT R. BIGG ◽  
MICHIEL R. VAN DEN BROEKE ◽  
...  
Keyword(s):  
Mass Balance ◽  
Climate Models ◽  
Local Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Reanalysis Data ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Degree Day ◽  
Positive Degree

ABSTRACTWe show results from a positive degree-day (PDD) model of Greenland ice sheet (GrIS) surface mass balance (SMB), 1870–2012, forced with reanalysis data. The model includes an improved daily temperature parameterization as compared with a previous version and is run at 1 km rather than 5 km resolution. The improvements lead overall to higher SMB with the same forcing data. We also compare our model with results from two regional climate models (RCMs). While there is good qualitative agreement between our PDD model and the RCMs, it usually results in lower precipitation and lower runoff but approximately equivalent SMB: mean 1979–2012 SMB (± standard deviation), in Gt a−1, is 382 ± 78 in the PDD model, compared with 379 ± 101 and 425 ± 90 for the RCMs. Comparison with in situ SMB observations suggests that the RCMs may be more accurate than PDD at local level, in some areas, although the latter generally compares well. Dividing the GrIS into seven drainage basins we show that SMB has decreased sharply in all regions since 2000. Finally we show correlation between runoff close to two calving glaciers and either calving front retreat or calving flux, this being most noticeable from the mid-1990s.

scholarly journals Assessment of Cloud Cover Characteristics in Satellite Datasets and Reanalysis Products for Greenland

2008 ◽  
Vol 21 (9) ◽  
pp. 1837-1849 ◽  
Author(s):  
J. A. Griggs ◽  
J. L. Bamber
Keyword(s):  
Cloud Cover ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Atmospheric Model ◽  
Reanalysis Data ◽  
Department Of Energy ◽  
Balance Model ◽  
Radiation Balance ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract Clouds have an important controlling influence on the radiation balance, and hence surface melting, over the Greenland ice sheet and need to be classified to derive reliable albedo estimates from visible imagery. Little is known, however, about the true cloud cover characteristics for the largest island on Earth, Greenland. Here, an attempt is made to address this knowledge gap by examining cloud characteristics, as determined by three complementary satellites sensors: the Advanced Very High Resolution Radiometer (AVHRR), the Along Track Scanning Radiometer-2 (ATSR-2), and the Moderate Resolution Imaging Spectroradiometer (MODIS). The first provides a multidecadal time series of clouds, albedo, and surface temperature, and is available, in the form of the extended AVHRR Polar Pathfinder dataset (APP-x), as a homogeneous, consistent dataset from 1982 until 2004. APP-x data, however, are also the most challenging to cloud classify over snow-covered terrain, due to the limited spectral capabilities of the instrument. ATSR-2 permits identification and classification using stereophotogrammetric techniques and MODIS has enhanced spectral sampling in the visible and thermal infrared but over more limited time periods. The spatial cloud fractions from the three sensors are compared and show good agreement in terms of both magnitude and spatial pattern. The cloud fractions, and inferred patterns of accumulation, are then assessed from three commonly used reanalysis datasets: NCEP–NCAR, the second NCEP–Department of Energy (DOE) Atmospheric Model Intercomparison Project (AMIP-II), and the 40-yr ECMWF Re-Analysis (ERA-40). Poor agreement between the reanalysis datasets is found. NCEP–DOE AMIP-II produces a cloud fraction similar to that observed by the satellites. NCEP–NCAR and ERA-40, however, bear little similarity to the cloud fractions derived from the satellite observations. This suggests that they may produce poor accumulation estimates over the ice sheet and poor estimates of radiation balance. Using these reanalysis data to force a mass balance model of the ice sheet, without appropriate downscaling and correction for the substantial biases present, may, therefore, produce substantial errors in surface melt rate estimates.

scholarly journals Measured and Modeled Snow Cover Properties across the Greenland Ice Sheet

2017 ◽  
Author(s):  
Sascha Bellaire ◽  
Martin Proksch ◽  
Martin Schneebeli ◽  
Masashi Niwano ◽  
Konrad Steffen
Keyword(s):  
Snow Cover ◽  
Ice Sheet ◽  
Geographical Location ◽  
Indirect Evidence ◽  
Greenland Ice Sheet ◽  
Reanalysis Data ◽  
Snow Accumulation ◽  
Water Infiltration ◽  
Spatial And Temporal Variability ◽  
Spatially Distributed

Abstract. The Greenland ice sheet (GrIS) is known to be contributing to sea level rise in a warming climate. The snow cover on the ice sheet is the direct link between a potentially warmer atmosphere and the ice itself. However, little is known about the microstructure and especially about the spatial and temporal variability of the snow cover, except from indirect evidence from remote sensing. The detailed snowpack stratigraphy is relevant for processes such as the albedo feedback, water infiltration and firn densification. During a field campaign in 2015, spatially distributed snow observations of the GrIS were gathered at stations belonging to the Greenland Climate Network (GC-Net). High-resolution snow profiles of density, specific surface area and hardness were measured. Hardness was measured with the SnowMicroPen, which was also used to assess the spatial variability of the snow density with depth. The snow cover model SNOWPACK was forced with reanalysis data from the model NHM-SMAP. The measured mean density of the upper snow cover was in good agreement with the simulations using constant densities for snow accumulation, i.e. new snow, depending on the geographical location on the GrIS. However, the observed stratigraphy in terms of density and SSA could not be reproduced. We found that for a one-dimensional snowpack model it is difficult to parameterize for snowpacks undergoing multiple erosion and redeposition events, as is typical for the GrIS and other perennial polar snowpacks. This limitation may be a drawback to understanding past and future changes of the snow, and the associated processes.

The Nioghalvfjerdsfjorden glacier project, North-East Greenland: a study of ice sheet response to climatic change

1997 ◽  
pp. 95-103 ◽  
Author(s):  
Henrik Højmark Thomsen ◽  
Niels Reeh ◽  
Ole B. Olesen ◽  
Carl Egede Bøggilde ◽  
Wolfgang Starzer ◽  
...  
Keyword(s):  
Climatic Change ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
East Greenland ◽  
Changing Climate ◽  
North East ◽  
Integrated Research ◽  
Research Themes ◽  
Advance Research ◽  
Inland Ice

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Højmark Thomsen, H., Reeh, N., Olesen, O. B., Egede Bøggilde, C., Starzer, W., Weidick, A., & Higgins, A. K. (1997). The Nioghalvfjerdsfjorden glacier project, North-East Greenland: a study of ice sheet response to climatic change. Geology of Greenland Survey Bulletin, 176, 95-103. https://doi.org/10.34194/ggub.v176.5073 _______________ Glaciological research was initiated in 1996 on the floating glacier tongue filling Nioghalvfjerdsfjorden in NorthEast Greenland (Fig. 1), with the aim of acquiring a better understanding of the response of the Greenland ice sheet (Inland Ice) to changing climate, and the implications for future sea level. The research is part of a three year project (1996–98) to advance research into the basic processes that contribute to changes in the ocean volume with a changing climate. Five nations are participants in the project, which is supported by the European Community (EC) Environment and Climate Programme. The Geological Survey of Denmark and Greenland (GEUS) and the Danish Polar Center are the Danish partners in the project, both with integrated research themes concentrated on and around Nioghalvfjerdsfjorden.

Could climate engineering save the Greenland Ice Sheet?

2016 ◽  
Author(s):  
Patrick J. Applegate ◽  
K. Keller
Keyword(s):  
Sea Level Rise ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Sea Level ◽  
Computer Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Upper Atmosphere ◽  
Climate Engineering ◽  
Air Temperatures

Engineering the climate through albedo modification (AM) could slow, but probably would not stop, melting of the Greenland Ice Sheet. Albedo modification is a technology that could reduce surface air temperatures through putting reflective particles into the upper atmosphere. AM has never been tested, but it might reduce surface air temperatures faster and more cheaply than reducing greenhouse gas emissions. Some scientists claim that AM would also prevent or reverse sea-level rise. But, are these claims true? The Greenland Ice Sheet will melt faster at higher temperatures, adding to sea-level rise. However, it's not clear that reducing temperatures through AM will stop or reverse sea-level rise due to Greenland Ice Sheet melting. We used a computer model of the Greenland Ice Sheet to examine its contributions to future sea level rise, with and without AM. Our results show that AM would probably reduce the rate of sea-level rise from the Greenland Ice Sheet. However, sea-level rise would likely continue even with AM, and the ice sheet would not regrow quickly. Albedo modification might buy time to prepare for sea-level rise, but problems could arise if policymakers assume that AM will stop sea-level rise completely.

scholarly journals Response of the Energy Balance on the Margin of the Greenland Ice Sheet to Temperature Changes

1990 ◽  
Vol 36 (123) ◽  
pp. 217-221 ◽  
Author(s):  
Roger J. Braithwaite ◽  
Ole B. Olesen
Keyword(s):  
Heat Flux ◽  
Energy Balance ◽  
Air Temperature ◽  
Sensible Heat Flux ◽  
Ice Sheet ◽  
Temperature Response ◽  
Greenland Ice Sheet ◽  
Energy Balance Model ◽  
Balance Model ◽  
Sensible Heat

AbstractDaily ice ablation on two outlet glaciers from the Greenland ice sheet, Nordbogletscher (1979–83) and Qamanârssûp sermia (1980–86), is related to air temperature by a linear regression equation. Analysis of this ablation-temperature equation with the help of a simple energy-balance model shows that sensible-heat flux has the greatest temperature response and accounts for about one-half of the temperature response of ablation. Net radiation accounts for about one-quarter of the temperature response of ablation, and latent-heat flux and errors account for the remainder. The temperature response of sensible-heat flux at QQamanârssûp sermia is greater than at Nordbogletscher mainly due to higher average wind speeds. The association of high winds with high temperatures during Föhn events further increases sensible-heat flux. The energy-balance model shows that ablation from a snow surface is only about half that from an ice surface at the same air temperature.

scholarly journals Melt season duration and ice layer formation on the Greenland ice sheet, 2000–2004

2007 ◽  
Vol 112 (F4) ◽  
Author(s):  
Libo Wang ◽  
Martin Sharp ◽  
Benoit Rivard ◽  
Konrad Steffen
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Layer Formation

scholarly journals Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet

2021 ◽  
Author(s):  
Jon R. Hawkings ◽  
Benjamin S. Linhoff ◽  
Jemma L. Wadham ◽  
Marek Stibal ◽  
Carl H. Lamborg ◽  
...  
Keyword(s):  
Natural Waters ◽  
Inorganic Mercury ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Annual Runoff ◽  
Arctic Ecosystems ◽  
High Mercury ◽  
Southwestern Margin ◽  
High Concentrations ◽  
Dissolved Mercury

AbstractThe Greenland Ice Sheet is currently not accounted for in Arctic mercury budgets, despite large and increasing annual runoff to the ocean and the socio-economic concerns of high mercury levels in Arctic organisms. Here we present concentrations of mercury in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet and evaluate the export of mercury to downstream fjords based on samples collected during summer ablation seasons. We show that concentrations of dissolved mercury are among the highest recorded in natural waters and mercury yields from these glacial catchments (521–3,300 mmol km−2 year−1) are two orders of magnitude higher than from Arctic rivers (4–20 mmol km−2 year−1). Fluxes of dissolved mercury from the southwestern region of Greenland are estimated to be globally significant (15.4–212 kmol year−1), accounting for about 10% of the estimated global riverine flux, and include export of bioaccumulating methylmercury (0.31–1.97 kmol year−1). High dissolved mercury concentrations (~20 pM inorganic mercury and ~2 pM methylmercury) were found to persist across salinity gradients of fjords. Mean particulate mercury concentrations were among the highest recorded in the literature (~51,000 pM), and dissolved mercury concentrations in runoff exceed reported surface snow and ice values. These results suggest a geological source of mercury at the ice sheet bed. The high concentrations of mercury and its large export to the downstream fjords have important implications for Arctic ecosystems, highlighting an urgent need to better understand mercury dynamics in ice sheet runoff under global warming.

scholarly journals A realistic Greenland ice sheet and surrounding glaciers and ice caps melting in a coupled climate model

2021 ◽  
Author(s):  
Marion Devilliers ◽  
Didier Swingedouw ◽  
Juliette Mignot ◽  
Julie Deshayes ◽  
Gilles Garric ◽  
...  
Keyword(s):  
Climate Model ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Coupled Climate Model ◽  
Ice Caps
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