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- Charalampidis, Charalampos, et al.
(author)
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Observed melt-season snowpack evolution on the Greenland ice sheet
- 2015
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In: Geological Survey of Denmark and Greenland Bulletin. - 1811-4598 .- 1604-8156. ; :33, s. 65-68
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Journal article (peer-reviewed)abstract
- Due to recent warm and record-warm summers in Greenland (Nghiem et al. 2012), the melt of the ice-sheet surface and the subsequent runoff are increasing (Shepherd et al. 2012). About 84% of the mass loss from the Greenland ice sheet between 2009 and 2012 resulted from increased surface runoff (Enderlin et al. 2014). The largest melt occurs in the ablation zone, the low marginal area of the ice sheet (Van As et al. 2014), where melt exceeds wintertime accumulation and bare ice is thus exposed during each melt season. In the higher regions of the ice sheet (i.e. the accumulation area), melt is limited and the snow cover persists throughout the year. It is in the vast latter area that models struggle to calculate certain mass fluxes with accuracy. A better understanding of processes such as meltwater percolation and refreezing in snow and firn is crucial for more accurate Greenland ice sheet mass-budget estimates (Van Angelen et al. 2013).In May 2012, the field campaign ‘Snow Processes in the Lower Accumulation Zone’ was organized by the Geological Survey of Denmark and Greenland (GEUS) at the KAN_U automatic weather station (67 degrees N, 47 degrees W; 1840 m above sea level), which delivers data to the Programme for Monitoring of the Greenland Ice Sheet (PROMICE; Van As et al. 2013) and is one of the few weather stations located in the lower accumulation area of Greenland. During the expedition, we installed thermistor strings, firn compaction monitors and a snowpack analyzer; we drilled firn cores, performed firn radar measurements, gathered meteorological data, dug snow pits and performed dye-tracing experiments. One important objective of the campaign was to understand the thermal variability in the snowpack during the melt season by monitoring with high-precision temperature probes [...].Below, we present observations from the period 02 May to 23 July and interpret the atmosphere–surface interaction and its impact on the subsurface snow layers, with the goal to quantify refreezing in the Greenland accumulation area.
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| 3. |
- Citterio, Michele, et al.
(author)
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Automatic weather stations for basic and applied glaciological research
- 2015
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In: Geological Survey of Denmark and Greenland Bulletin. - 1811-4598 .- 1604-8156. ; 33, s. 69-72
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Journal article (peer-reviewed)abstract
- Since the early 1980s, the Geological Survey of Denmark and Greenland (GEUS) glaciology group has developed automatic weather stations (AWSs) and operated them on the Greenland ice sheet and on local glaciers to support glaciological research and monitoring projects (e.g. Olesen & Braithwaite 1989; Ahlstrøm et al. 2008). GEUS has also operated AWSs in connection with consultancy services in relation to mining and hydropower pre-feasibility studies (Colgan et al. 2015). Over the years, the design of the AWS has evolved, partly due to technological advances and partly due to lessons learned in the field. At the same time, we have kept the initial goal in focus: long-term, year-round accurate recording of ice ablation, snow depth and the physical parameters that determine the energy budget of glacierised surfaces. GEUS has an extensive record operating AWSs in the harsh Arctic environment of the diverse ablation areas of the Greenland ice sheet, glaciers and ice caps [...].The GEUS AWS model in use now is a reliable tool that is adapted to the environmental and logistical conditions of polar regions. It has a proven record of more than 150 stationyears of deployment in Greenland since its introduction in 2007–2008, and a success rate of c. 90% defined as the fraction of months with more than 80% valid air-temperature measurements over the total deployment time of the 25 stations in the field. The rest of this paper focuses on the technical aspects of the GEUS AWS, and provides an overview of its design and capabilities.
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| 4. |
- Fausto, Robert S., et al.
(author)
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Greenland ice sheet melt area from MODIS (2000–2014)
- 2015
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In: Geological Survey of Denmark and Greenland Bulletin. - 1811-4598 .- 1604-8156. ; 33, s. 57-60
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Journal article (peer-reviewed)abstract
- The Greenland ice sheet is an excellent observatory for global climate change. Meltwater from the 1.8 million km2 large ice sheet influences oceanic temperature and salinity, nutrient fluxes and global sea level (IPCC 2013). Surface reflectivity is a key driver of surface melt rates (Box et al. 2012). Mapping of different ice-sheet surface types provides a clear indicator of where changes in ice-sheet surface reflectivity are most prominent. Here, we present an updated version of a surface classification algorithm that utilises NASA’s Moderateresolution Imaging Spectroradiometer (MODIS) sensor on the Terra satellite to systematically monitor ice-sheet surface melt (Fausto et al. 2007). Our aim is to determine the areal extent of three surface types over the 2000–2014 period: glacier ice, melting snow (including percolation areas) and dry snow (Cuff ey & Paterson 2010). Monthly 1 km2 resolution surface-type grids can be downloaded via the CryoClim internet portal (www.cryoclim.net). In this report, we briefly describe the updated classification algorithm, validation of surface types and inter-annual variability in surface types.
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