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Observed melt-season snowpack evolution on the Greenland ice sheet
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Geological Survey of Denmark and Greenland (GEUS). (Ice, Climate and Environment)ORCID iD: 0000-0003-0853-697X
Geological Survey of Denmark and Greenland (GEUS).ORCID iD: 0000-0002-6553-8982
2015 (English)In: Geological Survey of Denmark and Greenland Bulletin, ISSN 1811-4598, E-ISSN 1604-8156, no 33, 65-68 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2015. no 33, 65-68 p.
Keyword [en]
snow, Greenland, ice sheet, percolation, refreezing
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-261333ISI: 000359477400016OAI: oai:DiVA.org:uu-261333DiVA: diva2:850346
Stability and Variations of Arctic Land Ice (SVALI)Programme for Monitoring of the Greenland Ice Sheet (PROMICE)
Available from: 2015-09-01 Created: 2015-09-01 Last updated: 2016-06-15
In thesis
1. Climatology and firn processes in the lower accumulation area of the Greenland ice sheet
Open this publication in new window or tab >>Climatology and firn processes in the lower accumulation area of the Greenland ice sheet
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Greenland ice sheet is the largest Northern Hemisphere store of fresh water, and it is responding rapidly to the warming climate. In situ observations document the changing ice sheet properties in the lower accumulation area, Southwest Greenland. Firn densities from 1840 meters above sea level retrieved in May 2012 revealed the existence of a 5.5-meter-thick, near-surface ice layer in response to the recent increased melt and refreezing in firn. As a consequence, vertical meltwater percolation in the extreme summer 2012 was inefficient, resulting in surface runoff. Meltwater percolated and refroze at six meters depth only after the end of the melt season. This prolonged autumn refreezing under the newly accumulated snowpack resulted in unprecedented firn warming with temperature at ten meters depth increased by more than four degrees Celsius. Simulations confirm that meltwater reached nine meters depth at most. The refrozen meltwater was estimated at 0.23 meters water equivalent, amounting to 25 % of the total 2012 ablation.

A surface energy balance model was used to evaluate the seasonal and interannual variability of all surface energy fluxes at that elevation in the years 2009 to 2013. Due to the meltwater presence at the surface in 2012, the summer-averaged albedo was significantly reduced (0.71 in 2012; typically 0.78). A sensitivity analysis revealed that 71 % of the subsequent additional solar radiation in 2012 was used for melt, corresponding to 36 % of the total 2012 surface lowering. This interplay between melt and firn properties highlights that the lower accumulation area of the Greenland ice sheet will be responding rapidly in a warming climate.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 81 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1372
climate change, Greenland ice sheet, accumulation area, automatic weather stations, surface energy balance, melt–albedo feedback, surface mass budget, snow, firn, meltwater, percolation, refreezing, runoff
National Category
Climate Research Environmental Sciences Meteorology and Atmospheric Sciences
urn:nbn:se:uu:diva-284365 (URN)978-91-554-9571-8 (ISBN)
Public defence
2016-06-10, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:15 (English)
Stability and Variations of Arctic Land Ice (SVALI)Programme for Monitoring of the Greenland Ice Sheet (PROMICE)Greenland Analogue Project (GAP)
Available from: 2016-05-20 Created: 2016-04-17 Last updated: 2016-06-15

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