Climatology and firn processes in the lower accumulation area of the Greenland ice sheet
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 r...
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Uppsala universitet, Luft-, vatten- och landskapslära
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ftuppsalauniv:oai:DiVA.org:uu-284365 2023-05-15T13:11:47+02:00 Climatology and firn processes in the lower accumulation area of the Greenland ice sheet Charalampidis, Charalampos 2016 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-284365 eng eng Uppsala universitet, Luft-, vatten- och landskapslära Geological Survey of Denmark and Greenland (GEUS) Uppsala Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 1372 http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-284365 urn:isbn:978-91-554-9571-8 info:eu-repo/semantics/openAccess 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 Climate Research Klimatforskning Environmental Sciences Miljövetenskap Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning Doctoral thesis, comprehensive summary info:eu-repo/semantics/doctoralThesis text 2016 ftuppsalauniv 2023-02-23T21:52:11Z 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. Stability and Variations of Arctic Land Ice (SVALI) Programme for Monitoring of the Greenland Ice Sheet (PROMICE) Greenland Analogue Project (GAP) Doctoral or Postdoctoral Thesis albedo Arctic Climate change Greenland Ice Sheet Uppsala University: Publications (DiVA) Arctic Greenland |
institution |
Open Polar |
collection |
Uppsala University: Publications (DiVA) |
op_collection_id |
ftuppsalauniv |
language |
English |
topic |
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 Climate Research Klimatforskning Environmental Sciences Miljövetenskap Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning |
spellingShingle |
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 Climate Research Klimatforskning Environmental Sciences Miljövetenskap Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning Charalampidis, Charalampos Climatology and firn processes in the lower accumulation area of the Greenland ice sheet |
topic_facet |
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 Climate Research Klimatforskning Environmental Sciences Miljövetenskap Meteorology and Atmospheric Sciences Meteorologi och atmosfärforskning |
description |
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. Stability and Variations of Arctic Land Ice (SVALI) Programme for Monitoring of the Greenland Ice Sheet (PROMICE) Greenland Analogue Project (GAP) |
format |
Doctoral or Postdoctoral Thesis |
author |
Charalampidis, Charalampos |
author_facet |
Charalampidis, Charalampos |
author_sort |
Charalampidis, Charalampos |
title |
Climatology and firn processes in the lower accumulation area of the Greenland ice sheet |
title_short |
Climatology and firn processes in the lower accumulation area of the Greenland ice sheet |
title_full |
Climatology and firn processes in the lower accumulation area of the Greenland ice sheet |
title_fullStr |
Climatology and firn processes in the lower accumulation area of the Greenland ice sheet |
title_full_unstemmed |
Climatology and firn processes in the lower accumulation area of the Greenland ice sheet |
title_sort |
climatology and firn processes in the lower accumulation area of the greenland ice sheet |
publisher |
Uppsala universitet, Luft-, vatten- och landskapslära |
publishDate |
2016 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-284365 |
geographic |
Arctic Greenland |
geographic_facet |
Arctic Greenland |
genre |
albedo Arctic Climate change Greenland Ice Sheet |
genre_facet |
albedo Arctic Climate change Greenland Ice Sheet |
op_relation |
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 1372 http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-284365 urn:isbn:978-91-554-9571-8 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766248976742350848 |