Firn
Firn(/fɪərn/;fromSwiss Germanfirn"last year's", cognate withbefore) is partially compactednévé,a type ofsnowthat has been left over from past seasons and has beenrecrystallizedinto a substance denser than névé. It isicethat is at an intermediate stage between snow and glacial ice.[1]Firn has the appearance of wet sugar, but has a hardness that makes it extremely resistant to shovelling. Its density generally ranges from 0.35 g/cm3to 0.9 g/cm3,[1][2]and it can often be found underneath the snow that accumulates at the head of aglacier.
Snowflakesare compressed under the weight of the overlyingsnowpack.Individualcrystalsnear the melting point are semiliquid and slick, allowing them to glide along other crystal planes and to fill in the spaces between them, increasing the ice's density. Where the crystals touch, they bond together, squeezing the air between them to the surface or into bubbles.
In the summer months, the crystal metamorphosis can occur more rapidly because of water percolation between the crystals. By summer's end, the result is firn.[3]
The minimum altitude that firn accumulates on a glacier is called thefirn limit,firn lineorsnowline.
List of firns[edit]
- Antarctic Firn[1][4]
- Daniel Bruun Firn[5]
- Dreyer Firn[6]
- East Northwall Firn
- Rink Firn
- Sven Hedin Firn[7]
- West Northwall Firn
Other uses[edit]
In colloquial and technical language, "firn" is used to describe certain forms ofold snow,including:
- oldsnowfields,known asFirnfelder(lit. 'firn fields'), even if the snow is not yet one year old
- the more recent snow layers of a temperate, or "firned",glacier
- used in skiing, the uppermost, soft layer of snow that is frozen overnight and, as a result of spring sunshine and high air temperatures, melts and reforms on an area of old snow orharsch(lit. 'harsh',referring to the snow's rough texture)
As in the last context, a ski slope that experiences melting and refreezing intoharschis said to "firn up". In Switzerland, these slopes are calledSulz,but in Germany,Sulzmore often refers to a depth at which skiing downhill is no longer enjoyable.
References[edit]
- ^abcvan den Broeke, Michiel (1 May 2008)."Depth and Density of the Antarctic Firn Layer".Arctic, Antarctic, and Alpine Research.40(2): 432–438.doi:10.1657/1523-0430(07-021)[BROEKE]2.0.CO;2.ISSN1523-0430.S2CID198156588.
- ^Cuffey, Kurt M.;Paterson, W. S. B.(3 May 2010).The Physics of Glaciers(Fourth ed.). Elsevier.ISBN978-0123694614.LCCN2009050362.[page needed]
- ^Hays, Jeffrey."GLACIERS: TYPES, MECHANICS, DANGERS AND TERMS".factsanddetails.Retrieved2024-01-08.
- ^Veldhuijsen, Sanne; Van De Berg, Willem Jan; Brils, Max; Kuipers Munneke, Peter; van den Broeke, Michiel (1 December 2021)."Contemporary Characteristics of the Antarctic Firn Layer (1979-2020)".AGU Fall Meeting Abstracts.2021:C35E–0919.Bibcode:2021AGUFM.C35E0919V.
- ^"DanielBruun Firn".Mapcarta.Retrieved31 May2019.
- ^"Dreyer Firn".Mapcarta.Retrieved31 May2019.
- ^Sven Hedin Firn,Army Map Service,United States Army Corps of Engineers,Greenland 1:250,000
Sources[edit]
- "Firn".Encyclopædia Britannica.
- "Fundamentals of Physical Geography".physicalgeography.net.
- Machguth, Horst; MacFerrin, Mike; van As, Dirk; Box, Jason E.; Charalampidis, Charalampos; Colgan, William; Fausto, Robert S.; Meijer, Harro A. J.; Mosley-Thompson, Ellen; van de Wal, Roderik S. W. (April 2016)."Greenland meltwater storage in firn limited by near-surface ice formation"(PDF).Nature Climate Change.6(4): 390–393.Bibcode:2016NatCC...6..390M.doi:10.1038/nclimate2899.hdl:1874/335472.S2CID33914856.
- "USGS Glossary of Selected Glacier and Related Terminology".ulcan.wr.usgs.gov.
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