Penitente (snow formation)

Penitentes, or nieves penitentes (Spanish for "penitent snows"), are snow formations found at high altitudes. They take the form of elongated, thin blades of hardened snow or ice, closely spaced and pointing towards the general direction of the sun.[1]

The name comes from the resemblance of a field of penitentes to a crowd of kneeling people doing penance. The formation evokes the tall, pointed habits and hoods worn by brothers of religious orders in the Processions of Penance during Spanish Holy Week. In particular, the brothers' hats are tall, narrow, and white, with a pointed top.

These spires of snow and ice grow over all glaciated and snow-covered areas in the Dry Andes above 4,000 metres (13,000 ft).[2][3][4] They range in length from a few centimetres to over 5 metres (16 ft).[4][5]

First description

Penitentes were first described in scientific literature by Charles Darwin in 1839.[6] On March 22, 1835, he had to squeeze his way through snowfields covered in penitentes near the Piuquenes Pass, on the way from Santiago de Chile to the Argentine city of Mendoza, and reported the local belief (continuing to the present day) that they were formed by the strong winds of the Andes.

Formation

Snow surfaces facing the sun absorb more radiation, causing more sublimation and melting, leading to the formation of troughs and wedges. The wedges are usually nearly vertical, oriented east-west, and parallel to the solar beam. As the wedges form, sublimation occurs at the peaks as cold and dry air hits them, whereas melting occurs in the troughs, where radiation is concentrated and humid air can stagnate.[7]

The latent heat of melting is 335 J g−1 , whereas the latent heat of sublimation is 2838 J g−1 , a factor of 8.5 larger. The extreme topography of penitentes results from this 8.5-fold difference: the peaks remain dry and cold by sublimation, losing little mass, but in the troughs the air becomes stagnant and humid, so that sublimation cannot occur; the absorbed solar energy is instead consumed by melting, resulting in rapid loss of mass.[8]

An example of these conditions was noted by Louis Lliboutry on a November afternoon at 3500-m elevation. He noticed that the sublimating spikes of 50-cm height were hard and dry with a temperature of −5°C, whereas in the troughs between the spikes, the snow was wet, containing 14% liquid water. The air temperature outside the troughs was above freezing, but the dew point was below freezing.[9]

In the Southern Hemisphere the wedges become tilted toward the north, at approximately the noontime solar zenith angle, which varies seasonally. The lower limit to the altitude of penitente-formation as a function of latitude for North and South America is from the Cascades at 50°N to the southern Andes at 40°S; this altitude-limit varied from 3000 m at 50°N to 5300 m at the Equator.[10].

Many mathematical models and laboratory studies of penitente formation have been developed [11][12][13], but they ignore the critical role of melting [8]. Nevertheless, the effect of penitentes on the energy balance of the snow surface, and therefore their effect on snow melt and water resources, has also been studied.[14][15]


Non-terrestrial

Penitentes up to 15 metres (49 ft) high are suggested to be present in the tropics zone on Europa, a satellite of Jupiter.[16][17] However, subsequent work has cast serious doubts about whether the conditions required to form penitentes on Europa are plausible.[8][18]

According to a 2017 study, NASA's New Horizons mission discovered penitentes hundreds of meters high on Pluto, likely composed primarily of methane ice deposited seasonally from Pluto's thin atmosphere.[19][20] The structures occupy a region named Tartarus Dorsa, a name that was formally accepted by the IAU in August 2017.[21]

See also

References

  1. ^ "Penitentes ESO Australia". Retrieved 10 Jan 2019.
  2. ^ Lliboutry, L. (1954a). "Le Massif du Nevado Juncal ses penitentes et ses glaciers". Revue de Géographie Alpine (Submitted manuscript). 42 (3): 465–495. doi:10.3406/rga.1954.1142.
  3. ^ Lliboutry, L. (1954b). "The origin of penitentes". Journal of Glaciology. 2 (15): 331–338. Bibcode:1954JGlac...2..331L. doi:10.1017/S0022143000025181.
  4. ^ a b Lliboutry, L. (1965). Traité de Glaciologie, Vol. I & II (in French). Paris, France: Masson.
  5. ^ Naruse, R.; Lieva, J.C. (1997). "Preliminary study on the shape of snow penitents at Piloto Glacier, the Central Andes". Bulletin of Glacier Research. 15: 99–104.
  6. ^ Darwin, C. (1839). Journal of researches into the geology and natural history of the various countries visited by H. M. S. Beagle, under the command of Captain Fitz Roy, R.N., 1832 to 1836. London, UK: H. Colburn.
  7. ^ Lliboitry, Louis (1954). "The Origin of Penitents". Journal of Glaciology. 2 (15): 331–338. doi:10.3189/s0022143000025181. ISSN 0022-1430.
  8. ^ a b c Warren, Stephen G. (September 2022). "Snow spikes (penitentes) in the dry Andes, but not on Europa: a defense of Lliboutry's classic paper". Annals of Glaciology. 63 (87–89): 62–66. doi:10.1017/aog.2023.12. ISSN 0260-3055. This article incorporates text from this source, which is available under the CC BY 4.0 license.
  9. ^ Theakstone, Wilfred H. (1967). "Lliboutry, Louis. Traité de glaciologie. Tomes I et II. Paris, Masson et Cie, 1965". Cahiers de géographie du Québec. 11 (24): 602. doi:10.7202/020766ar. ISSN 0007-9766.
  10. ^ Ahlmann, Hans W:son; Troll, Carl (1944). "Büsserschnee in den Hochgebirgen der Erde. Ein Beitrag zur Geographie der Schneedecke und ihrer Ablationsformen". Geografiska Annaler. 26: 411. doi:10.2307/519925. ISSN 1651-3215.
  11. ^ Betterton, M. D. (2001-04-26). "Theory of structure formation in snowfields motivated by penitentes, suncups, and dirt cones". Physical Review E. 63 (5). arXiv:physics/0007099. doi:10.1103/physreve.63.056129. ISSN 1063-651X.
  12. ^ Claudin, P.; Jarry, H.; Vignoles, G.; Plapp, M.; Andreotti, B. (2015-09-25). "Physical processes causing the formation of penitentes". Physical Review E. 92 (3). arXiv:1511.01725. doi:10.1103/physreve.92.033015. ISSN 1539-3755.
  13. ^ Berisford, Daniel Floyd; Foster, Jeffrey Tyler; Kosberg, Jacob; Furst, Benjamin; Poston, Michael Joseph; Daimaru, Takuro; Lang, Maggie; Backman, Lavina; Hand, Kevin Peter (January 2024). "Laboratory formation of micro-penitentes at temperatures and pressures relevant to Earth and other worlds". Journal of Glaciology. 70: e58. doi:10.1017/jog.2024.67. ISSN 0022-1430.
  14. ^ Corripio, J.G. (2003). Modelling the energy balance of high altitude glacierised basins in the Central Andes (PDF) (PhD. thesis). Edinburgh, UK: University of Edinburgh. p. 151. Archived (PDF) from the original on 13 November 2013. Retrieved 7 September 2013.
  15. ^ Corripio, J.G.; Purves, R.S. (2005). "Surface Energy Balance of High Altitude Glaciers in the Central Andes: the Effect of Snow Penitentes" (PDF). In de Jong, C.; Collins, D.; Ranzi, R. (eds.). Climate and Hydrology in Mountain Areas. London: Wiley & Sons. p. 18. Retrieved 7 September 2013.
  16. ^ "Jupiter moon may have huge, jagged ice blades that complicate the search for alien life". NBC News. 9 October 2018.
  17. ^ "Europa's surface may be covered by blades of ice". Physics Today (10): 4147. 2013. Bibcode:2013PhT..2013j4147.. doi:10.1063/PT.5.027459. Archived from the original on 2013-12-22. Retrieved 2017-09-28.
  18. ^ Hand, K. P.; Berisford, D.; Daimaru, T.; Foster, J.; Hofmann, A. E.; Furst, B. (2019-12-02). "Penitente formation is unlikely on Europa". Nature Geoscience. 13 (1): 17–19. doi:10.1038/s41561-019-0496-2. ISSN 1752-0894.
  19. ^ Talbert, Tricia (2017-01-04). "Scientists Offer Sharper Insight into Pluto's Bladed Terrain". NASA. Archived from the original on 2017-01-05. Retrieved 2017-01-05.
  20. ^ Moores, John E.; Smith, Christina L.; Toigo, Anthony D.; Guzewich, Scott D. (2017-01-12). "Penitentes as the origin of the bladed terrain of Tartarus Dorsa on Pluto". Nature. 541 (7636): 188–190. arXiv:1707.06670. Bibcode:2017Natur.541..188M. doi:10.1038/nature20779. PMID 28052055. S2CID 4388677.
  21. ^ "Tartarus Dorsa". Gazetteer of Planetary Nomenclature – International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN). 2017-08-08. Retrieved 2023-04-21.

Further reading

  • Bergeron, Vance; Berger, Charles; Betterton, M. D. (2006). "Controlled Irradiative Formation of Penitentes". Physical Review Letters. 96 (98502) 098502. arXiv:physics/0601184. Bibcode:2006PhRvL..96i8502B. doi:10.1103/PhysRevLett.96.098502. PMID 16606324. S2CID 10549734.
  • Kotlyakov, V. M.; Lebedeva, I. M. (1974). "Nieve and ice penitentes, their way of formation and indicative significance". Zeitschrift für Gletscherkunde und Glazialgeologie (in German). X: 111–127. (Describes appearance and formation of these ablation features, with reference to those observed in eastern Pamir, U.S.S.K.)
  • Lliboutry, L. (1998). "Glaciers of the Dry Andes". In Williams, R. S. J.; Ferrigno, J. G. (eds.). Satellite Image Atlas of Glaciers of the World. USGS-p1386i. Archived from the original on 2008-06-02. Retrieved 2006-10-25. {{cite book}}: |work= ignored (help)
  • Media related to Ice and snow penitents at Wikimedia Commons
  • "Spiky glaciers are slower to melt", New Scientist (March 7, 2007).
This article is issued from Wikipedia. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.