Editing Mount Kilimanjaro (section)

=== Glaciers ===
[[File:Kilimanjaro dymamics2.jpg|alt=|thumb|Kilimanjaro's glaciers' retreat in 1912–2018]]

Kibo's ice cap exists because Kilimanjaro is a little-dissected, massive mountain that rises above the [[snow line]]. The cap is divergent and at the edges splits into individual glaciers. The central portion of the ice cap is interrupted by the presence of the Kibo crater.<ref name="AnAscentOfKilimanjaro"/>{{rp|5}} The summit glaciers and ice fields do not display significant horizontal movements because their low thickness precludes major deformation.<ref name="TraceElements"/>

Geological evidence shows five successive glacial episodes during the [[Quaternary]] period, namely First (500,000 [[Before Present|BP]]), Second (greater than 360,000 years ago to 240,000 BP), Third (150,000 to 120,000 BP), Fourth (also known as "Main") (20,000 to 17,000 BP), and Little (16,000 to 14,000 BP). The Third may have been the most extensive, and the Little appears to be statistically indistinguishable from the Fourth.<ref>{{cite journal |doi=10.1002/jqs.1222 |title=Quaternary glaciation in Africa: Key chronologies and climatic implications |journal=Journal of Quaternary Science |volume=23 |issue=6–7 |pages=589–608 |year=2008 |last1=Mark |first1=Bryan G. |last2=Osmaston |first2=Henry A. |bibcode=2008JQS....23..589M |citeseerx=10.1.1.529.4209 |s2cid=130605599 }}</ref>

A continuous ice cap covering approximately {{convert|400|km2|mi2|abbr=on}} down to an elevation of {{convert|3200|m|ft|abbr=on}} covered Kilimanjaro during the [[Last Glacial Maximum]] in the [[Pleistocene]] epoch (the Main glacial episode), extending across the summits of Kibo and Mawenzi.<ref name="Kaser"/><ref name="Glaciers of Middle East"/> Because of the exceptionally prolonged dry conditions during the subsequent [[Younger Dryas]] [[stadial]], the ice fields on Kilimanjaro may have become extinct around 11,500 years BP.<ref name="TraceElements">{{cite journal |doi=10.1016/j.quascirev.2014.03.007 |bibcode=2014QSRv...93....1G |title=Deglaciated areas of Kilimanjaro as a source of volcanic trace elements deposited on the ice cap during the late Holocene |journal=Quaternary Science Reviews |volume=93 |pages=1–10 |last1=Gabrielli |first1=P. |last2=Hardy |first2=D. R. |last3=Kehrwald |first3=N. |last4=Davis |first4=M. |last5=Cozzi |first5=G. |last6=Turetta |first6=C. |last7=Barbante |first7=C. |last8=Thompson |first8=L. G. |year=2014 }}</ref> [[Ice core]]s taken from Kilimanjaro's Northern Ice Field (NIF) indicates that the glaciers there have a basal age of about 11,700 years,<ref>{{cite journal | last=Thompson | first=Lonnie G | title=Kilimanjaro Ice Core Records: Evidence of Holocene Climate Change in Tropical Africa | journal=Science | volume=298 | issue=5593 | pages=589–593 | url=http://www.geo.umass.edu/climate/doug/pubs/thompson_etal_sci02.pdf | access-date=16 August 2012 | bibcode=2002Sci...298..589T | year=2002 | doi=10.1126/science.1073198 | pmid=12386332 | s2cid=32880316 | archive-url=https://web.archive.org/web/20120205025226/http://www.geo.umass.edu/climate/doug/pubs/thompson_etal_sci02.pdf | archive-date=5 February 2012  }}</ref> although an analysis of ice taken in 2011 from exposed vertical cliffs in the NIF supports an age extending only to 800 years BP.<ref>{{cite journal |bibcode=2015EGUGA..17.5091U |title=The controversial age of Kilimanjaro's plateau glaciers |journal=EGU General Assembly Conference Abstracts |volume=17 |page=5091 |last1=Uglietti |first1=Chiara |last2=Zapf |first2=Alexander |last3=Szidat |first3=Sönke |last4=Salazar |first4=Gary |last5=Hardy |first5=Doug |last6=Schwikowski |first6=Margit |year=2015 }}</ref> [[African humid period|Higher precipitation rates at the beginning]] of the [[Holocene]] epoch (11,500 years BP) allowed the ice cap to reform.<ref name="TraceElements"/> The glaciers survived a widespread drought during a three century period beginning around 4,000 years BP.<ref name="TraceElements"/><ref name="unabated">{{cite journal |doi=10.1073/pnas.0906029106 |pmid=19884500 |pmc=2771743 |bibcode=2009PNAS..10619770T |title=Glacier loss on Kilimanjaro continues unabated |journal=Proceedings of the National Academy of Sciences |volume=106 |issue=47 |pages=19770–5 |last1=Thompson |first1=L. G. |last2=Brecher |first2=H. H. |last3=Mosley-Thompson |first3=E. |last4=Hardy |first4=D. R. |last5=Mark |first5=B. G. |year=2009 |doi-access=free }}</ref>

[[File:Kibo-großer Gletscher(big glacier).jpg|thumb|left|Vertical margin wall of the [[Rebmann Glacier]] in 2005 with [[Mount Meru (Tanzania)|Mount Meru]], which is {{convert|70|km|mi|0|abbr=on}} away, in the background]]

In the late 1880s, the summit of Kibo was completely covered by an ice cap about {{convert|20|km2|mi2|abbr=on}} in extent with outlet glaciers cascading down the western and southern slopes, and except for the inner cone, the entire caldera was buried. Glacier ice also flowed through the Western Breach.<ref name="Kaser"/><ref name="Glaciers of Middle East">{{cite web | last=Young | first=James A. T. | title=Glaciers of the Middle East and Africa | url=http://pubs.usgs.gov/pp/p1386g/africa.pdf | work=U.S. Geological Professional Survey | publisher=U.S. Department of the Interior | pages=G61, G58, G59 G62 | access-date=16 August 2012 | archive-url=https://web.archive.org/web/20120728083729/http://pubs.usgs.gov/pp/p1386g/africa.pdf | archive-date=28 July 2012 | url-status=live }}</ref> The slope glaciers retreated rapidly between 1912 and 1953, in response to a sudden shift in climate at the end of the 19th century that made them "drastically out of equilibrium", and more slowly thereafter. Their continuing demise indicates they are still out of equilibrium in response to a constant change in climate over the past century.<ref name="Kaser"/>

In contrast to the persistent slope glaciers, the glaciers on Kilimanjaro's crater plateau have appeared and disappeared repeatedly during the Holocene epoch, with each cycle lasting a few hundred years.<ref>{{cite journal | last1=Kaser | first1=Georg | last2=Mölg | first2=Thomas | last3=Cullen | first3=Nicolas J. | last4=Hardy | first4=Douglas R. | last5=Winkler | first5=Michael | title=Is the decline of ice on Kilimanjaro unprecedented in the Holocene? | journal=The Holocene | volume=20 | issue=7 | year=2010 | pages=1079–1091 | issn=0959-6836 | doi=10.1177/0959683610369498| bibcode=2010Holoc..20.1079K |citeseerx = 10.1.1.211.435| s2cid=16945088 }}</ref>{{rp|1088}} It appears that decreasing specific humidity instead of temperature changes has caused the shrinkage of the slope glaciers since the late 19th century. No clear warming trend at the elevation of those glaciers occurred between 1948 and 2005. Although air temperatures at that elevation are always below freezing, solar radiation causes melting on vertical faces. Vertical ice margin walls are a unique characteristic of the summit glaciers and a major place of the shrinkage of the glaciers. They manifest stratifications, [[Ice calving|calving]], and other ice features.<ref name="SinghSingh2011"/> "There is no pathway for the plateau glaciers other than to continuously retreat once their vertical margins are exposed to solar radiation."<ref name="Kaser"/> The Kilimanjaro glaciers have been used for deriving ice core records, including two from the southern icefield. Based on this data, this icefield formed between 1,250 and 1,450 years BP.<ref>{{cite book |doi=10.1016/B0-44-452747-8/00351-3 |chapter=ICE CORE RECORDS &#124; Africa |title=Encyclopedia of Quaternary Science |pages=1220–1225 |year=2007 |last1=Thompson |first1=L.G. |last2=Davis |first2=M.E. |isbn=978-0-444-52747-9 }}</ref>

[[File:Kilimanjaro sunrise at GillmanPoint(1).jpg|thumb|A vertical glacier margin wall as seen from Gilman's Point on the crater rim at sunrise in 1998]]

Almost 85 percent of the ice cover on Kilimanjaro disappeared between October 1912 and June 2011, with coverage decreasing from {{convert|11.40|km2|mi2|abbr=on}} to <{{convert|1|km2|mi2|abbr=on}}<ref>{{cite journal |url=https://iopscience.iop.org/article/10.1088/2752-5295/ad1fd7 |title=Tropical glacier loss in East Africa: recent areal extents on Kilimanjaro, Mount Kenya, and in the Rwenzori Range from high-resolution remote sensing data |first1=Anne |last1=Hinzmann |first2=Thomas |last2=Mölg |first3=Matthias |last3=Braun |first4=Nicolas J |last4=Cullen |first5=Douglas R |last5=Hardy |first6=Georg |last6=Kaser |first7=Rainer |last7=Prinz |journal=Environmental Research: Climate |volume=3 |number=1 |date=2024 |doi=10.1088/2752-5295/ad1fd7}}</ref><ref name="Retreat"/>{{rp|423}} Between 1912 and 1953, there was about a 1.1 percent average annual loss of ice coverage.<ref name="unabated"/> The average annual loss for 1953 to 1989 was 1.4 percent, while the loss rate for 1989 to 2007 was 2.5 percent.<ref name="unabated"/> Of the ice cover still present in 2000, almost 40 percent had disappeared by 2011.<ref name="Retreat">{{cite journal | last1=Cullen | first1=N. J. | last2=Sirguey | first2=P. | last3=Mölg | first3=T. | last4=Kaser | first4=G. | last5=Winkler | first5=M. | last6=Fitzsimons | first6=S. J. | title=A century of ice retreat on Kilimanjaro: the mapping reloaded | journal=The Cryosphere | volume=7 | issue=2 | year=2013 | pages=419–431 | issn=1994-0424 | doi=10.5194/tc-7-419-2013| bibcode=2013TCry....7..419C | doi-access=free }}</ref>{{rp|425}} Ice climber Will Gadd noticed differences between his 2014 and 2020 climbs.<ref>{{Cite web|last=Zeinab|first=Noura Abou|date=15 October 2020|title='Big pieces' of Kilimanjaro 'missing' due to climate crisis, says ice climber Will Gadd|url=https://edition.cnn.com/2020/10/15/sport/will-gadd-ice-climber-climate-change-spt-intl/index.html|access-date=15 October 2020|website=CNN|archive-date=5 October 2024|archive-url=https://web.archive.org/web/20241005154229/https://edition.cnn.com/2020/10/15/sport/will-gadd-ice-climber-climate-change-spt-intl/index.html|url-status=live}}</ref> The glaciers are thinning in addition to losing areal coverage,<ref name="unabated"/> and do not have active accumulation zones; retreat occurs on all glacier surfaces. Loss of glacier mass is caused by both melting and [[sublimation (phase transition)|sublimation]].<ref name="TraceElements"/> While the current shrinking and thinning of Kilimanjaro's ice fields appear to be unique within its almost twelve-millennium history, it is contemporaneous with widespread [[Retreat of glaciers since 1850|glacier retreat]] in mid-to-low latitudes across the globe.<ref name="unabated"/> In 2013, it was estimated that, at the current [[Climate change|rate of global warming]], most of the ice on Kilimanjaro will disappear by 2040, and "it is highly unlikely that any ice body will remain after 2060".<ref name="Retreat"/>{{rp|430}}

The Furtwangler Glacier on Kilimanjaro is a remnant of the ice cap that once covered the mountain. This has retreated dramatically over the last century with over 80 percent glacial retreat. The glacier is named after Walter Furtwangler, who along with Ziegfried Koenig, was the fourth to ascend to the summit of Kilimanjaro in 1912.<ref>{{Cite web|last=Nkonge|first=Peninah|date=15 October 2022|title='Hiking Adventures In East Africa's Tallest Mountains|url=https://sunriseafricasafaris.com/hiking-adventures-east-africa/|access-date=15 October 2022|website=Sunrise Africa Tours and Safaris|archive-date=25 June 2024|archive-url=https://web.archive.org/web/20240625133055/https://sunriseafricasafaris.com/hiking-adventures-east-africa/|url-status=live}}</ref>

A complete disappearance of the ice would be of only "negligible importance" to the water budget of the area around the mountain. The forests of Kilimanjaro, far below the ice fields, "are [the] essential water reservoirs for the local and regional populations".<ref>{{cite journal |url=http://lindseynicholson.org/wp-content/uploads/2011/07/Moelg-et-al.-2013.pdf |title=East African glacier loss and climate change: Corrections to the UNEP article ''Africa without ice and snow'' |first1=Georg |last1=Kaser |first2=Thomas |last2=Mölg |first3=Nicolas J. |last3=Cullen |first4=Douglas R. |last4=Hardy |first5=Michael |last5=Winkler |first6=Rainer |last6=Prinz |first7=Lindsey |last7=Nicholson |name-list-style=amp |journal=Environmental Development |volume=6 |pages=1–6 |access-date=2014-10-09 |doi=10.1016/j.envdev.2013.02.001  |archive-url=https://web.archive.org/web/20141015173745/http://lindseynicholson.org/wp-content/uploads/2011/07/Moelg-et-al.-2013.pdf |archive-date=2014-10-15 |url-status=live }}</ref>