Quelccaya Ice Cap

The Quelccaya Ice Cap (also known as Quenamari Ice Cap) is the second largest glaciated area in the tropics, after Coropuna. Located in the Cordillera Oriental section of the Andes mountains in Peru, the cap covers an area of with ice up to thick. It is surrounded by tall ice cliffs and a number of outlet glaciers, the largest of which is known as Qori Kalis Glacier; lakes, moraines, peat bogs and wetlands are also present. There is a rich flora and fauna, including birds that nest on the ice cap. Quelccaya is an important source of water, eventually melting and flowing into the Inambari and Vilcanota Rivers.

A number of ice cores have been obtained from Quelccaya, including two from 1983 that were the first recovered outside of the polar regions. Past climate states have been reconstructed from data in these ice cores; these include evidence of the Little Ice Age, regional droughts and wet periods with historical significance and past and recent El Niño events. The ice cap is regularly monitored and has a weather station.

Quelccaya was much larger in the past, merging with neighbouring glaciers during the Pleistocene epoch. A secondary expansion occurred during either the Antarctic Cold Reversal or the Younger Dryas climate anomalies. At the beginning of the Holocene the ice cap shrank to a size smaller than present day; around 5,000 years ago, a neoglacial expansion began. A number of moraines – especially in the Huancané valley – testify to past expansions and changes of Quelccaya, although the chronology of individual moraines is often unclear.

After reaching a secondary highstand (area expansion) during the Little Ice Age, Quelccaya has been shrinking due to human-caused climate change; in particular the Qori Kalis Glacier has been retreating significantly. Life and lakes have been occupying the terrain left by retreating ice; these lakes can be dangerous as they can cause floods when they breach. Climate models predict that without climate change mitigation measures, Quelccaya is likely to disappear during the 21st or 22nd century.

Geography

The Quelccaya Ice Cap lies in the tropical highlands of southern Peru, in the Cordillera Oriental/eastern Andes. The Cordillera Vilcanota mountain range is northwest of Quelccaya, and Quelccaya is sometimes considered to be part of it; occasionally Quelccaya is also linked to the Cordillera Carabaya range. East of Quelccaya, the Andes drop off steeply to the Amazon basin. The Amazon rainforest – only away – is barely discernible from the summit of Quelccaya. Lake Titicaca is south of Quelccaya. Administratively, Quelccaya is part of the Cuzco Department.

The Andes in Peru, Ecuador, and Bolivia are subdivided into several separate mountain ranges, many of which are glaciated above elevation; Peru contains about 70% of all tropical glaciers. Together with the Coropuna volcano also in southern Peru and ice bodies in New Guinea and the Rwenzori Mountains in Africa, Quelccaya is one of the few tropical ice caps in the world; during glacial times there were more ice caps which may have resembled Quelccaya. The existence of two smaller ice caps south of Quelccaya was reported in 1968.

Human geography

The ice cap lies in a remote area. It is also known as Quenamari and is sometimes spelled Quelcaya. Since 2020, Quelccaya is part of the Área de Conservación Regional Ausangate, a protected area, and the local population considers Quelccaya an important , a holy spirit.

The region around the ice cap is sparsely populated. The city of Cuzco lies to the northwest of Quelccaya, and Sicuani is to the southwest. The closest road is still from the ice cap and the rest of the journey can take three days with pack animals to reach the ice cap. There are several camps at Quelccaya, including one close to the northwestern ice margin. A 1974 map shows a homestead on the Huancané River southwest from Quelccaya, about from the ice margin.

Ice cap

The Quelccaya ice cap extends up to from the north to south and between from east to west. Quelccaya is a low-elevation ice cap that rises above the surrounding terrain; the ice cap lies at elevation. The highest summit in the area of the ice cap is Joyllor Puñuna at elevation. Snowline elevation has been estimated at .

The ice forms a relatively thin and flat structure with several ice domes. The number of ice domes is variously considered to be two, three or four; the highest of which reaches elevation. Close to the summit of the ice cap the ice is thick, with a maximum thickness of about , and the ice has a total volume of over .

Between 1975 and 2010, Quelccaya covered a median area of . It has decreased over time, and by 2009 it had shrunk to making it smaller than the ice on Coropuna, which is not declining as quickly. Before this decline, Quelccaya was considered the largest ice area of the tropics.

The ice flows radially outward from the cap. Ice cliffs reaching heights of form most of the margin of Quelccaya. They often display banded layers that are thick, and there are flutes or grooves and icicles. Over interfluves, the border of the ice cap is embayed; that is, the borders of the ice cap retreat above the areas between outlet valleys or glaciers. On the southern and western sides, parts of the ice cap end at steep cliffs like those in polar regions. From the icefalls, short glaciers up to long descend to elevations of , with lower elevations reached on the eastern side. The largest of these glaciers is the Qori Kalis Glacier, which extends from the northern sector of Quelccaya westwards. There is a contrast between lobe-like glaciers that emanate into the shallow valleys of the south-western side of Quelccaya and steeper glaciers with crevasses that descend into deeper valleys elsewhere around the ice cap. On the southern side, the ice cap ends in four cirques with icefalls at their head and four sets of moraines downstream. Melting at Quelccaya occurs at the bottom, and meltwater is discharged at the margins. At the top of the ice cap, most ice loss is due to sublimation.

Physical structures

Conditions on the ice cap are polar, and the ice surface has structures such as penitentes and sastrugi. Penitentes occur especially at lower elevations on the ice cap; at higher elevations they become smaller and eventually vanish, replaced with plate-shaped ice crystals measuring . Towards the summit, the plates are replaced with column- or less commonly needle-shaped crystals, and eventually by dendritic crystals on the summit. On the summit there are lenses of ice, probably from melting.

Reconnaissance in 1974–1977 found glacier caves in the Quelccaya ice cap, including elongated caves where the ice has overrun an obstacle thus creating an empty space, and crevasse-associated caves that form when they roof over. Caves have fluted walls and contain cave corals, flowstones, stalactites and stalagmites; these cave formations are made out of ice.

Physical-chemical traits

The ice cap contains temperate ice. In 2003 the ice had similar temperatures throughout its thickness while a 1978 publication reported temperatures in the ice and its density increased with depth. Temperatures of the glaciers at the base of Quelccaya reach the pressure melting point, except at some locations. Radar data indicate the presence of water pockets in the ice.

The ice of Quelccaya does not appear to have been particularly erosive during the late Holocene, as indicated by the preservation of plant remains below it. The ice cap may have been in a temperate and erosive state when it was retreating (such as during the early Holocene), and cold-based and thus not very erosive during the expansion of the late Holocene. Cold-based glaciers do not produce much meltwater and do not erode the ground they rest on as they fluctuate.

Especially during the dry season, iron, silica and sodium accumulate on the ice cap in the form of microparticles; most of these microparticles originate in the Altiplano area of the Andes and possibly the sea. Sulfate and nitrate are also found and may originate in the Amazon; their concentrations at Quelccaya resemble these of snow in Andean regions. Particles are coarser when they are deposited during the wet season, perhaps due to wet-season storms. Diatoms, insects, their bodyparts and pollen have also been found in the ice. The composition of the ice may be influenced by the precipitation type.

During winter, most solar radiation is reflected off the ice, with an albedo (reflectivity) of 80%. As reported in 1979, 1981 and 2013, there is little energy available at the top of the Quelccaya ice cap as outgoing and incoming radiation are essentially balanced. This radiation pattern, along with temperature and wind, influence the appearance of the surface of the Quelccaya ice. Away from the ice cap, solar radiation is capable of quickly evaporating any snow.

Geomorphology

The plateau that Quelccaya rises from features smooth bedrock with a slope from the northeast to the southwest but is relatively flat, such that even a small rise in the freezing level will result in a large change in the ice. The plateau is surrounded by land forms known as ''escarpments'' and a number of valleys emanate from the plateau.

On the western side of Quelccaya these valleys include, from northwest of the ice cap southward, the Qori Kalis valley, Challpa Cocha valley, Huancané valley, and "South Fork" valley. The Huancané valley is wide and flat and has the "South Fork" valley as a tributary. The Huancané valley runs southwestwards away from Quelccaya and is occupied by the Huancané River. Moraines from glaciers lie in the valleys radiating from the ice cap and contain alluvial deposits and peat bogs, ponds and wetlands within depressions. Clay and peat are also found incorporated in moraines; they crop out where floods have eroded into moraines. Blocky boulders with sizes of up to dot the valley floors. In some places, glaciers have likely quarried the underlying rocks.

West of Quelccaya lies a high plain that is formed by glacial outwash and till. The terrain features landforms such as drift deposits, lakes, moraines and moraine-dammed lakes, outwash fans, peat bogs, rocks bearing glacial striations, streams and wetlands.

A number of lakes occur in the region of Quelccaya and the Cordillera Vilcanota, including Sibinacocha south of the Cordillera Vilcanota. Among the lakes close to the Quelccaya ice cap area:
* Laguna Accocancha/Aconcancha and Laguna Paco Cocha upvalley from Aconcancha both south of the Huancané valley.
* Challpacocha west-southwest from Qori Kalis; it is a tarn lake that receives meltwater from Quelccaya through several channels that flow through wetlands.
* Churuyo southwest from Quelccaya.
* Lado del Quelccaya, Lado del Quelccaya 2 and Laguna 5 due west.
* North Lake, Base Camp Lake and Boulder Lake west of Quelccaya. These three lakes lie at elevation and formed within bedrock depressions when the glaciers retreated.
* Pegador Pond west-northwest from the ice cap.
* "Yanacocha" in the "South Fork" valley west of Quelccaya. It also is a tarn lake and developed in a formerly glaciated basin below an ignimbrite headwall. It currently forms a separate watershed from Quelccaya as it does not receive meltwater.

Geology

Quelccaya lies on a plateau formed by ignimbrites and welded tuffs, which are of rhyolitic composition although the occurrence of andesite has also been reported. The rocks were emplaced during the Miocene six million years ago and only little erosion has taken place since then. The volcanics may correlate with the Quenamari volcanics farther east. West of Quelccaya a Holocene normal fault runs in north–south direction, part of the Ocongate fault system; this fault system extends across the Cordillera Vilcanota and has offset moraines, indicating it is active.

Climate

Annually, about of snow water equivalent accumulate on Quelccaya, in the form of graupel,about snow with rainfall sometimes occurring near its margins and also near its summit. This is much wetter than most of the tropical Andes, a consequence of Quelccaya's proximity to the Amazon. This moisture originates from the Amazon and the Atlantic Ocean and is transported to Quelccaya by trade winds; a temperature inversion and blocking effects of coastal topography prevent moisture from the Pacific Ocean from reaching the ice cap.

Most precipitation falls in austral summer during the summer monsoon, when high insolation leads to intense convection and showers. The location of the ice cap also generated orographic precipitation – a type of precipitation forced by the ascent of air over mountains. Most snowfall occurs during the passage of cold fronts and cold air inclusions; the net amount depends on the duration of the wet season. Most precipitation falls in the afternoon, but a second phase occurs during the night.

Unlike precipitation, temperatures are relatively stable throughout the year with daynight temperature differences exceeding seasonal ones. Temperatures at the top of Quelccaya are inferred to be between and . For the margin of Quelccaya, mean temperatures have been inferred under the assumption that the lapse rate is constant. Varying between , the mean temperature at the margin is during the dry season. During the wet season it varies between with a mean of . As a consequence of global warming, temperatures on the summit of Quelccaya sometimes rise above freezing, accelerating the shrinkage of the ice cap.

Winds are strongest during the day and mostly blow from the west, except during the rainy season when they also come from the east or north-east. The ice cap itself generates its own downslope katabatic wind, which blows over the ice and quickly peters out with distance from the ice margin.

Climate variability

The climate is influenced by the El Niño-Southern Oscillation and by the position of the Intertropical Convergence Zone; during El Niño years precipitation is much less as westerly winds suppress the transport of easterly moisture to Quelccaya. During the strong 2014–2016 El Niño event, there was a net decrease in snow height on Quelccaya. Further, during El Niño there is a "front-loading" of precipitation with an earlier onset of the monsoon and decreased precipitation in its middle and late phase. Temperatures are also modulated by El Niño events, during which an increase is observed although winter temperatures decrease.

Ice cores show evidence of past climate variability, such as increased precipitation in the years 1870–1984, 1500–1720, 760–1040 and with drought in the years 1720–1860, 1250–1310, 650–730, 570–610 and 540–560. One of these wet periods has been correlated to the Medieval Climate Anomaly 1,000–700years ago, while drought periods have been linked to cultural changes in the Peruvian Moche culture and the collapse of the pre-Columbian Tiwanaku empire. Apart from precipitation, climate at Quelccaya has been stable over the past 1500 years. During recent decades, precipitation has not fluctuated significantly but temperatures have been steadily increasing.

Vegetation and animal life

The terrain west of Quelccaya is sparsely vegetated with high elevation tundra vegetation. The vegetation in the region is known as puna grassland; above elevation it is defined as "super-Puna", and consists of herbs and shrubs such as ''Plantago'' and trees like ''Polylepis'' which grow to the ice cap and often have a krummholz appearance. The main human use of the area is livestock grazing but crop planting has also been reported.

There are over fifty plant species in the terrain around the ice cap. Aquatic plants are found in lakes. The glacial runoff and precipitation guarantee an ample water supply, leading to the development of wetlands known as ''bofedales'' and peat; The cushion plant ''Distichia muscoides'' is the dominant plant in the ''bofedales'' and these wetlands are hotspots of biodiversity, but tussock grasses have been expanding in the wetlands as ice retreats. Other plants include ''Festuca orthophylla'' (a grass), ''Jarava ichu'' (Peruvian feathergrass) and nettles. Twenty-three lichen

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