The Onyx River is an Antarctic meltwater stream which flows westward through the

Wright Valley The Wright Valley, named for Sir Charles Wright, is the central one of the three large Dry Valleys in the Transantarctic Mountains, located west of McMurdo Sound at approximately . Wright Valley contains the Onyx River, the longest river in ...

from Wright Lower Glacier and

Lake Brownworth Lake Brownworth is a meltwater lake immediately west of Wright Lower Glacier at the east end of Wright Valley, Victoria Land. The lake was mapped by the United States Geological Survey (USGS) from surveys and air photos obtained in 1956–1960. It ...

at the foot of the glacier to

Lake Vanda Lake Vanda is a lake in Wright Valley, Victoria Land, Ross Dependency, Antarctica. The lake is long and has a maximum depth of . On its shore, New Zealand maintained Vanda Station from 1968 to 1995. Lake Vanda is a hypersaline lake with a salin ...

, during the few months of the Antarctic summer. At in length, it is the longest river in Antarctica.

Geography

The Onyx River flows away from the ocean, an example of

endorheic An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes ...

drainage Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic condition ...

, as the Wright Lower Glacier blocks the mouth of the Wright Valley. It has several

tributaries A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainag ...

, and there are multiple meteorological stations along the length of the river. Flow levels are highly variable, both during the day and between summers, with the river failing to reach the lake some years. In contrast, it can cause significant

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

in flood years, and was rafted in 1984 by New Zealand researchers. At one time, the river's discharge reached .

Environment

There are no fish in the Onyx River, but it supports

microscopic life A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

, and the

algal bloom An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term ''algae'' encompass ...

s can be quite extensive. The environment consists mainly of cyanobacteria and other algae. A few

micro-animals Microfauna (Ancient Greek ''mikros'' "small" + New Latin ''fauna'' "animal") refers to microscopic animals and organisms that exhibit animal-like qualities. Microfauna are represented in the animal kingdom (e.g., nematodes, small arthropods) and ...

( nematodes,

tardigrade Tardigrades (), known colloquially as water bears or moss piglets, are a phylum of eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them Kleiner Wasserbä ...

s, and rotifers) live in the river.

Skua The skuas are a group of predatory seabirds with seven species forming the genus ''Stercorarius'', the only genus in the family Stercorariidae. The three smaller skuas, the long-tailed skua, the Arctic skua, and the pomarine skua are called ...

s are also occasionally present in the area.

Monitoring

The Onyx River is one of the many sites studied by the

United States Antarctic Program The United States Antarctic Program (or USAP; formerly known as the United States Antarctic Research Program or USARP and the United States Antarctic Service or USAS) is an organization of the United States government which has presence in the A ...

of the

National Science Foundation The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National ...

. Discharge data has been collected at the downstream gauge near Lake Vanda since 1969 and at the upstream gauge near the Wright Lower Glacier since 1972.Antarctica New Zealand program once maintained a semi-permanent camp at Lake Vanda which has since been removed. NSF's McMurdo Long Term Ecological Research site has been maintaining the Onyx River record since 1993. There is a small research shelter at Lake Vanda at its eastern end. Nearby is the

Comprehensive Nuclear-Test-Ban Treaty The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is a multilateral treaty to ban nuclear weapons test explosions and any other nuclear explosions, for both civilian and military purposes, in all environments. It was adopted by the United Nati ...

Seismic station at Bull Pass. Since records have been kept, the Onyx River's flow season has shifted earlier and gotten longer.

References

{{Reflist

External Links

*"Antarctica’s longest river", p 16, and "What the flood revealed", pp 15–21
Antarctic Sun
January 26, 2003
Onyx river and Dry Valleys low altitude aerial videosThe ground is softening. Something is shifting in Antarctica’s McMurdo Dry Valleys
Rivers of Antarctica Rivers of Victoria Land McMurdo Dry Valleys

Geography

Environment

Monitoring

See also

References

External Links