Geography

South Orkney Islands

May 25, 2011, 7:34 am

 

The South Orkney Islands are a group of islands in the Southern Ocean located (60° 35′ S, 45° 30′ W), approximately 400 miles (640 km) north east of the northern tip of the Antarctic Peninsula.

North lies the South Atlantic Ocean and south, the Weddell Sea in a region of the Southern Ocean referred to as the Scotia Sea after the ship of the 1903 Scottish National Antarctic Expedition which explored the area. The highest point is Mount Nivea at the head of Sunshine Glacier on Coronation Island (4050 ft; 1265 m). The islands are 85% glaciated.

Coronation Island, Laurie Island, Powell Island and Signy Island are the main islands of the South Orkneys, with a number smaller rocky outcrops. The total land area of the islands is approximately 240 square miles (620 square km).

There is no permanent human population on the South Orkney's. The primary presence on the islands is related to two research stations run by Argentina and Great Britain. Sovereignty is claimed by both Great Britain and Argentina.The Islands are under the Antarctic Treaty System which neither recognizes nor rejects claims of sovereignty.

History

The islands were discovered in December 1821 by seal hunters based in the South Shetland Islands. The discovery was led by British sealer George Powell and Amerivan sealer Nathaniel Palmer. In January 1823, James Weddell stoped at the islands also looking before seas, before sailing south into the sea that bears his name.

In 1903, the Scottish National Antarctic Expedition (also the Scotia Expedition) under the leadership of William Spiers Bruce establish a weather station in the South Orkneys on Laurie Island and took systematic meteorologic data through the winter. In the spring, while some stayed behind to continue data collection, the Bruce sailed to Buenos Aires where Bruce offered the weather station as a permanent addition to Antarctic science to the British representative there—they declined. Bruce went to the Argentines and they accepted. When the Scotia returned to the South Orkneys, three Argentines accompanied the expedition to take over the running of the first permanent weather station in the Southern Ocean.This station is now known as Orcadas Base and is permanently staffed.

In 1947, the British Antarctic Survey established Signy Research Station on Signy Island which continues to be operate, though, since 1997, personnel have been present only during the Antarctic spring and summer (November-April). A whaling station was established on Signy Island  by the early twentieth century.

Climate

The British Signy Research Station describes the climate as:

The weather on Signy is greatly affected by ice. In winter pack ice from the Weddell Sea moves nothwards and surrounds the South Orkney Islands and fast ice forms in the areas of water between the pack. As a result, Signy is effectively attached to the Antarctic continent and the weather assumes a more continental aspect than would be expected from the island's location, with low temperatures (record minimum -39.3°C) and relatively clear skies. Icebergs remain in the area all year and remnants of pack ice can be expected at any time during the summer.

During the summer, the pack ice retreats to the Weddell Sea, and Signy assumes a typical maritime climate. Weather patterns are determined by a series of depressions that pass north-east from the Antarctic Peninsula. These bring warm, wet conditions and are accompanied by much low cloud (the infamous "Signy mank"). Summer air temperatures are generally positive (record maximum 19.8°C), although sudden falls in temperature can occur throughout the summer (-7°C has been recorded in January).

Being north of the Antarctic circle, Signy is never subject to 24 hr days or nights. The Sun is below the horizon for a minimum of 4-5 hrs at mid-summer, although a twilight persists throughout the night close to the solstice. Cloud cover is over 80% in summer and rain may fall at any time, although this is rarely heavy. Total annual sun is only 14% of possible. However, bright, sunny ("dingle") days can occur, particularly in November and December. Signy is situated on the edge of the 'ozone-hole', and increased levels of UV light might be experienced from October to December.

Signy is extremely windy. The prevailing wind  direction is westerly, averages about 14 knots, and often exceeds the boating limit of 25 knots. Gales are recorded on about 60 days each year. An extreme gust of 115 knots has been recorded. Moving west from Signy, there is no landfall until the South Orkneys are re-encountered, therefore the island is exposed to any weather approaching from the west.

Ecology

The British Signy Research Station describes the biology around Signey as:

The underwater habitats around Signy consist of both hard and soft bottom areas. Marine life is plentiful, particularly on rock faces that are sheltered from ice-scouring. Amphipods, anemones, sea squirts, tube worms, brachipods, limpets, starfish, sponges and sea cucumbers are especially common. Large numbers of fish are also found at some sites.

Seals: A number of species of seal occur around Signy Island. Weddell seals pup on the sea-ice in winter, and may be seen on ice rafts around the Island during the summer. Elephant seals pup in early spring and form large pods on some beaches during the summer. Leopard seals haul out onto ice floes, usually individually and may be seen hunting around penguin colonies. Crabeater seals are rare in summer, but may be seen on ice floes. All these are 'true seals'.

The only 'eared seal' seen on Signy Island is the Antarctic fur seal. The population at Signy has been increasing rapidly through the 1980s and 1990s and there are now over 20,000 on the Island. Most of these are young, non-breeding males, although a few females and pups are seen each year.

Seabirds: There are three main species of penguin that breed on Signy Island, in increasing order of abundance; the Gentoo, Adélie and Chinstrap penguin. In addition, a few breeding pairs of Macaroni penguins may be found each year, and odd sightings of individual King and Emperor penguins have been made (the latter usually only in winter).

Twelve other species of bird breed on Signy Island: Southern Giant petrel, Cape petrel, Snow petrel, Antarctic prion, Wilson's Storm petrel, Blue-eyed shag, Snowy sheathbill, Brown skua, South Polar skua, Dominican/Kelp gull, Antarctic tern and Black-bellied Storm petrel. In addition, the Antarctic fulmar breeds on nearby islands and is regularly observed. Various visitors and vagrants (now numbering 27) have been recorded at different times, of which the most common are the Black-browed albatross and the Antarctic petrel in spring.

Glossary

Citation

Saundry, P. (2011). South Orkney Islands. Retrieved from http://www.eoearth.org/view/article/156137

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