The Weddell Sea is part of the Southern Ocean and is home to the Weddell Gyre. Its land boundaries are formed by the coastline of Coats Land and the Antarctic Peninsula. The easternmost point of the sea is Cape Norvegia, located on the Princess Martha Coast in Queen Maud Land. To the east of Cape Norvegia lies the King Haakon VII Sea. Much of the southern region of the Weddell Sea is covered by the Filchner-Ronne Ice Shelf, a large and permanent ice shelf.
The Weddell Sea is located within areas claimed by Argentina, the United Kingdom, and Chile in Antarctica. At its widest point, the sea spans about 2,000 kilometers (1,200 miles) and covers an area of approximately 2.8 million square kilometers (1.1 million square miles).
Many ice shelves, including the Filchner-Ronne Ice Shelf, surround the Weddell Sea. Some ice shelves on the eastern side of the Antarctic Peninsula, which once covered about 10,000 square kilometers (3,900 square miles) of the Weddell Sea, had completely disappeared by 2002. Scientists have noted that the Weddell Sea has the clearest water of any sea. In 1986, researchers from the Alfred Wegener Institute observed a Secchi disc, a tool used to measure water clarity, visible at a depth of 80 meters (260 feet). This depth was similar to that of distilled water.
In his 1950 book The White Continent, historian Thomas R. Henry wrote: "The Weddell Sea is, according to the testimony of all who have sailed through its berg-filled waters, the most treacherous and dismal region on Earth. The Ross Sea is relatively peaceful, predictable, and safe." He later described myths of a green-haired merman seen in the sea’s icy waters, the difficulty of navigating to the coast until 1949, and sudden freezes that trapped ships, such as Ernest Shackleton’s Endurance, in ice floes.
Etymology
The Weddell Sea is named after James Weddell, a Scottish sailor who lived from 1787 to 1834. He first entered the sea in 1823 and originally called it after King George IV. In 1900, the sea was renamed to honor James Weddell. In the same year, Benjamin Morrell, an American sealing captain, claimed he saw land about 10–12° east of the sea’s actual eastern edge. He named this land New South Greenland. However, this claim was later proven false when the sea was better explored in the early 20th century. Morrell traveled as far south as 74°S, which was the farthest point reached in the Weddell Sea between Weddell’s time and the modern era. This record was later surpassed in 1903 by William Speirs Bruce.
The Weddell Sea is an important place where deep water forms through a process called cabbeling, which is a major cause of thermohaline circulation. Deep water also forms through cabbeling in the North Atlantic. This process happens because of differences in water temperature and salt content. In the Weddell Sea, cabbeling is mainly caused by brine exclusion and wind cooling.
History
In 1823, British sailor James Weddell discovered the Weddell Sea.
The Antarctic Sound is named after the ship used by Otto Nordenskiöld during his expedition. This sound, which separates the tip of the Antarctic Peninsula from Dundee Island, is also called "Iceberg Alley" because large icebergs are often found there. Snow Hill, located east of the Antarctic Peninsula, is named for its mostly snow-covered surface. In 1902, an expedition built a cabin on the island. Nordenskiöld and three others had to stay there for two winters after his ship sank in 1903.
In 1915, Ernest Shackleton’s ship, the Endurance, became trapped in the sea and was later crushed by ice. After spending 15 months on the ice, Shackleton and his crew reached Elephant Island and safely returned home. In March 2022, it was announced that the Endurance’s well-preserved wreck was found four miles (6.4 km) from its expected location, at a depth of 3,008 metres (9,869 ft).
Geology
The Weddell Sea has a shared geological history with southernmost South America, similar to other nearby areas of Antarctica. In southern Patagonia, during the Jurassic period, stretching of the Earth's crust created the Rocas Verdes Basin, a type of basin formed behind a mountain arc. The part of this basin that extended southeastward still exists today as the Weddell Sea. In the Late Cretaceous period, the tectonic activity in the Rocas Verdes Basin changed, leading to its transformation into a compressional foreland basin called the Magallanes Basin during the Cenozoic era. While this change occurred in South America, the Weddell Sea portion of the basin avoided compressional forces and remained an oceanic basin.
Oceanography
The Weddell Sea is one of the few places in the World Ocean where deep and bottom water forms, contributing to the global thermohaline circulation. This circulation has been warming slowly over the past ten years. The properties of the water that leaves the Weddell Sea are shaped by interactions between surface conditions, sea ice processes, ocean movements near the edge of the continental shelf, and changes in water properties under ice shelves.
In the western Weddell Sea, water mainly flows northward. This current is part of a larger, wind-driven circular flow called the Weddell Gyre. The northward movement carries water out of the Weddell Sea, which is an important area for forming deep water and modifying ocean water, to the rest of the World Ocean. The Weddell Gyre consists of a cold, low-salt surface layer, separated by a thin, weak layer of rapidly changing density from a thick layer of warm, salty water called Weddell Deep Water (WDW), and a cold layer at the ocean floor.
Studying ocean circulation in the Weddell Sea has been challenging. Measurements from past data show only weak surface currents when looking at areas deeper than 1000 decibels. Similar calculations using more detailed data also show small currents. Scientists assumed the movement of water around the gyre is driven by a process called Sverdrup transport. The Weddell Sea is a major location for the formation of deep water.
In addition to the wind-driven gyre, a deeper circulation exists. This deeper movement is influenced by the input of dense water in the southern and southwestern parts of the Weddell Sea. However, available data does not provide enough information to measure the volume of water moving in this western boundary region or to determine the details of deep water movement along the western edge.
Climate
The strong surface winds that blow parallel to the narrow and tall mountain range of the Antarctic Peninsula are an important feature of the weather and climate in the western Weddell Sea area. These winds move cold air toward lower latitudes and change direction to become southwesterly winds farther north.
These winds are important not only because they influence the temperature patterns east of the peninsula but also because they push ice northeastward into the South Atlantic Ocean. This movement is part of a clockwise circulation in the lower layers of the atmosphere along the coasts of the Weddell Sea. For many years, scientists have known that there is a clear difference in wind, temperature, and ice conditions between the two sides of the Antarctic Peninsula.
Strong surface winds blowing toward the equator along the east side of the Antarctic Peninsula can occur in two types of weather patterns. One pattern involves a powerful storm over the central Weddell Sea. The other involves a wide, steady flow of cold air from east to west in the lowest 500-to-1000-meter layer of the atmosphere over the central and/or southern Weddell Sea toward the peninsula. These conditions cause cold air to build up on the east side of the mountains. This leads to the formation of a high-pressure area over the peninsula, mainly on the east side of the mountains, and causes the originally westward flow of air to shift to the right, following the mountain wall.
Ecology
The Weddell Sea has many whales and seals. Animals that live there include Weddell seals, killer whales, humpback whales, minke whales, leopard seals, and crabeater seals. These animals are often seen during trips to the Weddell Sea.
The Adélie penguin is the most common penguin in this area because it is able to live in the tough conditions. A group of more than 100,000 pairs of Adélie penguins lives on volcanic Paulet Island.
In 1997, scientists found the northernmost emperor penguin colony just south of Snowhill Island in the Weddell Sea. Because the Weddell Sea often has thick ice, special ships with helicopters are needed to reach this colony.
In 2021, scientists reported finding sponges and other unknown types of animals that filter food from water growing under the Filchner-Ronne Ice Shelf. These animals were found on a rock at a depth of 1,233 meters (872 meters of which were ice), 260 kilometers from open water.
In February 2021, the Alfred Wegener Institute for Polar and Marine Research, using the ship RV Polarstern, discovered a group of about 60 million Jonah's icefish living in the Weddell Sea. This group is thought to cover around 240 square kilometers, with one nest for every three square meters on average.