The Ross Sea is a deep bay in the Southern Ocean, located in Antarctica between Victoria Land and Marie Byrd Land. It is part of the Ross Embayment and is the southernmost sea on Earth. The sea is named after James Clark Ross, a British explorer who visited the area in 1841. To the west of the sea lies Ross Island and Victoria Land, while to the east are Roosevelt Island and the Edward VII Peninsula in Marie Byrd Land. The southernmost part of the Ross Sea is covered by the Ross Ice Shelf, which is about 200 miles (320 kilometers) from the South Pole. The New Zealand National Institute of Water and Atmospheric Research has defined the Ross Sea’s boundaries and area as covering 637,000 square kilometers (246,000 square miles).
Ocean currents in the Ross Sea are mainly driven by wind and are influenced by three underwater ridges that stretch from southwest to northeast. A warm, salty, and nutrient-rich water current called the circumpolar deep water flows onto the continental shelf in certain areas. The Ross Sea is covered in ice for most of the year.
The nutrient-rich water supports large amounts of plankton, which helps sustain a wide variety of marine life. At least ten mammal species, six bird species, and 95 fish species live in the Ross Sea, along with many invertebrates. Human activity in the area is limited. New Zealand claims the Ross Sea is part of its territory under the Ross Dependency. Scientists believe the Ross Sea has high biological diversity and is a major site for research. Some environmental groups have worked to protect the area as a world marine reserve. In 2016, an international agreement created the Ross Sea as a marine park.
Description
The Ross Sea was found by the Ross expedition in 1841. Ross Island, which has the Mt. Erebus volcano, is located to the west of the Ross Sea. Roosevelt Island is to the east. The southern part of the Ross Sea has the Ross Ice Shelf. In 1911, Roald Amundsen began his South Pole expedition from the Bay of Whales, which was on the Ross Ice Shelf. In the western parts of the Ross Sea, McMurdo Sound is a port that is usually without ice during the summer. The southernmost part of the Ross Sea is Gould Coast, which is about 200 miles (320 km) from the geographic South Pole.
Geology
The Ross Sea and Ross Ice Shelf are located over a deep continental shelf. While the average depth of continental shelves worldwide is about 130 meters, the Ross Shelf averages about 500 meters. The western part of the Ross Sea is shallower than the eastern part. This very deep area was formed by repeated cycles of erosion and sediment deposition caused by expanding and contracting ice sheets during the Oligocene and later periods. Similar features are found in other areas around Antarctica. Erosion mainly occurred in the inner parts of the shelf, while sediment buildup was more common in the outer parts, making the inner shelf deeper than the outer.
Studies in the second half of the 20th century identified major geological features of the Ross Sea. The deepest rocks, called basement rocks, are split into four large north-south trending graben systems, which act as basins for sediment. These basins include the Northern and Victoria Land Basin in the west, the Central Trough, and the Eastern Basin, which is about the same size as the others. The Coulman High separates the Victoria Land Basin and Central Trough, while the Central High separates the Central Trough and Eastern Basin. Most of the faulting and graben formation, along with crustal stretching, happened during the Cretaceous period when Zealandia separated from Antarctica. Later faulting and stretching were limited to the Victoria Land Basin and Northern Basin.
Basement grabens are filled with uncertain sediment from the time of rifting. A major layer of rock, called an unconformity (named RSU-6), cuts through the basement and sediment layers. Above this layer are glacial marine sediments deposited during multiple advances and retreats of the Antarctic Ice Sheet across the Ross Sea floor during the Oligocene and later periods.
Drill holes have retrieved rock samples from the western edges of the Ross Sea. Recent projects, such as the Cape Roberts Project (CRP) and ANDRILL, have provided detailed information. The Deep Sea Drilling Project (DSDP) Leg 28 drilled holes farther from land in the central and western parts of the sea, helping define the older glacial sediment layers from the Oligocene and later periods. The RSU-6 unconformity is thought to mark a major global climate event and the first appearance of the Antarctic Ice Sheet in the Oligocene.
In 2018, Expedition 374 of the International Ocean Discovery Program (IODP) drilled additional holes (U1521–1525) in the central Ross Sea to study Neogene and Quaternary ice sheet history.
Information about the basement rocks and graben fill is limited. Metamorphic rocks of unknown age were found at DSDP Leg 28 drill site 270 and in the eastern Ross Sea. These rocks show signs of deformation from the Cretaceous period, suggesting extreme stretching of the Ross Embayment during that time.
In western Marie Byrd Land, rocks exposed on the Edward VII Peninsula and Ford Ranges may be basement rocks for the eastern Ross Sea. The oldest rocks are Permian sediments from the Swanson Formation, slightly metamorphosed. Devonian granodiorite intrudes these sediments, and Cretaceous Byrd Coast granite intrudes older rocks. Basalt dikes cut through these layers. Late Cenozoic volcanic rocks are found in the Ford Ranges and Fosdick Mountains but not on the Edward VII Peninsula. Metamorphic rocks, including migmatites, are present in the Fosdick and Alexandra Mountains, deformed during the Cretaceous.
The Ross Supergroup and Beacon Supergroup: Rocks from the Ross System, exposed in Victoria Land and the Transantarctic Mountains, may form the basement beneath the Ross Sea's sediment layers. These rocks are from the upper Precambrian to lower Paleozoic, deformed during the Cambrian Ross Orogeny. They include calcium carbonate-rich rocks like limestone. Groups within the Ross System include the Robertson Bay, Priestley, Skelton, Beardmore, Byrd, Queen Maud, and Koettlitz groups. The Robertson Bay Group is similar to other Ross System members. Priestley Group rocks include dark slates, argillites, siltstones, fine sandstones, and limestones, found near Priestley and Campbell glaciers. The Skelton Group's calcareous greywackes and argillites are found for thirty miles along the lower Skelton Glacier. The Beardmore Group is located between the lower Beardmore and Shackelton glaciers. The Byrd Group consists of four block-faulted ranges north of the Nimrod Glacier. The Queen Maud Group is mainly post-tectonic granite.
Beacon Sandstone (Devonian–Triassic) and Ferarr volcanic rocks (Jurassic) are separated from the Ross Supergroup by the Kukri Peneplain. Beacon rocks were recovered in drill cores from the Cape Roberts Project near the western edge of the Ross Sea.
Oceanography
The Ross Sea circulation is mainly influenced by processes in polynyas, which are areas of open water surrounded by sea ice. This circulation is generally very slow. Circumpolar Deep Water (CDW) is a warm, salty, and nutrient-rich water mass that flows onto the continental shelf in certain parts of the Ross Sea. This water helps control the ice cover by transferring heat. The near-surface water also creates a warm environment that supports some animals and encourages the growth of plants and other organisms. CDW moves onto the shelf regularly and in cycles, often at locations shaped by the ocean floor’s shape. The circulation in the Ross Sea is mainly driven by wind, forming a large circular current. This flow is strongly affected by three underwater ridges that stretch from southwest to northeast. Below the surface layer, the flow consists of two circular currents that move in the same direction, connected by a central current that moves in the opposite direction. This flow is strongest during spring and winter because of tide influences. The Ross Sea is covered by ice for most of the year, with little melting in the south-central region. Ice coverage is affected by wind patterns, with ice remaining in the western area during austral spring and generally melting in January due to local heating. This causes very distinct layers of water and shallow mixing zones in the western Ross Sea. Observations and data collection in the region are managed by the Ross Sea Working Group of the Southern Ocean Observing System.
Ecological importance and conservation
The Ross Sea is one of the few areas of the ocean that has not been greatly affected by human activities. Because of this, many environmental groups have worked to make the Ross Sea a global marine reserve. They believe protecting the area will help stop threats to its environment. Scientists say the Ross Sea has a high level of biological diversity, and research on the area has been happening for more than 150 years.
The Ross Sea is home to at least 10 mammal species, about six bird species, 95 fish species, and over 1,000 invertebrate species. Birds that live in or near the Ross Sea include the Adélie penguin, emperor penguin, Antarctic petrel, snow petrel, and south polar skua. Marine mammals in the area include the Antarctic minke whale, killer whale, Weddell seal, crabeater seal, and leopard seal. Fish and other sea creatures in the Ross Sea include the Antarctic toothfish, Antarctic silverfish, Antarctic krill, crystal krill, and a special type of orca called Type C.
Albatrosses depend on wind to fly and cannot take off if the air is calm. Wind patterns called westerlies do not reach the edge of the ice, so albatrosses rarely travel to the ice-covered areas. If an albatross lands on an ice floe during calm weather, it may be stuck for many days.
Coastal areas of the Ross Sea have groups of Adélie and emperor penguins. These groups, called rookeries, have been observed near the coast and in open sea areas.
In 2007, a colossal squid measuring 10 meters (32.8 feet) long and weighing 495 kilograms (1,091 pounds) was caught in the Ross Sea.
In 2010, the Ross Sea Antarctic toothfish fishery was approved by the Marine Stewardship Council and received a "Good Alternative" rating from the Monterey Bay Aquarium Seafood Watch program. However, a 2008 report showed that toothfish populations in McMurdo Sound had dropped significantly since the start of industrial fishing in 1996. Other reports noted a decline in orca numbers around the same time. The report suggested stopping all fishing on the Ross shelf. In 2012, Philippa Ross, the great-great-great granddaughter of James Ross, expressed her opposition to fishing in the area.
In the southern winter of 2017, New Zealand scientists discovered the breeding ground of the Antarctic toothfish in the northern Ross Sea seamounts for the first time. This discovery showed how little is known about the species.
On October 28, 2016, the Ross Sea marine park was officially created by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) after an agreement was signed by 24 countries and the European Union. The park protected over 1.5 million square kilometers of ocean and was the largest protected area in the world at that time. The agreement included a 35-year "sunset provision," which means the protections would end after 35 years. This provision is controversial because it reduces the long-term effectiveness of the protections. The agreement also did not meet the definition of a marine protected area set by the International Union for Conservation of Nature, which requires protections to be permanent.
Starting in 2005, the CCAMLR began planning for Marine Protected Areas (MPAs) in Antarctica. In 2010, the CCAMLR approved a proposal to create MPAs for conservation. In 2012, the United States submitted a proposal for a Ross Sea MPA to the CCAMLR, which led to ongoing efforts by international and national environmental groups to speed up the process.
In July 2013, the CCAMLR met in Bremerhaven, Germany, to decide if the Ross Sea should become an MPA. The plan failed because Russia voted against it, saying the commission did not have the authority to create an MPA.
In October 2014, the MPA proposal was again rejected due to votes from China and Russia. In October 2015, a revised proposal from the United States and New Zealand was expanded with help from China, which changed the MPA’s focus to allow some commercial fishing. However, the proposal was still blocked by Russia.