Earth’s southernmost sea hides a half-kilometre shelf
The Ross Sea, a deep Southern Ocean bay between Victoria Land and Marie Byrd Land, is the planet’s southernmost sea, named for James Clark Ross’s 1841 visit. Ice covers it most of the year, yet nutrient-rich water fuels plankton and a crowded food web in a basin still comparatively lightly touched by people.
A wind-driven gyre, steered by three ridges running south-west to north-east, dominates circulation. The continental shelf averages about 500 metres deep, far below the usual global shelf break near 130 metres, because ice has gouged it out; it is shallower in the west than the east. Ross Island with Mount Erebus stands guard to the west, Roosevelt Island to the east, and the Ross Ice Shelf closes the south. Ten mammal species, six kinds of birds and 95 fish species live here alongside abundant invertebrates.
Amundsen set out for the Pole in 1911 from the Bay of Whales on the shelf, and McMurdo Sound anchors logistics in the west. New Zealand claims the sea as part of its Ross Dependency.
Seismic surveys in the late twentieth century revealed four north-trending rift basins in the bedrock: two western ones, the Northern and Victoria Land basins, plus the Central Trough and the Eastern Basin, separated by the Coulman High and Central High. Most of that faulting happened in the Cretaceous as the Zealandia microcontinent pulled away from Antarctica within Gondwana, with younger movement confined to the two western basins.
Rift sediments filling those basins are capped by a widespread erosion surface named RSU-6, above which lie glacial marine layers laid down as the Antarctic Ice Sheet advanced and retreated from the Oligocene onward. Cores from the Cape Roberts Project, ANDRILL and Deep Sea Drilling Project Leg 28 established that sequence, and RSU-6 may mark the ice sheet’s first appearance. In 2018 the International Ocean Discovery Program’s Expedition 374 drilled five more holes in the central sea to trace later ice history.
Source: Ross Sea
