Zhou and his colleagues suggested that weakening of offshore winds, as part of a natural cycle, is shrinking ice-producing areas.īoth the Weddell Sea and Australian Antarctic Basin observations are early warning signs of a slowing overturning circulation, Zhou said.
Meanwhile, a recent study led by oceanographer Shenjie Zhou, a postdoc at the British Antarctic Survey, showed a 20% slowdown in the Atlantic sector off Antarctica’s Weddell Sea. “Given that we expect the ice to continue melting, the most likely outcome is a continuation in the slowdown,” Gunn said.Īntarctic Bottom Water forms when cold, salty water sinks. This meltwater from glaciers makes the ocean surface less salty, and when it freezes, the waters below are less dense than normal, falling into the deep more slowly. “We’re in an area downstream of a lot of meltwater,” Gunn said. The largest changes occurred in flows from the Ross Sea. They found that the flows have become fresher, lighter, and smaller in volume since the 1990s and the abyssal circulation has slowed by almost a third. They used decadal observations from research ships and continuous measurements from moorings to track changes in temperature, salinity, oxygen, and flow in the three sources of bottom water this basin receives: the Weddell Sea, the Adélie Land coast, and the Ross Sea. “Given that we expect the ice to continue melting, the most likely outcome is a continuation in the slowdown.” Research vessels collected data near Antarctica. Gunn and her colleagues examined waters in the Australian Antarctic Basin-the section of the Pacific Ocean between East Antarctica and southern Australia.
But diminishing glaciers in West Antarctica-primarily the Amundsen Sea-are freshening the shelf waters in the Ross Sea and slowing the production of bottom water, according to research led by Kathy Gunn, a physical oceanographer at the Commonwealth Scientific and Industrial Research Organisation in Hobart, Tasmania.
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