Strong currents in the oceans have a major influence on Earth's climate, as well as currents around Antarctica called the Antarctic Circumpolar Current (AAC). Recent research shows evidence that the ACC is accelerating, as most climate models predict.
The winds around Antarctica are blowing forever to the east with such great strength. Observations over the years have shown that these forces are increasing, driven by a combination of rising global temperatures and depletion of stratospheric ozone. However, data on the waters below are less comprehensive.
Now Dr Jia-Rui Shi of the Woods Hole Oceanographic Institute has helped combine satellite data with evidence from ocean buoys to establish not only what happened to these currents, but also why. In Nature Climate Change, Shi and co-authors report that currents are getting stronger, and warmer ocean temperatures are to blame.
ACC exists because the wind pushes the water, especially the crest of the wave. Intuitively, we would expect stronger winds to match stronger currents. However, climate models predict above the current speed, the effect will be small because most of the additional energy supplied by the wind is lost in the eddies, where the water spins away from the main current, sometimes against the main direction.
"From observations and models, we found that changes in ocean heat caused the significant acceleration of ocean currents detected over the past few decades," Shi said in a statement.
While the weakening of the Gulf Stream is potentially catastrophic for northern Europe, the effects of a stronger ACC are not as clear-cut, but Shi mentions that the acceleration of this ACC, especially its jets centered on the Subantarctic Front, facilitated exchanges such as heat or carbon, between the basins. oceans and create opportunities for these conditions to increase in the subtropical subsurface.
The healing of the ozone hole is expected to partially balance the effects of increasing global warming on wind speeds around Antarctica. However for ACC, where ozone is only a minor factor, the increase in warmth is expected to lead to further gains for some time to come.
The healing of the ozone hole, though small, is expected to slightly offset the effects of increasing global warming on wind speeds around Antarctica. However for ACC, where ozone is only a minor factor, the increase in warmth is expected to lead to further gains for some time to come.
When South America and Australia merged with Antarctica, there was no way for the waters to move, and ocean currents carried warm water from the equator to the shores of Antarctica. This heat makes Antarctic summers temperate enough for forests to grow and prevents the formation of permanent ice sheets.
Even when the continents separated, enough was initially left behind to prevent the formation of the power we see today, which has a flow of over a hundred million cubic meters per second.
It was only about 30 million years ago, when the Drake Passage opened, and Tasmania moved far enough north to stop interfering with the eastward flow that formed the ACC and isolated Antarctica. The effect changes the temperature of the entire planet, as permanent ice reflects more light.
