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A spectacular slowdown in recondite sea currents touch a major reset in Earth ’s ice ages about 1 million year ago , raw grounds from the South Atlantic seafloor suggests .
The discovery does n’t mean the ocean stream stall - out is the only culprit behind the change in Earth ’s incessantice age , the work author said . However , the finding supply new evidence that Earth ’s oceans can importantly change its climate .
The thermohaline circulation is a global ocean current that redistributes warm surface water and cold, dense deep water.
" We can not say for sure what break the cycle , " say lead sketch generator Leopoldo Pena of the Lamont - Doherty Earth Observatory in New York . " Our evidence shows the sea played a major role . " [ Infographic : Tallest Mountain to Deepest Ocean Trench ]
For obscure reasons , about 950,000 days ago , Earth ’s ice years round suddenly lengthened , from 41,000 years to 100,000 eld . The major planet ’s thermoregulator was tweaked at the same time , with methamphetamine hydrochloride ages produce cold than before .
" This is the largest climatic variety that has materialize on our planet in the last 2 million years , " Pena said . " For many decades , scientist have been trying to understand what occur . "
The big transposition adopt place without the usual suspect , such as a drop in energy from the sun due to orbital wobble . So scientist become to climate alteration for a potential case . Pena and his co - author have now discovered that a hugeocean " conveyor belt"stalled at the same time as the shabu age switch . Their findings were published today ( June 26 ) in the daybook Science Express .
The conveyor belt is a globose current organization scientists call the thermohaline circulation ( THC ) . The circulation pattern moves warm airfoil water from the Southern Hemisphere toward the northerly latitudes , where it grows cold and piquant and sinks . The denser piddle then flows back toward the south along the rich seafloor . The Gulf Stream is part of this giant conveyor whang . Paleoclimate records show the THC current have operated for million of geezerhood . [ video recording : Animation let out Ocean Currents ]
Tracing ancient current
To track the strength of the ancient THC currents , Pena analyze levels ofneodymiumin minerals crust onto tiny shells of utter plankton . The mineral were encrusted after the plankton kick the bucket , as the shell send packing to the seafloor . The neodymium indicate where the deep seawater do from , Pena said . For example , waters from the North Atlantic have a distinct neodymium " relish " versus waters from the North Pacific .
By measuring the Nd in shell in seafloor clay deposited during the past million years , Pena can estimate whether North Atlantic pee were menstruate to the south , or if the current shut down .
When the sparkler years cycle was every 41,000 year , the THC currents were normal intensity level even duringglacial periods , the investigator found . But 950,000 years ago , something shut down the conveyor belt during a frigid menstruum . The crisis live 100,000 years , Pena say , and then the flow recover . However , after the transition , when Earth was in its 100,000 - year ice age cycle , the ocean flow rise weaker or stalled every metre there was an ice age .
The researchers suspect the cold ice long time after the big flip think large ice sheets in the North Atlantic close down the ocean conveyor belt ammunition .
But for now , Pena say scientists are n’t sure which make out first — bigger icing sheet or a broken ocean conveyor belt . There was also a huge free fall in carbon dioxide 950,000 years ago , which also played a role in cooling the major planet . The sulky conveyer knock could have contributed to this cliff by hoarding thegreenhouse gasin the mystifying sea , Pena said .
" It ’s a crybaby - and - ballock interrogative , " Pena said .
Christopher Charles , a climate scientist who was not involved in the study , fit in that it ’s unlikely a single cause will emerge . The mystifying ocean could be one of many triggers for the ice age change .
" It ’s exceedingly likely that the transposition in frosting age cycling was at least powerfully act upon by , if not controlled by , carbon cycling , " enunciate Charles , a professor at the Scripps Institution of Oceanography in San Diego . " It would not be at all surprising to me if ocean mixing somehow played a purpose in governing the depot of carbon copy in the mystifying ocean . "
