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Scientists say there is a high chance thatkey Atlantic Ocean currents will weakenover the coming decades due toclimate change — but whether they have already slowed is hotly moot . Now , a newfangled study finds that Atlantic circulation has remain stable since the sixties , suggest the system may be more bouncy to warming than scientist think .
But the outcome are controversial . Previous cogitation show sundry results , with somepapersconcluding that theAtlantic Meridional Overturning Circulation ( AMOC ) is weaker nowthan atany point in the past millenary , andothersfinding little to no evidence for a decline in current strength .
The Atlantic Meridional Overturning Circulation is a system of ocean currents that brings heat to the Northern Hemisphere.
" I would say that whether or not the AMOC has weakened is still an opened question,“Maya Ben - Yami , a climate researcher at the Technical University of Munich in Germany who was not involved in the new discipline , told Live Science in an email .
The AMOC is a system of Atlantic Ocean currents , including the Gulf Stream , that disseminate in a jumbo eyelet from Antarctica to Greenland . It delight rut to the Northern Hemisphere . Should it weaken , it could trigger significant cooling in Northern Europe anddramatic commotion to weather patternsworldwide .
Related:‘We are approaching the tipping point ' : Marker for the prostration of primal Atlantic electric current let on
The Gulf Stream is a branch of the AMOC that transports heat to the Northern Hemisphere.
verbatim observance of AMOC ’s strength only go back to 2004 . So to valuate longer - full term trends in Atlantic circulation , researchers rely on climate argument , or " fingerprints , " they think are linked to the AMOC . These admit sea surface temperature , brininess , sea surface height , water density and datum from marine deposit , Ben - Yami say .
" The reason we ’re not sure about the AMOC weakening is that all these different fingerprints can give us different results , " she enounce .
The results of the newfangled study , published Jan. 15 in the journalNature Communications , hint the AMOC has not weakened over the past 60 yr .
‘Rather inaccurate’ data
The scientists estimated AMOC military strength using the newest generation of climate good example , which are more sensitive to rising glasshouse gas concentrations in the standard atmosphere than former model . The researchers essay 24 models in total and found that the most commonly used fingermark , sea surface temperature , had a washy relationship to the AMOC than antecedently reckon .
So the squad or else focused on an indicator call the " ocean - air heat flux , " which simulate the exchange of heat between the ocean and the atmospheric state . Should the AMOC weaken , less heat would clear from the sea to the air in the North Atlantic . But the models showed no declination in heat transferral over the preceding 60 years , suggesting the AMOC has remained stable during this time .
" Our report says that the Atlantic overturning has not go down yet , " discipline co - authorNicholas Foukal , an assistant scientist at the Woods Hole Oceanographic Institution , said in astatement . " That does n’t say anything about its futurity , but it does n’t appear the anticipate variety have occurred yet . "
However , several investigator have pick apart the study . Climate example simulate sea - air passion fluxes by assimilate experimental data like temperature and salinity , meaning any assumptions and gaps in the observations can lead to erroneous fluxion estimates , Ben - Yami said .
Foukal and colleague acknowledge these precariousness in the paper , but they contend that their results are robust nevertheless .
uncounted factors can work transfer of heat from the ocean to the atm , saidStefan Rahmstorf , a prof and oceanographer who co - leads the Earth system of rules analysis research department at the Potsdam Institute for Climate Impact Research in Germany .
" Surface heat loss look also on air temperature , wind speed , humidness , radiation and swarm cover in complex slipway , all of which are not accurately jazz , " Rahmstorf told Live Science in an e-mail . " Therefore , these surface oestrus loss data point are rather inaccurate and in my view not so well suited to retrace the AMOC time evolution . "
The newest climate model may also not be well accommodate to this type of analysis , because of their sensitivity and failure to reproduce some past sea effect , Rahmstorf say . " I do not believe that the new effort to restore the AMOC is more honest than earlier methods , " he say .
Useful new insight
Other experts were less vital of the new research . " The Modern steer towards focusing on air - sea heat fluxes makes intuitive sensation and is utile raw insight,“David Thornalley , a professor of climate and ocean science at University College London who was not involved in the study , tell Live Science in an email .
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Thornalley’sprevious worksuggests the AMOC has weakened significantly , but that it did so during the 1800s , with a stop of comparative stability following in the 1900s . " The approximation that there may have been minuscule change over the preceding 60 years is not too new , " he said .
Regardless of the study ’s uncertainty , the new research contributes to a just understanding of the AMOC , Ben - Yami said . Ultimately , the question of whether the AMOC weakened in the past wo n’t radically impact what scientist think will come about run forward . " TheAMOC will definitely weakenin the future , " Ben - Yami state .
Other researchers agreed . Even with thick cuts to greenhouse gas emission , " it ’s almost solid at this power point that the Atlantic overturning will slow in the futurity , " Foukal reason out .
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