Ocean currents are getting faster
WordsbyStephaniePappasO
ceancurrentsaremovingfastertoday
thantheydidtwodecadesago.Recent
research,publishedinthejournal
ScienceAdvances, foundthatthis
accelerationisoccurringaroundtheglobe,
withthemostnoticeableeffectsinthe
tropicallatitudes.Theenhancedspeed
isn’tjustattheocean’ssurface,butis
occurringasdeepas2,000metres.
“Themagnitudeandextentofthe
accelerationinoceancurrentswedetected
throughouttheglobaloceanandto
2,000-metredepthwasquitesurprising,”
saidJanetSprintall,anoceanographeratthe
attheUniversityofCalifornia,SanDiego.
“Whileweexpectedsomeresponsetothe
increasedwindsoverthepasttwodecades,
thattheaccelerationwasaboveandbeyond
thatwasanunexpectedresponsethatismost
likelyduetoglobalclimatechange.”Windsovertheoceanhavebeenpickingup
ata rateof1.9percentperdecade,the
researchersfound.Thisincreaseinwind
speedtransfersenergytotheocean’ssurface,
andsubsequentlydeeperwaters.About 76 per
centoftheupper2,000metresoftheoceans
haveseenanincreaseinkineticenergysince
the1990s.Overalloceancurrentspeedshave
creptupabout5 percentperdecadesincethe
early1990s,thestudyfound.
Researcherswereinterestedin
understandingglobalchangestoocean
currentsbecausepriorresearchhadturned
upa confusingpicture.Forexample,currents
inthesubtropicsthattransferenergyfrom
theequatortothepoleshaveintensifiedover
thelastcentury.Butsomemajorregional
currents,suchastheKuroshiointhewestern
NorthPacificOcean,showlittleevidence
ofacceleration.Theteamreanalysedoldoceancurrent
datarecordedacrossthelastfewdecadesand
pullednewinformationfromtheArgo
mission,a scientificprojectthatuses
thousandsofautonomous,missile-shaped
floatstogatherinformationaboutocean
temperature,salinityandcurrents.
Thespeedupisn’timmediatelyobvious
becauseoceancurrentsmoveveryslowly.For
example,theSouthEquatorialCurrentinthe
PacificOceanmovesatonly1.6kilometresan
hour,soitwouldonlyspeedup0.
kilometresperhourina decade.Giventhe
enormousamountofwaterthat'sonthe
move,ittakesa significantamountofenergy
inputtocreatethatacceleration.These
changesaremuchlargerthanwhatwouldbe
expectedfromnaturalvariability,which
suggeststhatglobalwarmingcouldbe
causingtheincreasedspeed.016 HowIt Works http://www.howitworksdaily.com
IN ASSOCIATION WITHOcean currents
visualised using data
gathered between
2005 and 2007© © NASA/Goddard Space Flight Center Scientific Visualization StudioPLANET EARTH