low Indian reconstructed Bard & Rickaby 2009

Core/Site name:

MD96-2077

Elevation:

-3781

Archive:

marine sediments (downcore)

Proxy measurement:

SST alkenones

Sampling resolution:

millennial

Startyear:

798 ka BP

Endyear:

0 ka BP

Description:

Ice cores extracted from the Antarctic ice sheet suggest that glacialconditions, and the relationship between isotopically derivedtemperatures and atmospheric pCO2 have been constant over thelast 800,000 years of the Late Pleistocene epoch1. But independentlines of evidence, such as the extent of Northern Hemisphere icesheets2, sea level3 and other temperature records4, point towards afluctuating severity of glacial periods, particularly during the moreextreme glacial stadials centred around 340,000 and 420,000 yearsago (marine isotope stages 10 and 12). Previously unidentifiedmechanisms therefore appear to have mediated the relationshipbetween insolation, CO2 and climate. Here we test whether northwardmigration of the subtropical front (STF) off the southeasterncoast of South Africa acts as a gatekeeper for the Agulhas current5,6,which controls the transport of heat and salt from the Indo-PacificOcean to the Atlantic Ocean. Using a new 800,000-year record ofsea surface temperature and ocean productivity from ocean sedimentcore MD962077, we demonstrate that during cold stadials(particularly marine isotope stages 10 and 12), productivitypeaked and sea surface temperature was up to 6 6C cooler thanmodern temperatures. This suggests that during these coolerstadials, the STF moved northward by up to 76 latitude, nearlyshutting off the Agulhas current. Our results, combined withfaunal assemblages from the south Atlantic7,8 show that variablenorthwards migration of the Southern Hemisphere STF canmodulate the severity of each glacial period by altering thestrength of the Agulhas current carrying heat and salt to theAtlantic meridional overturning circulation. We show hence thatthe degree of northwards migration of the STF can partiallydecouple global climate from atmospheric partial pressure ofcarbon dioxide, pCO2 , and help to resolve the long-standing puzzleof differing glacial amplitudes within a consistent range of atmosphericpCO2 .

Data entered by name:

Martrat, Belen

Data entered by email:

This email address is being protected from spambots. You need JavaScript enabled to view it.

Main reference(s):

Bard, E. & Rickaby, R. E. M. Migration of the subtropical front as a modulator of glacial climate. Nature 460, 380-383, doi:http://www.nature.com/nature/journal/v460/n7253/suppinfo/nature08189_S1.html (2009).

Link to reference 1:

http://www.nature.com/nature/journal/v460/n7253/full/nature08189.html#abs

Data storage link 1:

http://www.nature.com/nature/journal/v460/n7253/suppinfo/nature08189.html

Comments:

woa09t_an0: 22.131001 ºC

Current dating method:

-- select --

Annual snow acc rate:

-- select --

Category: PIGS