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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 6 | Copyright

Special issue: Millennial-scale variability in the American tropics and...

Clim. Past, 11, 915-929, 2015
https://doi.org/10.5194/cp-11-915-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 22 Jun 2015

Research article | 22 Jun 2015

Thermal evolution of the western South Atlantic and the adjacent continent during Termination 1

C. M. Chiessi1, S. Mulitza2, G. Mollenhauer2,3, J. B. Silva4, J. Groeneveld2, and M. Prange2 C. M. Chiessi et al.
  • 1School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, Brazil
  • 2MARUM – Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
  • 3Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
  • 4Institute of Geosciences, University of São Paulo, São Paulo, Brazil

Abstract. During Termination 1, millennial-scale weakening events of the Atlantic meridional overturning circulation (AMOC) supposedly produced major changes in sea surface temperatures (SSTs) of the western South Atlantic, and in mean air temperatures (MATs) over southeastern South America. It has been suggested, for instance, that the Brazil Current (BC) would strengthen (weaken) and the North Brazil Current (NBC) would weaken (strengthen) during slowdown (speed-up) events of the AMOC. This anti-phase pattern was claimed to be a necessary response to the decreased North Atlantic heat piracy during periods of weak AMOC. However, the thermal evolution of the western South Atlantic and the adjacent continent is so far largely unknown. Here we address this issue, presenting high-temporal-resolution SST and MAT records from the BC and southeastern South America, respectively. We identify a warming in the western South Atlantic during Heinrich Stadial 1 (HS1), which is followed first by a drop and then by increasing temperatures during the Bølling–Allerød, in phase with an existing SST record from the NBC. Additionally, a similar SST evolution is shown by a southernmost eastern South Atlantic record, suggesting a South Atlantic-wide pattern in SST evolution during most of Termination 1. Over southeastern South America, our MAT record shows a two-step increase during Termination 1, synchronous with atmospheric CO2 rise (i.e., during the second half of HS1 and during the Younger Dryas), and lagging abrupt SST changes by several thousand years. This delay corroborates the notion that the long duration of HS1 was fundamental in driving the Earth out of the last glacial.

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Here we show that temperatures in the western South Atlantic increased markedly during the major slowdown event of the Atlantic meridional overturning circulation (AMOC) of the last deglaciation. Over the adjacent continent, however, temperatures followed the rise in atmospheric carbon dioxide, lagging changes in oceanic temperature. Our records corroborate the notion that the long duration of the major slowdown event of the AMOC was fundamental in driving the Earth out of the last glacial.
Here we show that temperatures in the western South Atlantic increased markedly during the major...
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