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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 10
Clim. Past, 11, 1335–1346, 2015
https://doi.org/10.5194/cp-11-1335-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Clim. Past, 11, 1335–1346, 2015
https://doi.org/10.5194/cp-11-1335-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 09 Oct 2015

Research article | 09 Oct 2015

Obliquity forcing of low-latitude climate

J. H. C. Bosmans1,2,a,*, F. J. Hilgen1, E. Tuenter1,2,b, and L. J. Lourens1 J. H. C. Bosmans et al.
  • 1Faculty of Geosciences, Utrecht University, the Netherlands
  • 2Royal Netherlands Meteorological Institute (KNMI), the Netherlands
  • anow at: Faculty of Geosciences, Utrecht University, the Netherlands
  • bnow at: Royal Netherlands Meteorological Institute (KNMI), the Netherlands
  • *Invited contribution by J. H. C. Bosmans, recipient of the EGU Outstanding Student Poster (OSP) Awards 2013.

Abstract. The influence of obliquity, the tilt of the Earth's rotational axis, on incoming solar radiation at low latitudes is small, yet many tropical and subtropical palaeoclimate records reveal a clear obliquity signal. Several mechanisms have been proposed to explain this signal, such as the remote influence of high-latitude glacials, the remote effect of insolation changes at mid- to high latitudes independent of glacial cyclicity, shifts in the latitudinal extent of the tropics, and changes in latitudinal insolation gradients. Using a sophisticated coupled ocean–atmosphere global climate model, EC-Earth, without dynamical ice sheets, we performed two idealized experiments of obliquity extremes. Our results show that obliquity-induced changes in tropical climate can occur without high-latitude ice sheet fluctuations. Furthermore, the tropical circulation changes are consistent with obliquity-induced changes in the cross-equatorial insolation gradient, suggesting that this gradient may be used to explain obliquity signals in low-latitude palaeoclimate records instead of the classical 65° N summer insolation curve.

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Our study shows that the influence of obliquity (the tilt of Earth's rotational axis) can be explained through changes in the insolation gradient across the tropics. This explanation is fundamentally different from high-latitude mechanisms that were previously often inferred to explain obliquity signals in low-latitude paleoclimate records, for instance glacial fluctuations. Our study is based on state-of-the-art climate model experiments.
Our study shows that the influence of obliquity (the tilt of Earth's rotational axis) can be...
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