Climate Dynamics

, Volume 39, Issue 12, pp 2917–2936

The response of the North Pacific Decadal Variability to strong tropical volcanic eruptions

  • Tao Wang
  • Odd Helge Otterå
  • Yongqi Gao
  • Huijun Wang
Article

DOI: 10.1007/s00382-012-1373-5

Cite this article as:
Wang, T., Otterå, O.H., Gao, Y. et al. Clim Dyn (2012) 39: 2917. doi:10.1007/s00382-012-1373-5

Abstract

In this study, the effects of volcanic forcing on North Pacific climate variability, on interannual to decadal time scales, are examined using climate model simulations covering the last 600 years. The model used is the Bergen Climate Model, a fully coupled atmosphere–ocean general circulation model. It is found that natural external forcings, such as tropical strong volcanic eruptions (SVEs) and variations in total solar irradiance, play an important role in regulating North Pacific Decadal Variability (NPDV). In response to tropical SVEs the lower stratospheric pole–to–equator temperature gradient is enhanced. The North polar vortex is strengthened, which forces a significant positive Arctic Oscillation. At the same time, dipole zonal wind anomalies associated with strong polar vortex propagate downward from the lower stratosphere. Through positive feedbacks in the troposphere, the surface westerly winds across the central North Pacific are significantly weakened, and positive sea level pressure anomalies are formed in the North Pacific. This anomalous surface circulation results in changes in the net heat fluxes and the oceanic advection across the North Pacific. As a result of this, warm water converges in the subtropical western North Pacific, where the surface waters in addition are heated by significantly reduced latent and sensible heat fluxes from the ocean. In the eastern and high–latitude North Pacific the ocean loses more heat, and large–scale decreases in sea surface temperatures are found. The overall response of this chain of events is that the North Pacific enters a negative phase of the Pacific decadal oscillation (PDO), and this negative phase of the PDO is maintained for several years. It is thus concluded that the volcanic forcing plays a key role in the phasing of the PDO. The model results furthermore highlight the important role of troposphere–stratosphere coupling, tropical–extratropical teleconnections and extratropical ocean–atmosphere interactions for describing NPDV.

Keywords

Strong tropical volcanic eruptionsNorth polar vortexNorth Pacific Decadal VariabilityCoupled modelOcean–atmosphere interactionTroposphere–stratosphere coupling

Supplementary material

382_2012_1373_MOESM1_ESM.doc (2.6 mb)
Supplementary material 1 (DOC 2633 kb)

Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Tao Wang
    • 1
  • Odd Helge Otterå
    • 2
    • 3
  • Yongqi Gao
    • 1
    • 3
    • 4
  • Huijun Wang
    • 1
    • 5
  1. 1.Nansen-Zhu International Research Center, Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina
  2. 2.Uni Bjerknes Centre, Uni ResearchBergenNorway
  3. 3.Bjerknes Center for Climate ResearchBergenNorway
  4. 4.Nansen Environmental and Remote Sensing CenterBergenNorway
  5. 5.Climate Change Research Center, Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina