Mechanisms and Predictability of Pacific Decadal Variability

摘要

Purpose of Review This paper reviews recent progress in the understanding and prediction of pacific decadal variability (PDV). The PDV is now recognized to consist of multiple ocean-atmosphere modes and to be caused by multiple processes. At the leading order, PDV can be viewed as the reddening process of stochastic atmospheric variability on the extratropical ocean. However, PDV is also strongly tied to teleconnection dynamics interacting with the tropics, primarily the interactions between meridional modes in the extra-tropics and ENSO, and between the ENSO teleconnections and the dominant modes of atmospheric variability in the mid-latitude. Recent Findings Extratropical oceanic Rossby waves are found to be crucial for determining the decadal time scales of the PDV and provide potentially an important source of predictability of PDV. Preliminary experiments with GCMs and empirical linear inverse models have shown some skill for the prediction of PDV in ocean surface temperatures. While the climate predictions in the first few years depend significantly on the oceanic initial condition, predictions of near decadal time scales are contributed mostly by the global warming trend. In addition, recent studies explored the role of ocean subsurface dynamics for multi-decadal predictability in the Pacific and suggest that subsurface dynamics may lead to important sources of decadal predictability in regional upwelling systems, namely the eastern boundary and polar gyre. Overall, the predictability of PDV and the related surface and subsurface signals remain to be much studied. Summary Recent studies also start to explore the relation between PDV and global warming. It has been suggested that PDV can slow down or accelerate the global warming trend significantly. The influence of the anthropogenic climate change on PDV, however, has remained unclear.