Picture: Ocean around the Maldives. Credit: Asad Photo (Pexels).

The global ocean has slow fluctuations that can be exploited to predict the climate over the next year to a decade. Previous studies have shown that both the Atlantic and Pacific Oceans can drive this decadal variability, hence predicting changes in one ocean could lead to a skilful forecast of the other. Here an international team of authors led by NCAR scientist and CLEX PI Jerry Meehl, along with CLEX CIs and AIs, propose that these ocean basins are mutually interactive, with each basin influencing and responding to processes in the other basin.

The study, published in Nature Geoscience, analyses observations and model simulations where sea surface temperatures are specified in one region while the rest of the coupled model is free to respond. This isolates the effects of one ocean basin on the other. There tends to be a weak opposite-sign sea surface temperature response in the tropical Pacific when observed temperatures are specified in the Atlantic while there is a weak same-sign SST response in the tropical Atlantic when observed SSTs are specific in the tropical Pacific. This indicates that the Pacific and Atlantic are mutually interactive through both mid-latitude teleconnections and the atmospheric Walker Circulation.

The implications from these findings are that mechanisms in both ocean basins, as well as their mutual interactions, must be simulated and predicted in order to provide skilful decadal climate prediction.

  • Paper: Meehl, G.A., A. Hu, F. Castruccio, M.H. England, S.C. Bates, G. Donabasoglu, S. McGregor, J.M. Arblaster, S.-P. Xie, and N. Rosenbloom, 2020: Atlantic and Pacific tropics connected by mutually interactive decadal-timescale processes, Nature Geo., doi:10.1038/s41561-020-00669-x