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Generation of hyper climate modes

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gl031087 1..5 Generation of hyper climate modes D. Dommenget1 and M. Latif1 Received 22 June 2007; revised 28 November 2007; accepted 13 December 2007; published 19 January 2008. [1] It is shown that some important aspects of the space- time structure of multidecadal sea surface temperature (SST) variability can be explained by local air-sea interactions. A concept for ‘‘Global Hyper Climate Modes’’ is formulated: surface heat flux variability associated with regional atmospheric variability patterns is integrated by the large heat capacity of the extra-tropical oceans, leading to a continuous increase of SST variance towards longer timescales. Atmospheric teleconnections spread the extra- tropical signal to the tropical regions. Once SST anomalies have developed in the Tropics, global atmospheric teleconnections spread the signal around the world creating a global hyper climate mode. A simple model suggests that hyper climate modes can vary on timescales longer than 1,000 years. Ocean dynamics may amplify theses modes and influence the regional expression of the variability, but are not at the heart of the mechanism which produces the hyper modes. Citation: Dommenget, D., and M. Latif (2008), Generation of hyper climate modes, Geophys. Res. Lett., 35, L02706, doi:10.1029/2007GL031087. 1. Introduction [2] Climate variability on multidecadal timescales of many decades has been described extensively from obser- vations of the last millennium [e.g., Mantua et al., 1997; Delworth and Mann, 2000; Latif et al., 2004]. Understand- ing the mechanisms generating the multidecadal climate variability is a prerequisite for an early detection of anthro- pogenic climate change. Multidecadal climate variability is reflected in many societal important aspects. Hurricane activity in the Atlantic sector, for instance, varies in phase with multidecadal sea surface temperature (SST) variations [Landsea et al., 1999]. Likewise, Sahelian rainfall exhibits similar multidecadal variations [Folland et al.,

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