Covariances and Linear Predictability of the Atlantic Ocean

4 The problem of understanding linear predictability of elements of the ocean circulation is 5 explored in the Atlantic Ocean for two disparate elements: (1) sea surface temperature (SST) 6 under the storm track in a small region east of the Grand Banks and, (2) the meridional 7 overturning circulation north of 30.5◦S. To be worthwhile, any nonlinear method would need 8 to exhibit greater skill, and so a rough baseline from which to judge more complex methods is 9 the goal. A 16-year ocean state estimate is used, under the assumption that internal oceanic 10 variability is dominating externally imposed changes. Linear predictability is the story of 11 time and space correlations, and some predictive skill exists for a few months in SST, with 12 some minor capability extending to a few years. Sixteen years is, however, far too short for an 13 evaluation for interannual, much less decadal, variability, although orders of magnitude are 14 likely stably estimated. The meridional structure of the meridional overturning circulation 15 (MOC), defined as the time-varying vertical integral to the maximum meridional volume 16 transport at each latitude, shows nearly complete decorrelation in the variability across 17 about 35◦N–the Gulf Stream system. If a time scale exists displaying coherence of the MOC 18 between sub-polar and subtropical gyres, it lies beyond the existing observation duration, 19 and that has consequences for observing system strategies and the more general problem of 20 detectability of change. 21