1 2 3 Covariances and Linear Predictability of the North Atlantic Ocean Extract of a Longer Preliminary Draft 4 5

• Main Author: Carl Wunsch
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2011
• Subjects: North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.419.4105; http://www.seas.harvard.edu/climate/seminars/pdfs/wunsch_inprep_2011.pdf

The problem of understanding linear predictability of elements of the ocean circulation is explored in the Atlantic Ocean for two disparate elements: (1) sea surface temperature (SST) under the storm track in a small region east of the Grand Banks and, (2) the meridional overturning circulation north of 30.5◦S. To be worthwhile, any nonlinear method would need to exhibit greater skill, and so a rough baseline is the goal. The focus is a16-year ocean state estimate, under the assumption that oceanic variability is dominating externally imposed changes. Predictablity values obtained for SST are compared to the 28-year long SST record obtained from satellite data. Linear predictability exists for a few months in SST, and there are indications of some skill for a few years. [Omitted here.] Sixteen years is, however, far too short for an evaluation for interannual much less decadal variability and predictability, although orders of magnitude are likely stably estimated. The meridional structure of the meridional overturning circulation (MOC), defined as the time-varying vertical integral to the maximum meridional volume transport at each latitude, shows nearly complete decorrelation in the variability across about 35◦N – the Gulf Stream system. Subtropical transport measurements would appear to have no descriptive or predictive skill for the subpolar region, although nothing can be said about the structure on time scales of many decades and longer – an issue which cannot be resolved with untestable long model runs. 24 (A shortened version of a longer paper in preparation.)