Observed MOC Variability at 26.5°N and 34.5°S: Structure and Time Scale Similarities and Differences in the North and South Atlantic
Thursday, 18 December 2014: 8:00 AM
Variations in the Meridional Overturning Circulation (MOC) have been connected in numerical models and paleo-climate records with changes in surface air temperature, precipitation patterns, and changes in hurricane intensification, but observations and models also suggest that the MOC is not an in-phase monolithic system driving simultaneous (or even identical lagged) variations at all latitudes and in all ocean basins. Prediction and understanding of MOC variability will require better comprehension of the latitudinal and temporal scales associated with MOC changes across the Atlantic. Continuous basin-wide MOC volume transport time series observations are available at 26.5°N from the RAPID-MOC/MOCHA/WBTS array for nearly a decade, and a 20-month continuous basin-wide MOC time series is available at 34.5°S based on the pilot arrays of the developing SAMBA array. At 26.5°N the longer record indicates that the bulk (nearly 50%) of the time variability in the record is at sub-annual periods – this energetic ‘high frequency noise’ illustrates the need for continuous-in-time (daily) measurements. The MOC at 34.5°S is similarly ‘noisy’ at sub-annual periods, and based on this short record there is no indication of coherence between the MOC time series at the two latitudes. Structure and variability comparisons between the two latitudes will be presented and discussed in the context of recent numerical model results, illustrating not only the veracity but also the limitations of the model results.