On the Variability of Wind Power Input to the Oceans with a Focus on the Subpolar North Atlantic

1 Variations in power input to the ocean using a recent global “reanalysis” extending back 2 to 1871 shows a strong trend in the net power input since then, a trend dominated by 3 the Southern Ocean region. This trend is interpreted as a spurious result of the changing 4 observational system. Focussing therefore, on the North Atlantic, where the data base is 5 somewhat more secure, the input power in the subpolar North Atlantic varies significantly in 6 time, showing a strong relationship to the North Atlantic Oscillation (NAO). During positive 7 NAO index years, power input is greater owing to enhanced synoptic activity. Furthermore, 8 cumulative power input to the subpolar North Atlantic is found to correlate significantly 9 with both the eddy kinetic energy there and the Atlantic Multidecadal Oscillation, although 10 the physical mechanism at work remains unclear. The assumption that the changing ocean 11 can be neglected relative to the changing atmosphere in calculating the power input is found 12 to be a usefully accurate approximation over the two decades for which changing ocean state 13 estimates are available. Strong dependence on synoptic weather systems of monthly average 14 stress distributions implies that paleo and future climate simulations must account properly 15 for changes in weather systems, not just the large-scale variations. 16