Evaluation of interannual to decadal variability in a global ocean model in the North Atlantic

Helen E. Phillips and Terrence M. Joyce

We describe the oceanic variability at Bermuda between 1989 and 1999, recorded in two over-lapping hydrographic time series. Station S and BATS, which are 60 km apart, both show that a multi-decadal trend of deep warming has reversed, likely a result of the increased production of Labrador Sea Water since the early 1980s. In addition to recording similar changes in water-mass properties, the two time-series show similar mean vertical structure and variance as a function of pressure for temperature, salinity and density above 1500 dbar. The seasonal cycles of these water properties at the two sites are statistically indistinguishable. The time-series differ in the individual eddy events they record and in their variability below 1500 dbar. We use the two time-series to investigate the propagation of eddy features. Coherence and phase calculated from the low-mode variability of density show westward propagation at ~ 3 cm/s of wavelengths around 300–500 km. We use satellite altimeter data to provide a broader spatial view of the eddy (or wave) field near Bermuda.