On using satellite altimetric heights to provide a spatial context for the Hawaii Ocean Time-series measurements

It is assumed that the Hawaiian Ocean Time-series (HOT) measurements would be usefully complemented by datasets capable of providing a spatial context for the variability observed at the HOT site. The potential usefulness of high quality sea surface heights from satellite altimeters is evaluated by analyzing data from the Topex/Poseidon (T/P) mission. Three signals are examined: an intra-annual oscillation, the annual variability, and an interannual sea level drop observed at the HOT site during 1993. The intra-annual signal observed at the HOT site is shown to be part of a propagating disturbance that moves energy to the northwest, but propagates phase to the southwest. Farther to the northwest, however, the energy and phase propagate nearly due west. At the annual period, the small amplitude observed at the HOT site is confirmed, but this is not true of the larger scale, where annual amplitudes reach 5-10 cm. The annual phase is largely consistent with the sea surface response to annual heating. Although the interannual event is barely resolved by the T/P series, the drop of dynamic height observed at the HOT site is shown to be part of a larger-scale event. This event is stationary in space and is initially characterized by positive height anomlies near the ridge and negative anomalies further offshore. The signs of these two anomalies reverse in just over 1 year. The observed pattern gives rise to significant meridional sea surface height gradients, and the associated mass transport anomalies are estimated to be 8 Sv. In all three cases the T/P time series, although less than 2 years in duration, provide information about the spatial structure of the signals that extends the descriptions that would be possible using the HOT data alone. Copyright (C) 1996 Elsevier Science Ltd