Narrow Results

Sea level variations collected in several areas in the world have been analyzed trying to infer their non linear characteristics. Analyzed data were acquired in several sites in West and East coasts of the North American continent, in the Hawaii and Bermuda islands, representing oceanic sites, and in Adriatic sea, representing a well known basin type. Data have been analyzed through Independent Component Analysis, False Nearest Neighbours and the estimation of correlation dimension using Grasberger and Procaccia integral. Results show a clear non linear features in all the sites, characterized by second and third order Landau mode.

The general relativistic Lense–Thirring effect can be detected by means of a suitable combination of orbital residuals of the laser-ranged LAGEOS and LAGEOS II satellites. While this observable is not affected by the orbital perturbation induced by the zonal Earth solid and ocean tides, it is sensitive to those generated by the tesseral and sectorial tides. The assessment of their influence on the measurement of the parameter μ_LT, with which the gravitomagnetic effect is accounted for, is the goal of this paper. After simulating the combined residual curve by calculating accurately the mismodeling of the more effective tidal perturbations, it has been found that, while the solid tides affect the recovery of μ_LT at a level always well below 1%, for the ocean tides and the other long-period signals Δμ depends strongly on the observational period and the noise level: Δμ_tides ≃ 2% after seven years. The aliasing effect of K₁1=3 p=1 tide and SRP(4241) solar radiation pressure harmonic, with periods longer than four years, on the perigee of LAGEOS II yield to a maximum systematic uncertainty on μ_LT of less than 4% over different observational periods. The zonal 18.6-year tide does not affect the combined residuals.

The dynamics which control the spread of tracers in the N.W. European Shelf Seas are reviewed. The perspective of this review is to allow a comparison with the vastly different regimes found in Australian waters. Whilst these N.W. European Shelf Seas are dominated by the influence of the M₂ semi-diurnal tide, the Gulfs off South Australia have significant diurnal constitutents and a peculiar near equality of M₂ and S₂—producing ‘dodge’ tides. Nevertheless, generalised expressions for both the annual mean and the seasonal amplitude of sea surface temperature (derived from North Atlantic data) are generally applicable.

The greater sensitivity of diurnal tidal constituents to bed friction coupled with the proximity to the related inertial latitude suggests that tidal propagation models may require more tuning of the bed stress coefficient. However the greatest contrast is for ‘estuaries’ where the excess of evaporation over precipitation and river flow produces ‘inverse estuaries’ unknown in Europe. Whilst flushing time concepts can be used in similar fashions, the extraction of tracers from such estuaries occurs close to the bed via ‘inverse’ salt wedges. This contrast with mean surface extraction in European estuaries will have significant influences on the related ecology.

A ‘Future Work’ section describes recent developments and plans to extend marine forecasting via Operational Oceanography. Whilst Australian requirements will differ considerably, the need to maintain awareness and adopt common practices is important to fulfill the wider goals of GOOS—the Global Ocean Observing System.