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Using a suite of ocean model simulations and a set of dedicated twin experiments, we show that the exchange flow between the Mediterranean and the North Atlantic leads to a drop in time mean European coastal sea level along the Atlantic coast north of Gibraltar. The drop is about 7 cm along the Portuguese coast and remains apparent (though reduced) as far north as the Norwegian coast. We also show that Mediterranean time and spatial mean sea level is about 9 cm lower than it would be without the exchange flow (but assuming a small supply from the Atlantic to balance evaporation). Each of these relationships makes possible an estimate of the magnitude of the exchange flow based on sea level measurements, and estimates of 0.8 and 0.91 sverdrups are made consistent with previous determinations based mainly on current measurements in the Strait of Gibraltar.

Combining ocean and earth models, we show that there is a region in the central Pacific ocean where ocean bottom pressure is a direct measure of interannual changes in ocean mass, with a noise level for annual means below 3 mm waterequivalent, and a trend error below 1 mm/yr. We demonstrate this concept using existing ocean bottom pressure measurements from the region, from which we extract the annual cycle of ocean mass (amplitude 8.5 mm, peaking in late September), which is in agreement with previous determinations based on complex combinations of global data sets. This method sidesteps a number of limitations in satellite gravity-based calculations, but its direct implementationis currently limited by the precision of pressure sensors, which suffer from significant drift. Development of a low-drift method to measure ocean bottom pressure at a few sites could provide an important geodetic constraint onthe earth system.

The GOCE satellite mission was launched in 2009 and the first gravity models were released in July 2010. Here we present an initial assessment of the GOCE data in terms of the mean circulation of the North Atlantic. We show thatwith just two months of data, the estimated circulation from GOCE is already superior to a similar estimate based on 8 years of GRACE observations. This result primarily depends on the fact that the GOCE mean dynamic topography (MDT) is generally less noisy than that obtained from the GRACE data. It therefore requires less smoothing and so there is less attenuation of the oceanographic signal.Our results provide a strong validation of the GOCE mission concept, and we anticipate further substantial improvements as the mission progresses

In this letter we examine the relationship between the North Atlantic Meridional Overturning Circulation (MOC) and sea level (SL) along the east coast of North America. In the eddy permitting ocean model OCCAM we find a distinctive, topography-following pattern of SL variability in the western North Atlantic that is closely linked with the changing strength of the MOC, with a 2 cm drop in SL along the US east coast corresponding to a 1Sv increase in the MOC. We find a similar pattern of SL variability in the altimetry record and show that this meridionally coherent SL mode dominates interannual SL variability at tide gauges along the North American east coast between 40–50N. Hence we conclude that North American coastal sea-level may indeed be a useful indicator of MOC variability on interannual timescales, allowing an observationally-based estimate of the likely range of interannual MOC fluctuations to be determined. Citation: Bingham, R. J., and C. W. Hughes (2009), Signature of the Atlantic meridional overturning circulation in sea level along the east coast of North America, Geophys. Res. Lett., 36, L02603, doi:10.1029/2008GL036215.

The availability of the full error variance-covariance matrices for the GOCE gravity field models is an important feature of the GOCE mission. Potentially, it will allow users to evaluate the accuracy of a geoid or mean dynamic topography (MDT) derived from the gravity field model at any particular location, design optimal filters to remove errors from the surfaces, and rigorously assimilate a geoid/MDT into ocean models, or otherwise combine the GOCE gravity field with other data. Here we present an initial investigation into the error characteristics of the GOCE gravity field models as they are realised in the calculated geoid anomalies. We examine how the error variances depend on location and spatial scale, and how they differ between models. The inhomogeneous and anisotropic nature of the error covariances are explored, and an example of how this information may be used in ocean data assimilation is provided. Finally, we consider some of the practical issues relating to the handling of the huge files containing the error variance-covariance information.

Three GOCE gravity models were released in July 2010 based on two months of observations. Subsequently, two second generation models, based on 8 months of observations, were released in March 2011. This paper compares these five models in terms of the mean North Atlantic circulation that can be derived from them. Because the high degree commission errors of all of the GOCE models are lower than those from the best satellite only GRACE solution, all of the derived GOCE MDTs are much less noisy than the GRACE MDT They therefore require less severe filtering and, as a consequence, the strength of the currents calculated from them are in better agreement with those from an in-situ drifter based estimate. Where the comparison is possible, the reduction in MDT noise from the first to second releases is also clear. However, given that some filtering is still required, this translates into only a small improvement in ocean currents. This is. primarily, a reflection of the limitation of the filtering method employed, and indicates the need for more sophisticated MDT filtering strategies.