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The ICES subdivisions in the North Sea (SD IIIa, SD IVa, and SD IVb) and the subdivisions in the Baltic Sea (SD 29, SD 27/28-2, and SD 25/26) are selected to compare the response in long term monitoring data (1970–2000) with respect to climate regime shifts. A modified AMOEBA model is applied to the data sets to identify the status and development of the North Sea and Baltic Sea system during two recent regime shifts. Biological regime shifts can be identified 1989/1990 in SD IIIa in the North Sea and in SD 25/26 in the Baltic Sea. A synchronous appearance of regime shifts could only be identified in the central and southern Baltic Sea for both regime shifts 1975/76 and 1989/90 where the AMOEBA model indicated a high similarity in ecosystem response. A clear difference was identified in the response of the North Sea and the Baltic Sea. Inter-annual and inter-decadal variability as well as regime shifts are driven in the Baltic Sea by direct atmospheric forcing only. In contrast, the changes in the North Sea are influenced by both the direct atmospheric forcing and the indirect forcing from the changes in North Atlantic. The fact that regime shifts as well as their synchronous appearance can be identified with the AMOEBA model might be of major interest for the management of sustainable use of ecosystem goods and services, the development of ecosystem approach to management and the implementation of the Marine Strategy Framework Directive (MSFD) of the European Union (EU).

A pool of less saline surface waters was observed in late June 2006 at the northern edge of the South Adriatic Pit (SAP). Three possible sources were considered: (1) Albanian rivers, (2) local Croatian rivers, or (3) relatively fresh West Adriatic Current (WAC) waters. Available CTD and ADCP data, together with satellite images, indicate that WAC waters are the most likely source. This requires an excursion of WAC water across the width of the Adriatic and is especially surprising as low winds and stable atmospheric conditions prevailed in mid/late June. However, quite strong NNW winds occurred during the first 12 days of June, with peak winds close to the western shore. These winds were the result of the translation of the Azorean high to the British Isles, producing strong pressure gradients over the Adriatic. The winds enhanced the WAC during early June 2006, preconditioning a cross-basin eddy circulation that appeared during the wind relaxation and calm conditions. As the unusually calm conditions persisted for more than two weeks, the WAC eddies and filaments grew freely and had enough time to reach middle east-Adriatic waters. Navy Coastal Ocean Model (NCOM) simulations, using high-resolution Adriatic bathymetry and realistic atmospheric forcing, show that such excursions are plausible and can occur when eddies and instabilities push WAC waters across the hyperbolic flow point separating the WAC and Eastern Adriatic Current near the Palagruža Sill. During the latter half of June 2006, NCOM simulations show that the hyperbolic point was particularly well formed as an anticyclonic WAC, a cyclonic SAP rim flow, an anticyclonic cell southeast of Lastovo Island, and a cyclonic cell over the centre of the Palagruža Sill all bordered on each other. A simplified channel model suggests that the presence of the escarpment is a critical factor for producing cross-basin exchange of the coastal current following the relaxation of strong winds with a cyclonic wind stress curl. However, the introduction of the Gargano Peninsula in the simulations was critical to the production of mesoscale eddies in the exchange flow, and such eddies qualitatively agree with the convoluted structures observed in satellite images.

International audience; Sea level time series derived from TOPEX altimeter and from tide gauge measurements in the Bay of Biscay (Eastern North Atlantic Ocean) are used to investigate the regional sea level rise. Altimetry sea level anomalies are computed from TOPEX measurements and resampled into fixed along track bins in order to obtain consistent records and to approach as close as possible to the coast. Tidal corrections are critical in the estimation of sea level trends; therefore an additional analysis has been carried out in order to identify and correct for residual tidal signals. The obtained mean sea level rise in the region is + 3.09 ± 0.21 mm/year over the period 1993–2002. Tide gauges have been corrected for vertical land motions by means of collocated GPS measurements. GPS-corrected tide gauges and nearby altimetry trends are found to be statistically consistent. The relationship with the atmospheric forcing is also investigated revealing that 15% of this sea level rise is attributed to the atmospheric pressure effects.

Mean temporal circulation at Ormen Lange (OL) off mid-Norway is strongly dominated by the Norwegian Atlantic Current. Tidal effects are weak. Observed events of short peak value in current speed along with peak in temperature close to the seabed at the shelf slope may be driven by strong pressure gradients. That is, strong atmospheric low pressures and/or internal pressure fronts between warmer Atlantic Water (AW) and colder Norwegian Sea Water (NSW). Along the shelf slope at OL there may be steepening of the isopycnals, separating AW and NSW, due to wind generated downwelling and strong Ekman veering during storms or approaching internal density fronts. During such events the density surfaces tend to undershoot their equilibrium level, and as the forcing weakens, the suppressed water may run up along the shelf slope. In this run up phase, peak values in the velocities are often found. Since the atmospheric forcing may be a major forcing mechanism behind the observed events, we have performed a numerical study of the sensitivity of near bottom velocities at OL to the pathway of low pressure disturbances and the strength and the radii of them. The results indicate how depth dependent currents at different locations respond to varying atmospheric forcing, with highest currents close to the surface, time delay of response at greater depths and highest impact of storms passing further out in the Nordic Seas than immediately over OL.

During the last 15 years, the knowledge of Mediterranean physical dynamics as well as of atmospheric forcing underwent a tremendous improvement because of the action within several international programs and the development of remote sensing and modelling approaches. Curiously, it is still very difficult to build up a climatological database for chemical and basic biological parameters for the whole basin because most of the data published in the open literature were preferentially related to meso- to small-scale processes. Within the European Union project Mass Transfer and Ecosystem Response (MATER), systematic measurements of routine chemical parameters, such as dissolved oxygen and nutrients, have been conducted. They will fill the existing gap between physical and chemical information. In this paper, we analyze the hydrographic data from a cruise conducted in the fall 1996 in the Central Mediterranean region and report, for the first time, on oxygen and nutrient concentrations, ranges and distributions. The joint analysis of T–S properties and chemical data also allows a better definition of water mass characteristics in this crucial area and hints at basic mechanisms relevant to water mass transformation and biological production in the basin. D 2002 Elsevier Science B.V. All rights reserved.

We use a hierarchy of diagnostic and prognostic numerical methods to investigate the formation mechanisms of Levantine Intermediate Water (LIW), determine the formation sites and estimate its annual formation rates. Although the three methods are different and use different hydrological/atmospheric forcing data, all of them reach the same qualitative and quantitative results: under mean climatological conditions the LIW is formed during winter in the Rhodes cyclonic gyre with an annual formation rate of 1.0 Sv. The preferred formation site is mainly controlled by the preconditioning of the hydrology, i.e., the presence of the Rhodes gyre, rather than the spatial distribution of surface forcing, which plays a significant role only during extreme meteorological episodes. The interannual variability experiments show that during severe winters, the formation rate is not increased significantly but instead, deep waters are formed in the center of the gyre, and the LIW formation area is extended towards the northeast Levantine. During mild winters, the formation rate is reduced considerably (