No abstract

All existing descriptions of nutrient distributions in the Strait of Gibraltar suggest that the Atlantic water brings to the Mediterranean Sea nutrients in the Redfield ratio (N:Si:P = 16:15:1). Here, the N:Si:P molar ratios (±Standard Error), obtained in April 1998, are used to show that in the Atlantic water at the western entrance of the Strait this ratio is lower (13.8(±0.5):12.1(±1.0):1) than the classical Redfield ratio; it is close to the Redfield ratio in the middle of the Strait (15.6(±0.6):10.7(±0.9):1), and increases dramatically to 23.6(±3.4):29.1(±4.5):1 at the eastern entrance of the Strait. In the Mediterranean water, the N:Si:P ratio has a quite similar trend with 31.5(±6.0):26.5(±3.6):1 in the east, 20.4(±0.2):31.5(±11.1):1 in the middle and 18.1(±0.6):17.6(±0.7):1 in the west of the Strait. The physical and biological processes that account for the observed spatial variability of the N:Si:P ratio along the Strait are identified. We estimated that in the Atlantic water entering the Mediterranean Sea, about 84% of the variability in N:Si:P molar ratio is due to biological and 16% to physical processes.

Recent observations of newly formed deep water in the Aegean sea prompts this analysis of whether such deep water could be formed locally by the combination of an increase in net evaporation and wintertime water mass transformation. River diversion projects in Russia and Egypt since the 1950s have effectively increased the amount of net evaporation over the eastern Mediterranean basin. Historical profiles show that low salinity intermediate waters separated the deep and upper waters in the Aegean in 1961-1962. Within a simple mixed layer model, imposing a small net evaporation of 10 cm•yr-1 on the observed hydrographic conditions in March 1962 results in the gradual erosion of the low salinity intermediate waters. After 25 years, the low salinity intermediate waters are absent in agreement with observations made in September 1987. Continuing to force the model with the small net evaporation and with monthly heat and freshwater exchange anomalies from March 1987, new deep water could have been formed as early as March 1988. In the model, major deep water formation events occurred during the severe winters of 1991-1992 and 1992-1993 resulting in the formation of saltier and notably colder deep waters. The effective increase in net evaporation slowly increases the salinity and decreases the stratification in the Aegean sea until a severe winter leads to deep convection and new bottom water formation. © 2001 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS Résumé − Causes des changements à long terme de l'eau profonde de la mer Égée. Des observations récentes de l'eau profonde nouvellement formée en mer Égée permettent de déterminer si son origine est locale, suite à l'action combinée de l'évaporation nette et de la transformation hivernale de la masse d'eau. Les détournements des cours de rivières en Russie et en Égypte depuis les années cinquante ont en effet accru l'évaporation nette dans le bassin oriental de la Méditerranée. Des profils historiques montrent que les eaux intermédiaires de basse salinité séparent les masses d'eaux profonde et supérieure en mer Égée depuis les années 1961-1962. L'utilisation d'un modèle simple de couche de mélange où une évaporation nette de 10 cm•an-1 a été appliquée aux conditions hydrologiques observées en mars 1962 conduit à une diminution graduelle des eaux intermédiaires de basse salinité. Après 25 ans, ces eaux intermédiaires de basse salinité disparaissent, ce qui est en accord avec les observations réalisées en septembre 1987. Si l'on continue le forçage du modèle avec la même évaporation et en tenant compte des anomalies mensuelles des échanges de chaleur et d'eau douce depuis mars 1987, l'eau profonde « nouvelle » pourrait avoir été formée dès mars 1988. Avec ce modèle, des événements majeurs assurant la formation de l'eau profonde apparaissent. Durant les hivers rigoureux de 1991-1992 et de 1992-1993, des eaux profondes plus salées et notablement plus froides furent ainsi formées. L'accroissement de l'évaporation nette accroît progressivement la salinit...

23MedCLIVAR is a project that promotes coordination of the large scientific community engaged in Mediterranean climate research. The main goals of MedCLIVAR include reconstruction of Mediterranean past climate variability and extremes and natural hazards, the description of patterns and mechanisms characterising its space-time variability, the identification of the forcing parameters responsible for the observed changes, and its response to future emission scenarios. The project focuses on long instrumental data as well as documentary and natural proxy evidence resolving different time and spatial scales. All these data sources are important for the construction of high quality data sets, in order to extend the record of past Mediterranean climate variability over decadal and centennial timescales.

Scientific meetings are important to the development of early career ocean scientists, yet little documentation exists regarding how meeting planners can develop activities that will be most useful to this group. Based upon the authors' experience gained through activities of the Scientific Committee on Oceanic Research and the World Climate Research Programme, as well as ideas offered by colleagues from other organizations, meeting organizers should take the following steps in planning early career activities: (1) form a subcommittee that will plan early career activities and include an early career scientist on it, (2) seek outside financial support for early career activities and for early career scientist travel support, (3) determine the criteria participants must meet to secure travel support, (4) design a registration form to collect information useful for designing activities for early career scientists, (5) plan oral and poster sessions with a variety of opportunities for early career scientists, (6) consider which social media will be best for communicating with early career meeting participants, (7) set aside a "career lounge" at the meeting, and (8) conduct a post-meeting survey. It is important to plan and announce all early career events and opportunities well before the meeting