Although NO,--is generally considered to limit primary productivity in most of the world's oceans, previous studies have suggested the Mediterranean Sea may be an exception. In this study of the southeastern Mediterranean, we found that all the POd3-was removed from the upper water column during the winter phytoplankton bloom in the core and boundary of a warm-core eddy, while measurable (0.3-0.6 PM) NO,-remained. The N: P (N0,-:P0,3-) ratio in the core and boundary of the Cyprus eddy was 27.4 and the slope of the linear portion of the N vs. P scattergram was 25.5 with a positive intercept of 0.5 PM on the NO,-axis. A similar N : P ratio (28-29), slope (21-23), and intercept (0.9-l. 1) was found for the water column across much of the southern Levantine basin. These data, taken together with the results of incubation experiments, lead us to conclude that the southeastern Mediterranean is strongly P limited. The degree of P limitation increases from west to east across the entire basin. We suggest that removal of PO,'-by adsorbtion on Fe-rich dust particles may bc an important process controlling the concentration of P in the water column.N03-is generally considered to be the master chemical variable limiting primary productivity throughout much of the ocean (Codispoti 1989). It is based principally on considerations of the N : P ratios of upwelling waters which are generally < 16 : 1 I At present: Department of Earth Science, Leeds University, Leeds L52 9JT, U.K. AcknowledgmentsThe chemical determinations of dissolved nutrients were carried out by L. Israilov. We thank U. Fiedler for technical help on-board ship; we also thank members of the Physics and Electronic department of IOLR. The data collected in September 1989 were sampled as part of a Group for Aquatic Productivity (GAP) cruise to the eddy organized by T. Berman. We thank the captain (A. Ben-Nun) and crew of the RV Shikmona. This manuscript was written while M.D.K. was on sabbatical leave at the University of Rhode Island. We thank M. E. Q. Pilson and D. Kester for the use of their facilities and for the many discussions which went into the preparation of this manuscript. We thank M. Wood for pointing out the importance of P limitation in this area and for critical reading of the manuscript by her and T. Berman. Finally we greatly appreciate the detailed comments of two reviewers, who helped us improve the quality of the final version of this manuscript.

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Abstract. This paper is the outcome of a workshop held in Rome in November 2011 on the occasion of the 25th anniversary of the POEM (Physical Oceanography of the Eastern Mediterranean) program. In the workshop discussions, a number of unresolved issues were identified for the physical and biogeochemical properties of the Mediterranean Sea as a whole, i.e., comprising the Western and Eastern sub-basins. Over the successive two years, the related ideas were discussed among the group of scientists who participated in the workshop and who have contributed to the writing of this paper.Three major topics were identified, each of them being the object of a section divided into a number of different subsections, each addressing a specific physical, chemical or biological issue:1. Assessment of basin-wide physical/biochemical properties, of their variability and interactions.2. Relative importance of external forcing functions (wind stress, heat/moisture fluxes, forcing through straits) vs. internal variability.3. Shelf/deep sea interactions and exchanges of physical/biogeochemical properties and how they affect the sub-basin circulation and property distribution.Furthermore, a number of unresolved scientific/methodological issues were also identified and are reported in each sub-section after a short discussion of the present knowledge. They represent the collegial consensus of the scientists contributing to the paper. Naturally, the unresolved issues presented here constitute the choice of the authors and therefore they may not be exhaustive and/or complete. The overall goal is to stimulate a broader interdisciplinary discussion among the scientists of the Mediterranean oceanographic community, leading to enhanced collaborative efforts and exciting future discoveries.

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We test the scaling performance of seven leading global climate models by using detrended fluctuation analysis. We analyze temperature records of six representative sites around the globe simulated by the models, for two different scenarios: (i) with greenhouse gas forcing only and (ii) with greenhouse gas plus aerosol forcing. We find that the simulated records for both scenarios fail to reproduce the universal scaling behavior of the observed records and display wide performance differences. The deviations from the scaling behavior are more pronounced in the first scenario, where also the trends are clearly overestimated.

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