Physical oceanography during POSEIDON cruise P298/2 [POS298/2]

The POSEIDON cruise POS298/2 was carried out by the Institute of Oceanography of the University of Hamburg. Members of the University of Venice and the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Trieste were participating in the cruise. The project was aimed at gaining a deeper knowledge on the water mass transformations occurring in the southern Adriatic and western Ionian Sea. To obtain this result CTD profiles, lADCP profiles and water samples for oxygen and salinity were taken and analysed. The cruise had several objectives: 1. Identifying the routes and characteristics of the fraction of deep water in the Ionian Sea which was generated in the Adriatic Sea. 2. Quantifying the mixing of the deep water generated in the Adriatic Sea with the ambient water masses on its way southward. 3. Estimating the importance of the deep water generated in the Adriatic Sea for the ventilation of the eastern Mediterranean Sea.

Physical oceanography and ADCP measurements during Maria S. Merian cruise MSM13/2

Up to the end of the eighties the main source of deep water masses in the Ionian Basin was the southern Adriatic Sea. However, during the nineties a dramatic climatic change took place in the eastern Mediterranean Sea: the Eastern Mediterranean Transient (EMT). Since then, deep water has been formed by waters originating in the Aegean Sea. Expeditions carried out in this region in recent years indicate that the process of deep water formation might reverse again. To what extent this assumption applies and what characteristics the deep water in the Ionian Sea exhibit nowadays, should be determined on the cruise. The process of a re-reversal of abyssal water production in the Ionian Sea is a long-term process and must therfore be monitored for several years. Hence, this cruise is part of a series of cruises investigating this question (POS98, M71/3, MSM13/1-2, MSM15/4). The investigations were carried out by means of CTD/lADCP measurements.

Physical oceanography and ADCP measurements during METEOR cruise M71/3

Work on M71-3 aimed to answer the question whether phosphate loss and incomplete utilisation of nitrate on the one hand, or dinitrogen fixation on the other hand are responsible for unusual nutrient ratios in the water column of the eastern Mediterranean Sea. We investigated the reason for unusually depleted 15N/14N ratios in dissolved nitrate, suspended matter and surface sediments of that oligotrohic ocean basin. During a total of 18 days of ship time on R/V METEOR, Leg 3 OF M71 performed water column and surface sediment work in the eastern Mediterranean Sea (Heraklion-Istanbul). Stations will be aligned on one E-W and two N-S transects and sampled all major basins and water masses. On stations, CTD casts were obtained and water samples for nutrient concentrations were taken. These samples and those of suspended matter and surface sediment will be analysed for the stable nitrogen isotope composition of dissolved nitrate, suspended matter, and surface sediments. In addition, phytoplankton samples were be taken and experiments were be carried out to determine N2 fixation rates, genetic expressions of nitrogen fixation, and the composition of microbial and algal assemblages. One mooring of sediment traps (Ierapetra Deep) was be deployed and will be recovered in September 2007 to monitor changes in particle flux and its isotope signature over a seasonal cycle.

Abundance patterns and isotopic signals of morphotypes of Globigerinoides ruber

The chemical composition of shells of the planktonic foraminifer Globigerinoides ruber (white) is frequently used to determine past sea surface conditions. Recently, it has been shown that arbitrarily defined morphotypes within this species exhibit different chemical and isotopic signatures. Here, we investigate the occurrence through time and in space of morphological types of G. ruber (white) in late Quaternary and Holocene sediments of the central and the eastern Mediterranean Sea. In 115 samples representing two distinct time intervals (MIS 1-2 and MIS 9-12) at ODP Site 964 and the piston core GeoTü-SL96, we have defined three morphological types within this species and determined their relative abundances and stable isotopic composition. A quantitative analysis of morphological variation within G. ruber (white) in four samples revealed that the subjectively defined morphotypes occupy separate segments of a continuous and homogenous morphospace. We further show that the abundance of the morphotypes changes significantly between glacials and interglacials and that the three morphotypes of G. ruber show significant offsets in their stable isotopic composition. These offsets are consistent within glacial and interglacial stages but their sign is systematically reversed between the two Sites. Since the isotopic shifts among the three G. ruber morphotypes are systematic and often exceed 1per mil, their understanding is essential for the interpretation of all G. ruber-based proxy records for the paleoceanographic development of the Mediterranean during the late Quaternary.

Organic carbon and opal fluxes from Ierapetra sediment trap (from June 2010 to May 2013)

We provide data on organic carbon and opal fluxes and d13C obtained with a sediment trap deployed in the Ierapetra Basin (eastern Mediterranean Sea), from June 2010 to May 2013. Data was obtained within the framework of the REDECO (Regional Drivers of Ecosystem Change and its Influence on Deep-Sea Populations in the Mediterranean) project.