Cruises

Within the scope of the current concern about global climate change there is an urgent need for high spatial and temporal resolution data that cover both the industrial and pre-industrial time intervals. Such sediments are present in deposition centres of the Golfo di Taranto and Golfo di Manfredonia. For both regions the stratigraphic framework is based on tephra chronology and high resolution AMS/210Pb datings. The sediments deposited at the distal end of the Po-river discharge plume, which is fed from the Po river draining the southern parts of the Alps, and local eastern Italian rivers draining the Apennines.

Pilot studies reveal that oceanographic conditions at and around the depo-centres reflect changes in temperature and bioproductivity that can be related to climate change and variation in river discharge, which in turn, can be related to both anthropogenic and natural climate forcing. However, it is not clear to what extent the variability observed in the distal end of the plume is induced by the Po-river or by the eastern Italian rivers. Furthermore, it is unknown in how far the variability reflects local climatic change or variability in extra-regional climatic systems such as the North Atlantic Oscillation.

The unique high quality of the core material from the depo-centres forms the basis for an international research initiative to study the effects of anthropogenic and natural climate forcing on the Eastern Mediterranean Climate during and prior to the industrial area. During cruise P411 the most promising core-sites in the South-western Adriatic Sea and Golfo di Taranto have been resampled with a gravity corer. Furthermore, to characterise the chemical, organic-geochemical, palynological, micropalaeontological, mineralogical, isotopical and elemental characteristics of the water and sediment load of the Po-river discharge plume from its source in the North Adriatic Sea toward its distal end in the Golfo di Taranto surface samples, suspended matter and water samples have been sampled.

This information will allow a detailed characterisation of the different source waters and associated sediments of the Po-river and easter Italian rivers, providing the basis for an adequate interpretation of the proxy signals from the gravity core sediments.

The region off NW Africa is one of the most productive regions on Earth as result of the presence of coastal upwelling and the year round terrestrial dust input. Both upwelling and dust input fertilize the ocean by nutrient and trace elements such as iron and phosphorus. However, the relationship between upper ocean fertilization, marine bioproduction and transport and burial of the upper ocean produced marine carbon is far from being completely understood. Notably the early diagenetic induced alteration of the total organic carbon flux as well as the modification of the chemical, organic geochemical, isotopic and elemental character of the organic matter (OM) and marine carbonate during transport though the water column and at the sediment/water interface is far from clear.

A factor that largely affects OM preservation is oxygen availability. Oxygen availability determines the respiratory types of benthic micro and macro organisms, with anaerobic consortia of micro-organisms being less efficient than aerobic micro-organisms and micro- and macrofauna. It has been suggested that redox oscillations, may enhance degradation by promoting symbiosis of aerobes and anaerobes. The residence time of organic matter in the water column strongly influences the exposure time of OM to aerobic conditions. For high productivity areas it has been suggested that some organic components can remain for several thousand years in suspension in the water column related to the existence of nepheloid layers at intermediate water depths. Within nepheloid layers individual organic matter compounds appear to show a difference in resistance to early sedimentary diagenesis during vertical transport.

During cruise P398 we intended to obtained more insight
into
(1) the effects of early diagenetic processes within intermediate depth nepheloid layers on the flux and character of the organic matter flux.

(2) the effects of the bottom water oxygen concentrations on the fixation or cycling of major elements and organic matter in the Benthic Boundary Layer and in surface sediments.

(3) the stable isotopic and elemental composition of the fossilisable calcareous remains of coccolithophorids and calcareous dinoflagellate cysts in relation to the environmental conditions and physical and chemical composition of the water column in which they are being formed.

For this we intent to investigate the atmosphere, water column and upper ocean sediments along two transects. Along a first W-E transect that crosses the lower shelf and upper slope off Cap Blanc, the atmospheric dust content will be sampled with two dust collectors. The suspension load in the water column will be collected using in-situ pumps and a CTD-rosette system. For detailed investigations on processes that take place within and near the bottom-boundary nepheloid layer in both oxic and anoxic environments, stations are planned above, within and below the here existing oxygen minimum zone (OMZ). To study the fate of different types of particulate organic matter and of nutrients, N, P, and Fe in the bottom-boundary-layer, bottom waters and sediment will be sampled with a Bottom Water Sampler, a Bottom Water Profiler and a Multicorer.

The second transect runs parallel the Moroccan coast. It crosses the area of maximal Saharan dust input. Here a continuous sampling of dust particles is planned. Furthermore, the CTD-rosette system and in-situ pumps will be deployed for sampling of the water column with focus on nepheloid layers in the upper part of the water column.

Figure 2. Cross section of the water column in 2008 along transect 1; oxygen concentration.

The Poseidon Cruise PERGAMOM: “Proxy Education and Research cruise off GAlicia, MOrocco and Mauritania” has been carried out within the scope of the International Graduate College EUROPROX (Proxies in Earth History) that is funded by the German and Dutch science foundations DFG and NWO. Within this college, marine scientists from the Universities of Bremen, Utrecht, Amsterdam, Newcastle, Paris, Southampton, the Alfred WegenerInstitute for Polar and Marine Research in Bremerhaven and the Massachussets Institute of Technology join their know-how as well as their scientific and educational resources within a joined scientific program. The central theme within this program forms the development, testing and improvement of so called “proxy parameters” and “proxy methods” in marine research which allow the accurate reconstruction of paleoceanographic, paleoclimatic and paleoenvironmental conditions from marine archives.

To date, there is an intense discussion among scientists, economists and politicians on the relative importance of natural climate forcing. Key issues regard the interactions between oceans and atmosphere, especially the exchange of CO2 and heat, and the implications of changing oceanic circulation, chemistry, and life. To unravel this complex interaction and to obtain insight into the nature of positive and negative feedback mechanisms, detailed and quantitative information is required about individual control parameters. While direct observations only exist for the last decades, so called “proxy records” that are derived from isotopic, fossil, chemical and physical properties of marine sediments, reach back millions of years. These describe past variations of e.g., global ice volume, sea surface temperature (SST) and salinity, nutrient availability, marine and terrestrial material fluxes, oxygenation and productivity of the oceans. For a sound application of proxies it is essential to obtain insight in the usability and limitations of them. To achieve this, information on the basic processes that control the various proxies is required and it is essential to test, adapt, and further develop the proxies. Expanding the range and reliability of proxy methods is an obvious and important world-wide research topic.

The study area of leg P366/1 - the Moroccan and Mauretanien shelf and slope between Cape Yubi and Cape Timiris - which is characterized by strong gradients and temporal variability in coastal upwelling and Saharan dust input represents an ideal site to study the influence of terrestrial and marine input as well as early diagenetic processes on the formation and preservation of various sedimentary proxy signals. For this purpose dust collectors, a rosette water sampler and CTD, in-situ pumps, a multicorer, a gravity corer, a sediment grab, a multi net and a hand net were deployed (1) to trace the transport of particulate material from the atmosphere, through the water column and towards and into the sediment, and (2) to identify and quantify the preservation and diagenetic overprint of various organic and inorganic sediment components under and in various geochemical conditions and environments (Table 1).

Cruise P366-2 had apart from a scientific purpose, a strong educational character and provided research students, doctorates of the granted 3rd phase of the EURPROX project (2008-10) with skills, materials and data for joint multi-proxy studies and engaged our 2 PostDocs in cruise planning and logistics.

To date, there is an intense discussion among scientists, economists and politicians about the extent to which human activities and/or natural processes influence global climate change.
One of the natural forces that can influence climate on short time-scales is variation in solar insolation. This variation is known to occur in quasicycles of ~11 (sunspot or Schwabe cycles), ~22 (Hale cycles), ~80 (Gleissberg cycles) and ~200 (Suess cycles) years. Although variation in the amount of insolation in itself cannot account for the pronounced changes in Holocene climates, positive feedback mechanisms related to the amount of solar UV emission, and cosmic ray intensity can amplify the solar forcing.

To obtain insight in how far these processes steer current climate variability, we urgently need palaeoclimatic reconstructions of industrial and pre-industrial times with a high temporal resolution and accuracy. To date, the majority of these records are of terrestrial origin, whereas most of our globe is covered with water and as such our view must be strongly biased. Moreover, the “land-records” cover short time intervals only.

A region where sediments are deposited during the last 5000 years with sedimentation rates high enough to cover this resolution is the Gallipoli Terrace in the Golfo di Taranto (Ionian Sea). Here sedimentation rates of 0.0645 ± 0.0007 cm y-1 are found (e.g. Cini Castagnoli et al. 1998). The Gallipoli Terrace is located downwind of the South-Italian volcanism and as a result its sediments contain numerous ash layers allowing detailed dating of these sediments.

During cruise P339 both surface sediments and core sediments have been received from this region that allow detailed high temporal resolution palaeoclimatic reconstructions.