(Table 1) Mean sea-ice properties from moored upward looking sonars along the Greenwich meridian

Sea-ice ocean interaction processes are of significant influence on the water mass formation in the Weddell gyre. On the basis of data obtained between 1984 and 2008 from eight repeat hydrographic sections, moored instruments and profiling floats in the Weddell gyre on the Greenwich meridian - almost all of them collected with R.V. Polarstern - we identified variations in the properties of the Winter Water and the sea ice draft. In the Winter Water the salinity was relatively low throughout the 1990s (with a minimum in 1992) and a maximum was observed in 2003. Observations of sea ice draft by moored upward looking sonars are available from 1996 onwards. In the southern part of the transect they display variations on a decadal time scale with a minimum in sea-ice thickness in 1998 and an increase since then. Salinity variations in the Winter Water layer cannot be explained only by variations in sea-ice formation and variable entrainment of underlying Warm Deep Water, but lateral advection of water and sea ice needs to be taken into account as well. Potential sources are melt water from the ice shelves in the western Weddell Sea or transport of water of low salinity entering the Weddell gyre from the east. Accompanying variations of the properties of Warm Deep Water are discussed in detail in a companion paper (Fahrbach et al., 2011, doi:10.1016/j.dsr2.2011.06.007).

Sapropel cycles in the Mediterranean Sea

Water column stratification increased at climatic transitions from cold to warm periods during the late Quaternary and led to anoxic conditions and sapropel formation in the deep eastern Mediterranean basins. High-resolution data sets on sea-surface temperatures (SST) (estimated from UK'37 indices) and d18O of planktonic foraminifer calcite (d18Ofc) across late Pleistocene sapropel intervals show that d18Ofc decreased (between 1 and 4.6 per mil) and SST increased (between 0.7° and 6.7°C). Maximal d18Oseawater depletion of eastern Mediterranean surface waters at the transition is between 0.5 and 3.0 per mil, and in all but one case exceeded the depletion seen in a western Mediterranean core. The depletion in d18Oseawater is most pronounced at sapropel bases, in agreement with an initial sudden input of monsoon-derived freshwater. Most sapropels coincide with warming trends of SST. The density decrease by initial freshwater input and continued warming of the sea surface pooled fresh water in the surface layer and prohibited deep convection down to ageing deep water emplaced during cold and arid glacial conditions. An exception to this pattern is "glacial" sapropel S6; its largest d18Oseawater depletion (3 per mil) is almost matched by the depletion in the western Mediterranean Sea, and it is accompanied by surface water cooling following an initially rapid warming phase. A second period of significant isotopic depletion is in isotope stage 6 at the 150 kyr insolation maximum. While not expressed as a sapropel due to cold SST, it is in accord with a strengthened monsoon in the southern catchment.

Benthic foraminiferal assemblages of the Barents Sea

Foraminiferal assemblages were studied in northern Barents Sea core ASV 880 along with oxygen and carbon isotope measurements in planktonic (N. pachyderma sin.) and benthic (E. clavatum) species. AMS C-14 measurements performed on molluscs Yoldiella spp. show that this core provides a detailed and undisturbed record of Holocene climatic changes over the last 10000 calendar years. Surface and deep waters were very cold (<0°C) at the beginning of the Holocene. C. reniforme dominated the highly diverse benthic foraminiferal assemblage. From 10 to 7.8 cal. ka BP, a warming trend culminated in a temperature optimum, which developed between 7.8 and 6.8 cal. ka BP. During this optimum, the input of Atlantic water to the Barents Sea reached its maximum. The Atlantic water mass invaded the whole Franz Victoria Trough and was present from subsurface to the bottom. No bottom water, which would form through rejection of brine during winter, was present at the core depth (388 m). The water stratification was therefore greatly reduced as compared to the present. An increase in percentage of I. helenae/norcrossi points to long seasonal ice-free conditions. The temperature optimum ended rather abruptly, with the return of cold polar waters into the trough within a few centuries. This was accompanied by a dramatic reduction of the abundance of C. reniforme. During the upper Holocene, the more opportunistic species E. clavatum became progressively dominant and the water column was more stratified. Deep water in Franz Victoria Trough contained a significant amount of cold Barents Sea bottom water as it does today, while subsurface water warmed progressively until about 3.7 cal. ka BP and reached temperatures similar to those of today. These long-term climatic changes were cut by several cold events of short duration, in particular one in the middle of the temperature optimum and another, which coincides most probably with the 8.2 ka BP cold event. Both long- and short-term climatic changes in the Barents Sea are associated with changes in the flow of Atlantic waters and the oceanic conveyor belt.

(Table 3) Oxygen isotope ratios of benthic foraminifera from DSDP Hole 80-548

Presently, the intermediate depths of the North Atlantic Ocean are occupied by a great lens of warm, saline water whose source is the Mediterranean Sea. This water flows both westward and northward, finally entering the Norwegian Sea where it may contribute to the formation of North Atlantic Deep Water. The Late Neogene history of Mediterranean Outflow in the Atlantic can be monitored at DSDP-IPOD Site 548 on the continental slope Southwest of Ireland using benthic Foraminifera oxygen isotope values. Isotopic data from 154 samples indicate that Mediterranean water was absent from the mid-depth North Atlantic from 3.4 to 3.2 Ma ago. However, at about 2.9 Ma ago the isotopic values at Site 548 diverge from those recorded from the deep North Atlantic and they can be interpreted to indicate the appearance of a new water mass, possibly Mediterranean water, in the North Atlantic water column. This appearance may be related to climatic changes that occurred around the Mediterranean Basin at about 2.9 Ma ago. The analysis of 189 samples for grain-size distributions shows that a significant increase in the silt-size fraction occurs at the same level that isotopic analysis indicates a change in bottom waters at Site 548. The grainsize data support the hypothesis that mid-depth water-mass changes occurred at about 2.9 Ma ago.

Stable carbon and oxygen isotope ratios of Planulina wuellerstorfi from sediments of the Sierra Leone Rise

Causes of change in deep water delta13C can be either global or local in extent. Global causes include (1) climatically-induced changes in the amount of terrestrial biomass which alter the average carbon isotopic composition of the oceanic reservoir (Shackleton, 1977), and (2) erosion and deposition of organic-rich, continental shelf sediments during sea level fluctuations which change the mean oceanic carbon: phosphorus ratio (Broecker, 1982 doi:10.1016/0079-6611(82)90007-6). Regional gradients of delta13C are created by remineralization of organic detritus within the deep ocean itself thus reflecting the distribution of water masses and modern thermohaline flow. Changes in a single geological record of benthic foraminiferal delta13C can result from any combination of these global and abyssal circulation effects. By sampling a large number of cores collected over a wide bathymetric range yet confined to a small geographical region we have minimized the ambiguity. We can assume that each delta13C record was equally affected by global causes of delta13C variation. The differences seen between the delta13C records must, therefore, reflect changes in the distribution of delta13C in the deep ocean. We interpret these differences in distribution in terms of changes in the ocean's abyssal circulation. Benthic foraminiferal carbon isotopic evidence from a suite of Sierra Leone Rise cores indicates that the deeper parts of the eastern Atlantic basins underwent a reduction in [O2] during the maximum of the last glaciation. Reduced advection of O2-rich deep water through low-latitude fracture zones, associated with increased delivery of organic matter to the deep ocean, lowered the delta13C of deep water SumCO2 at all depths below the sill separating the eastern and western Atlantic basins (Metcalf et al., 1964 doi:10.1016/0011-7471(64)91078-2). This decreased advection into the eastern Atlantic Ocean coincides with the overall decrease in deep water production in the North Atlantic during the last glacial maximum (Curry and Lohmann, 1982 doi:10.1016/0033-5894(82)90071-0; Boyle and Keigwin, 1982 doi:10.1126/science.218.4574.784; Schnitker, 1979 doi:10.1016/0377-8398(79)90020-3; Streeter and Shackleton, 1979 doi:10.1126/science.203.4376.168).

Biomass and stable isotope composition of plankton in five size fractions along a zonal transect (24°N) from the Canary Islands to Florida in January-March 2011

The spatial variability of biomass and stable isotopes in plankton size fractions in the upper 200 m was studied in a high spatial resolution transect along 24°N from Canary Islands to Florida (January - March 2011) during Leg 8 of the Malaspina-2010 expedition (http://www.expedicionmalaspina.es) to determine nitrogen and carbon sources. Plankton samples were collected by vertical tows of a microplankton net (40 mm mesh size) and a mesoplankton net (200 mm mesh size) through the upper 200 m of the water column. Sampling was between 10:00 and 16:00 h GMT. Plankton was separated into five size fractions (40 - 200, 200 - 500, 500 - 1000, 1000 - 2000 and > 2000 mm) by gentle filtration of the samples by a graded series of nylon sieves (2000, 1000, 500, 200 and 40 mm). Large gelatinous organisms were removed before filtration. Aliquots for each size fraction were collected on pre-weighed glass-fibre filters, dried (60°C, 48 h) and stored in a desiccator before determination of biomass (dry weight), carbon and nitrogen content and natural abundance of stable carbon and nitrogen isotopes ashore. Vertical advection of waters predominated in lateral zones while the central Atlantic (30-70°W) was characterized by a strong stratification and oligotrophic surface waters. Plankton biomass was low in the central zone and high in both eastern and western sides, with most of the variability due to either large (>2000 µm) and small plankton (<500 µm). Carbon isotopes reflected mainly the advection the deep water in lateral zones. Stable nitrogen isotopes showed a nearly symmetrical spatial distribution in all fractions, with the lowest values (delta15N <1per mill) in the central zone, and were inversely correlated to carbon stable isotopes (delta13C) and to the abundance of the nitrogen-fixer Trichodesmium. Diazotrophy was estimated to account for >50% of organic nitrogen in the central zone, and even >30% in eastern and western zones. The impact of diazotrophy increased with the size of the organisms, supporting the wide participation of all trophic levels in the processing of recently fixed nitrogen. These results indicate that atmospheric sources of carbon and nitrogen prevail over deep water sources in the subtropical North Atlantic and that the zone influenced by diazotrophy is much larger than reported in previous studies.

Benthic foraminifers of the Barrow Group, Northwest Shelf, Australia

Micropaleontological analysis of the Barrow Group of Sites 762 and 763 has been undertaken with a view to determining the stratigraphic age and depositional environment of the unit. The stratigraphic age of the unit is Berriasian-Valanginian at both sites, in line with palynological findings. The unit is interpreted as having been deposited in a marine deltaic environment. Paleobathymetry at Site 763 (proximal) and Site 762 (distal) is interpreted as having been of the order of 100 m and 200-500 m, respectively. Paleontological evidence for the presence of deep-water submarine fans at Site 763 is lacking. The paleobathymetric significance of the observed variations in the benthic foraminiferal populations at Site 763 remains unclear.

Foraminifer, coarse fraction and carbonate characteristics of sediments from ODP Leg 198 sites on Shatsky Rise

Holes 1209A and 1211A on Southern High, Shatsky Rise contain expanded, nearly continuous records of carbonate-rich sediment deposited in deep water of the equatorial Pacific Ocean during the Paleocene and Eocene. In this study, we document intervals of carbonate dissolution in these records by examining temporal changes in four parameters: carbonate content, coarse size fraction (>38 µm), benthic foraminiferal abundance, and planktonic foraminiferal fragmentation ratio. Carbonate content is not a sensitive indicator of carbonate dissolution in the studied sections, although rare intervals of low carbonate may reflect times of relatively high dissolution. The proportion of coarse size fraction does not accurately record carbonate dissolution either because the relative abundance of nannofossils largely determines the grain-size distribution. Benthic abundance and fragmentation covary (r**2 = 0.77) and are probably the best indicators for carbonate dissolution. For both holes, records of these parameters indicate two episodes of prominent dissolution. The first of these occurs in the upper Paleocene (~59-58 Ma) and the second in the middle to upper Eocene (~45-33.7 Ma). Other intervals of enhanced carbonate dissolution are located in the upper Paleocene (~56 Ma) and in the upper lower Eocene (~51 Ma). Enhanced preservation of planktonic foraminiferal assemblages marks the start of both the Paleocene and Eocene epochs.

Chemical composition of hydrothermal deposits and vulcanites from the Menez Gwen vent field, Mid-Atlantic Ridge

Surface hydrothermal deposits of the shallow-water Menez Gwen vent field located in the rift zone of the Mid-Atlantic Ridge are mostly composed of nonmetalliferous minerals in contrast to sulfide deposits of deep-water fields. Here sulfide minerals occur only in dispersed form. High-temperature sulfide deposits strongly enriched in copper and zinc occur only immediately below the surface of the bottom. This is related to subsurface boiling and phase separation of initial high-temperature hydrothermal ore-bearing solution that ascends from the interior to the floor surface.

Salinity and concentrations of organic carbon in bays of the White Sea

Organic carbon in bays of the White Sea was studied for the first time in 1987. Bays of various types in the Kandalaksha Gulf and the Onega Gulf were investigated. Concentration of C_org ranged from 3.5 to 9 mg/l. The highest weighted-mean concentration of C_org occurred in shallow bays of the Onega Gulf (Suma Bay - 6.17 mg/l, Kolezhma Bay - 5.25 mg/1); slightly lower levels occurred in the Soroka Bay (4.85 mg/l) and Kem' Bay (4.78 mg/l). The lowest concentrations were in deep bays of the Kandalaksha Gulf (Chupa Bay - 4.35 mg/l, Velikaya Salma Bay - 4.10 mg/l). As a rule C_org concentration decreases with depth in deep-water bays (but increases slightly in the thermocline layer). The key factor governing organic matter concentration in the bays of the Onega Gulf with river runoff is allochthonous terrigenous organic matter, as indicated by negative correlation of C_org with salinity (R=-0.83+/-0.07, p=0.96) and nonsignificant correlation with primary production.

Benthic foraminifers, isotopes and varimax factors at DSDP Holes 72-517 and 72-518

Pliocene changes in the vertical water mass structure of the western South Atlantic are inferred from changes in benthic foraminiferal assemblages and stable isotopes from DSDP Holes 516A, 517, and 518. Factor analysis of 34 samples from Site 518 reveals three distinct benthic foraminiferal assemblages that have been associated with specific subsurface water masses in the modern ocean. These include a Nuttalides umbonifera assemblage (Factor 1) associated with Antarctic Bottom Water (AABW), a Globocassidulina subglobosa-Uvigerina peregrina assemblage (Factor 2) associated with Circumpolar Deep Water (CPDW), and an Oridorsalis umbonatus-Epistominella exigua assemblage associated with North Atlantic Deep Water (NADW). Bathymetric gradients in d13C between Holes 516A (1313 m), 517 (2963 m), and 518 (3944 m) are calculated whenever possible to monitor the degree of similarity and/or difference in the apparent oxygen utilization (AOU) of water masses located at these depths during the Pliocene. Changes in bathymetric d13C gradients coupled with benthic foraminiferal assemblages record fundamental changes in the vertical water mass structure of the Vema Channel during the Pliocene from 4.1 to 2.7 Ma. At Site 518, the interval from 4.1 to 3.6 Ma is dominated by the N. umbonifera (Factor 1) and O. umbonatus-E. exigua (Factor 3) assemblages. The d13C gradient between Holes 518 (3944 m) and 516A (1313 m) undergoes rapid oscillations during this interval though no permanent increase in the gradient is observed. However, d13C values at Site 518 are clearly lighter during this interval. These conditions may be related to increased bottom water activity associated with the re-establishment of the West Antarctic Ice Sheet in the late Gilbert Chron (-4.2 to 3.6 Ma) (Osborn et al., 1982). The interval from 3.6 to 3.2 Ma is marked by a dominance of the G. subglobosa-U. peregrina (Factor 2) assemblage and lack of a strong d13C gradient between Holes 518 (3944 m) and 516A (1313 m). We suggest that shallow circumpolar waters expanded to depths of a least 3944 m (Site 518) during this time. The most profound faunal and isotopic change occurs at 3.2 Ma, and is marked by dominance of the N. umbonifera (Factor 1) and O. umbonatus-E. exigua (Factor 3) assemblages, a 1.1 per mil enrichment in d18O, and a large negative increase in the d13C gradient between Holes 518 and 516A. These changes at Site 518 record the vertical displacement of circumpolar waters by AABW and NADW. This change in vertical water mass structure at 3.2 Ma was probably related to a global cooling event and/or final closure of the Central American seaway. A comparison of the present-day d13C structure of the Vema Channel with a reconstruction between 3.2 and 2.7 Ma indicates that circulation patterns during this late Pliocene interval were similar to those of the modern western South Atlantic.

Cenomanian benthic foraminifera of Demerara Rise

This study is based on Cenomanian sediments of Ocean Drilling Program (ODP) Sites 1258 and 1260 from Demerara Rise (Leg 207, western tropical Atlantic, off Suriname, ~1000 and ~500 m paleo-water depth, respectively). Studied sediments consist of laminated black shales with TOC values between 3 and 18% and include the Mid Cenomanian Event (MCE), a positive carbon isotope excursion predating the well-known Oceanic Anoxic Event 2 (OAE 2). Benthic foraminiferal assemblages of the continuously eutrophic environment at Demerara Rise are characterized by low diversities (<= 9 species per sample) and large fluctuations in abundances, indicating oxygen depletion and varying organic matter fluxes. Dominant species at both sites are Bolivina anambra, Gabonita levis, Gavelinella dakotensis, Neobulimina albertensis, Praebulimina prolixa, and Tappanina cf. laciniosa. Benthic foraminiferal assemblages across the MCE show a threefold pattern: (1) stable ecological conditions below the MCE interval indicated by relatively high oxygenation and fluctuating organic matter flux, (2) decreasing oxygenation and/or higher organic matter flux during the MCE with decreasing benthic foraminiferal numbers and diversities (Site 1258) and a dominance of opportunistic species (Site 1260), and (3) anoxic to slightly dysoxic bottom-water conditions above the MCE as indicated by very low diversities and abundances or even the absence of benthic foraminifera. Slightly dysoxic conditions prevailed until OAE 2 at Demerara Rise. A comparison with other Atlantic Ocean and Tethyan sections indicates that the MCE reflects a paleoceanographic turning point towards lower bottom-water oxygenation, at least in the proto-North Atlantic Ocean and in the Tethyan and Boreal Realms. This general trend towards lower oxygenation of bottom waters across the MCE is accompanied by ongoing climate warming in combination with rising sea-level and the development of vast shallow epicontinental seas during the Middle and Late Cenomanian. These changes are proposed to have favoured the formation of warm and saline waters that may have contributed to intermediate- and deep-water masses at least in the restricted proto-North Atlantic and Tethyan Ocean basins, poor oxygenation of the Late Cenomanian sediments, and the changes in benthic foraminiferal assemblages across the MCE.

Radiolarians in the Sea of Okhotsk

To assess the relationship of radiolarian production, species distribution in water and surface sediment to water-mass characteristics, biological productivity and export regimes in the Sea of Okhotsk (SOk) we accomplished a quantitative analysis of radiolarian assemblages obtained from 35 surface-sediment samples and 115 plankton samples recording the radiolarian depth distribution in the upper 1000 m of the water column at 23 locations. This study augments the knowledge on the autecological demands of radiolarians dwelling in a specific hydrographic and biological environment, and extracts new information on the significance of radiolarians for the assessment of past oceanographic and climatic development in high latitudes. Highest radiolarian accumulation rates and seasonal radiolarian standing stocks are encountered in the western part of the SOk close to Sakhalin, marking the environmental conditions in this area as most favorable for radiolarian production. Maximum standing stocks occur during summer, indicating that the radiolarian signal preserved in the sediment record is mainly produced during this season when the mesopelagic biomass is at highest activity. We identified seven radiolarian species and groups related to specific water-mass characteristics, depth habitats, and productivity regimes. Of those, Dictyophimus hirundo and Cycladophora davisiana are most prominent in the Sea of Okhotsk Intermediate Water (200-1000 m), the latter representing an indicator of the occurrence of cold and well ventilated intermediate/deep water and enhanced export of organic matter from a highly productive ocean surface. While Antarctissa (?) sp. 1 is typically related to the cold-water Sea of Okhotsk Dicothermal Layer (SODL), ranging between 50 and 150 m water depth, the surface waters above the SODL affected by strong seasonal variability are inhabited predominantly by taxa belonging to the Spongodiscidae, having a broad environmental tolerance. Taxa only found in the sediment record show that the plankton study did not cover all assemblages occurring in the modern SOk. This accounts for an assemblage restricted to the western Kurile Basin and apparently related to environmental conditions influenced by North Pacific and Japan Sea waters. Other important taxa include species of the Plagoniidae group, representing the most prominent contributors to the SOk plankton and surface sediments. These radiolarians show a more opportunistic occurrence and are indicative of high nutrient supply in a hydrographic environment characterized by pronounced stratification enhancing heterotrophic activity and phytodetritus export.