Organic carbon and carbohydrates in waters of the Amazon River, Atlantic Ocean, and Tropical Indian Ocean

A method is presented to study carbohydrate composition of marine objects involved into sedimento- and diagenesis (plankton, particulate matter, benthos, and bottom sediments). Analysis of the carbohydrates is based on consecutive separation of their fractions with different solvents (water, alkali, and acid). Ratios of carbohydrate fractions allows to evaluate lability of carbohydrate complexes. They are also usable as an indicators of biogeochemical processes in the ocean, as well of genesis and degree of transformation of organic matter in bottom sediments and nodules. Similarity in monosaccharide composition is shown for dissolved organic matter and aqueous and alkaline fractions of seston and particulate matter.

Observation of manganese deposits made during the 1936 transect of C/S Lord Kelvin through the Northern Atlantic Ocean

In May and June 1936 Dr. C. S. Piggot of the Geophysical Laboratory, Carnegie Institution of Washington, took a series of 11 deep-sea cores in the North Atlantic Ocean between the Newfoundland banks and the banks off the Irish coast. These cores were taken from the Western Union Telegraph Co.'s cable ship Lord Kelvin with the explosive type of sounding device which Dr. Piggot designed. All but two of these cores (Nos. 8 and 11) are more than 2.43 meters (8 feet) long, and all contain ample material for study. Of the two short cores, No. 8 was taken from the top of the Faraday Hills, as that part of the mid-Atlantic ridge is known, where the material is closely packed and more sandy and consequently more resistant; No. 11 came from a locality where the apparatus apparently landed on volcanic rock that may be part of a submarine lava flow.

Stable carbon and oxygen isotope ratios of late Eocene and Oligocene foraminifera from the Atlantic Ocean

Oxygen isotope analyses of late Eocene and Oligocene planktonic foraminifers from low and middle latitude sites in the Atlantic Basin show that different species from the same samples can yield significantly different isotopic values. The range of isotopic values observed between species is greatest at low-latitudes and declines poleward. Many planktonic foraminifers exhibit a systematic isotopic ranking with respect to each other and can therefore be grouped on the basis of their isotopic ranking. The isotopic ranking of some taxa, however, appears to vary geographically and/or through time. Isotopic and paleontologic data from DSDP Site 522 indicate that commonly used isotopic temperature scales underestimate Oligocene sea surface temperatures. We suggest these temperature scales require revision to reflect the presence of Oligocene glaciation. Comparison of isotopic and paleontologic data from Sites 522, 511 and 277 suggests cold, low-salinity surface waters were present in high southern latitudes during the early Oligocene. Lowsalinity, high latitude surface waters could be caused by Eocene/Oligocene paleogeography or by the production of warm saline bottom water.

Description and chemical composition of manganese nodules in a core located in the Nares Abyssal Plain, Atlantic Ocean

Three nodules from a core taken north of Puerto Rico are composed chiefly of an x-ray amorphous, hydrated, iron-manganese oxide, with secondary goethite, and minor detrital silicates incorporated during growth of the nodules. No primary manganese mineral is apparent. The nodules are enriched in iron and depleted in manganese relative to Atlantic Ocean averages. The formation of these nodules appears to have been contemporary with sedimentation and related to volcanic activity.

In situ pore water oxygen microprofiles from the Polar Front, Southern South Atlantic Ocean

Without doubt, global climate change is directly linked to the anthropogenic release of greenhouse gases such as carbon dioxide (CO2) and methane (UN IPCC-Report 2007). Therefore, research efforts to comprehend the global carbon cycle have increased during the last years. In the context of the observed changes, it is of particular interest to decipher the role of the hydro-, bio- and atmospheres and how the different compartments of the earth system are affected by the increase of atmospheric CO2. Due to its huge carbon inventory, the marine carbon cycle represents the most important component in this respect. Numerous findings suggest that the Southern Ocean plays a key role in terms of oceanic CO2 uptake. However, an exact quantification of such fluxes of material is hard to achieve for large areas, not least on account of the inaccessibility of this remote region. In particular, there exist so far only few accurate data for benthic carbon fluxes. The latter can be derived from high resolution pore water oxygen profiles, as one possible method. However the ex situ flux determinations carried out on sediment cores, tend to suffer from temperature and pressure artefacts. Alternatively, oxygen microprofiles can be measured in situ, i.e. at the seafloor. Until now, no such data have been published for the Southern Ocean. During the Antarctic Expedition ANT-XXI/4, within the framework of this thesis, in situ and ex situ oxygen profiles were measured and used to derive benthic organic carbon fluxes. Having both types of measurements from the same locations, it was possible to establish a depth-related correction function which was applied subsequently to revise published and additional unpublished carbon fluxes to the seafloor. This resulted in a consistent data base of benthic carbon inputs covering many important sub-regions of the Southern Ocean including the Amundsen and Bellingshausen Seas (southern Pacific), Scotia and Weddell Seas (southern South Atlantic) as well as the Crozet Basin (southern Indian Ocean). Including additional locations on the Antarctic Shelf, there are now 134 new and revised measurement locations, covering almost 180° of the Southern Ocean, for which benthic organic carbon fluxes and sedimentary oxygen penetration depth values are available. Further, benthic carbon fluxes were empirically related to dominant diatom distributions in surface sediments as well as to long-term remotely sensed chlorophyll-a estimates. The comparison of these results with benthic carbon fluxes of the entire Atlantic Ocean reveals significantly higher export efficiencies for the Southern Ocean than have previously been assumed, especially for the area of the opal belt.

Composition of organic matter in bottom sediments from the Antarctic sector of the Atlantic Ocean

We identify geochemical features of sedimentary organic matter in various morphostructural zones of the Antarctic sector of the Atlantic. We present background geochemical organic parameters for shelf and deep-sea sediments from the Weddell and Scotia Seas and the Bransfield Strait. Geochemical organic parameters are good indicators of environmental and facial variations in sediments and could be used for environmental monitoring of the World Ocean.

Age models and stable isotope record of sediment cores from the Atlantic Ocean

The high-resolution delta18O and delta13C records of benthic foraminifera from a 150,000-year long core from the Caribbean Sea indicate that there was generally high delta13C during glaciations and low delta13C during interglaciations. Due to its 1800-m sill depth, the properties of deep water in the Caribbean Sea are similar to those of middepth tropical Atlantic water. During interglaciations, the water filling the deep Caribbean Sea is an admixture of low delta13C Upper Circumpolar Water (UCPW) and high delta13C Upper North Atlantic Deep Water (UNADW). By contrast, only high delta13C UNADW enters during glaciations. Deep ocean circulation changes can influence atmospheric CO2 levels (Broecker and Takahashi, 1985; Boyle, 1988 doi:10.1029/JC093iC12p15701; Keir, 1988 doi:10.1029/PA003i004p00413; Broecker and Peng, 1989 doi:10.1029/GB003i003p00215). By comparing delta13C records of benthic foraminifera from cores lying in Southern Ocean Water, the Caribbean Sea, and at several other Atlantic Ocean sites, the thermohaline state of the Atlantic Ocean (how close it was to a full glacial or full interglacial configuration) is characterized. A continuum of circulation patterns between the glacial and interglacial extremes appears to have existed in the past. Subtracting the deep Pacific (~mean ocean water) delta13C record from the Caribbean delta13C record yields a record which describes large changes in the Atlantic Ocean thermohaline circulation. The delta13C difference varies as the vertical nutrient distribution changes. This new proxy record bears a striking resemblance to the 150,000-year-long atmospheric CO2 record (Barnola et al., 1987 doi:10.1038/329408a0). This favorable comparison between the new proxy record and the atmospheric CO2 record is consistent with Boyle's (1988a) model that vertical nutrient redistribution has driven large atmospheric CO2 changes in the past. Changes in the relative contribution of NADW and Pacific outflow water to the Southern Ocean are also consistent with Broecker and Peng's (1989) recent model for atmospheric CO2 changes.

Age deterimation of sediment cores from the Atlantic Ocean

High resolution benthic oxygen isotope records combined with radiocarbon datings, from cores retrieved in the North, Equatorial, and South Atlantic are used to establish a reliable cronostratigraphy for the last 60 ky. This common temporal framework enables us to study the timing of the sub-Milankovitch climate variability in the entire surface Atlantic during this period, as reflected in planktonic oxygen isotope records. Variations in sea surface temperatures in the Equatorial and South Atlantic reveal two warm periods during the mid-stage 3 which are correlated to the warming observed in the North Atlantic after Heinrich events (HL) 5 and 4. However, the records show that the warming started about 1500 y earlier in the South Atlantic. A zonally averaged ocean circulation model simulates a similar north-south thermal antiphasing between the latitudes of our coring sites, when pertubated by a freshwater flux anomaly. We infer that the observed phase relationship between the northern and the southern Atlantic is related to periods of reduced NADW production in the North Atlantic, such as during HL5 and HL4.

Late Pliocene sea-surface temperature record of DSDP Hole 80-548 from the Northeast Atlantic Ocean (Table 1)

Application of quantitative micropaleontologic methods of sea-surface temperature (SST) estimation to the planktic foraminiferal faunas at Hole 548 in the northeast Atlantic between 3.5 and 2.0 Ma provide a detailed record of Pliocene surface temperature changes during the onset of major Northern Hemisphere glaciation. SST estimates indicate a relatively warm interval of "enhanced interglacials (warm peaks)" between 3.2 and 2.8 Ma followed by steady cooling with a significant step-like change toward colder temperatures occurring about 2.4 Ma. This record compares well with faunal and SST records from other North Atlantic sites.

Fe-Mn crusts from the Atlantic Ocean

Mineral and chemical compositions of a set of crust samples collected from the North, Central and South Atlantic were examined by means of analytical electron microscopy and ICP-MS, chemical, and microchemical elemental analysis. Vernadite, asbolane, and goethite are dominant mineral phases of the crusts, ferrihydrite is minor, hematite and feroxyhyte are rare. The samples show wide variability in major and trace element contents; however, their characteristic geochemical signatures indicate hydrogenous origin. A comparison between compositions of oceanic hydrogenous and hydrothermal crusts and metalliferous hydrothermal sediments from different ocean areas suggests that the geochemical approach may be insufficient in some cases and fail to identify hydrothermal input in ferromanganese crusts of mixed composition.

Planktonic foraminifera and Quaternary paleoceanology of the Atlantic Ocean

An original method of paleotemperature analysis on planktonic foraminifera is substantiated and actively used for stratigraphy of bottom sediments and paleoceanologic reconstructions. On the base of this method, as well as on lithological, geochemical, and oxygen isotope data, radiocarbon dating, constructions of other investigators, etc., the main features of dynamic Quaternary paleoceanology of the Atlantic Ocean is reconstructed. It is discussed in the context of global paleogeography. Paleotemperature field, climatic zonation, paleoecology of foraminifera, position of the main water masses, water fronts, currents, distribution of sea ice boundaries, upwelling activity, benthic circulation, processes of sedimentation are econstructed and analyzed.