Lead isotopes of feldspar in North Atlantic Ocean sediments

The provenance of ice-rafted debris (IRD) deposited in the North Atlantic before, during, and after Heinrich event 2 has been determined through measuring the lead isotopic composition of single feldspar grains and multiple-grain composites from the larger than 150-µm size fraction, from cores from the eastern and western North Atlantic and from the Labrador Sea. Single-grain analyses are used to identify the specific continental sources of the IRD, whereas composite samples are used to assess the relative IRD contributions from different sources. All single grains from Heinrich layer 2 (H 2) as well as H 2 composites plot along a correlation line on a 207Pb/204Pb versus 206Pb/204Pb diagram characteristic of the Churchill province of the Canadian shield. This is yet another strong piece of evidence that this Heinrich event was dominated by a massive iceberg discharge of the Laurentide ice sheet lobe located over Hudson Bay. In contrast, single grains from the ambient glacial sediment (above and below H 2) have multiple sources: many of them also lie along the correlation line with H 2 grains, but many others have Pb signatures consistent with derivation from the Grenville province and the Appalachian range in North America and possibly from Scandinavia and Greenland. Composites from the ambient sediment generally lie well to the right of the H 2 reference line in agreement with the results of the single-grain analyses. The evidence provided by lead isotopes regarding the dominant role played by the Hudson Bay lobe of the Laurentide ice sheet in the development of the Heinrich events lends support to the binge/purge model advanced by MacAyeal [1993a, b] that invokes trapping of geothermal heat by the base of the icecap and subsequent basal melting as the mechanism that triggered the Heinrich events.

Total and species abundance of Polychaeta during POLARSTERN cruise ANT-XXIV/2, ANDEEP-SYSTCO, in the Southern Ocean

In the course of the ANDEEP-SYSTCO project, during the ANT XXIV-2 expedition in austral summer 2007/2008, the diversity and composition of the Polychaeta of the Antarctic deep-sea and adjacent South Atlantic basins were analyzed. A total of 847 individuals of 31 families were found belonging to 86 different species. Calculation of diversity (Shannon-Wiener Index, Pielou's Evenness) and the general species composition of Polychaeta showed patterns typical for the deep sea, with high species richness and low abundances. Lowest diversity was found in the Agulhas Basin in over 4000 m water depth. Lowest Evenness was found on top of Maud Rise where one-third of all Polychaeta belonged to one species. Cluster analyses resulted in higher affinities of Maud Rise to the Agulhas Basin than to the Antarctic continental slope. Explanations are sought in similarities of environmental factors (e.g., sediment, food input).

(Table 2) Particulate organic carbon concentrations in the water column of the Barents Sea in August-September 1997

A comparative estimation of particulate organic matter concentration in seawater in various regions of the Barents Sea was carried out on the basis of materials collected by authors in August-September 1997. It is shown that the major feature of near-bottom distribution of particulate organic matter is distinct decrease in its concentration from off-shore areas of the Murman and Novaya Zemlya coasts and the Franz Josef Land Archipelago toward the central part of the Barents Sea. Using a method of mean and maximum concentrations of particulate organic matter, an attempt was made to estimate its fluxes from the surface to the bottom.

Carbon sources in the North Sea evaluated by means of carbon isotope tracers

A multitracer approach is applied to assess the impact of boundary fluxes (e.g., benthic input from sedi- ments or lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry, of the North Sea. Analyses of both basin-wide observations in the North Sea and transects through tidal basins at the North-Frisian coastline, reveal that surface distributions of the d13C signature of dissolved inorganic carbon (DIC) are predominantly controlled by a balance between biological production and respiration. In particular, variability in metabolic DIC throughout stations in the well-mixed southern North Sea indi- cates the presence of an external carbon source, which is traced to the European continental coastline using naturally occurring radium isotopes (224Ra and 228Ra). 228Ra is also shown to be a highly effective tracer of North Sea total alkalinity (AT) compared to the more conventional use of salinity. Coastal inputs of meta- bolic DIC and AT are calculated on a basin-wide scale, and ratios of these inputs suggest denitrification as a primary metabolic pathway for their formation. The AT input paralleling the metabolic DIC release prevents a significant decline in pH as compared to aerobic (i.e., unbuffered) release of metabolic DIC. Finally, long- term pH trends mimic those of riverine nitrate loading, highlighting the importance of coastal AT production via denitrification in regulating pH in the southern North Sea.

Abundance of large protists from the Infrakingdom Rhizaria in the global ocean

The present data set is a worldwide compilation from 11 oceanographic expeditions during which an underwater vision profiler (UVP) was deployed in situ to determine the vertical distribution (abundance) of 10 taxonomic/morphological groups of plankton larger than 600 µm, belonging to the Infrakingdom Rhizaria, including Phaeodaria, Radiolaria, Collodaria and Acantharia.

Active methane seepage in the Southern Ocean, off the sub-Antarctic island of South Georgia

An extensive submarine cold-seep area was discovered on the northern shelf of South Georgia during R/V Polarstern cruise ANT-XXIX/4 in spring 2013. Hydroacoustic surveys documented the presence of 133 gas bubble emissions, which were restricted to glacially-formed fjords and troughs. Video-based sea floor observations confirmed the sea floor origin of the gas emissions and spatially related microbial mats. Effective methane transport from these emissions into the hydrosphere was proven by relative enrichments of dissolved methane in near-bottom waters. Stable carbon isotopic signatures pointed to a predominant microbial methane formation, presumably based on high organic matter sedimentation in this region. Although known from many continental margins in the world's oceans, this is the first report of an active area of methane seepage in the Southern Ocean. Our finding of substantial methane emission related to a trough and fjord system, a topographical setting that exists commonly in glacially-affected areas, opens up the possibility that methane seepage is a more widespread phenomenon in polar and sub-polar regions than previously thought.

Isopoda E(S100) and surface sediment characteristics of ANDEEP I-III stations in the Southern Ocean deep sea

Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa1. The deeper parts of the Southern Ocean exhibit some unique environmental features, including a very deep continental shelf2 and a weakly stratified water column, and are the source for much of the deep water in the world ocean. These features suggest that deep-sea faunas around the Antarctic may be related both to adjacent shelf communities and to those in other oceans. Unlike shallow-water Antarctic benthic communities, however, little is known about life in this vast deep-sea region2, 3. Here, we report new data from recent sampling expeditions in the deep Weddell Sea and adjacent areas (748-6,348 m water depth) that reveal high levels of new biodiversity; for example, 674 isopods species, of which 585 were new to science. Bathymetric and biogeographic trends varied between taxa. In groups such as the isopods and polychaetes, slope assemblages included species that have invaded from the shelf. In other taxa, the shelf and slope assemblages were more distinct. Abyssal faunas tended to have stronger links to other oceans, particularly the Atlantic, but mainly in taxa with good dispersal capabilities, such as the Foraminifera. The isopods, ostracods and nematodes, which are poor dispersers, include many species currently known only from the Southern Ocean. Our findings challenge suggestions that deep-sea diversity is depressed in the Southern Ocean and provide a basis for exploring the evolutionary significance of the varied biogeographic patterns observed in this remote environment.

Standard meteorological measurements on board of POLARSTERN during expedition ANT-IV (PS08, 4 cruises, south summer 1985/86) in the Atlantic and Weddell Sea, Antarctica

During the fourth Antarctic voyage ANT-IV of the research icebreaker POLARSTERN standard meteorological measurements have been performed. The measurements include 3-hourly synoptic observations as well as daily upper air soundings. The measurements started on September 6 1985 at Bremerhaven and were terminated at April 28 1986 in Punta Arenas. The 3-hourly synoptic observations are performed following the instructions of the FM 13 ships code defined by the World Meteorological Organization (WMO). The datasets include automatic measurements such as mean ship's speed, wind velocity, wind direction, air temperature, water temperature as well as visual observations such as total cloud amount, present weather, clouds, height and period of swell waves, ice classification. The visual observation are not performed during night time. For the upper air soundings VAISALA RS80 radiosondes, carried by helium-filled balloons (TOTEX 350 - 1500) were used. Data reception and evaluation were carried out by a MicroCora System (VAISALA). The upper air soundings include profile measurements of pressure, temperature, relative humidity and wind vector. Usually the soundings started at the heliport (10 m above sea level) and terminated between 15 and 37 km. The height of the measurements was calculated by applying the barometric formula. The wind vector was determined with the aid of the OMEGA navigation system.