Barium/Calcium and Cadmium/Calcium ratios of sediment core RC13-229

A new benthic foraminiferal Ba/Ca and Cd/Ca data set from core RC13-229 in the deep Cape Basin indicates only small variations in bottom water nutrient concentrations in Circumpolar Deep Water (CPDW) over the last 450 kyr. Variability in the Ba record is characterized by somewhat higher values during glacial periods, consistent with a reduction in the flux of Ba-depleted North Atlantic Deep Water to the Southern Ocean during glacial periods. The small changes in the Ba and Cd records contrast with the large and systematic increase in CPDW nutrients during glacial periods implied by the benthic delta13C record. This discrepancy, essentially an extension of the well-known Southern Ocean Cd-delta13C conflict, is evaluated by transforming RC13-229 paleochemical data into carbonate parameters using the modern oceanic relationships between delta13C, Cd, and SumCO2 and between Ba and alkalinity. Calculations using Cd/Ca to estimate past variations in CPDW SumCO2 and Ba/Ca to estimate past variations in CPDW alkalinity yield carbonate ion concentrations that exceed calcite saturation throughout the record length, with generally higher carbonate ion values associated with glacial intervals (opposite in sense to the RC13-229 %CaCO3 record). Substituting delta13C to estimate SumCO2 leads to extreme calcite undersaturation at this site during glacial periods, clearly inconsistent with the preservation of calcite throughout the length of RC13-229. Accepting the carbon isotope record as a direct measure of past variations in CPDW SumCO2 concentrations requires that both the Cd and Ba evidence for limited nutrient and alkalinity changes be disregarded.

Sedimentology on sediment cores from the eastern Weddell Sea, Antarctica

Sediment cores from nine sites along a profile on the Antarctic continental margin off Kapp Norvegia were analysed sedimentologicaly. The carbonate and organic carbon content, grain size distribution, composition of the coarse fraction and clay minerals were determined. d18O- and d13C-isotope ratios were also measured. The distribution of ice rafted debris was determined by a new method. Sedimentation-rates were obtained from 230Th- and 14C-analyses. A segregation into seven different sediment facies was made possible by different sedimentological parameters, which can be attributed to different sedimentation environments and conditions. Thr profile can be divided morphologicaly into shelf, upper continental slope, slope terrace and lower continental slope. The paratill facies is deposited on the shelf during an interglacial phase and consists mainly of ice rafted sediments. A portion of the fine fraction is being carried away by the antarctic coastel current. The sedimentation rate lies between 0 and 3 cm/1000 a. The coarse grained deposits of the upper, relatively steep continental slope, were specified as a rest sediment. Current and gravity sediment transport are responsible for the intensive sorting of ice rafted material coming from the shelf. The fine sediment is carried away by currents while sand and silt are deposited as small turbidites on the slope terrace. The morainic facies only appears at the base of the upper continental slope and defines ice advances, beyond the shelf margin. The facies mainly consists of transported shelf sediments. The interglacial facies, deposited during the interglacial phases on the continental slope, are characterized by high proportions of ice raft, coarse mean grain size, low content of montmorillonite and a carbonate content, which mainly originates from planktonic foraminifera (N. pachyderma). At the central part of the slope the sedimentation rate is at its lowest (2 cm/1000 a) and increases to 3-4 cm/1000 a towards the sea, due to high production of biogenic components and towards the continent due to an increasing input of terrigenous material. Sedimentary conditions during glacial times are depicted in the glacial facies by a low content of ice rafted debris, a lower mean grain size and a high content of montmorillonite. Biogeneous components are absent. The sedimentation rate is generally about 1 cm/1000a. A transition facies is deposited during the transition from glacial to interglacial conditions. Typical for this facies, with a terrigenous composition similar to the interglacial facies, is a high content of radiolaria. The reason for the change of plankton from a siliceous to a carbonacous fauna may have been the changing hydrography caused by the sea ice. The surge facies is deposited at the continental margin under the ice shelf and is a sediment exclusively delivered by currents. With the aid of this facies it was, for the first time possible to prove the existence of Antarctic ice surges, an aspect wh ich has been discussed for the past 20 years.

Sea surface temperature reconstruction for the LGM

The southwest Pacific Ocean covers a broad range of surface-water conditions ranging from warm, salty water in the subtropical East Australian Current to fresher, cold water in the Circumpolar Current. Using a new database of planktonic foraminifera assemblages (AUSMAT-F2), we demonstrate that the modern analog technique can be used to accurately reconstruct the magnitude of sea-surfacetemperature (SST) in this region. We apply this technique to data from 29 deep-sea cores along a meridional transect of the southwest Pacific Ocean to estimate the magnitude of SST cooling during the Last Glacial Maximum. We find minimal cooling in the tropics (0°-2°C), moderate cooling in the subtropical midlatitudes (2°-6°C), and maximum cooling to the southeast of New Zealand (6°-10°C). The magnitude of cooling at the sea surface from the tropics to the temperate latitudes is found to generally be less than cooling at the surface of adjacent land masses.

Age model of firn core DML05C98_32 (B32)

In the framework of the European Project for Ice Coring in Antarctica (EPICA), a comprehensive glaciological pre-site survey has been carried out on Amundsenisen, Dronning Maud Land, East Antarctica, in the past decade. Within this survey, four intermediate-depth ice cores and 13 snow pits were analyzed for their ionic composition and interpreted with respect to the spatial and temporal variability of volcanic sulphate deposition. The comparison of the non-sea-salt (nss)-sulphate peaks that are related to the well-known eruptions of Pinatubo and Cerro Hudson in AD 1991 revealed sulphate depositions of comparable size (15.8 ± 3.4 kg/km**2) in 11 snow pits. There is a tendency to higher annual concentrations for smaller snow-accumulation rates. The combination of seasonal sodium and annually resolved nss-sulphate records allowed the establishment of a time-scale derived by annual-layer counting over the last 2000 years and thus a detailed chronology of annual volcanic sulphate deposition. Using a robust outlier detection algorithm, 49 volcanic eruptions were identified between AD 165 and 1997. The dating uncertainty is ±3 years between AD 1997 and 1601, around ±5 years between AD 1601 and 1257, and increasing to ±24 years at AD 165, improving the accuracy of the volcanic chronology during the penultimate millennium considerably.

Sedimentological investigations of a sediment core profile from the continental slope of the South Orkney Islands

Sediment patterns such as texture, composition, and facies from three selected areas of the Antarctic continental margin of the Weddell Sea are discussed in relation to environmental variations of the Quaternary hydrosphere and kryosphere. Advance and retreat of ice shelves as well as oscillations in sea ice coverage are reflected by particular sediment facies. The distribution of ice-rafted detritus tracks the Antarctic Coastal Current, and the Weddell Sea Bottom water contour current can be recognized by its distinctive winnowing and erosion pattern. Distribution and abundance of biogenic sediment components are mainly controlled by duration of sea ice coverage reflecting the long-term climatic evolution.

Sedimentology of cores from the shelf of Lazarev Sea, East Antarctica

Distinct facies types, classified in radiocarbon-dated sediments from the shelf of the Lazarev Sea, East Antarctica, reveal a detailed history of processes that have controlled sedimentation during the deglaciation over the last 10,000 yr. The ice retreat on this part of the Antarctic shelf started 9500 yr BP, marked by the deposition of laminated sediments, deposited from a floating ice shelf. These laminites, which occur on top of diamictons laid down from a grounded ice sheet, are the basal sediments of the postglacial sequence. The intensity of the Antarctic Coastal Current (ACC), directed by shelf morphology, controlled sedimentation of the postglacial facies. A residual glaciomarine sediment with the fine fraction winnowed by strong currents developed from 9000-8000 yr BP in the western part of the investigation area and from 9000-5000 yr BP in the eastern part, closer to the prominent 'Fenno Deep' trough. Current velocities apparently decreased between 8000 and 2000 yr BP due to a deflection of the ACC by advancing ice tongues to the east of the investigation area during the 'Hypsithermal'. This led to a deposition of fine-grained sediments, and clay mineralogy suggests a continental source, possibly near the grounding line of the Nivl Ice Shelf, rather than a winnowing of sediments near the shelf break or advection from deeper water. Current velocities intensified after 2000 yr BP, removed fine material from these sediments and led to a relict sediment, consisting of coarse bryozoan and molluscan debris.

Physical oceanography during POLARSTERN cruise ANT-V/3

The work carried out by the physical oceanography group on POLARSTERN Leg ANT-V/3 concentrated on four major topics: A. A large scale survey of the eastern boundary between the Weddell gyre and the open ocean. On the way to the coastal polynya in early October 12 CTD stations were carried out between 54°30'S, 6°E and 70°30'S 8°W. Another set of 16 stations was obtained in early December on the way back north. During this transsect three current meter moorings were recovered at Maud Rise. The path between the current meter arrays was used to run an additional section to the NNE across the top of Maud Rise. B. A large scale survey of the Antarctic Coastal Current along the eastern shelf area. To obtain the water mass characteristics along the eastern Weddell shelf 36 CTD stations were carried out between Atka Bay and the Filchner Trench. Most of the stations were located on the shelf. Cross shelf sections were obtained both near Drescher Inlet and off Halley Bay, in the divergence area of the Coastal Current where the continental slope turns to the west and south of Vestkapp at Neptune's Point. A longshore section over 120 km was run north of Vestkapp. C. A mesoscale survey of the Antarctic Coastal Current off Drescher Inlet. The experimental work consisted of 37 CTD-stations and direct current measurements. The CTD-profiles were grouped into seven sections perpendicular to the coast line off Drescher Inlet extending once over 70 km but normally over 35 km. The profile depth ranged from 300 m on one section to the complete water column at two sections. Most sections consist of five stations providing highest resolution over the upper continental slope with offshore increasing spacing. The stations were chosen to represent the shelf (450 m), the shelf break (800 m), the upper slope (1600 m), the lower slope (2400 m) and the transition to the abyssal plain (3400 m). Rough topography and difficult ice conditions made it impossible to meet those requirements in all cases. D. A small scale survey of the hydrographic conditions under the sea ice. The motivation for these studies arose during the cruise. Consequently a suitable Instrumentation had to be developed at sea. This was done with a NB-Smart CTD which was inserted on an L-shaped lever through a hole in the ice. However, various water intrusions into the instrument resulted in the failure of this technique. In consequence a special lever system was built to position a NB Mark 3b weighing about 40 kg below the ice. Twenty four profiles were obtained reaching from the bottom of the ice down to 2 m below the ice surface with a maximum distance of 1 m from the entry hole. As the conductivity sensor was influenced by nearby ice platelets, salinity samples where drawn to check the sensor.

Age model of firn core DML03C98_09

The influence of atmospheric circulation patterns on sea salt aerosol deposition in the study area of the new EPICA (European Project for Ice Coring in Antarctica) deep drilling in Dronning Maud Land (DML), Antarctica, has been investigated. Comparison of ice core records with reanalysis data showed that recent sea salt concentrations are strongly influenced by the occurrence of a blocking high pressure ridge over the eastern and enhanced storm activity over the western Atlantic sector of the Southern Ocean (SO) leading to marine intrusions, thus enhanced sea salt export, into DML. These variations occur with periods of 4-5 and 12-14 yr, the prior being associated with the Antarctic Circumpolar Wave (ACW). The prevalence of these periodicities in a 2000 year ice core record from DML shows for the first time that the ACW is a prevalent feature of SO atmosphere dynamics over the last two millennia.

Clay mineralogy of South Atlantic surface sediments

Surface samples, mostly from abyssal sediments of the South Atlantic, from parts of the equatorial Atlantic, and of the Antarctic Ocean, were investigated for clay content and clay mineral composition. Maps of relative clay mineral content were compiled, which improve previous maps by showing more details, especially at high latitudes. Large-scale relations regarding the origin and transport paths of detrital clay are revealed. High smectite concentrations are observed in abyssal regions, primarily derived from southernmost South America and from minor sources in Southwest Africa. Near submarine volcanoes of the Antarctic Ocean (South Sandwich, Bouvet Island) smectite contents exhibit distinct maxima, which is ascribed to the weathering of altered basalts and volcanic glasses. The illite distribution can be subdivided into five major zones including two maxima revealing both South African and Antarctic sources. A particularly high amount of Mg- and Fe-rich illites are observed close to East Antarctica. They are derived from biotite-bearing crystalline rocks and transported to the west by the East Antarctic Coastal Current. Chiorite and well-crystallized dioctaedral illite are typical minerals enriched within the Subantarctic and Polarfrontal-Zone but of minor importance off East Antarctica. Kaolinite dominates the clay mineral assemblage at low latitudes, where the continental source rocks (West Africa, Brazil) are mainly affected by intensive chemical weathering. Surprisingly, a slight increase of kaolinite is observed in the Enderby Basin and near the Filchner-Ronne Ice shelf. The investigated area can be subdivided into ten, large-scale clay facies zones with characteristic possible source regions and transport paths. Clay mineral assemblages of the largest part of the South Atlantic, especially of the western basins are dominated by chlorite and illite derived from the Antarctic Peninsula and southernmost South America and supported by advection within the Circumantarctic Deep Water flow. In contrast, the East Antarctic provinces are relatively small. Assemblages of the eastern basins north of 30°S are strongly influenced by African sources, controlled by weathering regimes on land and by a complex interaction of wind, river and deep ocean transport. The strong gradient in clay mineral composition at the Brazilian slope indicate a relatively low contribution of tropically derived assemblages to the western basins.

Proportion of bryozoa, isopoda and ostracoda, and bryozoan species richness on the Antarctic continental shelf, slope and abyss

The Antarctic continental slope spans the depths from the shelf break (usually between 500 and 1000 m) to ~3000 m, is very steep, overlain by 'warm' (2-2.5 °C) Circumpolar Deep Water (CDW), and life there is poorly studied. This study investigates whether life on Antarctica's continental slope is essentially an extension of the shelf or the abyssal fauna, a transition zone between these or clearly distinct in its own right. Using data from several cruises to the Weddell Sea and Scotia Sea, including the ANDEEP (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) I-III, BIOPEARL (Biodiversity, Phylogeny, Evolution and Adaptive Radiation of Life in Antarctica) 1 and EASIZ (Ecology of the Antarctic Sea Ice Zone) II cruises as well as current databases (SOMBASE, SCAR-MarBIN), four different taxa were selected (i.e. cheilostome bryozoans, isopod and ostracod crustaceans and echinoid echinoderms) and two areas, the Weddell Sea and the Scotia Sea, to examine faunal composition, richness and affinities. The answer has important ramifications to the link between physical oceanography and ecology, and the potential of the slope to act as a refuge and resupply zone to the shelf during glaciations. Benthic samples were collected using Agassiz trawl, epibenthic sledge and Rauschert sled. By bathymetric definition, these data suggest that despite eurybathy in some of the groups examined and apparent similarity of physical conditions in the Antarctic, the shelf, slope and abyssal faunas were clearly separated in the Weddell Sea. However, no such separation of faunas was apparent in the Scotia Sea (except in echinoids). Using a geomorphological definition of the slope, shelf-slope-abyss similarity only changed significantly in the bryozoans. Our results did not support the presence of a homogenous and unique Antarctic slope fauna despite a high number of species being restricted to the slope. However, it remains the case that there may be a unique Antarctic slope fauna, but the paucity of our samples could not demonstrate this in the Scotia Sea. It is very likely that various ecological and evolutionary factors (such as topography, water-mass and sediment characteristics, input of particulate organic carbon (POC) and glaciological history) drive slope distinctness. Isopods showed greatest species richness at slope depths, whereas bryozoans and ostracods were more speciose at shelf depths; however, significance varied across Weddell Sea and Scotia Sea and depending on bathymetric vs. geomorphological definitions. Whilst the slope may harbour some source populations for localised shelf recolonisation, the absence of many shelf species, genera and even families (in a poorly dispersing taxon) from the continental slope indicate that it was not a universal refuge for Antarctic shelf fauna.

Circumpolar Landscape Units, links to GeoTIFFs

Requirements for space based monitoring of permafrost features had been already defined within the IGOS Cryosphere Theme Report at the start of the IPY in 2007 (IGOS, 2007). The WMO Polar Space Task Group (PSTG, http://www.wmo.int/pages/prog/sat/pstg_en.php) identified the need to review the requirements for permafrost monitoring and to update these requirements in 2013. Relevant surveys with focus on satellite data are already available from the ESA DUE Permafrost User requirements survey (2009), the United States National Research Council (2014) and the ESA - CliC - IPA - GTN -P workshop in February 2014. These reports have been reviewed and specific needs discussed within the community and a white paper submitted to the WMO PSTG. Acquisition requirements for monitoring of especially terrain changes (incl. rock glaciers and coastal erosion) and lakes (extent, ice properties etc.) with respect to current satellite missions have been specified. About 50 locations ('cold spots') where permafrost (Arctic and Antarctic) in situ monitoring has been taking place for many years or where field stations are currently established have been identified. These sites have been proposed to the WMO Polar Space Task Group as focus areas for future monitoring by high resolution satellite data. The specifications of these sites including meta-data on site instrumentation have been published as supplement to the white paper (Bartsch et al. 2014, doi:10.1594/PANGAEA.847003). The representativity of the 'cold spots' around the arctic has been in the following assessed based on a landscape units product which has been developed as part of the FP7 project PAGE21. The ESA DUE Permafrost service has been utilized to produce a pan-arctic database (25km, 2000-2014) comprising Mean Annual Surface Temperature, Annual and summer Amplitude of Surface Temperature, Mean Summer (July-August) Surface Temperature. Surface status (frozen/unfrozen) related products have been also derived from the ESA DUE Permafrost service. This includes the length of unfrozen period, first unfrozen day and first frozen day. In addition, SAR (ENVISAT ASAR GM) statistics as well as topographic parameters have been considered. The circumpolar datasets have been assessed for their redundancy in information content. 12 distinct units could be derived. The landscape units reveal similarities between North Slope Alaska and the region from the Yamal Peninsula to the Yenisei estuary. Northern Canada is characterized by the same landscape units like western Siberia. North-eastern Canada shows similarities to the Laptev coast region. This paper presents the result of this assessment and formulates recommendations for extensions of the in situ monitoring networks and categorizes the sites by satellite data requirements (specifically Sentinels) with respect to the landscape type and related processes.

Water stable oxygen isotope records from six Antarctic ice core sites for the present and last interglacial periods

We compare the present and last interglacial periods as recorded in Antarctic water stable isotope records now available at various temporal resolutions from six East Antarctic ice cores: Vostok, Taylor Dome, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML), Dome Fuji and the recent TALDICE ice core from Talos Dome. We first review the different modern site characteristics in terms of ice flow, meteorological conditions, precipitation intermittency and moisture origin, as depicted by meteorological data, atmospheric reanalyses and Lagrangian moisture source diagnostics. These different factors can indeed alter the relationships between temperature and water stable isotopes. Using five records with sufficient resolution on the EDC3 age scale, common features are quantified through principal component analyses. Consistent with instrumental records and atmospheric model results, the ice core data depict rather coherent and homogenous patterns in East Antarctica during the last two interglacials. Across the East Antarctic plateau, regional differences, with respect to the common East Antarctic signal, appear to have similar patterns during the current and last interglacials. We identify two abrupt shifts in isotopic records during the glacial inception at TALDICE and EDML, likely caused by regional sea ice expansion. These regional differences are discussed in terms of moisture origin and in terms of past changes in local elevation histories, which are compared to ice sheet model results. Our results suggest that elevation changes may contribute significantly to inter-site differences. These elevation changes may be underestimated by current ice sheet models