Hydrochemistry, phytoplankton pigment concentration and phytoplankton abundance in water samples obtained in the Kuroshio Extension Front in October 2009

This data was collected during a cruise to the Kuroshio Extension Front in October 2009. Several chemical and biological parameters were measured: dissolved nutrients, picophytoplankton (by flow cytometry), microphytoplankton (by light microscopy) and phytoplankton pigments (HPLC).

Density of 9 sediment cores from the Weddell Sea

The wet bulk density is one of the most important parameters of the physical and geological properties of marine sediments. The density is connected directly with sedimentation history and a few sedirnent properties. Knowledge of the fine scale density-depth structure is the base for many model calculations, for both sedimentological and palaeoclimatic research. A density measurement system was designed and built at the Alfred Wegener Institute in Bremerhaven for measuring the wet buk density of sediment cores with high resolution in a non-destructive way. The density is deterrnined by measuring the absorption of Gamma-rays in the sediment. This principle has been used since the 50's in materials research and in the geosciences. In the present case, Cs137 is used as the radioactive source and the intensity is measured by a detector system (scintillator and photomultiplier). Density values are obtainable in both longitudinal core sections and planar cross-sections (the latter are a function of the axial rotation angle). Special studies on inhomogenity can be applied with core rotation. Detection of ice rafted debris (IRD) is made possible with this option. The processes that run the density measurement system are computer controlled. Besides the absorption measurement the core diameter at every measurement point is determined with a potentiometric system. The data values taken are stored on a personal computer. Before starting routine measurements on the sediment cores, a few experiments conceming the statistical aspects of the gamma-ray signal and its accuracy were carried out. These experiments led to such things as the optimum operational parameters. A high spatial resolution in the mm-range is possible with the 4mm-thin gamma-ray measurements. Within five seconds the wet bulk density can be deterrnined with an absolute accuracy of 1%. A comparison between data measured with the new system and conventional measurements on core samples after core splitting shows an agreement within +I- 5% for most of the values. For this thesis, density determinations were carried out on ten sediment cores. A few sediment characteristics are obtainable from using just the standard measurement results without core rotation. In addition to differentes and steps in the absolute density range, variations in the "frequency" of the density-depth structure can be detected due to the close spatial measurement interval and high resolution. Examples from measurements with small (9°) and great (90°) angle increments show that abrupt and smooth transitional changes of sedirnent layers as well as ice rafted debris of several dimensions can be detected and distiflguished clearly. After the presentation of the wet bulk density results, a comparison with data from other investigations was made. Measurements of the electrical resistivity correlated very well with the density data because both parameters are closely related to the porosity of the sedirnent. Additionally, results from measurements of the magnetic susceptibility and from ultra-sonic wave velocity investigations were considered for a integrative interpretation. The correlation of these both parameters and wet bulk density data is strongly dependent on the local (environmental) conditions. Finally, the densities were compared with recordings from sediment-echographic soundings and an X-ray computer tomography analysis. The individual results of all investigations were then finally combined into an accurate picture of the core. Problems of ambiguity, which exist when just one Parameter is determined alone, can be reduced more or less according to the number of parameters and sedimentary characteristics measured. The important role of the density data among other parameters of such an integrated interpretation is evident. Evidence of this role include the high resolution of the measurement, the excellent accuracy and the key position within methods and parameters concerning marine sediments.

Tidal-induced mixing and diapycnal nutrient fluxes in the Mauritanian upwelling region

The Mauritanian coastal area is one of the most biologically productive upwelling regions in the world ocean. Shipboard observations carried out during maximum upwelling season and short-term moored observations are used to investigate diapycnal mixing processes and to quantify diapycnal fluxes of nutrients. The observations indicate strong tide-topography interactions that are favored by near-critical angles occurring on large parts of the continental slope. Moored velocity observations reveal the existence of highly nonlinear internal waves and bores and levels of internal wave spectra are strongly elevated near the buoyancy frequency. Dissipation rates of turbulent kinetic energy at the slope and shelf determined from microstructure measurements in the upper 200 m averages to ? = 5 × 10-8 W kg-1. Particularly elevated dissipation rates were found at the continental slope close to the shelf break, being enhanced by a factor of 100 to 1000 compared to dissipation rates farther offshore. Vertically integrated dissipation rates per unit volume are strongest at the upper continental slope reaching values of up to 30 mW m-2. A comparison of fine-scale parameterizations of turbulent dissipation rates for shelf regions and the open ocean to the measured dissipation rates indicates deficiencies in reproducing the observations. Diapycnal nitrate fluxes above the continental slope at the base of the mixed layer yielding a mean value of 12 × 10-2 µmol m-2 s-1 are amongst the largest published to date. However, they seem to only represent a minor contribution (10% to 25%) to the net community production in the upwelling region.

Experiment: changing carbonate chemistry influence on coccoliths formed by Emiliania huxleyi

The coccolithophore Emiliania huxleyi is a marine phytoplankton species capable of forming small calcium carbonate scales (coccoliths) which cover the organic part of the cell. Calcification rates of E. huxleyi are known to be sensitive to changes in seawater carbonate chemistry. It has, however, not yet been clearly determined how these changes are reflected in size and weight of individual coccoliths and which specific parameter(s) of the carbonate system drive morphological modifications. Here, we compare data on coccolith size, weight, and malformation from a set of five experiments with a large diversity of carbonate chemistry conditions. This diversity allows distinguishing the influence of individual carbonate chemistry parameters such as carbon dioxide (CO2), bicarbonate (HCO3- ), carbonate ion (CO32-), and protons (H+) on the measured parameters. Measurements of fine-scale morphological structures reveal an increase of coccolith malformation with decreasing pH suggesting that H+ is the major factor causing malformations. Coccolith distal shield area varies from about 5 to 11 µm2. Changes in size seem to be mainly induced by varying [HCO3- ] and [H+] although influence of [CO32-] cannot be entirely ruled out. Changes in coccolith weight were proportional to changes in size. Increasing CaCO3 production rates are reflected in an increase in coccolith weight and an increase of the number of coccoliths formed per unit time. The combined investigation of morphological features and coccolith production rates presented in this study may help to interpret data derived from sediment cores, where coccolith morphology is used to reconstruct calcification rates in the water column.

Global 2009 1km MODIS (MOD35/MOD09) cloud frequency and MOD35 processing path

Identifying cloud interference in satellite-derived data is a critical step toward developing useful remotely sensed products. Most MODIS land products use a combination of the MODIS (MOD35) cloud mask and the 'internal' cloud mask of the surface reflectance product (MOD09) to mask clouds, but there has been little discussion of how these masks differ globally. We calculated global mean cloud frequency for both products, for 2009, and found that inflated proportions of observations were flagged as cloudy in the Collection 5 MOD35 product. These erroneously categorized areas were spatially and environmentally non-random and usually occurred over high-albedo land-cover types (such as grassland and savanna) in several regions around the world. Additionally, we found that spatial variability in the processing path applied in the Collection 5 MOD35 algorithm affects the likelihood of a cloudy observation by up to 20% in some areas. These factors result in abrupt transitions in recorded cloud frequency across landcover and processing-path boundaries impeding their use for fine-scale spatially contiguous modeling applications. We show that together, these artifacts have resulted in significantly decreased and spatially biased data availability for Collection 5 MOD35-derived composite MODIS land products such as land surface temperature (MOD11) and net primary productivity (MOD17). Finally, we compare our results to mean cloud frequency in the new Collection 6 MOD35 product, and find that landcover artifacts have been reduced but not eliminated. Collection 6 thus increases data availability for some regions and land cover types in MOD35-derived products but practitioners need to consider how the remaining artifacts might affect their analysis.

Sea ice habitat characteristics and number of narwhal (Monodon monoceros) sightings in Disko Bay, West Greenland

There is a paucity of information on abundance, densities, and habitat selection of narwhals Monodon monoceros in the offshore pack ice of Baffin Bay, West Greenland, despite the critical importance of winter foraging regions and considerable sea ice declines in the past decades. We conducted a double-platform visual aerial survey over a narwhal wintering ground to obtain pack ice densities and develop the first fully corrected abundance estimate using point conditional mark-recapture distance sampling. Continuous video recording and digital images taken along the trackline allowed for in situ quantification of winter narwhal habitat and for the estimation of fine-scale narwhal habitat selection and habitat-specific sighting probabilities. Abundance at the surface was estimated at 3484 (coefficient of variation [CV] = 0.46) including whales missed by observers. The fully corrected abundance of narwhals was 18 044 (CV = 0.46), or approximately one-quarter of the entire Baffin Bay population. The narwhal wintering ground surveyed (~9500 km**2) had 2.4 to 3.2% open water based on estimates from satellite imagery (NASA Moderate Resolution Imaging Spectroradiometer) and 1565 digital photographic images collected on the trackline. Thus, the ~18 000 narwhals had access to 233 km**2 of open water, resulting in an average density of ~77 narwhals/km**2 open water. Narwhal sighting probability near habitats with <10% or 10 to 50% open water was significantly higher than sighting probability in habitats with >50% open water, suggesting narwhals select optimal foraging areas in dense pack ice regardless of open water availability. This study provides the first quantitative ecological data on densities and habitat selection of narwhals in pack ice foraging regions that are rapidly being altered with climate change.

Nutrients of pore water in sediments of the central equatorial Pacific

Shipboard whole-core squeezing was used to measure pore water concentration vs depth profiles of [NO3]-, O2 and SiO2 at 12 stations in the equatorial Pacific along a transect from 15°S to 11°N at 135°W. The [NO3]- and SiO2 profiles were combined with fine-scale resistivity and porosity measurements to calculate benthic fluxes. After using O2 profiles, coupled with the [NO3]- profiles, to constrain the C:N of the degrading organic matter, the [NO3]- fluxes were converted to benthic organic carbon degradation rates. The range in benthic organic carbon degradation rates is 7-30 ?mol cm**-2 y**-1, with maximum values at the equator and minimum values at the southern end of the transect. The zonal trend of benthic degradation rates, with its equatorial maximum and with elevated values skewed to the north of the equator, is similar to the pattern of primary production observed in the region. Benthic organic carbon degradation is 1-2% of primary production. The range of benthic biogenic silica dissolution rates is 6.9-20 µmol cm**-2 y**-1, representing 2.5-5% of silicon fixation in the surface ocean of the region. Its zonal pattern is distinctly different from that of organic carbon degradation: the range in the ratio of silica dissolution to carbon degradation along the transect is 0.44-1.7 mol Si mol C**-1, with maximum values occurring between 12°S and 2°S, and with fairly constant values of 0.5-0.7 north of the equator. A box model calculation of the average lifetime of the organic carbon in the upper 1 cm of the sediments, where 80 +/- 11% of benthic organic carbon degradation occurs, indicates that it is short: from 3.1 years at high flux stations to 11 years at low flux stations. The reactive component of the organic matter must have a shorter lifetime than this average value. In contrast, the average lifetime of biogenic silica in the upper centimeter of these sediments is 55 +/- 28 years, and shows no systematic variations with benthic flux.

Glycerol dialkyl glycerol tetraethers (GDGT) abundance of sediment core GeoB15103-1

Marine microorganisms adapt to their habitat by structural modification of their membrane lipids. This concept is the basis of numerous molecular proxies used for paleoenvironmental reconstruction. Archaeal tetraether lipids from ubiquitous marine planktonic archaea are particularly abundant, well preserved in the sedimentary record and utilized in several molecular proxies. We here introduce the direct, extraction-free analysis of these compounds in intact sediment core sections using laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). LDI FTICR-MS can detect the target lipids in single sub-mm sized spots on sediment sections, equivalent to a sample mass in the nanogram range, and could thus pave the way for biomarker-based reconstruction of past environments and ecosystems at subannual to decadal resolution. We demonstrate that ratios of selected archaeal tetraethers acquired by LDI FTICR-MS are highly correlated with values obtained by conventional LC/MS protocols. The ratio of the major archaeal lipids, caldarchaeol and crenarchaeol, analyzed in a 6.2-cm intact section of Mediterranean sapropel S1 at 250-µm resolution (~4-year temporal resolution), provides an unprecedented view of the fine-scale patchiness of sedimentary biomarker distributions and the processes involved in proxy signal formation. Temporal variations of this lipid ratio indicate a strong influence of the 200-yr de Vries solar cycle on reconstructed sea surface temperatures with possible amplitudes of several degrees, and suggest signal amplification by a complex interplay of ecological and hydrological factors. Laser-based biomarker analysis of geological samples has the potential to revolutionize molecular stratigraphic studies of paleoenvironments.

(Appendix) Gephyrocapsa coccolith abundance and holocene paleotemperature assessment

A global sea surface temperature calibration based on the relative abundance of different morphotypes within the coccolithophore genus Gephyrocapsa in Holocene deep-sea sediments is presented. There is evidence suggesting that absolute sea surface temperature for a given location can be calculated from the relative abundance of Gephyrocapsa morphotypes in sediment samples, with a standard error comparable to temperature estimates derived from other temperature proxies such as planktic foraminifera transfer functions. A total of 110 Holocene sediment samples were selected from the Pacific, Indian, and Atlantic Oceans covering a mean sea surface temperature gradient from 13.6° to 29.3°C. Standard multiple linear regression analyses were applied to this data set, linking the relative abundance of Gephyrocapsa morphotypes to sea surface temperature. The best model revealed an r**2 of 0.83 with a standard residual error of 1.78°C for the estimation of mean sea surface temperature. This new proxy provides a unique opportunity for the reconstruction of paleotemperatures with a very small amount of sample material due to the minute size of coccoliths, permitting examination of thinly laminated sediments (e.g., a pinhead of material from laminated sediments for the reconstruction of annual sea surface temperature variations). Such fine-scale resolution is currently not possible with any other proxy. Application of this new paleotemperature proxy may allow new paleoenvironmental interpretations in the late Quaternary period and discrepancies between the different currently used paleotemperature proxies might be resolved.

Land cover classification of Samoylov Island and Landsat subpixel water cover of Lena River Delta, Siberia, with links to ESRI grid files

Ignoring small-scale heterogeneities in Arctic land cover may bias estimates of water, heat and carbon fluxes in large-scale climate and ecosystem models. We investigated subpixel-scale heterogeneity in CHRIS/PROBA and Landsat-7 ETM+ satellite imagery over ice-wedge polygonal tundra in the Lena Delta of Siberia, and the associated implications for evapotranspiration (ET) estimation. Field measurements were combined with aerial and satellite data to link fine-scale (0.3 m resolution) with coarse-scale (upto 30 m resolution) land cover data. A large portion of the total wet tundra (80%) and water body area (30%) appeared in the form of patches less than 0.1 ha in size, which could not be resolved with satellite data. Wet tundra and small water bodies represented about half of the total ET in summer. Their contribution was reduced to 20% in fall, during which ET rates from dry tundra were highest instead. Inclusion of subpixel-scale water bodies increased the total water surface area of the Lena Delta from 13% to 20%. The actual land/water proportions within each composite satellite pixel was best captured with Landsat data using a statistical downscaling approach, which is recommended for reliable large-scale modelling of water, heat and carbon exchange from permafrost landscapes.

Distribution of major carbon pools in a cyanobacterial mat from Salin de Giraud, Camargue, France

The fine-scale depth distribution of major carbon pools and their stable carbon isotopic signatures (d13C) were determined in a cyanobacterial mat (Salin-de-Giraud, Camargue, France) to study early diagenetic alterations and the carbon preservation potential in hypersaline mat ecosystems. Particular emphasis was placed on the geochemical role of extracellular polymeric substances (EPS). Total carbon (Ctot), organic carbon (Corg), total nitrogen (Ntot), total hydrolysable amino acids (THAA), carbohydrates, cyanobacteria-derived hydrocarbons (8-methylhexadecane, n-heptadec-5-ene, n-heptadecane) and EPS showed highest concentrations in the top millimetre of the mat and decreased with depth. The hydrocarbons attributed to cyanobacteria showed the strongest decrease in concentration with depth. This correlated well with the depth profiles of oxygenic photosynthesis and oxygen, which were detected in the top 0.6 and 1.05 mm, respectively, at a high down-welling irradiance (1441 µmol photons m**-2 s**-1). At depths beneath the surface layer, the Corg was composed mainly of amino acids and carbohydrates. A resistance towards microbial degradation could have resulted from interactions with diverse functional groups present in biopolymers (EPS) and with minerals deposited in the mat. A 13C enrichment with depth for the total carbon pool (Ctot) was observed, with d13C values ranging from -16.3 permil at the surface to -11.3 permil at 9-10 mm depth. Total lipids depicted a d13C value of -17.2 permil in the top millimetre and then became depleted in 13C with depth (-21.7 to -23.3 permil). The d13C value of EPS varied only slightly with depth (-16.1 to -17.3 permil) and closely followed the d13C value of Corg at depths beneath 4 mm. The EPS represents an organic carbon pool of preservation potential during early stages of diagenesis in recent cyanobacterial mats as a result of a variety of possible interactions. Their analyses might improve our understanding of fossilized microbial remains from mat ecosystems.

(Table T2) Biogenic opal in Palmer Deep sediments at ODP Site 178-1098

High-resolution records of sedimentary proxies provide insights into fine-scale geochemical responses to climatic forcing. Gamma-ray attenuation (GRA) bulk-density data and magnetic stratigraphy records from Palmer Deep, Site 1098, show variability close to the same scale as ice cores, making this site ideal for high-resolution geochemical investigations. In conjunction with shipboard geophysical measurements, silica records allow high-resolution evaluation of the frequencies and amplitudes of biogenic variability. This provides investigators additional data sets to evaluate the global extent of climatic events that are presently defined by regional oceanic data sets (e.g., Younger Dryas in the North Atlantic) and to evaluate the potential mechanisms that link biological productivity and climate in the Southern Ocean. In addition, because of the observed links between diatom blooms and export productivity (Michaels and Silver, 1988, doi:10.1016/0198-0149(88)90126-4), biogenic silica may be an indicator of the efficiency of the biological pump (removal of organic carbon from the euphotic zone and burial within the sediments). Because the net removal of CO2 (on short time scales up to millennial, the balance between upwelled CO2, carbon fixation, and the removal of organic carbon from the surface ocean) can determine the atmospheric concentration; proxies that allow us to quantify export production yield insights into carbon cycle responses. In today's ocean, diatoms are integrally linked with new production (production based on the use of nitrate and molecular nitrogen rather than ammonium, which is generated by the microbial degradation of organic carbon) (Dugdale and Goering, 1967). Thus, as with nutrient utilization proxies, biogenic silica may be a good indicator of export production. The difficulties lie in translating the biogenic opal burial records to export production. Numerous factors control the preservation of sedimentary biogenic silica, including depth of the water column, water temperature, trace element chemistry, grazing pressure, bloom structure, and species composition of the diatom assemblage (Nelson et al., 1995, doi:10.1029/95GB01070). In addition, several recent investigations have noted additional complications. Iron limitation increases the uptake of Si relative to carbon (Hutchins et al., 1998, ; Takeda, 1998, doi:10.1038/31674). In the Southern Ocean, iron limitation could produce more robust, and thus better preserved, diatoms; thus, the burial record may be a record of iron limitation rather than of the export of organic carbon (Boyle, 1998). In addition, laboratory experiments show that bacteria accelerate the dissolution of biogenic silica (Bidle and Azam, 1999, doi:10.1038/17351). Both the species composition and temperature seem to influence the amount of dissolution. Evidence of recycling of silicic acid within the photic zone (Brzezinski et al., 1997) suggests that the silica pump (removal from the euphotic zone of silica relative to nitrogen and phosphorus) may work with variable efficiency. This becomes an issue when trying to reconstruct the removal of organic carbon from sedimentary biogenic silica records. In fact, there is a wide range in the Si:Corganic molar ratio in the Southern Ocean (0.18-0.81) (Nelson et al., 1995; Ragueneau et al., 2000, doi:10.1016/S0921-8181(00)00052-7). Thus, the presence (or absence) of biogenic silica alone may tell us little about the export productivity, complicating the interpretation of age-related trends. One recent assessment has added some hope to links between productivity and opal burial in the Southern Ocean (Pondaven et al., 2000). Quantitative comparison of different productivity proxies will greatly aid in this evaluation.

Gravity mapping in the southern Weddell Sea region, Antarctica (Scale 1:2 000 000)

New maps of free-air and the Bouguer gravity anomalies on the Weddell Sea sector (70-81° S, 6-75° W) of Antarctica are presented. These maps are based on the first computer compilation of available gravity data collected by ''Sevmorgeologia'' in 1976-89 in the southern Weddell Sea and adjacent coasts of western Dronning Maud Land (WDML) and Coats Land. The accomplished gravity studies comprise airborne observations with a line spacing of about 20 km and conventional measurements at over-the-ice points, which were spaced at 10-30 km and supplemented by seismic soundings. Hence, anomalies on the maps represent mainly large-scale and deep crustal features. The dominant feature in free-air gravity map is a large dipolar gravity anomaly stretching along the continental margin. Following the major grain of seabed morphology this shelf-edge/slope anomaly (SESA) is clearly divided into three segments characterized by diverse anomaly amplitudes, wavelengths and trends. They are associated with continental margins of different geotectonic provinces of Antarctica surrounding the Weddell Sea. Apparent distinctions in the SESA signatures are interpreted as the gravity expression of tectonic, deep crustal structure segmentation of the continental margin. The prominent gravity highs (100-140 mGal) of the shelf edge anomaly mapped along WDML are assumed to represent high-density mantle injections intruded into the middle/lower crust during initial rifting of continental breakup. Enlarged wavelengths and diminished amplitudes of the gravity anomaly westwards, along the Weddell Sea embayment (WSE) margin, reflect a widening of the continental slope and a significant increase in thickness of underlying sediment strata. Low amplitude, negative free-air anomalies in the Filchner-Ronne Ice Shelves (FRIS) contrast sharply with the dominating positive anomalies offshore. This indicates a greater sedimentary thickness of the basin in this area. Crustal response to the enlarged sediment load is impressed in mostly positive features of the Bouguer gravity field observed here. Two pronounced positive Bouguer anomalies of 50-70 mGal and an average widths of 200 km dominate the Weddell Sea embayment margins towards the Antarctic Peninsula and the East Antarctic craton. They correlate well with very deep seabed troughs (> 1000 m below sea level). The gravity highs are most likely caused by a shallow upper mantle underneath graben-rift structures evolved at the margins of the WSE basin. A regional zone (> 100 km in width) of the prominent Bouguer and free-air negative anomalies (-40 to -60 mGal) adjacent Coats Land to the north of the ice shelf edge may indicate the presence of the thick old cratonic crust far offshore beneath the Weddell Sea Embayment.

Geological map of HANSSONHORNA, Heimefrontfjella, Antarctica (Scale 1:25,000)

Topographic data of this geological map were obtained through stereoscopic aerial photo interpretation. The photogrammetric photo flights were undertaken in 1986 by the Institut für Angewandte Geodäsie, Frankfurt. Horizontal ground control points required for aerial photo interpretation were determined by means of Doppler satellite observation during the 2nd German Neuschwabenland Expedition 1985/86. Vertical ground control points were taken from unpublished map drafts at 1:100 000 scale by Norsk Polarinstitutt, Oslo. The elevation above mean sea level was transferred to Heimefrontfjella barometrically. For this reason assertions concerning the absolute elevation (referred to sea level) are uncertain. Contours and spot heights presented on the map were obtained from the photogrammetric evaluation of the photography taken in 1986; relative elevation data (hight differences) are accurate to approximately ±10 m.