Beryllium ages, sedimentology and weathering characteristics of Reedy Glacier deposits

Deposits corresponding to multiple periods of glaciation are preserved in ice-free areas adjacent to Reedy Glacier, southern Transantarctic Mountains. Glacial geologic mapping, supported by 10Be surface-exposure dating, shows that Reedy Glacier was significantly thicker than today multiple times during the mid-to-late Cenozoic. Longitudinal-surface profiles reconstructed from the upper limits of deposits indicate greater thickening at the glacier mouth than at the head during these episodes, indicating that Reedy Glacier responded primarily to changes in the thickness of the West Antarctic Ice Sheet. Surface-exposure ages suggest this relationship has been in place since at least 5 Ma. The last period of thickening of Reedy Glacier occurred during Marine Isotope Stage 2, at which time the glacier surface near its confluence with the West Antarctic Ice Sheet was at least 500 m higher than today.

Soil characteristics of cryosols from two sites on King George Island, maritime Antarctica

This study presents soil temperature and moisture regimes from March 2008 to January 2009 for two active layer monitoring (CALM-S) sites at King George Island, Maritime Antarctica. The monitoring sites were installed during the summer of 2008 and consist of thermistors (accuracy of ±0.2 °C), arranged vertically with probes at different depths and one soil moisture probe placed at the bottommost layer at each site (accuracy of ± 2.5%), recording data at hourly intervals in a high capacity datalogger. The active layer thermal regime in the studied period for both soils was typical of periglacial environments, with extreme variation in surface temperature during summer resulting in frequent freeze and thaw cycles. The great majority of the soil temperature readings during the eleven month period was close to 0 °C, resulting in low values of freezing and thawing degree days. Both soils have poor thermal apparent diffusivity but values were higher for the soil from Fildes Peninsula. The different moisture regimes for the studied soils were attributed to soil texture, with the coarser soil presenting much lower water content during all seasons. Differences in water and ice contents may explain the contrasting patterns of freezing of the studied soils, being two-sided for the coarser soil and one-sided for the loamy soil. The temperature profile of the studied soils during the eleven month period indicates that the active layer reached a maximum depth of approximately 92 cm at Potter and 89 cm at Fildes. Longer data sets are needed for more conclusive analysis on active layer behaviour in this part of Antarctica.

Sedimentary history and chemical characteristics of clay minerals from the Bengal Fan

The purpose of this study is to clarify the sedimentary history and chemical characteristics of clay minerals found in sediments deposited in the distal part of the Bengal Fan since the Himalayas were uplifted 17 m.y. ago. A total of seventy-eight samples were collected from three drilled cores which were to be used for the clay mineral analyses by means of XRD and ATEM. The results obtained from the analyses show that individual clay mineral species in the sediment samples at each site have similar features when the samples are of the same age, whereas these species have different features in samples of differing geological ages. Detrital clay minerals such as illite and chlorite were deposited in greater amounts than kaolinite and smectite during the Early to Middle Miocene. This means that the Himalayan uplift was vigorous at least until the Middle Miocene. In the Pliocene chemical weathering was more prevalent so that instead, in the distal part of the Bengal Fan, kaolinite shows the highest concentrations. This would accord with weaker uplift in the Himalayas. In the Pleistocene period, vigorous Himalayan uplift is characterized by illite-rich sediment in place of kaolinite. In the Holocene, smectite shows the highest concentration in place of the illite and kaolinite which were the predominant clay minerals of the earlier periods. Increasing smectite concentration suggests the Himalayan uplift to have been stable after the Pleistocene period. The smectite analyzed here is found to be dioctahedral Fe-beidellite, and it originated largely from the augite-basalt on the Indian Deccan Traps. The tri-octahedral chlorite is subdivided into three sub-species, an Fe-type, a Mg-type and an intermediate type. The mica clay mineral can be identified as di-octahedral illite which is rich in potassium. The chemical composition and morphology of each clay mineral appears to exhibit no change with burial depth in the sedimentary columns. This implies that there was no systematic transformation of clay minerals with time.

Retreat characteristics and geometries for 59 glaciers in West Greenland between 2000-2009

Recent changes in the dynamics of Greenland's marine terminating outlet glaciers indicate a rapid and complex response to external forcing. Despite observed ice front retreat and recent geophysical evidence for accelerated mass loss along Greenland's northwestern margin, it is unclear whether west Greenland glaciers have undergone the synchronous speed-up and subsequent slow-down as observed in southeastern glaciers earlier in the decade. To investigate changes in west Greenland outlet glacier dynamics and the potential controls behind their behavior, we derive time series of front position, surface elevation, and surface slope for 59 marine terminating outlet glaciers and surface speeds for select glaciers in west Greenland from 2000 to 2009. Using these data, we look for relationships between retreat, thinning, acceleration, and geometric parameters to determine the first-order controls on glacier behavior. Our data indicate that changes in front positions and surface elevations were asynchronous on annual time scales, though nearly all glaciers retreated and thinned over the decade. We found no direct relationship between retreat, acceleration, and external forcing applicable to the entire region. In regard to geometry, we found that, following retreat, (1) glaciers with grounded termini experienced more pronounced changes in dynamics than those with floating termini and (2) thinning rates declined more quickly for glaciers with steeper slopes. Overall, glacier geometry should influence outlet glacier dynamics via stress redistribution following perturbations at the front, but our data indicate that the relative importance of geometry as a control of glacier behavior is highly variable throughout west Greenland.

Physical properties, velocity and attenuation characteristics, and mineralogy of gabbros from ODP Hole 176-735B

Laboratory compressional wave (Vp) and shear wave (Vs) velocities were measured as a function of confining pressure for the gabbros from Hole 735B and compared to results from Leg 118. The upper 500 m of the hole has a Vp mean value of 6895 m/s measured at 200 MPa, and at 500 meters below seafloor (mbsf), Vp measurements show a mean value of 7036 m/s. Vs mean values in the same intervals are 3840 m/s and 3857 m/s, respectively. The mean Vp and Vs values obtained from log data in the upper 600 m are 6520 and 3518 m/s, respectively. These results show a general increase in velocity with depth and the velocity gradients estimate an upper mantle depth of 3.32 km. This value agrees with previous work based on dredged samples and inversion of rare element concentrations in basalts dredged from the conjugate site to the north of the Atlantis Bank. Laboratory measurements show Vp anisotropy ranging between 0.4% and 8.8%, with the majority of the samples having values less than 3.8%. Measurements of velocity anisotropy seem to be associated with zones of high crystal-plastic deformation with predominant preferred mineral orientations of plagioclase, amphiboles, and pyroxenes. These findings are consistent with results on gabbros from the Hess Deep area and suggest that plastic deformation may play an important role in the seismic properties of the lower oceanic crust. In contrast to ophiolite studies, many of the olivine gabbros show a small degree of anisotropy. Log derived Vs anisotropy shows an average of 5.8% for the upper 600 m of Hole 735B and tends to decrease with depth where the overburden pressure and the age of the crustal section suggests closure of cracks and infilling of fractures by alteration minerals. Overall the results indicate that the average shear wave splitting in Hole 735B might be influenced by preferred structural orientations and the average value of shear wave splitting may not be a maximum because structural dips are <90°. The maximum fast-wave orientation values could be influenced by structural features striking slightly oblique to this orientation or by near-field stress concentrations. However, flexural wave dispersion analyses have not been performed to confirm this hypothesis or to indicate to what extent the near-field stresses may be influencing shear wave propagation. Acoustic impedance contrasts calculated from laboratory and logging data were used to generate synthetic seismograms that aid in the interpretation of reflection profiles. Several prominent reflections produced by these calculations suggest that Fe-Ti oxides and shear zones may contribute to the reflective nature of the lower oceanic crust. Laboratory velocity attenuation (Q) measurements from below 500 m have a mean value of 35.1, which is consistent with previous vertical seismic profile (VSP) and laboratory measurements on the upper 500 m.

Oceanographical and meterological observations in the Westafrican area of upwelling during the 'Deutsche Nordatlantische Expedition' 1937

In 1937 the "Meteor" performed the cruises of the first part of the "Deutsche Nordatlantische Expedition". This publication treats seven stations of three-day-anchoring occupied during that time, five of which are located on the shelf, one on the continental slope and one on a ridge between the Capverde islands. The Bohnecke current meter, an instrument developed for the expedition, is described briefly and it's accuracy studied by comparing the measurements of two instruments which operated simultaneously at the same depth. It is shown that it is very sensitive for movements of the anchored ship because of the very short measuring intervall (2 minutes). The influence of the ship's movements could not be eliminated completely, the mode of using the instrument at different depths being unsuitable for this. Considering the stratification the accuracy of it's representation by the mean temperature and salinity distributionis studied. It is shown that under certain conditions a distribution estimated from observed values gives more exact results. This especially applies to the TS-diagram. Station Meteor336, located on the shelf near Cape Juby, shows temperatures 4 °C less than the open ocean and so belongs to the area of upwelling. During the observation period, however, internal tides are prominent. The diurnal component is of considerable influence, the distinction from inertial oscillations (25.5 hours) not being possible, however. Station Meteor341, on the shelf off Spanish-Sahara, gives an excellent example of the movements in the centre of the area of upwelling. Changing it's direction by 45° at the beginning of the measurements, the wind causes a change of current direction at all depths which, after some inertial oscillations (period 28.3 hours), settles down to a final value. At the beginning and the end of the observations the current at the upper depths is directed off-shore, the angle between current and wind being 22°, while at the lower depths it is orientated towards the shore. The depth of the upper homogenous layer gives the origin of the water transported upwards When during the inertial oscillations the current goes offshore at all depths temporarily, a sudden disturbance occurs in the temperature measurements. Station Meteor311 is located similar to station Meteor341 but was occupied one month earlier. At that time the wind situation was unnormal, the usual wind direction of 45° occuring at the end of the station. Therefore an unnormally high vertical shear of current speed and direction has been observed, the current vector being directed off-shore at the surface and near the bottom, towards the coast inbetween. The TS-diagram shows that the bottom water is replaced first so that upwelling does not occur during observation time. The state reached at the end of the station does not seem to be stable. Station Meteor369, on the continental slope, is governed by internal waves. Besides the internal tide of 12.4 hours a wave of 6.5 hour period is observed, being possibly amplified by the large bottom slope. In 40 - 60 m depth, where the thermocline is located, a wave with 3.3 hour period is observed which is argued to be an internal boundary wave. Station Meteor334 is located on the shelf NW of the mouth of the Senegal river. A marked temperature stratification, associated with large disturbances, and nearly constant salinity have been found there. The current was going slowly towards S or SW in the upper 20 - 30 m, towards N underneath. At the boundary of the current systems intense turbulence developed,including as it seems a water type of less salinity which is transported from the Senegal river by the lower current. Station Meteor327, located at 100 m depth between two of the Capverde islands, shows oceanic characteristics. The semidiurnal tide is found mainly, the diurnal component having considerable influence. Furtheron an internal wave of 6 hour period is seen the maximum amplitude of which is moving slowly downwards. Two possibilities of explaining it are discussed. Station Meteor366 is found in the area of ceasing winds off the coast of upper Guinea. The temperature there depends strongly on the depth, the salinity being nearly constant. The currents are divided into an upper and a lower system with large variations in both of them. A change of wind direction of nearly 90° is supposed to be the reason. The variations in salinity accordingly are interpreted as the influence of fresh water outflow from land which is felt in a different way at different wind directions. In the last section the daily changes in air and water temperature are studied. The upwelling having large influence on these, a centre of the area of upwelling can be located at about 100 miles north of Cape Blanc (Station Meteor311). The semidiurnal tidal component is compared with previous results for the Atlantic Ocean yielding considerable differences for the direction and time of occurence of the current maximum which might be due to the topographical influences around the shelf.

(Table 1) Characteristics of snow pits on De Geerfonna and Vestfonna during the IPY 2007-2010

Extensive glaciological field measurements were carried out on the ice cap Vestfonna as well as on the minor ice body De Geerfonna (Nordaustlandet, Svalbard) within the framework of IPY Kinnvika. Field campaigns were conducted during the period 2007-2010 in spring (April/May) and summer (August). In this study we compile and present snow cover information obtained from 22 snow pits that were dug on Vestfonna during this period. Locations are along two transects on the northwestern, land terminating slope of the ice cap, on its central summit, Ahlmann Summit, and at a set of several other locations in the eastern and northern part of the ice cap. Snow-cover information acquired from four snow pits on adjacent De Geerfonna is also incorporated in this study. Field data are analysed regarding snow stratigraphy, snow density, snow hardness and snow temperature. Results reveal mean snow densities of around 400 kg/m**3 for the snowpack of Vestfonna with no apparent spatial or interannual variability. A distinctly higher value of more than 450 kg/m**3 was obtained for De Geerfonna. A spatial comparison of snow water equivalents above the previous end-of-summer surface serves for obtaining insights into the spatial distribution of snow accumulation across Vestfonna. Altitude was found to be the only significant spatial parameter for controlling snow accumulation across the ice cap.

Physiological and biochemical characteristics of polar cod (Boreogadus saida) from Kongsfjorden

Seasonality of biomarker baseline levels were studied in polar cod (Boreogadus saida), caught in Kongsfjorden, Svalbard, in April, July, September and December, 2006-2007. Physiological parameters (condition factor, gonado- and hepato-somatic indexes, energy reserves, potential metabolic activity and antifreeze activity) in polar cod were used to interpret the seasonality of potential biomarkers. The highest levels of ethoxyresorufin-O-deethylase (EROD) activity occurred concomitantly with the highest potential metabolic activity in July due to e.g. intense feeding. During pre-spawning, EROD showed significant inhibition and gender differences. Hence, its potential use in environmental monitoring should imply gender differentiation at least during this period. Glutathione S-transferase and catalase activities were stable from April to September, but changed in December suggesting a link to low biological activity. Knowledge of the biomarker baseline levels and their seasonal trends in polar cod is essential for a trustworthy interpretation of forthcoming toxicity data and environmental monitoring in the Arctic.

Effective stress, porosity, p-wave velocity and mineral composition of ODP Hole 174A-1073A sediments

Porosity, permeability, and compressional (P-wave) velocity were measured as a function of stress on sediments from Ocean Drilling Program Site 1073, U.S. Mid-Atlantic continental slope. Thin sections, scanning electron microscopy, and X-ray diffraction analyses provided mineralogical characteristics of the samples. Uniaxial strain boundary conditions were imposed on the samples during consolidation tests with the maximum effective axial stress reaching 13 MPa. The maximum effective radial stress necessary to maintain uniaxial strain was 7.6 MPa. Over an effective axial stress interval of 0 to 5.2 MPa, Sample 174A-1073A-26X-2, 82-89 cm (226.65 meters below seafloor [mbsf]), exhibited the largest decrease in porosity (51% to 41%), whereas Sample 71X-1, 2-8 cm (644.70 mbsf), exhibited the smallest decrease in porosity (48% to 45%). All samples showed negligible porosity increases during unloading. The permeability (on the order of 1 x 10-17 m**2) of Sample 174A-1073A-71X-1, 2-8 cm, was twice that measured on Sample 8H-1, 23-26 cm (63.75 mbsf), even though the former was considerably deeper and older. The differences in porosity-stress behavior and permeability between shallow and deep samples is related to lithologic, mineralogic, and diagenetic differences between the sediments above and below the Pliocene-Pleistocene to Miocene unconformity. P-wave velocity for Samples 174A-1073A-41X-5, 97-103 cm (372.35 mbsf), and 71X-1, 2-8 cm, increased with decreasing porosity, but did not change significantly during unloading.