(Table 3) Air temperatures, and snow and ice characteristics of fresh and brackish water lakes in the Northwest Territories, Canada

The algorithms designed to estimate snow water equivalent (SWE) using passive microwave measurements falter in lake-rich high-latitude environments due to the emission properties of ice covered lakes on low frequency measurements. Microwave emission models have been used to simulate brightness temperatures (Tbs) for snowpack characteristics in terrestrial environments but cannot be applied to snow on lakes because of the differing subsurface emissivities and scattering matrices present in ice. This paper examines the performance of a modified version of the Helsinki University of Technology (HUT) snow emission model that incorporates microwave emission from lake ice and sub-ice water. Inputs to the HUT model include measurements collected over brackish and freshwater lakes north of Inuvik, Northwest Territories, Canada in April 2008, consisting of snowpack (depth, density, and snow water equivalent) and lake ice (thickness and ice type). Coincident airborne radiometer measurements at a resolution of 80x100 m were used as ground-truth to evaluate the simulations. The results indicate that subsurface media are simulated best when utilizing a modeled effective grain size and a 1 mm RMS surface roughness at the ice/water interface compared to using measured grain size and a flat Fresnel reflective surface as input. Simulations at 37 GHz (vertical polarization) produce the best results compared to airborne Tbs, with a Root Mean Square Error (RMSE) of 6.2 K and 7.9 K, as well as Mean Bias Errors (MBEs) of -8.4 K and -8.8 K for brackish and freshwater sites respectively. Freshwater simulations at 6.9 and 19 GHz H exhibited low RMSE (10.53 and 6.15 K respectively) and MBE (-5.37 and 8.36 K respectively) but did not accurately simulate Tb variability (R= -0.15 and 0.01 respectively). Over brackish water, 6.9 GHz simulations had poor agreement with airborne Tbs, while 19 GHz V exhibited a low RMSE (6.15 K), MBE (-4.52 K) and improved relative agreement to airborne measurements (R = 0.47). Salinity considerations reduced 6.9 GHz errors substantially, with a drop in RMSE from 51.48 K and 57.18 K for H and V polarizations respectively, to 26.2 K and 31.6 K, although Tb variability was not well simulated. With best results at 37 GHz, HUT simulations exhibit the potential to track Tb evolution, and therefore SWE through the winter season.

Planktic foraminiferal flux and faunal composition of sediment trap L1_K276 in the northeastern Atlantic

Planktic foraminiferal (PF) flux and faunal composition from three sediment trap time series of 2002-2004 in the northeastern Atlantic show pronounced year-to-year variations despite similar sea surface temperature (SST). The averaged fauna of the in 2002/2003 is dominated by the species Globigerinita glutinata, whereas in 2003/2004 the averaged fauna is dominated by Globigerinoides ruber. We show that PF species respond primarily to productivity, triggered by the seasonal dynamics of vertical stratification of the upper water column. Multivariate statistical analysis reveals three distinct species groups, linked to bulk particle flux, to chlorophyll concentrations and to summer/fall oligotrophy with high SST and stratification. We speculate that the distinct nutrition strategies of strictly asymbiontic, facultatively symbiontic, and symbiontic species may play a key role in explaining their abundances and temporal succession. Advection of water masses within the Azores Current and species expatriation result in a highly diverse PF assemblage. The Azores Frontal Zone may have influenced the trap site in 2002, indicated by subsurface water cooling, by highest PF flux and high flux of the deep-dwelling species Globorotalia scitula. Similarity analyses with core top samples from the global ocean including 746 sites from the Atlantic suggest that the trap faunas have only poor analogs in the surface sediments. These differences have to be taken into account when estimating past oceanic properties from sediment PF data in the eastern subtropical North Atlantic.

AMS 14C ages and isotopic compositions of samples from the Derugin Basin, Sea of Okhotsk

An area of massive barite precipitations was studied at a tectonic horst in 1500 m water depth in the Derugin Basin, Sea of Okhotsk. Seafloor observations and dredge samples showed irregular, block- to column-shaped barite build-ups up to 10 m high which were scattered over the seafloor along an observation track 3.5 km long. High methane concentrations in the water column show that methane expulsion and probably carbonate precipitation is a recently active process. Small fields of chemoautotrophic clams (Calyptogena sp., Acharax sp.) at the seafloor provide additional evidence for active fluid venting. The white to yellow barites show a very porous and often layered internal fabric, and are typically covered by dark-brown Mn-rich sediment; electron microprobe spectroscopy measurements of barite sub-samples show a Ba substitution of up to 10.5 mol% of Sr. Rare idiomorphic pyrite crystals (~1%) in the barite fabric imply the presence of H2S. This was confirmed by clusters of living chemoautotrophic tube worms (1 mm in diameter) found in pores and channels within the barite. Microscopic examination showed that micritic aragonite and Mg-calcite aggregates or crusts are common authigenic precipitations within the barite fabric. Equivalent micritic carbonates and barite carbonate cemented worm tubes were recovered from sediment cores taken in the vicinity of the barite build-up area. Negative d13C values of these carbonates (>-43.5 per mill PDB) indicate methane as major carbon source; d18O values between 4.04 and 5.88 per mill PDB correspond to formation temperatures, which are certainly below 5°C. One core also contained shells of Calyptogena sp. at different core depths with 14C-ages ranging from 20 680 to >49 080 yr. Pore water analyses revealed that fluids also contain high amounts of Ba; they also show decreasing SO4**2- concentrations and a parallel increase of H2S with depth. Additionally, S and O isotope data of barite sulfate (d34S: 21.0-38.6 per mill CDT; d18O: 9.0-17.6 per mill SMOW) strongly point to biological sulfate reduction processes. The isotope ranges of both S and O can be exclusively explained as the result of a mixture of residual sulfate after a biological sulfate reduction and isotopic fractionation with 'normal' seawater sulfate. While massive barite deposits are commonly assumed to be of hydrothermal origin, the assemblage of cheomautotrophic clams, methane-derived carbonates, and non-thermally equilibrated barite sulfate strongly implies that these barites have formed at ambient bottom water temperatures and form the features of a Giant Cold Seep setting that has been active for at least 49 000 yr.

Biomarker and radiogenic isotopes from sediment core POS362-2_33

The termination of the African Humid Period in northeastern Africa during the early Holocene was marked by the southward migration of the rain belt and the disappearance of the Green Sahara. This interval of drastic environmental changes was also marked by the initiation of food production by North African huntergatherer populations and thus provides critical information on human-environment relationships. However, existing records of regional climatic and environmental changes exhibit large differences in timing and modes of the wet/dry transition at the end of the African Humid Period. Here we present independent records of changes in river runoff, vegetation and erosion in the Nile River watershed during the Holocene obtained from a unique sedimentary sequence on the Nile River fan using organic and inorganic proxy data. This high-resolution reconstruction allows to examine the phase relationship between the changes of these three parameters and provides a detailed picture of the environmental conditions during the Paleolithic/Neolithic transition. The data show that river runoff decreased gradually during the wet/arid transition at the end of the AHP whereas rapid shifts of vegetation and erosion occurred earlier between 8.7 and about 6 ka BP. These asynchronous changes are compared to other regional records and provide new insights into the threshold responses of the environment to climatic changes. Our record demonstrates that the degradation of the environment in northeastern Africa was more abrupt and occurred earlier than previously thought and may have accelerated the process of domestication in order to secure sustainable food resources for the Neolithic African populations.

(Table 1) Water-extractable and acid-extractable carbohydrates in DSDP Leg 65 samples

Selected parts of ten frozen core samples from Holes 482A, 482B, 483A, and 485A, Leg 65 of the Deep Sea Drilling Project (DSDP), were analyzed for residual carbohydrates in order to determine the provenance and history of the organic material in the sediments. The samples, which represented silty-clay, shale, and nannofossil- chalk sediments, were analyzed for water-soluble monosaccharides, acid-soluble monosaccharides, and for starch and cellulose. Most samples yielded positive results for acid-extractable (polymeric) arabinose, fucose, xylose, mannose, galactose, and glucose. Amylose was detected in seven of the samples, whereas cellulose was found in only one. Possible explanations for the relatively high levels of free sugars are suggested in the conclusions to this chapter.

(Table 1) Biological and chemical characteristics of surface water stations during Nathaniel B. Palmer cruise NBP06-08 to the Ross Sea

We present results from a field study of inorganic carbon (C) acquisition by Ross Sea phytoplankton during Phaeocystis-dominated early season blooms. Isotope disequilibrium experiments revealed that HCO3? was the primary inorganic C source for photosynthesis in all phytoplankton assemblages. From these experiments, we also derived relative enhancement factors for HCO3?/CO2 interconversion as a measure of extracellular carbonic anhydrase activity (eCA). The enhancement factors ranged from 1.0 (no apparent eCA activity) to 6.4, with an overall mean of 2.9. Additional eCA measurements, made using membrane inlet mass spectrometry (MIMS), yielded activities ranging from 2.4 to 6.9 U/[?g chl a] (mean 4.1). Measurements of short-term C-fixation parameters revealed saturation kinetics with respect to external inorganic carbon, with a mean half-saturation constant for inorganic carbon uptake (K1/2) of ~380 ?M. Comparison of our early springtime results with published data from late-season Ross Sea assemblages showed that neither HCO3? utilization nor eCA activity was significantly correlated to ambient CO2 levels or phytoplankton taxonomic composition. We did, however, observe a strong negative relationship between surface water pCO2 and short-term 14C-fixation rates for the early season survey. Direct incubation experiments showed no statistically significant effects of pCO2 (10 to 80 Pa) on relative HCO3? utilization or eCA activity. Our results provide insight into the seasonal regulation of C uptake by Ross Sea phytoplankton across a range of pCO2 and phytoplankton taxonomic composition.

H, O, Sr, and Nd isotope ratios and water, Rb, Sr, Sm, and Nd content of ODP Hole 116-717C and 116-718C samples (Table 2)

Mineralogical and H, O, Sr, and Nd isotope compositions have been analyzed on a set of representative samples from the 17-m.y. section in ODP Leg 116 Holes 717C and 718C. Based on the mineralogical composition of the fraction <2 µm together with the lithogenic-biogenic composition of the fraction >63 µm, the whole section can be subdivided into three major periods of sedimentation. Between 17.1 and 6 m.y., and between 0.8 m.y. to present, the sediments are characterized by sandy and silty turbiditic inputs with a high proportion of minerals derived from a gneissic source without alteration. In the fraction <2 µm, illite and chlorite are dominant over smectite and kaolinite. The granulometric fraction >63 µm contains quartz, muscovite, biotite, chlorite, and feldspars. The 6-to 0.8-m.y. period is represented by an alternation of sandy/silty horizons, muds, and calcareous muds rich in smectite, and kaolinite (50% to 85% of the fraction <2 µm) and bioclastic material. The presence of smectite and kaolinite, as well as the 18O/16O and the 87Sr/86Sr ratios of the fraction <2 µm, imply an evolution in a soil environment and exchanges with meteoric ground water. The ranges of isotopic compositions are limited throughout the section: d18O quartz = 11.7 to 13.3 per mil, 87Sr/86Sr = 0.733 to 0.760 and epsilon-Nd (0) = -17.4 to -13.8. These values are within those of the High Himalaya Crystalline series, and they are considered to reflect this source region. The data imply that, since 17 Ma, this formation has supplied the major part of the eroded material.

Bottom water properties observed during Nathanial B. Palmer cruises NBP00-08 and NBP04-08 to the Southern Ocean

We report on observations of dense shelf water overflows and Antarctic Bottom Water (AABW) formation along the continental margin of the Adelie and George V Land coast between 140°E and 149°E. Vertical sections and bottom layer water mass properties sampled during two RVIB Nathaniel B Palmer hydrographic surveys (NBP00-08, December 2000/January 2001 and NBP04-08, October 2004) describe the spreading of cold, dense shelf water on the continental slope and rise from two independent source regions. The primary source region is the Adelie Depression, exporting high-salinity dense shelf water through the Adelie Sill at 143°E. An additional eastern source region of lower-salinity dense shelf water from the Mertz Depression is identified for the first time from bottom layer properties northwest of the Mertz Sill and Mertz Bank (146°E-148°E) that extend as far as the Buffon Channel (144.75°E) in summer. Regional analysis of satellite-derived ice production estimates over the entire region from 1992 to 2005 suggests that up to 40% of the total ice production for the region occurs over the Mertz Depression and therefore this area is likely to make a significant contribution to the total dense shelf water export. Concurrent time series from bottom-mounted Microcats and ADCP instruments from the Mertz Polynya Experiment (April 1998 to May 1999) near the Adelie Sill and on the upper continental slope (1150 m) and lower continental rise (3250 m) to the north describe the seasonal variability in downslope events and their interaction with the ambient water masses. The critical density for shelf water to produce AABW is examined and found to be 27.85 kg/m**3 from the Adelie Depression and as low as 27.80 kg/m**3 from the Mertz Depression. This study suggests previous dense shelf water export estimates based on the flow through the Adelie Sill alone are conservative and that other regions around East Antarctica with similar ice production to the Mertz Depression could be contributing to the total AABW in the Australian-Antarctic Basin.