Micro-facies and µXRF element scanning data of Dead Sea sediment cores DSEn and 5017-1

Laminated lake sediments from the Dead Sea basin provide high-resolution records of climatic variability in the eastern Mediterranean region, which is especially sensitive to changing climatic conditions. In this study, we aim on detailed reconstruction of climatic fluctuations and related changes in the frequency of flood and dust deposition events at ca. 3300 and especially at 2800 cal. yr BP from high-resolution sediment records of the Dead Sea basin. A ca. 4-m-thick, mostly varved sediment section from the western margin of the Dead Sea (DSEn - Ein Gedi profile) was analysed and correlated to the new International Continental Scientific Drilling Program (ICDP) Dead Sea Deep Drilling Project core 5017-1 from the deep basin. To detect even single event layers, we applied a multi-proxy approach of high-resolution microscopic thin section analyses, micro-X-ray fluorescence (µ-XRF) element scanning and magnetic susceptibility measurements, supported by grain size data and palynological analyses. Based on radiocarbon and varve dating, two pronounced dry periods were detected at ~3500-3300 and ~3000-2400 cal. yr BP which are differently expressed in the sediment records. In the shallow-water core (DSEn), the older dry period is characterised by a thick sand deposit, whereas the sedimentological change at 2800 cal. yr BP is less pronounced and characterised mainly by an enhanced frequency of coarse detrital layers interpreted as erosion events. In the 5017-1 deep-basin core, both dry periods are depicted by halite deposits. The onset of the younger dry period coincides with the Homeric Grand Solar Minimum at ca. 2800 cal. yr BP. Our results suggest that during this period, the Dead Sea region experienced an overall dry climate, superimposed by an increased occurrence of flash floods caused by a change in synoptic weather patterns.

Products of chlorophyll diagenesis from DSDP Leg 57 Holes

Tetrapyrrole pigments isolated from sediments retrieved during Leg 57 include pheophytin-a, a myriad of chlorins, free-base deoxophylloerythroetioporphyrin (DPEP), as well as copper and nickel porphyrins. Their richness, both qualitatively and quantitatively, in chlorin tetrapyrroles affords a relatively complete study on the early diagenesis of chlorophyll. Our studies, coupled with those in the preceding chapter by Louda et al., point out the influence of pre- and postdepositional environments upon the mode of chlorophyll diagenesis. Formation of tetrapyrroles, collectively called "petroporphyrins," is seen to occur in only a limited set of environmental conditions (see Baker and Palmer, 1978). The more generalized route of chlorophyll diagenesis, at least in the ocean, results in removal of tetrapyrrole pigment, from the fossil record. Late diagenetic products, metalloporphyrins, are found to represent an extremely minor component of the tetrapyrrole assemblage in sediments studied from the Japan Trench. The products of chlorophyll diagenesis isolated from Japan Trench sediments allow expansion of previous diagenetic schemes (Baker and Palmer, 1978; Triebs, 1936) and indicate directions for future studies.

Downwelling solar irradiance, upwelling solar radiance, sky leaving radiance, and cloud cover observed during ARCHEMHAB study (on Maria S. Merian Leg MSM21/3) from 2012-07-26 to 2012-08-10

The need to obtain ocean color essential climate variables (OC-ECVs) using hyperspectral technology has gained increased interest in recent years. Assessing ocean color on a large scale in high latitude environments using satellite remote sensing is constrained by polar environmental conditions. Nevertheless, on a small scale we can assess ocean color using above-water and in-water remote sensing. Unfortunately, above-water remote sensing can only determine apparent optical properties leaving the sea surface and is susceptible to near surface environmental conditions for example sky and sunglint. Consequently, we have to rely on accurate in-water remote sensing as it can provide both synoptic inherent and apparent optical properties of seawater. We use normalized water leaving radiance LWN or the equivalent remote sensing reflectance RRS from 27 stations to compare the differences in above-water and in-water OC-ECVs. Analysis of above-water and in-water RRS spectra provided very good match-ups (R2 > 0.97, MSE<1.8*10**-7) for all stations. The unbiased percent differences (UPD) between above-water and in-water approaches were determined at common OC-ECVs spectral bands (410, 440, 490, 510 and 555) nm and the classic band ratio (490/555) nm. The spectral average UPD ranged (5 - 110) % and band ratio UPD ranged (0 - 12) %, the latter showing that the 5% uncertainty threshold for ocean color radiometric products is attainable. UPD analysis of these stations West of Greenland, Labrador Sea, Denmark Strait and West of Iceland also suggests that the differences observed are likely a result of environmental and instrumental perturbations.

Organic facies variations in the Mesozoic South Atlantic DSDP Holes

Visual kerogen and total organic carbon determinations indicate that there are two periods of organic enrichment events in the Mesozoic sediments of the South Atlantic. The first period, from the Late Jurassic through the late Aptian, is recorded in sediments from the Falkland Plateau, the Cape Basin, and the Angola Basin. Apparently, salinity stratification in the restricted basin, coupled with rising sea level, led to bottom water anoxia and organic enrichment. The second event, from the late Albian to the Santonian period, is recorded in sediments from the Angola Basin and the Sao Paulo Plateau. It appears to have been caused by development of an anoxic oxygen minimum zone at midwater depths. Organic matter sedimentation in the Mesozoic South Atlantic is controlled by geologic, climatic, eustatic, and Oceanographic factors.

Impacts of passive warming chambers on soil parameters in Antarctica

Passive chambers are used to examine the impacts of summer warming in Antarctica but, so far, impacts occurring outside the growing season, or related to extreme temperatures, have not been reported, despite their potentially large biological significance. In this review, we synthesise and discuss the microclimate impacts of passive warming chambers (closed, ventilated and Open Top Chamber-OTC) commonly used in Antarctic terrestrial habitats, paying special attention to seasonal warming, during the growing season and outside, extreme temperatures and freeze-thaw events. Both temperature increases and decreases were recorded throughout the year. Closed chambers caused earlier spring soil thaw (8-28 days) while OTCs delayed soil thaw (3-13 days). Smaller closed chamber types recorded the largest temperature extremes (up to 20°C higher than ambient) and longest periods (up to 11 h) of above ambient extreme temperatures, and even OTCs had above ambient temperature extremes over up to 5 consecutive hours. The frequency of freeze-thaw events was reduced by ~25%. All chamber types experienced extreme temperature ranges that could negatively affect biological responses, while warming during winter could result in depletion of limited metabolic resources. The effects outside the growing season could be as important in driving biological responses as the mean summer warming. We make suggestions for improving season-specific warming simulations and propose that seasonal and changed temperature patterns achieved under climate manipulations should be recognised explicitly in descriptions of treatment effects.

Concentrations of PCBs, DDT and thyroid hormones in gray (Halichoerus grypus) and ringed (Phoca hispida) seals

The high levels of polychlorinated biphenyls (PCBs) and DDT in gray seal (Halichoerus grypus) and ringed seal (Phoca hispida botnica) in the Baltic Sea have been associated with pathological disruptions, including bone lesions and reproductive failures. The underlying environmental and toxicological mechanisms leading to these pathological changes are not yet fully understood. The present study investigated the relationship between the individual contaminant load and bone- and thyroid-related effects in adult gray seals (n = 30) and ringed seals (n = 46) in the highly contaminated Baltic Sea and in reference areas (Sable Island, Canada, and Svalbard, Norway). In the gray seals, multivariate and correlation analyses revealed a clear relationship between circulating 1,25-dihydroxyvitamin D3 (1,25(OH)2D), calcium, phosphate, and thyroid hormone (TH) levels and hepatic PCB and DDT load, which suggests contaminant-mediated disruption of the bone and thyroid homeostasis. Contaminants may depress 1,25(OH)2D levels or lead to hyperthyroidism, which may cause bone resorption. In the ringed seals, associations between circulating 1,25(OH)2D, THs, and hepatic contaminants were less prominent. These results suggest that bone lesions observed in the Baltic gray seals may be associated with contaminant-mediated vitamin D and thyroid disruption.

Geochemistry of tetrapyrrole, carotenoid, and perylene pigments in sediments at DSDP Holes 63-467 and 63-471

Twenty-one core samples from DSDP/IPOD Leg 63 were analyzed for products of chlorophyll diagenesis. In addition to the tetrapyrrole pigments, perylene and carotenoid pigments were isolated and identified. The 16 core samples from the San Miguel Gap site (467) and the five from the Baja California borderland location (471) afforded the unique opportunity of examining tetrapyrrole diagenesis in clay-rich marine sediments that are very high in total organic matter. The chelation reaction, whereby free-base porphyrins give rise to metalloporphyrins (viz., nickel), is well documented within the downhole sequence of sediments from the San Miguel Gap (Site 467). Recognition of unique arrays of highly dealkylated copper and nickel ETIO-porphyrins, exhibiting nearly identical carbonnumber homologies (viz., C-23 to C-30; mode = C-26), enabled subtraction of this component (thought to be derived from an allochthonous source) and thus permitted description of the actual in situ diagenesis of autochthonous chlorophyll derivatives.

Ogranic geochemistry and SST reconstruction for Pliocene and Miocene Madeira Abyssal Plain turbidites

Free and "bound" long-chain alkenones (C37?2 and C37?3) in oxidized and unoxidized sections of four organic matter-rich Pliocene and Miocene Madeira Abyssal Plain turbidites (one from Ocean Drilling Program site 951B and three from site 952A) were analyzed to determine the effect of severe post depositional oxidation on the value of Uk'37. The profiles of both alkenones across the redox boundary show a preferential degradation of the C37?3 compared to the C37?2 compound. Because of the high initial Uk'37 values and the way of calculating the Uk'37 this degradation hardly influences the Uk'37 profiles. However, for lower Uk'37 values, measured selective degradation would increase Uk'37 up to 0.17 units, equivalent to 5°C. For most of the Uk'37 band-width, much smaller degradation already increases Uk'37 beyond the analytical error (0.017 units). Consequently, for interpreting the Uk'37 record in terms of past sea surface temperatures, selective degradation needs serious consideration.