Geochemical composition of surface snow, ice and debris from glaciers in Norway, Nepal and New Zealand

Alpine glacier samples were collected in four contrasting regions to measure supraglacial dust and debris geochemical composition. A total of 70 surface glacier ice, snow and debris samples were collected in 2009 and 2010 in Svalbard, Norway, Nepal and New Zealand. Trace elemental abundances in snow and ice samples were measured via inductively coupled plasma mass spectrometry (ICP-MS). Supraglacial debris mineral, bulk oxide and trace element composition were determined via X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF). A total of 45 elements and 10 oxide compound abundances are reported. The uniform data collection procedure, analytical measurement methods and geochemical comparison techniques are used to evaluate supraglacial dust and debris composition variability in the contrasting glacier study regions. Elemental abundances revealed sea salt aerosol and metal enrichment in Svalbard, low levels of crustal dust and marine influences to southern Norway, high crustal dust and anthropogenic enrichment in the Khumbu Himalayas, and sulfur and metals attributed to quiescent degassing and volcanic activity in northern New Zealand. Rare earth element and Al/Ti elemental ratios demonstrated distinct provenance of particulates in each study region. Ca/S elemental ratio data showed seasonal denudation in Svalbard and Norway. Ablation season atmospheric particulate transport trajectories were mapped in each of the study regions and suggest provenance pathways. The in situ data presented provides first order glacier surface geochemical variability as measured from four diverse alpine glacier regions. This geochemical surface glacier data is relevant to glaciologic ablation rate understanding as well as satellite atmospheric and land-surface mapping techniques currently in development.

Composition of Upper Quaternary bottom sediments from the Syrian area of the Mediterranean Sea

Results of a lithological study of bottom sediments in the Syrian region of the Mediterranean Sea during Cruise 27 of R/V Vityaz (1993) are reported. Suspended sediment discharge of the Nile River are of the greatest importance for terrigenous sedimentation in the SE part of the Mediterranean Sea, especially in deep-sea areas. Suspended load entering from the Syrian catchment area plays an important role in formation of recent shelf and slope deposits. Supply of aerosols from Syrian and Arabian deserts was distinguished by the patchiness of surface distribution of quartz. During Late Quaternary accumulation of terrigenous material supplied from both the Syrian and the Nile drainage areas was irregular. Sedimentation was remarkably enhanced during sapropel formation 7000-9000 years BP.

Surface exposure ages of samples obtained from Reedy Glacier, Antarctica

Fresh deposits above the margins of Reedy Glacier show that maximum ice levels during the last glaciation were several hundred meters above present near the glacier mouth and converged to less than 60 m above the present-day surface at the head of the glacier. Exposure ages of samples from five sites along its margin show that Reedy Glacier and its tributaries thickened asynchronously between 17 and 7 kyr BP At the Quartz Hills, located midway along the glacier, maximum ice levels were reached during the period 17-14 kyr BP. Farther up-glacier the ice surface reached its maximum elevation more recently: 14.7-10.2 kyr BP at the Caloplaca Hills; 9.1-7.7 kyr BP at Mims Spur; and around 7 kyr BP at Hatcher Bluffs. We attribute this time-transgressive behavior to two different processes: At the glacier mouth, growth of grounded ice and subsequent deglaciation in the Ross Sea embayment caused a wave of thickening and then thinning to propagate up-glacier. During the Lateglacial and Holocene, increased snow accumulation on the East Antarctic Ice Sheet caused transient thickening at the head of the glacier. An important result of this work is that moraines deposited along Reedy Glacier during the last ice age cannot be correlated to reconstruct a single glacial maximum longitudinal profile. The profile steepened during deglaciation of the Ross Sea, thinning at the Quartz Hills after 13 kyr BP while thickening upstream. Near its confluence with Mercer Ice Stream, rapid thinning beginning prior to 7-8 kyr BP reduced the level of Reedy Glacier to close to its present level. Thinning over the past 1000 years has lowered the glacier by less than 20 m.

Rare earth and other element contents in surface layer bottom sediments and ferromanganese nodules along the Transatlantic profile

Behavior of rare earth elements (REE) and Th is studied along the Transatlantic transect at 22°N. It is shown that both REE and Th contents relative to Al (the most lithogenic element) increase toward the pelagic region. The increasing trend becomes more complicated due to variations in content of biogenic calcium carbonate that acts as a diluting component in sediments. REE composition varies symmetrically relative to the Mid-Atlantic Ridge (MAR) emphasizing weak hydrothermal influence on sediments of the ridge axis, although the well-known criteria for hydrothermal contribution, such as Al/(Al+Mn+Fe) and (Fe+Mn)/Ti, do not reach critical values. Variations in REE content and composition allowed to distinguish the following five sediment zones in the transect: (I) terrigenous sediments of the Nares abyssal plain; (II) pelagic sediments of the North American Basin; (III) carbonate ooze of the MAR axis; (IV) pelagic sediments of the Canary Basin; and (V) terrigenous clay and calcareous mud of the African continental slope and slope base. Ferromanganese nodules of the hydrogenous type with extremely high Ce (up to 1801 ppm) and Th (up to 138 ppm) contents occur in pelagic sediments. It is ascertained that P, REE, and Th contents depend on Fe content in Atlantic sediments. Therefore, one can suggest that only minor amount of phosphorus is bound with bone debris. Low concentration of bone debris phosphorus is a result of relatively high sedimentation rates in the Atlantic Ocean, as compared with those in pelagic regions of the Pacific Ocean.

Composition of surface layer bottom sediments from the Chukchi Sea

Abundance of noble metals and bulk chemical composition have been studied in bottom sediments of the Chukchi Sea. Distribution of noble metals and their correlation with major and trace elements in the sediments have been analyzed using multicomponent statistics. It was established that average contents of noble metals in the bottom sediments of the Chukchi Sea significantly exceed those both in shelf terrigenous sediments and stratisphere. Osmium and iridium enrich mixed and pelitic sediments relative to shallow-water sediments and their influx is presumably determined by erosion of coastal and bottom unconsolidated deposits. High Ag, Ru, Au, and Pt contents were identified in clayey sediments enriched in biogenic elements in the some areas of the Southern Chukchi plain (Chukchi Sea) confined to intersection zones of submeridional and sublatitudinal structures of the graben-rift system, which formed in Mesozoic and activated in Late Cenozoic.

Geochemical composition of surface sediments in the Trondheimsfjord, central Norway

High sedimentation rates in fjords provide excellent possibilities for high resolution sedimentary and geochemical records over the Holocene. As a baseline for an improved interpretation of geochemical data from fjord sediment cores, this study aims to investigate the inorganic/organic geochemistry of surface sediments and to identify geochemical proxies for terrestrial input and river discharge in the Trondheimsfjord, central Norway. Sixty evenly distributed surface sediment samples were analysed for their elemental composition, total organic carbon (Corg), nitrogen (Norg) and organic carbon stable isotopes (d13Corg), bulk mineral composition and grain size distribution. Our results indicate carbonate marine productivity to be the main CaCO3 source. Also, a strong decreasing gradient of marine-derived organic matter from the entrance towards the fjord inner part is consistent with modern primary production data. We show that the origin of the organic matter as well as the distribution of CaCO3 in Trondheimsfjord sediments can be used as a proxy for the variable inflow of Atlantic water and changes in river runoff. Furthermore, the comparison of grain size independent Al-based trace element ratios with geochemical analysis from terrigenous sediments and bedrocks provides evidence that the distribution of K/Al, Ni/Al and K/Ni in the fjord sediments reflect regional sources of K and Ni in the northern and southern drainage basin of the Trondheimsfjord. Applying these findings to temporally well-constrained sediment records will provide important insights into both the palaeoenvironmental changes of the hinterland and the palaeoceanographic modifications in the Norwegian Sea as response to rapid climate changes and associated feedback mechanisms.

Sea surface temperature reconstruction for ODP Hole 178-1098B

The disintegration of ice shelves, reduced sea-ice and glacier extent, and shifting ecological zones observed around Antarctica (Cook et al., 2005, doi:10.1126/science.1104235; Stammerjohn et al., 2008, doi:10.1016/j.dsr2.2008.04.026) highlight the impact of recent atmospheric (Steig et al., 2009, doi:10.1038/nature07669) and oceanic warming (Gille, 2002, doi:10.1126/science.1065863) on the cryosphere. Observations (Cook et al., 2005, doi:10.1126/science.1104235; Stammerjohn et al., 2008, doi:10.1016/j.dsr2.2008.04.026) and models (Pollard and DeConto, 2009, doi:10.1038/nature07809) suggest that oceanic and atmospheric temperature variations at Antarctica's margins affect global cryosphere stability, ocean circulation, sea levels and carbon cycling. In particular, recent climate changes on the Antarctic Peninsula have been dramatic, yet the Holocene climate variability of this region is largely unknown, limiting our ability to evaluate ongoing changes within the context of historical variability and underlying forcing mechanisms. Here we show that surface ocean temperatures at the continental margin of the western Antarctic Peninsula cooled by 3-4 °C over the past 12,000?years, tracking the Holocene decline of local (65° S) spring insolation. Our results, based on TEX86 sea surface temperature (SST) proxy evidence from a marine sediment core, indicate the importance of regional summer duration as a driver of Antarctic seasonal sea-ice fluctuations (Huybers and Denton, 2008, doi:10.1038/ngeo311). On millennial timescales, abrupt SST fluctuations of 2-4 °C coincide with globally recognized climate variability (Mayewski et al., 2004, doi:10.1016/j.yqres.2004.07.001). Similarities between our SSTs, Southern Hemisphere westerly wind reconstructions (Moreno et al., 2010, doi:10.1130/G30962.1) and El Niño/Southern Oscillation variability (Conroy et al., 2008, doi:10.1016/j.quascirev.2008.02.015) indicate that present climate teleconnections between the tropical Pacific Ocean and the western Antarctic Peninsula (Yuan et al., 2004, doi:10.1017/S0954102004002238) strengthened late in the Holocene epoch. We conclude that during the Holocene, Southern Ocean temperatures at the western Antarctic Peninsula margin were tied to changes in the position of the westerlies, which have a critical role in global carbon cycling (Moreno et al., 2010, doi:10.1130/G30962.1; Anderson et al., 2009, doi:10.1126/science.1167441).

Depth profiles of pore-water and solid-phase constituents, respiration rates and grain size distribution in sediments of the Clarion-Clipperton Fracture Zone

Manganese nodules of the Clarion-Clipperton Fracture Zone (CCFZ) in the NE Pacific Ocean are highly enriched in Ni, Cu, Co, Mo and rare-earth elements, and thus may be the subject of future mining operations. Elucidating the depositional and biogeochemical processes that contribute to nodule formation, as well as the respective redox environment in both, water column and sediment, supports our ability to locate future nodule deposits and evaluates the potential ecological and environmental effects of future deep-sea mining. For these purposes we evaluated the local hydrodynamics and pore-water geochemistry with respect to the nodule coverage at four sites in the eastern CCFZ. Furthermore, we carried out selective leaching experiments at these sites in order to assess the potential mobility of Mn in the solid phase, and compared them with the spatial variations in sedimentation rates. We found that the oxygen penetration depth is 180 - 300 cm at all four sites, while reduction of Mn and NO3- is only significant below the oxygen penetration depth at sites with small or no nodules on the sediment surface. At the site without nodules, potential microbial respiration rates, determined by incubation experiments using 14C-labelled acetate, are slightly higher than at sites with nodules. Leaching experiments showed that surface sediments covered with big or medium-sized nodules are enriched in mobilizable Mn. Our deep oxygen measurements and pore-water data suggest that hydrogenetic and oxic-diagenetic processes control the present-day nodule growth at these sites, since free manganese from deeper sediments is unable to reach the sediment surface. We propose that the observed strong lateral contrasts in nodule size and abundance are sensitive to sedimentation rates, which in turn, are controlled by small-scale variations in seafloor topography and bottom-water current intensity.

Chemistry of altered basaltic glass shards and zeolites of volcaniclastic sediments from ODP Hole 157-953C

Trace element concentrations of altered basaltic glass shards (layer silicates) and zeolites in volcaniclastic sediments drilled in the volcanic apron northeast of Gran Canaria during Ocean Drilling Program (ODP) leg 157 document variable element mobilities during low-temperature alteration processes in a marine environment. Clay minerals (saponite, montmorillonite, smectite) replacing volcanic glass particles are enriched in transition metals and rare earth elements (REE). The degree of retention of REE within the alteration products of the basaltic glass is correlated with the field strength of the cations. The high field-strength elements are preferentially retained or enriched in the alteration products by sorption through clay minerals. Most trace elements are enriched in a boundary layer close to the interface mineral-altered glass. This boundary layer has a key function for the physico-chemical conditions of the subsequent alteration process by providing a large reactive surface and by lowering the fluid permeability. The release of most elements is buffered by incorporation into secondary precipitates (sodium-rich zeolites, phillipsite, Fe- and Mn-oxides) as shown by calculated distribution coefficients between altered glasses and authigenic minerals. Chemical fluxes change from an open to a closed system behavior during prograde low-temperature alteration of volcaniclastic sediments with no significant trace metal flux from the sediment to the water column.

(Table 1) Redox potential and chemical element contents in CaCO3 and amorphous silica free matter in surface layer bottom sediments of the Pacific Ocean from Hawaiian Islands to Mexico coast

Distribution of Fe, Mn, P, Ti, Cu, Ni, Co, V, Cr, W, Mo, and As in the surface sediment layer on the section from the Hawaiian Islands to the coast of Mexico (Mexico section) is studied. Contents of all studied elements increase from biogenic-terrigenous sediments off the coast of Mexico to pelagic red clays of the Northeast Basin, and more sharply for mobile elements - Mn, Mo, Cu, Ni, Co, and As. In near Hawaii sediments rich in coarsely fragmented volcanic-terrigenous and pyroclastic material of basaltic composition with high contents of Ti, Fe, V, Cr, W, and P, contents of these elements increase sharply, and contents of Mn, Mo, Ni, Co, and Cu for the same reason decrease sharply in comparison with red clay. Abnormally high contents of Mn, Mo, Cu, Ni, Co, and As in the upper layer of hemipelagic and transition sediments of the Mexico section result from diagenetic redistribution and their accumulation on the surface. Processes of diagenetic redistribution in hemipelagic and transition sediment mass of the Mexico section are more rapid than in similar sediments of the Japan section due lower sedimentation rates and higher initial concentrations of Mn. Basic similarity of element distribution regularities in sediments of Japan and Mexico sections is shown.

Sea surface temperature reconstruction of sediment profile W8709A-8

Assessment of changes in surface ocean conditions, in particular, sea-surface temperature (SST), is essential to understand long-term changes in climate especially in regions where continental climate is strongly influenced by oceanographic processes. To evaluate changes in SST in the northeast Pacific, we have analyzed long-chain alkenones of prymnesiophyte origin at 38 depths in a piston and associated trigger core collected beneath the contemporary core of the California Current System at 42°N, ~270 km off the coast of Oregon/California. The samples span 30,000 years of deposition at this location. Unsaturation patterns (UK'37) in the alkenone series display a statistically significant difference (p <<0.001) between interglacial (0.44 ± 0.02, n = 11) and glacial (0.29 ± 0.04, n = 20) intervals of the cores. Detailed examination of other compositional features of the C37, C38, C39 alkenone series and a related C36 alkenoate series measured downcore suggests the published UK'37 - temperature calibration (UK'37 = 0.034 * T + 0.039 ) , defined for cultures of a strain of Emiliania huxleyi isolated from the subarctic Pacific, provides best estimates of winter SST at our study site. This inference is purely statistical and does not imply, however, that the phytoplankton source of these biomarkers is most productive in winter or at the ocean surface. The temperature record for UK'37 implies (1) an ~4°C shift occurred in winter SST from ~7.5 ± 1.1°C at the last glacial maximum to ~11.7 ± 0.7°C in the present interglacial period, and (2) this warming trend was confined to the time frame 14-10 Ka within the glacial to interglacial transition period. These conclusions are corroborated entirely by results from an independent SST transformation of radiolarian species assemblage data obtained from the same core materials.