Age determination and grwoth rates of stalagmites and stalactites from the Okshola cave, Fauske, northern Norway

The sensitivity of terrestrial environments to past changes in heat transport is expected to be manifested in Holocene climate proxy records on millennial to seasonal timescales. Stalagmite formation in the Okshola cave near Fauske (northern Norway) began at about 10.4 ka, soon after the valley was deglaciated. Past monitoring of the cave and surface has revealed stable modern conditions with uniform drip rates, relative humidity and temperature. Stable isotope records from two stalagmites provide time-series spanning from c. 10380 yr to AD 1997; a banded, multi-coloured stalagmite (Oks82) was formed between 10380 yr and 5050 yr, whereas a pristine, white stalagmite (FM3) covers the period from ~7500 yr to the present. The stable oxygen isotope (delta18Oc), stable carbon isotope (delta13Cc), and growth rate records are interpreted as showing i) a negative correlation between cave/surface temperature and delta18Oc, ii) a positive correlation between wetness and delta13Cc, and iii) a positive correlation between temperature and growth rate. Following this, the data from Okshola show that the Holocene was characterised by high-variability climate in the early part, low-variability climate in the middle part, and high-variability climate and shifts between two distinct modes in the late part. A total of nine Scandinavian stalagmite delta18Oc records of comparable dating precision are now available for parts or most of the Holocene. None of them show a clear Holocene thermal optimum, suggesting that they are influenced by annual mean temperature (cave temperature) rather than seasonal temperature. For the last 1000 years, delta18Oc values display a depletion-enrichment-depletion pattern commonly interpreted as reflecting the conventional view on climate development for the last millennium. Although the delta18Oc records show similar patterns and amplitudes of change, the main challenges for utilising high-latitude stalagmites as palaeoclimate archives are i) the accuracy of the age models, ii) the ambiguity of the proxy signals, and iii) calibration with monitoring data.

Stable carbon and oxygen isotope record of foraminifera of IODP Site 303-1307

A major tipping point of Earth's history occurred during the mid-Pliocene: the onset of major Northern-Hemisphere Glaciation (NHG) and of pronounced, Quaternary-style cycles of glacial-to-interglacial climates, that contrast with more uniform climates over most of the preceding Cenozoic and continue until today (Zachos et al., 2001, doi:10.1126/science.1059412). The severe deterioration of climate occurred in three steps between 3.2 Ma (warm MIS K3) and 2.7 Ma (glacial MIS G6/4) (Lisiecki and Raymo, 2005, doi:10.1029/2004PA001071). Various models (sensu Driscoll and Haug, 1998, doi:10.1126/science.282.5388.436) and paleoceanographic records (intercalibrated using orbital age control) suggest clear linkages between the onset of NHG and the three steps in the final closure of the Central American Seaways (CAS), deduced from rising salinity differences between Caribbean and the East Pacific. Each closing event led to an enhanced North Atlantic meridional overturning circulation and this strengthened the poleward transport of salt and heat (warmings of +2-3°C) (Bartoli et al., 2005, doi:10.1016/j.epsl.2005.06.020). Also, the closing resulted in a slight rise in the poleward atmospheric moisture transport to northwestern Eurasia (Lunt et al., 2007, doi:10.1007/s00382-007-0265-6), which probably led to an enhanced precipitation and fluvial run-off, lower sea surface salinity (SSS), and an increased sea-ice cover in the Arctic Ocean, hence promoting albedo and the build-up of continental ice sheets. Most important, new evidence shows that the closing of the CAS led to greater steric height of the North Pacific and thus doubled the low-saline Arctic Throughflow from the Bering Strait to the East Greenland Current (EGC). Accordingly, Labrador Sea IODP Site 1307 displays an abrupt but irreversible EGC cooling of 6°C and freshening by ~2 psu from 3.25/3.16-3.00 Ma, right after the first but still reversible attempt of closing the CAS.

Dust flux records from the Subarctic North Pacific

We present a new record of eolian dust flux to the western Subarctic North Pacific (SNP) covering the past 27000 years based on a core from the Detroit Seamount. Comparing the SNP dust record to the NGRIP ice core record shows significant differences in the amplitude of dust changes to the two regions during the last deglaciation, while the timing of abrupt changes is synchronous. If dust deposition in the SNP faithfully records its mobilization in East Asian source regions, then the difference in the relative amplitude must reflect climate-related changes in atmospheric dust transport to Greenland. Based on the synchronicity in the timing of dust changes in the SNP and Greenland, we tie abrupt deglacial transitions in the 230Th-normalized 4He flux record to corresponding transitions in the well-dated NGRIP dust flux record to provide a new chronostratigraphic technique for marine sediments from the SNP. Results from this technique are complemented by radiocarbon dating, which allows us to independently constrain radiocarbon paleoreservoir ages. We find paleoreservoir ages of 745 ± 140 yr at 11653 yr BP, 680 ± 228 yr at 14630 yr BP and 790 ± 498 yr at 23290 yr BP. Our reconstructed paleoreservoir ages are consistent with modern surface water reservoir ages in the western SNP. Good temporal synchronicity between eolian dust records from the Subantarctic Atlantic and equatorial Pacific and the ice core record from Antarctica supports the reliability of the proposed dust tuning method to be used more widely in other global ocean regions.

Varved sediments of the Arabian Sea

The upper Holocene marine section from a kasten core taken from the oxygen minimum zone off Karachi (Pakistan) at water depth 700 m contains continuously laminated sediments with a sedimentation rate of 1.2 mm/yr and a unique record of monsoonal climatic variability covering the past 5000 years. Our chronostratigraphy is based on varve counts verified by conventional and AMS14C dating. Individual hemipelagic varve couplets are about 0.8-1.5 mm thick, with light-colored terrigenous laminae (A) deposited mainly during the winter monsoon alternating with dark-colored laminae (B) rich in marine organic matter, coccoliths, and fish debris that reflect deposition during the high-productivity season of the late summer monsoon (August-October). Precipitation and river runoff appear to control varve thickness and turbidite frequency. We infer that precipitation decreased in the river watershed (indicated by thinning varves) after 3500-4000 yr B.P. This is about the time of increasing aridification in the Near East and Middle East, as documented by decreasing Nile River runoff data and lake-level lowstands between Turkey and northwestern India. This precipitation pattern continued until today with precipitation minima about 2200-1900 yr B.P., 1000 yr B.P., and in the late Middle Ages (700-400 yr B.P.), and precipitation maxima in the intervening periods. As documented by spectral analysis, the thickness of varve couplets responds to the average length of a 250-yr cycle, a 125-yr cycle, the Gleissberg cycle of solar activity (95 yr), and a 56-yr cycle of unknown origin. Higher frequency cycles are also present at 45, 39, 29-31, and 14 yr. The sedimentary gray-value also shows strong variability in the 55-yr band plus a 31-yr cycle. Because high-frequency cyclicity in the ENSO band (ca. 3.5 and 5 yr) is only weakly expressed, our data do not support a straightforward interaction of the Pacific ENSO with the monsoon-driven climate system of the Arabian Sea.

Nd, Pb, and Be isotopes of ferromanaganese crusts of the South Pacific

The application of radiogenic isotopes to the study of Cenozoic circulation patterns in the South Pacific Ocean has been hampered by the fact that records from only equatorial Pacific deep water have been available. We present new Pb and Nd isotope time series for two ferromanganese crusts that grew from equatorial Pacific bottom water (D137-01, 'Nova', 7219 m water depth) and southwest Pacific deep water (63KD, 'Tasman', 1700 m water depth). The crusts were dated using 10Be/9Be ratios combined with constant Co-flux dating and yield time series for the past 38 and 23 Myr, respectively. The surface Nd and Pb isotope distributions are consistent with the present-day circulation pattern, and therefore the new records are considered suitable to reconstruct Eocene through Miocene paleoceanography for the South Pacific. The isotope time series of crusts Nova and Tasman suggest that equatorial Pacific deep water and waters from the Southern Ocean supplied the dissolved trace metals to both sites over the past 38 Myr. Changes in the isotopic composition of crust Nova are interpreted to reflect development of the Antarctic Circumpolar Current and changes in Pacific deep water circulation caused by the build up of the East Antarctic Ice Sheet. The Nd isotopic composition of the shallower water site in the southwest Pacific appears to have been more sensitive to circulation changes resulting from closure of the Indonesian seaway.

Abundance of phytoplankton, heterotrophic nanoflagellates and bacteria through the water column at time series station L4 in the Western English Channel. 2007-2011

The marine laboratories in Plymouth have sampled at two principle sites in the Western English Channel for over a century in open-shelf (station E1; 50° 02'N, 4° 22'W) and coastal (station L4; 50° 15'N, 4° 13'W) waters. These stations are seasonally stratified from late-April until September, and the variable biological response is regulated by subtle variations in temperature, light, nutrients and meteorology. Station L4 is characterized by summer nutrient depletion, although intense summer precipitation, increasing riverine input to the system, results in pulses of increased nitrate concentration and surface freshening. The winter nutrient concentrations at E1 are consistent with an open-shelf site. Both stations have a spring and autumn phytoplankton bloom; at station E1, the autumn bloom tends to dominate in terms of chlorophyll concentration. The last two decades have seen a warming of around 0.6°C per decade, and this is superimposed on several periods of warming and cooling over the past century. In general, over the Western English Channel domain, the end of the 20th century was around 0.5°C warmer than the first half of the century. The warming magnitude and trend is consistent with other stations across the north-west European Shelf and occurred during a period of reduced wind stress and increased levels of insolation (+20%); these are both correlated with the larger scale climatic forcing of the North Atlantic Oscillation.

Studies of the microbial diversity on analyzed samples from from Peru Margin, Equatorial Pacific, Hydrate Ridge, and Juan de Fuca Ridge

Marine sediments harbor an enormous quantity of microorganisms, including a multitude of novel species. The habitable zone of the marine sediment column begins at the sediment-water interface and probably extends to depths of several thousands of meters. Studies of the microbial diversity in this ecosystem have mostly relied on molecular biological techniques. We used a complementary method - analysis of intact polar membrane lipids - to characterize the in-situ microbial community in sediments covering a wide range of environmental conditions from Peru Margin, Equatorial Pacific, Hydrate Ridge, and Juan de Fuca Ridge. Bacterial and eukaryotic phospholipids were only detected in surface sediments from the Peru Margin. In contrast, deeply buried sediments, independent of their geographic location, were dominated by archaeal diether and tetraether lipids with various polar head groups and core lipids. We compared ring distributions of archaeal tetraether lipids derived from polar glycosidic precursors with those that are present as core lipids. The distributions of these related compound pools were distinct, suggestive of different archaeal sources, i.e., the polar compounds derive from sedimentary communities and the core lipids are fossil remnants from planktonic communities with possible admixtures of decayed sedimentary archaea. This in-situ production of distinct archaeal lipid populations potentially affects applications of the TEX86 paleotemperature proxy as demonstrated by offsets in reconstructed temperatures between both pools. We evaluated how varying cell and lipid stabilities will influence the sedimentary pool by using a box-model. The results are consistent with (i) a requirement of continuous inputs of freshly synthesized lipids in subsurface sediments for explaining the observed distribution of intact polar lipids, and (ii) decreasing lipid inputs with increasing burial depth.

Lithology, biostratigraphy, and geochemistry of the Black Sea sediments, DSDP Leg 42 (pt. 2) data

The monograph presents results of deep-sea drilling in the Black Sea carried out in 1975. Detailed lithological, biostratigraphic and geochemical studies of Miocene-Holocene sediments have been carried out by specialists from institutes of the USSR Academy of Sciences, Moscow State University and other organizations. Drilling results are compared with geophysical data. Geological history of the Black Sea basin is considered as well.

Sedimentology and stable oxygen isotope ratios of foraminifera from cores of the Porcupine Seabight, Northeast Atlantic

Large carbonate mound structures have been discovered in the northern Porcupine Seabight (Northeast Atlantic) at depths between 600 and 1000 m. These mounds are associated with the growth of deep-sea corals Lophelia pertusa and Madrepra oculata. In this study, three sediment cores have been analysed. They are from locations close to Propeller Mound, a 150 m high ridge-like feature covered with a cold-water coral ecosystem at its upper flanks. The investigations are concentrated on grain-size analyses, carbon measurements and on the visual description of the cores and computer tomographic images, to evaluate sediment content and structure. The cores portray the depositional history of the past ~31 kyr BP, mainly controlled by sea-level fluctuations and the climate regime with the advance and retreat of the Irish Ice Sheet onto the Irish Mainland Shelf. A first advance of glaciers is indicated by a turbiditic release slightly older than 31 kyr BP, coherent with Heinrich event 3 deposition. During Late Marine Isotope Stage 3 (MIS 3) and MIS 2 shelf erosion prevailed with abundant gravity flows and turbidity currents. A change from glaciomarine to hemipelagic contourite sedimentation during the onset of the Holocene indicates the establishment of the strong, present-day hydrodynamic regime at intermediate depths. The general decrease in accumulation of sediments with decreasing distance towards Propeller Mound suggests that currents (turbidity currents, gravity flows, bottom currents) had a generally stronger impact on the sediment accumulation at the mound base for the past ~31 kyr BP, respectively.

Bulk geochemical analysis and planktonic foraminifera of sediment core GeoB7112-5

A multivariable approach utilising bulk sediment, planktonic Foraminifera and siliceous phytoplankton has been used to reconstruct rapid variations in palaeoproductivity in the Peru-Chile Current System off northern Chile for the past 19000 cal. yr. During the early deglaciation (19000-16000 cal. yr BP), our data point to strongest upwelling intensity and highest productivity of the past 19 000 cal. yr. The late deglaciation (16000-13000 cal. yr BP) is characterised by a major change in the oceanographic setting, warmer water masses and weaker upwelling at the study site. Lowest productivity and weakest upwelling intensity are observed from the early to the middle Holocene (13000-4000 cal. yr BP), and the beginning of the late Holocene (<4000 cal. yr BP) is marked by increasing productivity, mainly driven by silicate-producing organisms. Changes in the productivity and upwelling intensity in our record may have resulted from a large-scale compression and/or displacement of the South Pacific subtropical gyre during more productive periods, in line with a northward extension of the Antarctic Circumpolar Current and increased advection of Antarctic water masses with the Peru-Chile Current. The corresponding increase in hemispheric thermal gradient and wind stress induced stronger upwelling. During the periods of lower productivity, this scenario probably reversed.

Geochemical parameters of sediments and water of the Black Sea, data of Cruise 8 of R/V Vityaz-2

The book presents results of comprehensive geological investigations carried out during Cruise 8 of R/V "Vityaz-2" to the western part of the Black Sea in 1984. Systematic studies in the Black Sea during about hundred years have not weakened interest in the sea. Lithological and geochemical studies of sediments in estuarine areas of the Danube and the Kyzyl-Irmak rivers, as well as in adjacent parts of the deep sea and some other areas were the main aims of the cruise. Data on morphological structures of river fans, lithologic and chemical compositions of sediments in the fans and their areal distribution, forms of occurrence of chemical elements, role of organic matter and gases in sedimentation and diagenesis are given and discussed in the book.

Stable oxygen isotopes of calcite veins in ODP Site 146-892

In situ secondary ionization mass spectrometry (SIMS) analyses of oxygen isotopes in authigenic calcite veins were obtained from an active thrust fault system drilled at Ocean Drilling Program (ODP) Site 892 (44°40.4'N, 125°07.1'W) along the Cascadia subduction margin. The average d18OPDB value of all samples is -9.9 per mil and the values are the lowest of any measured in active accretionary prisms. Ranges in individual veins can be as much as 19.6 per mil. There is an isotopic stratigraphy related to the structural stratigraphy. Mean isotope values in the hanging wall, thrust, and footwall are -14.4 per mil, -9.5 per mil, and -5.2 per mil, respectively. Several veins and crosscutting vein sequences show a general trend from lower to higher d18O values over time. Isotopic and textural data indicate several veins formed by a crack-seal mechanism and growth into open fractures. The best explanation for the strong 18O depletions is periodic rapid flow from 2-3 km deeper in the prism. Relatively narrow isotopic ranges for most veins suggest that fluids were derived from a similar source depth for each episode of fluid pulse and calcite crystallization. Structural and mass balance considerations are consistent with a record preserved in the veins of ten to hundreds of thousands of years. The fluid pulses may relate to periodic large earthquake events such as those recognized in the paleoseismicity records from the Cascadia margin.

Petrography and geochemistry of organic matter at DSDP Holes 80-549 and 80-550B

Three lower Barremian to middle/upper Cenomanian samples from DSDP Hole 549 and three lower Cenomanian to lower Maestrichtian samples from DSDP Hole 550B were investigated by organic geochemical and organic petrographic methods. The samples came from wells drilled in the area of the Goban Spur in the northeastern Atlantic; they represent gray to greenish gray carbonaceous mud or siltstones from the deeper parts of the Cretaceous sequences penetrated and light-colored chalks from the shallower ones. The total amount of organic carbon is below 1% in all samples; it is especially low in the Cenomanian to Maestrichtian chalks. Terrigenous organic matter predominates; only the Barremian sample shows a moderate number of marine phytoclasts. As indicated by several parameters, the maturity of the organic matter is low, corresponding to about 0.4% vitrinite reflectance.

Paleoceanographic record since 13kyr BP of sediment core LaPAS-KF02

In this paper we present a paleoceanographic reconstruction of the southwestern South Atlantic for the past 13 kyr based on faunal and isotopic analysis of planktonic foraminifera from a high-resolution core retrieved at the South Brazil Bight continental slope. Our record indicates that oceanographic changes in the southwestern South Atlantic during the onset of the Holocene were comparable in strength to those that occurred during the Younger Dryas. Full interglacial conditions started abruptly after 8.2 kyr BP with a sharp change in faunal composition and surface hydrography (SST and SSS). Part of the observed events may be explained in terms of changes in thermohaline circulation while the other part suggests a dominant role of winds. Our data indicate that during the Early Holocene upwelling was significantly strengthened in the South Brazil Bight promoting high productivity and preventing the establishment of the typically interglacial menardiiform species. In general terms, oceanographic changes recorded by core KF02 occurred in synchrony with Antarctica's climate.

Concentrations of natural and anthropogenic organohalogens in water and air samples in the Canadian Arctic during IPY (2007-2008)

Shipboard measurements of organohalogen compounds in air and surface seawater were conducted in the Canadian Arctic in 2007-2008. Study areas included the Labrador Sea, Hudson Bay, and the southern Beaufort Sea. High volume air samples were collected at deck level (6 m), while low volume samples were taken at 1 and 15 m above the water or ice surface. Water samples were taken within 7 m. Water concentration ranges (pg/L) were as follows: alpha-hexachlorocyclohexane (alpha-HCH) 465-1013, gamma-HCH 150-254, hexachlorobenzene (HCB) 4.0-6.4, 2,4-dibromoanisole (DBA) 8.5-38, and 2,4,6-tribromoanisole (TBA) 4.7-163. Air concentration ranges (pg/m**3) were as follows: alpha-HCH 7.5-48, gamma-HCH 2.1-7.7, HCB 48-71, DBA 4.8-25, and TBA 6.4-39. Fugacity gradients predicted net deposition of HCB in all areas, while exchange directions varied for the other chemicals by season and locations. Net evasion of alpha-HCH from Hudson Bay and the Beaufort Sea during open water conditions was shown by air concentrations that averaged 14% higher at 1 m than 15 m. No significant difference between the two heights was found over ice cover. The alpha-HCH in air over the Beaufort Sea was racemic in winter (mean enantiomer fraction, EF = 0.504 ± 0.008) and nonracemic in late spring-early summer (mean EF = 0.476 ± 0.010). This decrease in EF was accompanied by a rise in air concentrations due to volatilization of nonracemic alpha-HCH from surface water (EF = 0.457 ± 0.019). Fluxes of chemicals during the southern Beaufort Sea open water season (i.e., Leg 9) were estimated using the Whitman two-film model, where volatilization fluxes are positive and deposition fluxes are negative. The means ± SD (and ranges) of net fluxes (ng/m**2/d) were as follows: alpha-HCH 6.8 ± 3.2 (2.7-13), gamma-HCH 0.76 ± 0.40 (0.26-1.4), HCB -9.6 ± 2.7 (-6.1 to -15), DBA 1.2 ± 0.69 (0.04-2.0), and TBA 0.46 ± 1.1 ng/m**2/d (-1.6 to 2.0).