27 resultados para Blooming Grove


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Pollen analytical investigations of glacier ice from the Kesselwandferner in the Ötztal Alps, Tyrol, generally confirmed the palynologycal findings of Vareschi (1942) and brought new results. Annual layers were found which distinguish themselves by an increased content of Pl:cea pollen according to extreme Picea-blooming years. These can be used as "guiding horizons" in the firn-area of the glaciers. Long distance transport of African pollen (Ephedra) was proved. The absolute average pollen rain in 3300 m was determined by 28.000 pollen grains per year and dm**2. The investigation of fens near glaciers made it possible to determine the oscillations of the tree-line and the forest-linc and to date them by 0-14. These oscillations could be connected with moraines also dated by 0-14. Oscillations of the forest-line and thus probably glacier oscillations, too, could be determined for the period from 6700 to 6000 B.C. and the periods about 4500, 2600 and 1600 B.C.

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Chemical group composition of particulate lipids from the intermediate zone between the Kara and Laptev Seas is studied by thin-layer chromatography with flame ionization detection (IATROSCAN TH-10). Hydrocarbons and complex polar lipids similar to those found in the previously studied southeastern area of the Kara Sea are basic components of particulate lipids. High content of triglycerides in the upper layers of the water mass north of the Severnaya Zemlya Islands is a characteristic feature of group composition of particulate lipids. Distribution of triglycerides correlates with localization of the ice cover boundary and complies with process of phytoplankton blooming in the ice edge zone. Distribution of lipid concentration depends on water stratification in the intermediate zone between the Kara and Laptev Seas.

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A dynamic crystallization study was undertaken to provide a framework for linking the textural variations observed in the Hole 648B lavas with the size and morphology of cooling units inferred from drilling and submersible observation. The textures produced in cooling rate experiments carried out using a Serocki lava (ALV-1690-20) are comparable to the groundmass textural characteristics of lavas from Serocki volcano. The results of the dynamic crystallization study provide a quantitative link between texture, cooling rate, and eruption temperature. The maximum half-width of cooling units estimated from textural characteristics is on the order of 3 m, a value consistent with constraints from drilling and submersible observation. Textural characteristics indicate that the temperature from which cooling began was slightly above the liquidus. The relation between cooling rate and texture are also tested on a drill core sample of basalt of similar composition from a 9-m-thick flow in DSDP Hole 396B.

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Sea-surface temperatures (SSTs) in the Sea of Okhotsk were reconstructed based on alkenone unsaturation indices in two sediment cores. Alkenone-SSTs were found to range from 3 to 9 °C over the last 85 kyr with higher SST values in warm periods: Holocene and the oxygen isotope stage (OIS) 5a. In the last glacial periods (OIS 4 and 3), average alkenone SST was estimated to be 4 °C, which was 4 °C lower than the Holocene on average. However, alkenone SSTs around the last glacial maximum (LGM) are as high as those of the Holocene. The variation patterns of U37K' in the Okhotsk Sea were found to be similar to those reported in the Sea of Japan [Org. Chem. 32 (2001) 57] over the last 30 kyr, although the SSTs were lower in the Sea of Okhotsk. The higher U37K' values around the LGM may be a rather common phenomenon in semi-closed marginal seas such as the Japan Sea and the Okhotsk Sea, which are both adjacent to the northwestern Pacific. Such an anomaly in the LGM may have been caused by either a seasonal shift of coccolith blooming or a contribution from a different strain or species that produces alkenones

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The success of any efforts to determine the effects of climate change on marine ecosystems depends on understanding in the first instance the natural variations, which contemporarily occur on the interannual and shorter time scales. Here we present results on the environmental controls of zooplankton distribution patterns and behaviour in the eastern Weddell Sea, Southern Ocean. Zooplankton abundance and vertical migration are derived from the mean volume backscattering strength (MVBS) and the vertical velocity measured by moored acoustic Doppler current profilers (ADCPs), which were deployed simultaneously at 64°S, 66.5°S and 69°S along the Greenwich Meridian from February, 2005, until March, 2008. While these time series span a period of full three years they resolve hourly changes. A highly persistent behavioural pattern found at all three mooring locations is the synchronous diel vertical migration (DVM) of two distinct groups of zooplankton that migrate between a deep residence depth during daytime and a shallow depth during nighttime. The DVM was closely coupled to the astronomical daylight cycles. However, while the DVM was symmetric around local noon, the annual modulation of the DVM was clearly asymmetric around winter solstice or summer solstice, respectively, at all three mooring sites. DVM at our observation sites persisted throughout winter, even at the highest latitude exposed to the polar night. Since the magnitude as well as the relative rate of change of illumination is minimal at this time, we propose that the ultimate causes of DVM separated from the light-mediated proximal cue that coordinates it. In all three years, a marked change in the migration behaviour occurred in late spring (late October/early November), when DVM ceased. The complete suspension of DVM after early November is possibly caused by the combination of two factors: (1) increased availability of food in the surface mixed layer provided by the phytoplankton spring bloom, and (2) vanishing diurnal enhancement of the threat from visually oriented predators when the illumination is quasi-continuous during the polar and subpolar summer. Zooplankton abundance in the water column, estimated as the mean MVBS in the depth range 50-300 m, was highest end of summer and lowest mid to end winter on the average annual cycle. However, zooplankton abundance varied several-fold between years and between locations. Based on satellite and in situ data of chlorophyll and sea ice as well as on hydrographic measurements, the interannual and spatial variations of zooplankton mean abundance can be explained by differences in the magnitude of the phytoplankton spring bloom, which develops during the seasonal sea ice retreat. Whereas the vernal ice melt appears necessary to stimulate the blooming of phytoplankton, it is not the determinator of the blooms magnitude, its areal extent and duration. A possible explanation for the limitation of the phytoplankton bloom in some years is top-down control. We hypothesise that the phytoplankton spring development can be curbed by grazing when the zooplankton had attained high abundance by growth during the preceding summer.

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In this study we reconstruct sea surface temperatures (SSTs) using two lipid-based biomarker proxies (alkenone unsaturation index UK'37 and TEX86 index based on glycerol dibiphytanyl glycerol tetraethers) in 36 surface sediment samples from the Indonesian continental margin off west Sumatra and south of Java and the Lesser Sunda Islands. Comparison of measured temperatures (World Ocean Atlas 09) to reconstructed temperatures suggests that SST-UK'37 reflects the SE monsoon SST in the upwelling area south of Java and the Lesser Sunda Islands, whereas Temp-TEXH86 estimates are up to 2°C lower than SST-UK'37. This offset is possibly related to either one or a combination of two factors: i) the depth habitats of the source organisms; ii) different seasonal production and/ or seasonality of export associated with phytoplankton blooming triggered by primary productivity. In the non-upwelling area off west Sumatra, the alkenone-based SSTs are cooler than measured temperatures during the entire year, likely due to the reduced sensitivity of the UK'37 proxy beyond 28°C. However, reconstructed temperatures based on TEXH86 are consistent with mean annual SST, implying that the Temp-TEXH86 reflects the mean annual SST in the non-upwelling area of the tropical Eastern Indian Ocean.