The KOSMA large-scale CO survey of clouds in the Galactic Molecular Ring

We present the status of the KOSMA large-scale observations of clouds in the Galactic Molecular Ring (GMR) in CO J=3-2, 2-1 and ¹³CO 2-1 following up on the BU-FCRAO ¹³CO 1-0 survey. The GMR is one of the prominent large scale structures in the Milky Way and an interesting laboratory to studystar formation. Whereas the ¹³CO data yield a good measureof the overall column density structure, the new observations of CO 2-1provide a picture of the thin extended gas and the CO 3-2 data show thedistribution of the dense and warm molecular gas. The combination of observations of these lines thus allows to distinguish between extended,quiescent gas, dense cold parts, and warm regions, influenced by star formation. In performing large scale observations we are able to analysethe structure of this material.     

Age constraints in the double pulsar system J0737–3039

We investigate the age constraints that can be placed on the double pulsar system using models for the spin-down of the first-born 22.7-ms Pulsar A and the 2.77-s Pulsar B with characteristic ages of 210 and 50 Myr, respectively. Standard models assuming dipolar spin-down of both pulsars suggest that the time since the formation of Pulsar B is ∼50 Myr, that is, close to Pulsar B's characteristic age. However, adopting models which account for the impact of Pulsar A's relativistic wind on Pulsar B's spin-down, we find that the formation of Pulsar B took place either 80 or 180 Myr ago, depending on the interaction mechanism. Formation 80 Myr ago, closer to Pulsar B's characteristic age, would result in the contribution from J0737−3039 to the inferred coalescence rates for double neutron star binaries increasing by 40 per cent. The 180 Myr age is closer to Pulsar A's characteristic age and would be consistent with the most recent estimates of the coalescence rate. The new age constraints do not significantly impact recent estimates of the kick velocity, tilt angle between pre- and post-supernova orbital planes or pre-supernova mass of Pulsar B's progenitor.     

PSR J1740−3052: a pulsar with a massive companion

We report on the discovery of a binary pulsar, PSR J1740−3052, during the Parkes multibeam survey. Timing observations of the 570-ms pulsar at Jodrell Bank and Parkes show that it is young, with a characteristic age of 350 kyr, and is in a 231-d, highly eccentric orbit with a companion whose mass exceeds 11 M_⊙. An accurate position for the pulsar was obtained using the Australia Telescope Compact Array. Near-infrared 2.2-μm observations made with the telescopes at the Siding Spring observatory reveal a late-type star coincident with the pulsar position. However, we do not believe that this star is the companion of the pulsar, because a typical star of this spectral type and required mass would extend beyond the orbit of the pulsar. Furthermore, the measured advance of periastron of the pulsar suggests a more compact companion, for example, a main-sequence star with radius only a few times that of the Sun. Such a companion is also more consistent with the small dispersion measure variations seen near periastron. Although we cannot conclusively rule out a black hole companion, we believe that the companion is probably an early B star, making the system similar to the binary PSR J0045−7319.     

Channel evolution of Des Moines Lobe till drainage ditches in southern Minnesota (USA)

Some drainage ditches in the intensively managed row-crop agricultural region of southern Minnesota evolved from a trapezoidal form to multi-staged channel forms similar to natural streams. Older ditches constructed in cohesive sediment of the Des Moines Lobe till tend to follow a channel evolution model developed by Simon and Hupp. Site cross sections, longitudinal water and bed profiles and bed material particle size were determined according to Harrelson and others at 24 older ditch reaches, 5 newly constructed ditch reaches and 13 natural stream reaches. Morphological features were hypothesized to change from trapezoidal form to flat bench banks, similar to benches found in natural stream channels. All data were statistically analyzed with respect to drainage area using regression, because channel form is directly related to drainage area for a given climate, geology and land use. Results show similar regression slope and intercept for bankfull channel width and bankfull cross-sectional area (CSA) of older ditches and natural streams compared to typical trapezoidal designed ditches. Evolved ditches developed a small floodplain bench above the ditch bed and adjusted their bankfull widths similar to natural stream channels with respect to drainage area. Old ditches showed a relatively strong R ² (0.82, 0.68) for channel CSA and width, a weaker R ² (0.45) for water surface slope, and little to no correlation with bed particle size. Channel form appears to have adjusted more quickly than bed facets and/or bed particle size distribution. However, stepwise regression determined that D₈₄, width/depth ratio and mean bankfull depth explained 83?% of the variability of channel features across varying drainage areas. Findings suggest a possible reduction of long-term maintenance costs if older ditches are allowed to evolve over time. A stable ditch form similar to natural streams is typically self-sustaining, suggesting that prior to a scheduled clean-out, the ditch should be examined for hydraulic capacity, sediment transport and bank stability.     

A late quaternary ostracod record from the Tso Kar basin (North India) with a note on the distribution of recent species

The fossil ostracod associations from a radiocarbon dated sediment core (15.3–0 cal kyr) of the high altitude (4,527 m a.s.l.) hyperhaline Tso Kar lake in North India reveal changes in ostracod species abundances and composition. These document the process of lake formation and ongoing desiccation during the latest quaternary and broadly confirm the results of previous geochemical, geomorphological and pollen analysis. The most striking feature of the core record is a period of freshwater conditions between 9.0 and 6.5 cal kyr BP, as calculated by means of an ostracod-based conductivity transfer function. This early- to mid-Holocene interval of the core correlates with similar ostracod assemblages (Cytherissa lacustris—Candona candida—Eucypris afghanistanensis) of an outcrop section at the basin margin, about 98 m above the modern lake level and marks the highest lake level under the influence of an intensified Indian Summer Monsoon. After 6.5 cal kyr BP, Limnocythere inopinata is the sole representative of the ostracod fauna in the sediment core, which suggests rising salinity conditions most probably due to lake shallowing. From 3.2 cal kyr BP to present, the near absence of ostracods in the core Tk106 is most likely a consequence of salinisation of the lake towards the hyperhaline conditions that are realised at present. Although the modern morphology and physico-chemical properties of Tso Kar lake are in contrast to the past lake conditions, most of the ostracod species, except for Limnocythere mirabilis found in the sediment core, are also identified from surface sediment and outcrop samples. In contrast, Heterocypris salina and Eucypris dulcifons are widespread in the shallow surface waters with a total dissolved solids content ranging from 0.6 to 15.0 g L^?1, but are excluded from the core record and outcrop strata. At a basinal scale, the lake shrinkage and segregation into the Tso Kar and hydrologically open freshwater lake Startsapuk Tso have forced diversification of ostracod taxa, probably as an effect of the emergence of new ecological niches under enhanced “environmental pressure”.     

Thermal evolution of the mantle underneath the Mid-German crystalline rise: Evidence from mantle xenoliths from the Rhön area (Central Germany)

Summary A suite of ultramafic xenoliths (spinel peridotites, one olivine-clinopyroxene hornblendite, and one spinel pyroxenite) from Tertiary basalt vents and lava flows of the Rhön area (Central Germany) were investigated petrologically and geochemically. With regard to P-T estimates two distinct groups of peridotite xenoliths can be discriminated: (I) A low- to intermediate-temperature group of spinel lherzolites and wehrlites mainly displaying coarse equant textures yielded temperature estimates in the range of 840–1050 °C at rather variable pressures of 11–24 kbar. The strong variability of the P-T estimates is attributed to mineral chemical disequilibria and different diffusion rates of the elements used for geothermometry and geobarometry. Spinel-pyroxene symplectites within part of these xenoliths point to a former position in the stability field of garnet lherzolite. These xenoliths are variably depleted in the basaltic component by partial melt extraction. They often show an enrichment in LREE and MREE which is due to a later overprinting by cryptic metasomatism. (II) A high-temperature group of xenoliths, which mainly consists of porphyroclastic and subordinate coarse equant spinel lherzolites and harzburgites, experienced temperatures of 1190–1270 °C at 19–26 kbar. The P-T values for these xenoliths fall close to a geothermal gradient of about 90 mW/m² and illustrate intense heating processes in the mantle which were often coupled with ductile deformation caused by lithospheric stretching. The thermal disturbance which led to the reequilibration of these peridotites must have occurred during the Tertiary magmatic event as indicated by the absence of retrograde mineral zoning, missing textural reequilibration, and the presence of partial melting phenomena in clinopyroxene. Unlike sheared xenoliths from other locations, the porphyroclastic high-temperature peridotites from the Rhön are depleted in basaltic component, in HREE, Y, and Sc. An olivine-clinopyroxene hornblendite is classified as some kind of basaltic cumulate which - according to its P-T estimate of about 1150 °C at 9 kbar - originates from hte transition zone between the lower crust and the upper mantle.⁴⁰Ar-³⁹Ar dating of kaersutite from this sample indicates an age of about 25 Ma which is in accordance with the beginning of Tertiary volcanism in the Rhön area. These investigations show that part of the lithospheric mantle underneath the Rhön area experienced a thermal reequilibration during the Tertiary magmatic event while other parts give evidence of an older history, i.e. a cryptic metasomatism and a transition from the garnet- to the spinel-lherzolite field. A possible geotectonic scenario for the transition could be the post-Variscan crustal reequilibration.

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Thermische Entwicklung des Mantels unter der Mitteldeutschen Kristallinschwelle abgeleitet aus Mantelxenolithen der Rhön

Zusammenfassung Eine Reihe von ultramafischen Xenolithen (Spinell-Peridotite, ein Olivin-KlinopyroxenHornblendit und ein Spinell-Pyroxenit) aus tertiären Basalten der Rhön wurde petrologisch and geochemisch untersucht. Zwei Gruppen von Peridotiten können hinsichtlich ihrer Äquilibrierungstemperaturen unterschieden werden: (I) Spinell-Lherzolithe and -Wehrlite mit niedrigen und mittleren Temperaturen von 840–1050 °C bei Drucken von 11-24 kbar zeigen zumeist granulare Gefüge. Die große Schwankungsbreite dieser P-T-Abschätzungen ist durch mineralchemische Ungleichgewichte und unterschiedliche Schließungstemperaturen der Geothermometer und Geobarometer bedingt. Spinell-Pyroxen-Symplektite, die in einigen dieser Xenolithe auftreten, weisen auf eine vormalige Position im Stabilitätsfeld von GranatLherzolith hin. Diese Xenolithe sind durch partielle Schmelzextraktion unterschiedlich stark depletiert. Häufig zeigen she eine Anreicherung der leichten and mittleren Seltenerdelemente, was durch eine spätere kryptometasomatische Überprägung bedingt ist. (II) Eine Gruppe hochtemperierter, vorwiegend porphyroklastischer und untergeordnet granularer Spinell-Lherzolithe und -Harzburgite wurde unter Temperaturen von 1190–1270 °C bei Drucken von 19–26 kbar überprägt. Die P-T Werte für diese Xenolithe liegen auf einem geothermischen Gradienten von über 90 mW/m², was auf intensive Aufheizprozesse im Mantel hinweist. Oftmals wurde these Aufheizung von einer duktilen Deformation begleitet, deren Ursache eine Dehnung der Mantellithosphäre war. Aufgrund der fehlenden Gleichgewichtstexturen, der Abwesenheit von retrograden Mineralzonierungen und partieller Schmelzprozesse bei den Klinopyroxenen dieser Xenolithe müssen ihre Deformation and Hochtemperaturüberprägung während des tertiären Magmatismus stattgefunden haben. Die porphyroklastischen, hochtemperierten Xenolithe zeigen die stärkste Abreicherung an basaltischer Komponente, den schweren Seltenerdelementen sowie an Y and Sc. Bei dem Olivin-Klinopyroxen-Hornblendit handelt es sich um ein basaltisches Kumulat, welches aufgrund seiner P-T Abschätzung (um 1150 °C bei 9 kbar) aus dem Übergangsbereich von unterer Kruste zu oberem Mantel stammt. Eine⁴⁰Ar-³⁹Ar Datierung von Kaersutiten dieser Probe weist auf ein Alter von etwa 25 Ma, was in Übereinstimmung mit dem Beginn des tertiären Vulkanismus in dieser Region ist. Diese Untersuchungen verdeutlichen, daß ein Teil des lithosphärischen Mantels unter der Rhön eine thermische Äquilibrierung während des tertiären magmatischen Ereignisses erfuhr. Dagegen zeigen andere Teile noch Relikte einer älteren Geschichte, speziell eine kryptische Metasomatose and den Übergang vom Stabilitätsfeld des Granat-Lherzoliths zum Spinell-Lherzolith. Ein mögliches geotektonisches Szenario für diesen Transfer könnte die postvariscische Krustenreäquilibrierung sein.

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With 7 Figures     

Sensitivity of FORGRO to climatic change scenarios: A case study on Betula pubescens, Fagus sylvatica and Quercus robur in The Netherlands

The impacts of the climate change predictions of four general circulation models (GFDL, GISS, OSU and UKMO) on net primary production (NPP) ofBetula pubescens, Fagus sylvatica and Quercus robur in The Netherlands were analysed using the process-based model FORGRO. FORGRO is a model suitable to simulate growth of managed mono-species stands. For the GCMs mentioned, both transient and equilibrium 2 × CO₂ scenarios of temperature and precipitation change were evaluated and compared with responses under current climate. It was found that the NPP increases in the transient scenarios, but remains the same or declines in the 2 × CO₂ scenarios. This is because respiration increases more with rising temperature than photosynthesis. During the transient scenarios this effect gradually increases, while in the 2 × CO₂ scenario this effect is operating over the entire simulation period.If water limitation is taken into account, then the NPP of the reference scenario is reduced. In both the transient and 2 × CO₂ scenarios mis water limitation is annulated, resulting in a stronger response of NPP compared to the situation without water limitation. This enhancement of the response is most pronounced in the transient scenario due to the gradual effect of temperature on respiration.Similar results were obtained with a version of FORGRO in which the photosynthesis module of HYBRID (PGEN) is incorporated, although the response in FORGRO-PGEN is usually higher than that of FORGRO. This is because the response of photosynthesis to CO₂ rises with increasing temperature as defined in the PGEN-model, but not according to FORGRO.     

Observed mid-to-high latitude interchange of atmospheric angular momentum and some implications

The global distribution of atmospheric angular momentum (M) during 1977–1978 and 1982–1983 is examined to identify evidence of prominent short term interchanges of relative atmospheric momentum between mid and high latitude zones, in both hemispheres. Thirty day detrended angular momentum time series, prepared from the NMC gridded zonal wind data are examined in latitude bands. These data exhibit obvious quasi-coherent oscillations with periods near 30 days plus variations with shorter periods. An examination of latitude/altitude cross sections of zonal winds reveals that the oscillations are present almost simultaneously at all altitude levels between 1000 and 50 mb. Cross latitude teleconnections, evident as strong anticorrelated signatures between adjacent latitude bands are observed in the midlatitudes of both hemispheres. Comparison of these signatures with the time integrated flux of angular momentum across the nodal interface confirms that direct eddy transport of momentum is occurring. Transport of momentum from the mid latitude bands results in an increase in the momentum of the higher latitude bands and vice versa. Transport of planetary angular momentum by a Hadley/Ferrel type meridional circulation is specifically ruled out although that process may contribute to seasonal and longer term modulations. The short term oscillations in M can reach magnitudes which dominate the global variation in momentum, as noted in the recent 1982–83 El Niño episode in which the January 1983 momentum peaked at a decadal high. Similar El-Niño like changes in the trans-latitude momentum redistribution are observed in the Southern Hemisphere winters, following the Northern Hemisphere episode. Overall, our results confirm and describe in more detail the long recognized fact that momentum can be selectively redistributed between tropical, temperate, and high latitudes, in patterns indicative of the development and dissipation of interacting regions, described variously in studies of the index cycle, seesaws and teleconnections. In emphasizing the large scale coordination of these interchanges, and moreover their occasional very short time scales, these results will hopefully stimulate studies relating atmospheric behavior in distant regions thereby contributing to improvements in forecasting the circulation process.     

Characterization of multiple functional groups on kaolinite

Multiple proton functional group conditional binding constants (K′_i) and their concentrations (C_i) are determined from detailed acid/base titration data. The C-K′ information is obtained for kaolinite by assuming that the distribution can be approximated by cumulative independent mono protic groups. Linear programming optimization techniques are used to Fit the data. In addition, the electrode calibration is optimized in the data fit. This adjustment is important for high and low pHs. Discrete concentration dependent pXs of about 3.4, 4.5, 6.7 and 9.8 are determined for a reference kaolinite. These correspond reasonably well to designations made by Wehrli et al. (1990, Aquatic Sciences, Vol. 52, pp. 1–31 ) to A10H2 and AlOH proton reactions at edge and surface sites and to silanol exchange. There is an ionic strength effect for one site. Long and short reaction times and reversibility affect the results.     

Apparent copper complexation capacity and conditional stability constants in north atlantic waters

Surface water samples were collected in the north Atlantic Ocean in July–August 1983. Their apparent complexation capacity for copper (CC_Cu) was determined on board, using differential pulse anodic stripping voltammetry under clean room conditions. Measurements were carried out by direct titrations as well as after equilibration of copper spikes. CC_Cu and conditional stability constants (K′) were calculated, by means of three different methods, which are compared.On the basis of salinity, temperature, silicate and phosphate concentrations the following surface waters could be distinguished: North Atlantic Drift (I), East Greenland Current (II), Labrador Current (III) and Gulf Stream waters (IV, V). CC_Cu and K′ were found to differ between these waters. The range of values for CC_Cu and their mean values given in parentheses, as calculated from van den Berg plots for waters I–IV are: I, 53–65 (59); II, 47–66 (55); III, 37–53 (45); IV, 20–42 (33) nM Cu. The range and mean values for log K′ are: I, 8.23–8.33 (8.28); II, 7.89–8.11 (7.98); III, 8.40–8.41 (8.41); IV, 7.90–8.21 (8.06).Information on complexation kinetics extracted from the titration curve revealed that k_f^′ is area-specific. The complexation rate constant in the northern part (Area I) is about two times larger than that in the southern area IV, (3.6 ± 0.3) and (2.2 ± 0.2) × 10⁴s⁻¹M⁻¹ Cu, respectively.Preliminary results for deep water samples suggest smaller but still existent CC_Cu and higher K′ than those found for surface waters.