40Ar‐39Ar and cosmic‐ray exposure ages of nakhlites—Nakhla,Lafayette, Governador Valadares—and Chassigny

Abstract– We present ⁴⁰Ar‐³⁹Ar dating results of handpicked mineral separates and whole‐rock samples of Nakhla, Lafayette, and Chassigny. Our data on Nakhla and Lafayette and recently reported ages for some nakhlites and Chassigny ( Misawa et al. 2006 ; Park et al. 2009 ) point to formation ages of approximately 1.4 Ga rather than 1.3 Ga that is consistent with previous suggestions of close‐in‐time formation of nakhlites and Chassigny. In Lafayette mesostasis, we detected a secondary degassing event at approximately 1.1 Ga, which is not related to iddingsite formation. It may have been caused by a medium‐grade thermal event resetting the mesostasis age but not influencing the K‐Ar system of magmatic inclusions and the original igneous texture of this rock. Cosmic‐ray exposure ages for these meteorites and for Governador Valadares were calculated from bulk rock concentrations of cosmogenic nuclides ³He, ²¹Ne, and ³⁸Ar. Individual results are similar to literature data. The considerable scatter of T₃, T₂₁, and T₃₈ ages is due to systematic uncertainties related to bulk rock and target element chemistry, production rates, and shielding effects. This hampers efforts to better constrain the hypothesis of a single ejection event for all nakhlites and Chassigny from a confined Martian surface terrain ( Eugster 2003 ; Garrison and Bogard 2005 ). Cosmic‐ray exposure ages from stepwise release age spectra using ³⁸Ar and neutron induced ³⁷Ar from Ca in irradiated samples can eliminate errors induced by bulk chemistry on production rates, although not from shielding conditions.     

Observing upper troposphere–lower stratosphere climate with radio occultation data from the CHAMP satellite

High quality observations of the atmosphere are particularly required for monitoring global climate change. Radio occultation (RO) data, using Global Navigation Satellite System (GNSS) signals, are well suited for this challenge. The special climate utility of RO data arises from their long-term stability due to their self-calibrated nature. The German research satellite CHAllenging Minisatellite Payload for geoscientific research (CHAMP) continuously records RO profiles since August 2001 providing the first opportunity to create RO based climatologies for a multi-year period of more than 5 years. A period of missing CHAMP data from July 3, 2006 to August 8, 2006 can be bridged with RO data from the GRACE satellite (Gravity Recovery and Climate Experiment). We have built seasonal and zonal mean climatologies of atmospheric (dry) temperature, microwave refractivity, geopotential height and pressure with 10° latitudinal resolution. We show representative results with focus on dry temperatures and compare them with analysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF). Although we have available only about 150 CHAMP profiles per day (compared to millions of data entering the ECMWF analyses) the overall agreement between 8 and 30 km altitude is in general very good with systematic differences <0.5 K in most parts of the domain. Pronounced systematic differences (exceeding 2 K) in the tropical tropopause region and above Antarctica in southern winter can almost entirely be attributed to errors in the ECMWF analyses. Errors resulting from uneven sampling in space and time are a potential error source for single-satellite climatologies. The average CHAMP sampling error for seasonal zonal means is <0.2 K, higher values occur in restricted regions and time intervals which can be clearly identified by the sampling error estimation approach we introduced (which is based on ECMWF analysis fields). The total error of this new type of temperature climatologies is estimated to be <0.5 K below 30 km. The recently launched Taiwan/U.S. FORMOSAT-3/COSMIC constellation of 6 RO satellites started to provide thousands of RO profiles per day, but already now the single-satellite CHAMP RO climatologies improve upon modern operational climatologies in the upper troposphere–lower stratosphere and can act as absolute reference climatologies for validation of more bias-sensitive climate datasets and models.     

Comparison of mid-Pliocene climate predictions produced by the HadAM3 and GCMAM3 General Circulation Models

The mid-Pliocene warm period (ca. 3 to 3.3 million years ago) has become an important interval of time for palaeoclimate modelling exercises, with a large number of studies published during the last decade. However, there has been no attempt to assess the degree of model dependency of the results obtained. Here we present an initial comparison of mid-Pliocene climatologies produced by the Goddard Institute for Space Studies and Hadley Centre for Climate Prediction and Research atmosphere-only General Circulation Models (GCMAM3 and HadAM3). Whilst both models are consistent in the simulation of broad-scale differences in mid-Pliocene surface air temperature and total precipitation rates, significant variation is noted on regional and local scales. There are also significant differences in the model predictions of total cloud cover. A terrestrial data/model comparison, facilitated by the BIOME 4 model and a new data set of Piacenzian Stage land cover [Salzmann, U., Haywood, A.M., Lunt, D.J., Valdes, P.J., Hill, D.J., (2008). A new global biome reconstruction and data model comparison for the Middle Pliocene. Global Ecology and Biogeography 17, 432-447, doi:10.1111/j.1466-8238.2007.00381.x] and combined with the use of Kappa statistics, indicates that HadAM3-based biome predictions provide a closer fit to proxy data in the mid to high-latitudes. However, GCMAM3-based biomes in the tropics provide the closest fit to proxy data.     

Solar-Cycle-Related Variations in the Solar Differential Rotation and Meridional Flow: A Comparison

We have analysed a large set of sunspot group data (1874 – 2004) and find that the meridional flow strongly varies with the phase of the solar cycle, and the variation is quite different in the northern and the southern hemispheres. We also find the existence of considerable cycle-to-cycle variation in the meridional velocity, and about a 11-year difference between the phases of the corresponding variations in the northern and the southern hemispheres. In addition, our analysis also indicates the following: (i) the existence of a considerable difference (about 180^°) between the phases of the solar-cycle variations in the latitude-gradient terms of the northern and the southern hemispheres’ rotations; (ii) the existence of correlation (good in the northern hemisphere and weak in the southern hemisphere) between the mean solar-cycle variations of meridional flow and the latitude-gradient term of solar rotation; (iii) in the northern hemisphere, the cycle-to-cycle variation of the mean meridional velocity leads that of the equatorial rotation rate by about 11 years, and the corresponding variations have approximately the same phase in the southern hemisphere; and (iv) the directions of the mean meridional velocity is largely toward the pole in the longer sunspot cycles and largely toward the equator in the shorter cycles.     

Geochemical subdivision and correlation of clay-rich beds in Turonian sediments of northern Germany

Thin, clay-rich beds form a key component of the lithostratigraphic scheme established for Middle and Upper Turonian sediments in northern Germany. Previously, using limited petrographic evidence, clay-rich beds across much of this region have been classified as either containing altered volcanic ash (bentonites) or detrital clays. This paper demonstrates that the use of rare-earth element (REE) data enables a rapid and reliable subdivision of clay-rich beds into those composed of bentonitic clays and those composed of detrital clays. Application of this method to the Lower Saxony region of northern Germany demonstrates that four bentonites (T_C T_di, T_e and T_f) and a number of detrital beds can be reliably identified and correlated. Three beds previously proposed to be bentonites are reinterpreted as being composed of detrital clays (T_o, T_D2 and T_G) and a revision of the stratigraphic nomenclature is proposed. Analysis of clay-rich beds from the Munster Basin demonstrates that it is possible to correlate individual bentonites and detrital beds between Lower Saxony and the Miinster Basin, and between shallow and deep water facies.     

Echelle spectroscopy of narrow line regions of Seyfert galaxies

Preliminary results of spectroscopic studies of selected Seyfert galaxies employing a new Cassegrain echelle spectrograph completed at ESO are presented. Subjects reported are the asymmetric profiles of narrow emission lines, spatial variation of narrow emission line profiles, and the interstellar absorption lines.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Comparative analysis of sodar and ozone profile measurements in a complex structured boundary layer and implications for mixing height estimation

Profile data from simultaneous sodar and tethered balloon measurements have been analyzed with respect to the complex structure of the atmospheric boundary layer in the Upper Rhine Valley. Special attention was focused on ozone concentration profiles measured with a novel lightweight ozone sensor at the balloon. In general, good agreement was found between the signature of the ozone concentration profiles and special features of the backscattered sound intensity profiles. This allows reliable estimation of the mixing height from the sodar data even in a complex stable ABL, except for very shallow mixing layers (below about 75 m), which could not be detected by the sodar.     

An analysis of the salt water inflow into the Baltic in 1975 to 1976

Time series measurements from light vessel and coastal stations in the transition area of the Kattegat and the Baltic Sea are analyzed for the period August 1975 to March 1976. The data consist of daily sampled salinities from different depth levels and daily means of sea levels, surface current, and wind, respectively. The purpose of this paper is to examine the dynamics of the mass- and salt-transport during a major salt water inflow.The principal conclusions of this paper are that