Brain macrophages in human cortical contusions as indicator of survival period

The aim of this study was to establish a morphologic time scheme with which cases of cerebral contusion with unknown survival periods can be dated. Our study of 275 cases was limited to qualitative and quantitative changes in macrophages. The appearance of macrophages and their distribution as well as their content of neutral fat, esterified cholesterol, erythrocytes, siderin, hematoidin, and ceroid were correlated with the survival period. For each cytologic criterium, the observation period, distribution-free limits of tolerance, and relative frequency of identification in different survival periods were determined, and the limits of confidence calculated. The findings permit the dating of trauma in cases with unknown survival periods. Moreover, the probability of this dating was calculated

Response of Recent Benthic Foraminiferal Assemblages to Contrasting Environments in Baffin Bay and the Northern Labrador Sea, Northwest Atlantic

Modern deep-water benthic foraminiferal assemblages in Baffin Bay and the northern Labrador Sea, Western North Atlantic, were sampled from box cores and analyzed to determine assemblage composition. The two marine basins are separated by the shallow waters of Davis Strait. Assemblages of Baffin Bay contained only agglutinated foraminifera, whereas samples from the Labrador Sea contained both calcareous and agglutinated species, which resulted in significantly higher species richness. The absence of benthic calcareous taxa in Baffin Bay is attributed to cold, saline, CO2-rich bottom waters related to the Baffin Bay Bottom Water and the Baffin Bay Atlantic Water. Modern foraminiferal assemblage distribution supports the model of increased organic flux under seasonal open-water conditions that feed a rich agglutinated assemblage, but lead to oxidation of organic matter and increased carbonate dissolution. Deep-water sediments contain ice-rafted coarse-grained components and biogenic elements such as sponge spicules that are heavily used by numerous agglutinated species for test construction. Robust, tubular suspension feeders occupy regions under the influence of bottom currents that deliver nutrients. Although disturbances of the sediment-water interface cannot be excluded with sampled box cores, small-scale patchiness can be confirmed by varying abundances of infaunal taxa. Absolute counts of specimens in subsamples vary signif­icantly, whereas species evenness among subsamples is less variable. These findings call for caution when interpreting lateral faunal changes on the basis of small core samples.Nous avons échantillonné des assemblages modernes de foraminifères benthiques d’eau profonde prélevés dans la baie de Baffin et le nord de la mer du Labrador, Atlantique du Nord-Ouest, à partir de carottes à boîte, puis nous les avons analysés afin d’en déterminer la composition. Les deux bassins marins sont séparés par les eaux peu profondes du détroit de Davis. Les assemblages de la baie de Baffin ne renfermaient que des foraminifères agglutinants, tandis que les échantillons de la mer du Labrador contenaient à la fois des espèces calcaires et des espèces agglutinantes, ce qui a donné lieu à une richesse d’espèces considérablement supérieure. L’absence de taxons calcaires benthiques dans la baie de Baffin s’explique par la présence d’eau de fond froide, saline et riche en CO2 provenant de l’eau de fond de la baie de Baffin et de l’eau atlantique de la baie de Baffin. La répartition des assemblages foraminifères modernes cadre avec le modèle du flux organique accru moyennant des conditions saisonnières en eaux libres qui alimentent un riche assemblage agglutinant, mais qui se traduisent par l’oxydation de la matière organique et l’intensification de la dissolution du carbonate. Les sédiments en eau profonde contiennent des composantes glacielles à grains grossiers et des éléments biogènes tels que le spicule de spongiaire dont dépendent de nombreuses espèces agglutinantes pour la construction de tests. Des suspensivores robustes et tubulaires occupent les régions sous l’influence de courants de fond qui déposent des nutriments. Bien que la perturbation de l’interface sédiment-eau ne puisse pas être excluse à l’aide des carottes à boîte, une microrépartition à petite échelle peut être confirmée au moyen de l’abondance variable des taxons benthiques. Les dénombrements absolus de spécimens des sous-échantillons varient considérablement, tandis que l’homogénéité des espèces parmi les sous-échantillons est moins variable. Ces constatations font appel à la prudence quand vient le temps d’interpréter les changements fauniques latéraux en fonction de petites carottes

The observation of the thin-ice thickness distribution within the Laptev Sea polynya using MODIS data

Polynyas are of high research interest since these features are areas of extensive new ice formation. The calculation of accurate ice-production values requires the knowledge of polynya area and thin-ice thickness distribution. These two variables can be derived by remote sensing data. However, a cross-validation study of various remote sensing data sets indicates that the spatial resolution issue is essential for the retrieval of accurate thin-ice thickness distribution. Thus, high-resolution remote sensing data must be used. MODIS thermal-infrared data with a spatial resolution of 1 km × 1 km is appropriate for the retrieval of thin-ice thickness distribution within the polynya. The algorithm to derive thermal-infrared thin-ice thickness is improved to state-of-the-art parameterizations. The mean absolute error of thin-ice thickness is ±4.7 cm for ice below 20 cm of thickness. The thin-ice thickness maps lack full coverage due to the restriction of the algorithm to cloud-free and nighttime data. Therefore, a compositing method is applied to compute daily thin-ice thickness maps. These maps cover on average 70 % of the Laptev Sea polynya. In order to fill the remaining gaps a combined remote sensing – model approach is developed to provide a consistent time series of high-resolution thin-ice thickness maps. This data set is valuable for the retrieval of accurate ice production within polynyas

Monitoring of thin ice in the Laptev Sea Polynya

It is estimated that a considerable fraction of new ice formation on Arctic shelf areas takes place in the Laptev Sea polynyas. However, the different studies reveal strong discrepancies in ice production rates. For an accurate monitoring of surface heat loss and hence, ice production within polynyas it is important to know the thin ice distribution within the polynya. We use an established thin-ice algorithm with several modifications to retrieve the thin ice thickness distribution up to 50 cm based on MODIS ice surface temperatures and atmospheric data from model simulations. We verify the MODIS ice surface temperatures with a data set measured during a field campaign in the Laptev Sea. For the calculation of thin ice thicknesses we use NCEP reanalyses, GME analyses and COSMO simulations in comparison as different atmospheric forcing data. We find that from the several atmospheric variables the air temperature at 2 m has the greatest impact on the ice thickness calculation. At ice thicknesses above 20 cm the algorithm responds sensitively to errors in the atmospheric data. In regions of very thin ice the errors in the atmospheric data are masked due to larger temperature differences between surface and atmosphere. However, a reliable atmospheric data set is necessary for the calculation of accurate thin ice thicknesses

Einfluss von atmophärischen Antriebsdaten auf Simulationen der Dynamik der Laptev-See_Polynjen mit dem Meereis-Ozean-Modell FESOM

Die Polynjen der Laptev-See nehmen eine Schlüsselrolle in den Schelfgebieten der sibirischen Arktis ein. Hier wird ein beachtlicher Teil des Meereisvolumens im arktischen Ozean gebildet. Zur Simulation der Dynamik der Polynjen und Quantifizierung der Eisproduktion verwenden wir das numerische Meereis-Ozean-Modell FESOM (Finite Element Sea Ice-Ocean-Model) (AWI Bremerhaven). In den bisherigen Simulationen wurde das FESOM mit täglichen NCEP (National Centers for Environmental Prediction) Daten angetrieben. Für den 1. April bis 9. Mai 2008 untersuchen wir den Einfluss von folgenden verschiedenen Antriebsdaten: Tägliche und 6-stündliche NCEP/DOE (Department of Energy) Reanalysen 2 (1.875 ̊ x 1.875 ̊), 6-stündliche NCEP/NCAR (National Centers for Atmospheric Research) Reanalysen 1 (2.5 ̊ x 2.5 ̊), 6-stündliche Analysen des GME (Globalmodell des Deutschen Wetterdienstes) (0.5 ̊ x 0.5 ̊) und hoch aufgelöste stündliche COSMO (Consortium for Small-Scale Modelling) Daten (5 km x 5 km). Vergleiche mit In-situ-Messungen des TRANSDRIFT XIII-2 Experiments 2008 zeigen, dass der Wind von allen atmosphärischen Antriebsdaten realistisch über dem Festeis wiedergegeben wird. Mit Ausnahme der FESOM-Simulationen mit täglichen NCEP-Daten werden die Öffnungs- und Schließvorgänge der Polynjen in guter Übereinstimmung mit AMSR-E (Advanced Microwave Scanning Radiometer - Earth Observing System) Produkten simuliert. Allerdings bestehen beträchtliche Diskrepanzen zwischen den Meereisproduktionsraten der unterschiedlichen Simulationen. Um die Eisproduktion in Polynjen zu quantifizieren sind stündliche, hoch aufgelöste atmosphärische Daten notwendig

Simulation von Dünneisdickenin den Laptev-See-Polynjen mit dem Ozean-Meereismodell FESOM

Die Laptev-See Polynjen spielen eine Schlüsselrolle für den arktischen Meereishaushalt aufgrund der starken Eisproduktion und des windgetriebenen Eisexportes von der Laptev-See in die zentrale Arktis. Für dieWinter 2007 bis 2009 haben wir mit dem Ozean-Meereismodell FESOM des Alfred-wegener Instituts mehrwöchige Simulationen für die Laptev-See mit einer horizontalen Auflösung von 5 km durchgeführt. Vergleiche mit dem aus AMSRE-Daten täglich abgeleitetem Eisbedeckungsgrad zeigen für den April 2008 unter Vorgabe einer Festeismaske grundsätzlich eine Übereinstimmung zwischen Simulation und Beobachtung bzgl. des Öffnen und Schließen der Polynjen. Im Dezember 2007 und im März 2009 hingegen sind die Polynjaflächen in den Simulationen wesentlich größer als die der AMSR-Daten. Aus MODIS Satellitendaten abgeleitete Dünneisdicken zeigen, dass die Größe der simulierten Polynjen realitätsnah ist, die Polynjen aber aufgrund einer dünnen Eisbedeckung nicht von den AMSR-E-Daten erfasst werden. Allerdings sind die Polynjen in den bisherigen FESOM-Simulationen nicht homogen mit dünnem Eis bedeckt, sondern teilweise mit dickem Eises und teilweise eisfrei. Dafür haben wir die Parametrisierung des Schließens von Meereis so modifiziert, dass bei starker Eisbildungsrate (> 10 cm/d) nicht nur Konvergenz sondern auch Eisbildung den Anteil offenen Wassers reduziert. Simulationen mit der geänderten Parametrisierung zeigen, dass damit Dünneisdicken in den Laptev-See Polynjen realitätsnah simuliert werden

Simulation of Laptev Sea polynya dynamics using the FESOM model with different atmospheric forces

The Laptev Sea polynyas play a key role for the shelf areas of the Siberian Arctic due to their impact on ice production. Changes in polynya dynamics result in modified fluxes of energy, momentum and matter in the atmosphere-ocean-sea ice system. An improved understanding and quantification of polynya effects in the Laptev Sea can be achieved by high-resolution sea ice-ocean models. Here we use the well-established Finite Element Sea Ice-Ocean Model FESOM (5 km x 5 km) (AWI Bremerhaven). It consists of a hydrostatic primitive-equation ocean model and a dynamic-thermodynamic sea ice model. In our study the model is forced by 6-hourly GME analyses (0.5° x 0.5°), daily and 6-hourly NCEP/NCAR reanalyses (2.5° x 2.5°) and hourly COSMO data (5 km x 5 km) to investigate a polynya event during the TRANSDRIFT winter experiment 2008. The input data consists of 10 m-wind, 2 m-temperature and specific humidity, total cloudiness and precipitation rate. In order to test the quality of the forcing data, comparisons with in-situ have been performed. They show shortcomings of the atmospheric analyses model data with respect to the daily course of the temperature, but very good agreement for the wind. The opening process of a main polynya event on 29 April 2008 is represented with all atmospheric forcing fields (except the daily NCEP data) in a similarly good way. However, there are differences in direction and velocity of the icedrift and in the location and development of the polynyas. Small-scale structures are best represented by applying the high-resolution COSMO data. The maximum sensible heat flux is 220 W/m2, the maximum latent heat flux is 120 W/m2, the maximum advective ice thickness reduction is 5 cm/h and the maximum thermal ice thickness production is 5 mm/h

Holocene record of Tuggerah Lake estuary development on the Australian east coast: sedimentary responses to sea-level fluctuations and climate variability

We investigated the Holocene palaeo-environmental record of the Tuggerah Lake barrier estuary on the south-east coast of Australia to determine the influence of local, regional and global environmental changes on estuary development. Using multi-proxy approaches, we identified significant down-core variation in sediment cores relating to sea-level rise and regional climate change. Following erosion of the antecedent land surface during the post-glacial marine transgression, sediment began to accumulate at the more seaward location at ~8500. years before present, some 1500. years prior to barrier emplacement and ~4000. years earlier than at the landward site. The delay in sediment accumulation at the landward site was a consequence of exposure to wave action prior to barrier emplacement, and due to high river flows of the mid-Holocene post-barrier emplacement. As a consequence of the mid-Holocene reduction in river flows, coupled with a moderate decline in sea-level, the lake experienced major changes in conditions at ~4000. years before present. The entrance channel connecting the lake with the ocean became periodically constricted, producing cyclic alternation between intervals of fluvial- and marine-dominated conditions. Overall, this study provides a detailed, multi-proxy investigation of the physical evolution of Tuggerah Lake with causative environmental processes that have influenced development of the estuary