A simple model for air/snow fractionation of aerosol components over the Antarctic Peninsula     

Alan L. Dick 《Journal of Atmospheric Chemistry》1990,11(1-2):179-196

A model has been set up to investigate the wet and dry aerosol removal processes which occur in clean air over the Antarctic Peninsula. Input for the model was obtained from bulk chemical analysis and scanning electron microscopy of aerosol and snow samples collected simultaneously at remote sites around the Peninsula. The model predicts that sulphate and sea-salt aerosol will be removed mainly in-cloud by riming of falling snow and ice crystals. Crustal aerosol is principally removed by acting as nuclei for these crystals and by impaction on falling snow. For the largest, locally-generated aerosol dry deposition is indicated as the major removal process. These findings suggest a possible mechanism for the observed air/snow fractionation.  相似文献   

Gezeitenströmungen um Sylt Numerische Untersuchungen zur halbtägigen Hauptmondtide (M2)     

Stephan Dick 《Ocean Dynamics》1987,40(1):25-44

  相似文献   

Arctic Underwater Operations: Edited by Louis Rey. Graham & Trotman, London, 1985     

E.H. Padbury  A.K.P. Dick 《Organic Geochemistry》1986,9(6)

  相似文献   

Petrology and geochemistry of basalts from the American-Antarctic Ridge,Southern Ocean: implications for the westward influence of the Bouvet mantle plume     

Anton P. le Roex  Henry J. B. Dick  Arch M. Reid  Fred A. Frey  Anthony J. Erlank  Stan R. Hart 《Contributions to Mineralogy and Petrology》1985,90(4):367-380

Ridge segments and fracture zones from the American-Antarctic Ridge have been systematically dredge sampled from 4° W to 18° W. Petrographic studies of the dredged basalts show that the dominant basalt variety is olivine-plagioclase basalt, although olivine-plagioclase-clinopyroxene basalt is relatively common at some localities. Selected samples have been analysed for major and trace elements, rare earth elements and Sr and Nd isotopes. These data show that the majority of samples are slightly evolved (Mg#=69-35) N-type MORB, although a small group of samples from a number of localities have enriched geochemical characteristics (T- and P-type MORB).These different types of MORB are readily distinguished in terms of their incompatible trace element and isotopic characteristics: N-type MORB have high Zr/Nb (17–78), Y/Nb (4.6–23) and ¹⁴³Nd/¹⁴⁴Nd (0.51303–0.51308) ratios, low Zr/Y (2.2–4.2) and ⁸⁷Sr/⁸⁶Sr (0.70263–0.70295) ratios and have (La/Sm)_N<1.0; T-type MORB have lower than chondritic Zr/Nb ratios (8.8–15.5), relatively low Y/Nb (1.9–4.3) and ¹⁴³Nd/¹⁴⁴Nd (0.51296–0.51288) ratios and relatively high Zr/Y (3.1–4.7), ⁸⁷Sr/⁸⁶Sr (0.70307–0.70334) and (La/Sm)_N (1.1–1.5) ratios; the single sample of P-type MORB has low Zr/Nb (6.3), Y/Nb (0.9) and ¹⁴³Nd/¹⁴⁴Nd (0.51287) ratios and high Zr/Y (7.1), ⁸⁷Sr/⁸⁶Sr (0.70351) and (La/Sm)_N (2.4) ratios. The geochemical characteristics of this sample are essentially identical to those of the Bouvet Island lavas.Geochemically enriched MORB are less abundant on the American-Antarctic Ridge than on the Southwest Indian Ridge but their geochemical characteristics are identical. The compositions of T- and P-type MORB are consistent with a regional mixing model involving normal depleted mantle and Bouvet plume type magma. On a local scale the composition of T-type MORB is consistent with derivation from depleted mantle which contains 4% veins of P-type melt.We propose a model for the evolution of the American-Antarctic Ridge lavas in which N-type MORB is derived from mantle with negligible to low vein/mantle ratios, T-type MORB is derived from domains with moderate and variable vein/mantle ratios and P-type MORB from regions with very high vein/mantle ratios where vein material comprises the major portion of the melt. The sparse occurrence of enriched lavas and by implication enriched mantle beneath the American-Antarctic Ridge, some distance (500–1,200 km) from the Bouvet plume location, is interpreted to be the result of lateral dispersion of enriched mantle domains by asthenospheric flow away from the Bouvet mantle plume towards the American-Antarctic Ridge.  相似文献   

Impact of the East African Rift System on the routing of the deep-water drainage network offshore Tanzania,western Indian Ocean     

Vittorio Maselli  Dick Kroon  David Iacopini  Bridget S. Wade  Paul N. Pearson  Henk de Haas 《Basin Research》2020,32(5):789-803

The East African Rift System (EARS) exerted a major influence on river drainage basins and regional climate of east Africa during the Cenozoic. Recent studies have highlighted an offshore branch of the EARS in the western Indian Ocean, where the Kerimbas Graben and the Davie Ridge represent its sea floor expression. To date, a clear picture of the impact and timing of this EARS offshore branch on the continental margin of the western Indian Ocean, and associated sediment dispersal pathways, is still missing. This study presents new evidence for four giant canyons along the northern portion of the Davie Ridge offshore Tanzania. Seismic and multibeam bathymetric data highlight that the southernmost three canyons are now inactive, supra-elevated relative to the adjacent sea floor of the Kerimbas Graben and disconnected from the modern slope systems offshore the Rovuma and Rufiji River deltas. Regional correlation of dated seismic horizons, integrated with well data and sediment samples, proves that the tectonic activity driving the uplift of the Davie Ridge in this area has started during the middle-upper Miocene and is still ongoing, as suggested by the presence of fault escarpments at the sea floor and by the location and magnitude of recent earthquakes. Our findings contribute to placing the Kerimbas Graben and the Davie Ridge offshore Tanzania in the regional geodynamic context of the western Indian Ocean and show how the tectonics of the offshore branch of the EARS modified the physiography of the margin, re-routing the deep-water drainage network since the middle Miocene. Future studies are needed to understand the influence of changing sea floor topography on the western Indian Ocean circulation and to evaluate the potential of the EARS offshore tectonics in generating tsunamigenic events.  相似文献   

The astrometric properties of the Tautenburg Schmidt telescope and its possible contributions to the realization of an inertial reference frame     

Wolfgang R. Dick 《Astronomische Nachrichten》1990,311(2):140-140

  相似文献   

N. M. Swerulow,O. Neugebauer: Mathematical Astronomy in Copernicus's De Revolutionibus. (studies on the history of Mathematics and Physical Sciences,Vol. 10). In two Parts. With 222 Figures. New York,Berlin, Heidelberg,Tokyo: Springer-Verlag, 1984. XXI + 711 pp. Preis     

W. R. Dick 《Astronomische Nachrichten》1985,306(6):341-342

  相似文献   

A Programme to derive from terrestrial observations the rotation of the HIPPARCOS system with reference to the inertial system     

W. R. Dick  G. Ruben  E. Schilbach  R.-D. Scholz 《Astronomische Nachrichten》1987,308(3):211-216

The connection of the HIPPARCOS system with a quasi-inertial system can be reached by transforming the HIPPARCOS proper motions to absolute proper motions. The Tautenburg Schmidt telescope provides such proper motions with respect to extragalactic objects with an accuracy of 0″.6/100a. The telescope as well as the measuring and reduction technique are described. The accuracy of the link of the HIPPARCOS system to extragalactic objects depends on the accuracy of the transformation matrix which represents the time-depending part of the rotation matrix to be applied to the whole HIPPARCOS catalogue. To obtain a reliable estimate for the error of transformation we used the error propagation law. An accuracy of 0″.12/100a for the transformation can be achieved with six Tautenburg fields.  相似文献   

Exchange of matter and energy between the Wadden Sea and the coastal waters of the German Bight-Estimations based on numerical simulations and field measurements     

S. Dick  U. H. Brockmann  J. E. E van Beusekom  B. Fabiszisky  M. George  U. Hentschke  K. -J. Hesse  B. Mayer  Th. Nitz  Th. Pohlmann  K. Poremba  K. Schaumann  W. Schönfeld  A. Starke  U. Tillmann  G. Weide 《Ocean Dynamics》1999,51(2-3):181-219

  相似文献   

Currents at the light-vessel “Deutsche Bucht”: A comparison between ADCP measurements and the BSH forecast model     

Holger Klein  Stephan Dick 《Ocean Dynamics》1999,51(4):465-475

  相似文献