ABSTRACT. The method of Brillouin spectroscopy has been used to measure the dynamic elastic moduli of local homogeneous regions in ice samples representing four different environments of formation . These included artificial ice frozen from distilled water, clear monocrystalline glacial ice, bubbly lake ice, and sea ice. The samples studied were found to have identical local elastic properties. Accordingly the elastic properties of homogeneo us monocrystalline ice have been found not to vary with sa mple age, with impurities present at the time of freezing , or with crystal quality. The bulk elastic properties of ice remain , of course, subject to modification by different crystal grain textures and the presence of inclusions of various sorts. Because the elastic constants obtained in the present work are subject to smaller overall uncertainty than values meas ured previously, it is believed that they are the most reliable obtained to date. The values at -16°C were determined to be c II = 139.29 ± 0.41 , Cl2 = 70.82 ± 0.39, Cl3 = 57.65 ± 0.23 , C33 = 150.10 ± 0.46, C44 = 30.14 ± 0. 11 (units of 10 8 N m -2 or kbar). A full range of derived elastic parameters for monocrystalline ice and for homogeneous isotropic polycrystalline ice has been calculated. RESUME . Conslanles idasliques d'echanlillons de glace arlificielle el nalurelle par speclrographie deBril/ouin. On a utilise la methode de la spectrographie de Brillouin pour mesurer les modules dynamiques elastiques de region s localement homogenes dans des echantillons de glace representant quatre diffe re ntes circonstances de formation. [\ s'agissa it d'une glace artificielle obtenue a partir d'eau distillee, d' une glace c laire monocri stalline, d' une glace bulleuse de lac et d' une glace de mer. On a trouve que les ec hantillons etudies avaient des proprietes elastiques locales identiques. Logiquement, les proprietes elastiques d ' une glace homogene mo nocri stalline ont ete trouvees independantes de I'age de I'echantillon, des impuretes pfl!Sentes au moment de la congelation ou de la qualite du crista!' Les proprietes elastiques globales de la glace demeurent, naturellement, s ujettes a modificatio ns selon les differentes textures cri stallines des grain s et la presence d'in c lu sion de differentes sortes. Comme les constantes eIastiques obtenues dan s la presente etude son t affectees d ' un e incertitude globa le inferieure aux va leurs precedemment mesurees on pense qu'elles sont les plu s dignes de con fiance obtenues jusqu 'ici. Les valcurs obtenues a -16°C ont ete: cll = 139, 29 ± 0 ,41 , CI2 =70,82± 0,39, cl3 =S 7.6S ± 0,23, c33= ISO, 10 ± 0,46 , c44 = 30,14 ± 0, 11 (unites: 10 8 Nm -2 ou kbars). Toute une serie de para metres eIas tiques derives ont ete calcules pour de la glace monocristalline et pour une glace polycristalline homogene et isotrope. ZUSAMMENFASSUNG. Elasliche Konslanlen von kiinsllichen und Ilalurlichen E isp roben, gel\lonnen mil Brillollin-speklroskopie.Das Verfahren der Brillouin-Spektroskopie wurde zur Mess ung der dyn...

The method of Brillouin spectroscopy has been used to measure the dynamic elastic moduli of local homogeneous regions in ice samples representing four different environments of formation. These included artificial ice frozen from distilled water, clear monocrystalline glacial ice, bubbly lake ice, and sea ice. The samples studied were found to have identical local elastic properties. Accordingly the elastic properties of homogeneous monocrystalline ice have been found not to vary with sample age, with impurities present at the time of freezing, or with crystal quality. The bulk elastic properties of ice remain, of course, subject to modification by different crystal grain textures and the presence of inclusions of various sorts. Because the elastic constants obtained in the present work are subject to smaller overall uncertainty than values measured previously, it is believed that they are the most reliable obtained to date. The values at −16 °C were determined to be c11 = 139.29 ± 0.41, c12 = 70.82 ± 0.39, c13 = 57.65 ± 0.23, c33 = 150.10 ± 0.46, c44 = 30.14 ± 0.11 (units of 108 N m− 2 or kbar). A full range of derived elastic parameters for monocrystalline ice and for homogeneous isotropic polycrystalline ice has been calculated.

Fine scale measurements of the vertical temperature profile in an Arctic water column show the presence of several cascaded isothermal layers. Layers between the depths of 300 anid 350 meters range from 2 to 10 meters in thickness, while the temperature change between adjacent layers is approximately 0.026 degrees C. The individual layers are isothermal to within +/- 0.001 degrees C.

Complete high-pressure single-crystal structure determinations have been performed up to 90 kbar on ruby (Al2O3 with less than 0.05 wt% Cr2O3) using an automatic diffractometer. The rhombohedral lattice constant aR is found to decrease linearly within the given error limits from aR=5.136±0.004 to aR=5.075±0.005 Å at 90 kbar. The rhombohedral angle αR=55.30°±0.06° as well as the atom-position parameters u (Al, Cr) =0.3520±0.0004 for Al (or Cr) and u (0) =0.556±0.003 for oxygen remain constant up to at least 86 kbar. These results are in very good agreement with earlier measurements up to 25 kbar by Schiferl and Jamieson as well as with the Birch and Murnaghan equations of state with the literature values of the isothermal compresssibility K0 and its pressure derivative K′.

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Marked step‐like structure exists in vertical profiles of temperature and salinity obtained in the Arctic Ocean. This structure occurs between 200 and 500 meters depth, where both temperature and salinity increase with depth. Nominally, the structure consists of thin sheets (0.1 meter thick) separating adjacent homogeneous layers (3 meters thick) that differ in temperature by 0.02°C and in salinity by 0.01‰. While the step structure is quite persistent, its character varies markedly with depth. Intermediate layers have been observed, as well as noncoincident temperature and salinity gradient sheets. Analysis of the data lends support to the hypothesis that this type of layering arises from the double‐diffusive process.

Table 1. Au-C1 distances in the coordination octahedra at different pressuresUsing a gasketed diamond-anvil high-pressure cell, which has been adapted to the automatic four-circle diffractometer, we have studied the structural changes e (Pax 10 -8) of single crystals of the mixed-valence compound 10_3 Cs2AuIAuIIIC16 under high hydrostatic pressure.

We present results from an experimental investigation of the interaction between a shelf break jet and a submarine canyon and of the response of this system to a single upwelling favorable wind event. The field site was Carson Canyon, located at the edge of the Grand Bank of Newfoundland. The shelf break jet is the Labrador Current. The time‐averaged current measurements indicate that the interaction between the Labrador Current and the canyon topography is nonlinear and that the mean current crosses isobaths to flow into the canyon on the upstream side but is steered off shelf on the downstream side. The mean flow vorticity balance in the near field and far field is examined, using a two‐layer model with the lower layer at rest. In the far field we obtain an interesting result which suggests that the cross‐stream shear in combination with bottom friction can drive a significant on‐shelf flow. This flow is equivalent to a volume transport of about 60 m3 s−1 per 100 m of along‐shelf distance, which is comparable to typical wind‐driven Ekman transports on and off continental shelves and which appears to have important implications for the on‐off‐shelf transport of icebergs in the Grand Banks region. In the near field the Rossby number is of order unity and bottom friction is less important. Many of the observed flow properties can be explained qualitatively in terms of an upstream inertial boundary layer and potential vorticity conservation. The time‐dependent response to upwelling favorable winds was registered by current meters in the canyon and at the shelf break at the canyon perimeter. These observations indicate an amplified upwelling response at the shelf break and vertical ascent rates within the canyon of about 0.7 cm s−1.