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.

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Triaxial experiments, at confining pressures in the range 0–13.79 MPa, have been performed on glacial ice collected from four icebergs and one glacier. Tests were conducted at strain rates in the range of 5 × 10−5 to 5 × 10−5s−1 and at four temperatures in the range of −1° to −16°C. Depending on test conditions, the ice failed by one of four possible modes ductile deformation, due to extensive non-interacting microcracks; fracture along a shear plane followed by continuous or stick-slip sliding; large-scale brittle fracture; and combined ductile and shear-plane fracture and slip The strength Increased with decreasing temperature, increasing strain rate up to 5 × 10−3s−1 and increasing confining pressure at the lower temperatures. The strength at 5 × 10−2s−1 was lower than at 5 × 10−3s−1 probably because extension and interaction of microcracks is enhanced at the higher rate. For higher confining pressures at −1°C, the strength decreased due to freezing-point depression. The ice from the different sources exhibited different mean uniaxial compressive strengths. The mean number of air bubbles per unit volume correlated with the mean uniaxial compressive strengths and this may be the dominant factor distinguishing the strengths of the various ice types.

Triaxial experiments, at confining pressures in the range 0–13.79 MPa, have been performed on glacial ice collected from four icebergs and one glacier. Tests were conducted at strain rates in the range of 5 × 10−5 to 5 × 10−5s−1 and at four temperatures in the range of −1° to −16°C. Depending on test conditions, the ice failed by one of four possible modes ductile deformation, due to extensive non-interacting microcracks; fracture along a shear plane followed by continuous or stick-slip sliding; large-scale brittle fracture; and combined ductile and shear-plane fracture and slip The strength Increased with decreasing temperature, increasing strain rate up to 5 × 10−3s−1 and increasing confining pressure at the lower temperatures. The strength at 5 × 10−2s−1 was lower than at 5 × 10−3s−1 probably because extension and interaction of microcracks is enhanced at the higher rate. For higher confining pressures at −1°C, the strength decreased due to freezing-point depression. The ice from the different sources exhibited different mean uniaxial compressive strengths. The mean number of air bubbles per unit volume correlated with the mean uniaxial compressive strengths and this may be the dominant factor distinguishing the strengths of the various ice types.