2
522 A. Physical Oceanography OLR (1988)35 (6) along the eastern coastline, confined to the part of the basin east of the Mid-Atlantic Ridge. The blocking effect of the Mid-Atlantic Ridge is reduced considerably at lower latitudes, and the meridional variation of the internal Rossby radius leads to a strongly modified wave field. The E-W wave length increases toward lower latitudes and exceeds the width of the basin at 10°N, thereby giving rise to a phase speed of 10 cm/sec in northerly directions and a group velocity of 19 cm/sec headed southwest. Inst. fur Meeresk. an der Univ. Kiel, Abt. Theo- retische Ozeanogr., Dusternbrooker Weg 20, 2300 Kiel 1, FRG. 88:3271 Yezerskiy, A.B. and V.V. Papko, 1986. Laboratory investigation of large-scale potential flows, in- duced by a packet of surface waves. Izv. Atmos. Ocean Phys. (a translation of Fiz. Atmos. Okeana), 22(9):756-761. Because of viscous and nonlinear effects, the propagation of surface waves induces mean volume flows that have time and space scales much larger than the original perturbations. The generation of such flows is investigated theoretically and exper- imentally. Velocity and particle displacement fields are determined, and a mechanism for the generation of internal waves by excitation of the surface packet is described. Inst. of Appl. Phys., Acad. of Sci., USSR. (fcs) 88:3272 Yu, Zhouwen and Pingxing Ding, 1987. Simplified proof and extension of integral properties of gravity waves of finite amplitude. Acta oceanol. sin. (English version), 6(3):335-343. A simple and direct method is used to deduce relations between the kinetic energy of waves and horizontal momentum, and between different kinds of energies of waves. Several important integral properties of two-dimensional, irrotational, periodic and permanent waves generalized to the case with uniform current existing, establish the concept of wave excess, and some important integral properties of wave excess are deduced. Shandong Coll. of Oceanogr., Qingdao, People's Republic of China. 88:3273 Zufiria, J.A., 1987. Symmetry breaking in periodic and solitary gravity-capillary waves on water of finite depth. J. Fluid Mech., 184:183-206. A weakly nonlinear model is developed to study the bifurcation structure of gravity-capillary waves on water of finite depth. In addition to a very rich structure of symmetric solutions, non-symmetric Wilton's ripples exist. They appear via a sponta- neous symmetry-breaking bifurcation from symmet- ric solutions similar to that for gravity waves. The solitary wave with surface tension is studied with the same model close to a critical depth; the solution is not unique, and further non-symmetric solitary waves are possible. The bifurcation tree has the same structure as for the case of periodic waves. Appl. Math. Dept., Calif. Inst. of Tech., Pasadena, CA 91125, USA. AI80. Internal waves and tides 88:3274 Bunimovich, L.A. and V.V. Zhmur, 1986. Scattering of internal waves in a horizontally nonuniform ocean. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 286(1-6):196-199. This paper addresses a number of global properties of internal wave dynamics using a stochastic analysis to define global properties from local trajectory characteristics. In addition to showing that the presence of oceanic finestructure allows effective scattering of internal wave energy, the authors derive the equilibrium angular spectra of the internal wave field for a flow with velocity shear and illustrate its strong dependence upon stratification. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. (emm) 88:3275 Grigor'yev, P.L., A.S. Tibilov and V.A. Yakovlev, 1986. Scattering of internal waves by a weakly inhomogeneous perturbation of the liquid density field with the shape of the free surface and bottom taken into account. Izv. Atmos. Ocean Phys. (a translation of Fie. Atmos. Okeana), 22(9):734- 737. A210. Ice 88:3276 Galdi, G.P., L.E. Payne, M.R.E. Proctor and B. Straughan, 1987. Convection in thawing snhsea permafrost. Proc. R. Soc., Lond., (A)414(1846): 83-102. Detailed quantitative values are obtained for the critical values of the salt Rayleigh number for both linear and nonlinear stability, for a simplified model appropriate to the onset of buoyant, relatively fresh water motion in a layer of salty subsea sediments. The geophysical problem that motivates this work arises because of the formation of substantial permafrost around the Earth's shores some 18,000

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Page 1: Convection in thawing subsea permafrost

522 A. Physical Oceanography OLR (1988) 35 (6)

along the eastern coastline, confined to the part of the basin east of the Mid-Atlantic Ridge. The blocking effect of the Mid-Atlantic Ridge is reduced considerably at lower latitudes, and the meridional variation of the internal Rossby radius leads to a strongly modified wave field. The E-W wave length increases toward lower latitudes and exceeds the width of the basin at 10°N, thereby giving rise to a phase speed of 10 cm/sec in northerly directions and a group velocity of 19 cm/sec headed southwest. Inst. fur Meeresk. an der Univ. Kiel, Abt. Theo- retische Ozeanogr., Dusternbrooker Weg 20, 2300 Kiel 1, FRG.

88:3271 Yezerskiy, A.B. and V.V. Papko, 1986. Laboratory

investigation of large-scale potential flows, in- duced by a packet of surface waves. Izv. Atmos. Ocean Phys. (a translation of Fiz. Atmos. Okeana), 22(9):756-761.

Because of viscous and nonlinear effects, the propagation of surface waves induces mean volume flows that have time and space scales much larger than the original perturbations. The generation of such flows is investigated theoretically and exper- imentally. Velocity and particle displacement fields are determined, and a mechanism for the generation of internal waves by excitation of the surface packet is described. Inst. of Appl. Phys., Acad. of Sci., USSR. (fcs)

88:3272 Yu, Zhouwen and Pingxing Ding, 1987. Simplified

proof and extension of integral properties of gravity waves of finite amplitude. Acta oceanol. sin. (English version), 6(3):335-343.

A simple and direct method is used to deduce relations between the kinetic energy of waves and horizontal momentum, and between different kinds of energies of waves. Several important integral properties of two-dimensional, irrotational, periodic and permanent waves generalized to the case with uniform current existing, establish the concept of wave excess, and some important integral properties of wave excess are deduced. Shandong Coll. of Oceanogr., Qingdao, People's Republic of China.

88:3273 Zufiria, J.A., 1987. Symmetry breaking in periodic

and solitary gravity-capillary waves on water of finite depth. J. Fluid Mech., 184:183-206.

A weakly nonlinear model is developed to study the bifurcation structure of gravity-capillary waves on water of finite depth. In addition to a very rich structure of symmetric solutions, non-symmetric

Wilton's ripples exist. They appear via a sponta- neous symmetry-breaking bifurcation from symmet- ric solutions similar to that for gravity waves. The solitary wave with surface tension is studied with the same model close to a critical depth; the solution is not unique, and further non-symmetric solitary waves are possible. The bifurcation tree has the same structure as for the case of periodic waves. Appl. Math. Dept., Calif. Inst. of Tech., Pasadena, CA 91125, USA.

AI80. Internal waves and tides

88:3274 Bunimovich, L.A. and V.V. Zhmur, 1986. Scattering

of internal waves in a horizontally nonuniform ocean. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 286(1-6):196-199.

This paper addresses a number of global properties of internal wave dynamics using a stochastic analysis to define global properties from local trajectory characteristics. In addition to showing that the presence of oceanic finestructure allows effective scattering of internal wave energy, the authors derive the equilibrium angular spectra of the internal wave field for a flow with velocity shear and illustrate its strong dependence upon stratification. Shirshov Inst. of Oceanol., Acad. of Sci., Moscow, USSR. (emm)

88:3275 Grigor'yev, P.L., A.S. Tibilov and V.A. Yakovlev,

1986. Scattering of internal waves by a weakly inhomogeneous perturbation of the liquid density field with the shape of the free surface and bottom taken into account. Izv. Atmos. Ocean Phys. (a translation of Fie. Atmos. Okeana), 22(9):734- 737.

A210. Ice

88:3276 Galdi, G.P., L.E. Payne, M.R.E. Proctor and B.

Straughan, 1987. Convection in thawing snhsea permafrost. Proc. R. Soc., Lond., (A)414(1846): 83-102.

Detailed quantitative values are obtained for the critical values of the salt Rayleigh number for both linear and nonlinear stability, for a simplified model appropriate to the onset of buoyant, relatively fresh water motion in a layer of salty subsea sediments. The geophysical problem that motivates this work arises because of the formation of substantial permafrost around the Earth's shores some 18,000

Page 2: Convection in thawing subsea permafrost

OLR (1988) 35 (6) A. Physical Oceanography 523

years ago. With the rise of sea levels the permafrost has responded to the relatively warm and salty sea, which has created a thawing front and a layer of salty sediments beneath the sea bed. Our analysis is based on a model developed by W. Harrison and D. Swift, who have studied this phenomenon off the coast of Alaska. Dipart. di Matematica, Univ. di Ferrara, Via Machiavelli 35, 44100 Ferrara, Italy.

88:3277 Kagan, B.A., V.A. Ryabchenko and A.S. Safray,

1986. A thermodynamic model of marine ice. Dokl. Earth Sci. Sect. (a translation of Dokl. Akad. Nauk SSSR), 286(1-6):203-206.

While sea ice resembles the atmospheric cloud cover as an insulative barrier and a source of latent heat, it differs dynamically, inducing oscillations with pe- riods of several years. A thermodynamic model of sea ice which distinguishes between three seasonal periods (winter, spring, summer/autumn) is devel- oped for incorporation into a seasonal ocean/at- mosphere model and compared against sea ice data for the Northern Hemisphere. Shirshov Inst. of Oceanol., Acad. of Sci., Leningrad, USSR. (emm)

88:3278 McLaren, A.S., M.C. Serreze and R.G. Barry, 1987.

Seasonal variations of sea ice motion in the Canada Basin and their implications. Geophys. Res. Letts, 14(11):1123-1126.

Ice velocities and sea level pressure data from Arctic drifting buoys for 1979-85 are used to examine the seasonal variation of sea ice drift in the Canada Basin. A recurring reversal of the mean anticyclonic gyre is demonstrated in late summer, in response to changes in atmospheric forcing. The identification of this reversal of ice motion is significant for numer- ical modelling of Arctic atmosphere-ocean-ice interactions. Coop. Inst. for Res. in Environ. Sci., Univ. of Colorado, Boulder, CO 80309, USA.

88:3279 Simmonds, Ian and Martin Dix (comment), 1987.

Comment on 'Sea-ice and the Antarctic winter circulation: a numerical experiment,' by J.F.B. Mitchell and T.S. Hills (October 1986, 112, 953-969). Q. Jl R. met. Soc., 113(478): 1396-1403. Dept. of Meteorol., Univ. of Melbourne, Park- ville, 3052, Australia.

A250. Electromagnetic properties

88:3280 Voyt, S.S., V.V. Zhmur and V.V. Fomin, 1986.

Secondary electromagnetic fields of sea currents

in the coaslal zone. Izv. A tmos. Ocean Phys. (a translation of Fiz. Atmos. Okeana), 22(9):738- 742. Inst. of Oceanol., Acad. of Sci., USSR.

A260. Acoustics

88:3281 Bates, B.J. and S.M. Bates, 1987. Stochastic simu-

lation and first-order multiple scatter solutions for acoustic propagation through oceanic internal waves. J. acoust. Soc. Am., 82(6):2042-2050.

The existing theory is modified by (1) the redefi- nition of acoustic scattering to correspond to scattering from internal wave phase fronts as in a phase grating; and (2) recomputation of the frac- tional sound speed to insure statistical agreement with the Garrett and Munk spectrum. The results are then used to compute coherent acoustic intensity as a first-order multiple scatter approximation and by stochastic simulation. The computational results are compared with each other and with the existing theory. Naval Underwater Systems Center, Newport, RI 02841, USA. (emm)

88:3282 Gindler, I.V. and V.G. Petnikov, 1987. Sound

attenuation in a multipath wavegnide for radiation and reception at various depths. Soy. Phys. Acoust. (a translation of Akust. Zh.), 33(2):207- 208. Inst. of Gen. Phys., Acad. of Sci., USSR.

88:3283 Ingenito, F., 1987. Scattering from an object in a

stratified medium. J. acoust. Soc. Am., 82(6): 2051-2059. Naval Res. Lab., Washington, DC 20375, USA.

88:3284 Kravtsov, Yu.A. and V.M. Kuz'kin, 1987. Average

characteristics of the field created by an extended source in an underwater sound channel. Soy. Phys. Acoust. (a translation of Akust. Zh.), 33(2):156- 159. Inst. of Gen. Phys., Acad. of Sci., USSR.

88:3285 Kravtsov, Yu.A. and V.G. Petnikov, 1986. On the

possibilities of phase tomography of the ocean using normal waves. Izv. A tmos. Ocean Phys. (a translation of Fiz. Atmos. Okeana), 22(9):769- 771. Inst. of Gen. Phys., Acad. of Sci., USSR.

88:3286 McDaniel, S.T., 1987. Physical optics theory of

scattering from the ice canopy. J. acoust. Soc.