摘要:

The polar oceans contain sea ice of many thicknesses ranging from open water to thick pressure ridges. Since many of the physical properties of the ice depend upon its thickness, it is natural to expect its large‐scale geophysical properties to depend on the relative abundance of the various ice types. The ice pack is treated as a mixture whose constituents are determined by their thickness and whose composition is determined by the area covered by each constituent. A dimensionless functiong(h), the ice thickness distribution, is defined such thatg(h)dhis the fraction of a given area covered by ice of thickness greater thanhbut less thanh+dh. A theory is developed to explain how the ice thickness distribution changes in response to thermal and mechanical forcing. The theory models the changes in thickness due to melting and freezing and the rearrangement of existing ice to form leads and pressure ridges. In its present form the model assumes as inputs a growth rate function and the velocity field of the ice pack. The model is tested using strain data derived from the positions of three simultaneous manned drifting stations in the central Arctic during the period 1962–1964 and growth rates inferred from climatological heat flux averages. The results are compared with estimates ofgbased on submarine measurements of ice thickn

ISSN:0148-0227    

DOI:10.1029/JC080i033p04501

年代:1975

数据来源: WILEY

摘要:

A large‐scale area of pack ice contains ice of various thicknesses from zero to many meters. As the area deforms, thin ice is ridged into thicker ice, in a way that depends on the strain rate and the instantaneous thickness distribution. By equating the plastic work to the production of gravitational potential energy and the frictional dissipation in this ridging process we relate the yield curve for plastic deformation of the ice pack to the way ice thicknesses are redistributed by ridgin

ISSN:0148-0227    

DOI:10.1029/JC080i033p04514

年代:1975

数据来源: WILEY

摘要:

Airborne laser profiles of swell entering the drift ice off the east coast of Newfoundland were made using a Geodolite profiler mounted in a DC‐4 ice patrol aircraft. Concurrent infrared imagery along the track enabled the floe size distribution to be recorded. A linear decay of wave energy with ‘effective penetration’ (distance penetrated multiplied by fractional ice cover) was found, the decay rate increasing with wave frequency. A simple theoretical model based on progressive reflection from rows of floes gave good agreement with the observa

ISSN:0148-0227    

DOI:10.1029/JC080i033p04520

年代:1975

数据来源: WILEY

摘要:

A monochromatic unidirectional wave train, incident on a plane beach and strongly reflected there, is shown to transfer energy to edge waves of lower frequency through a weak nonlinear interaction. For any angle of wave incidence the most readily excited edge wave perturbation consists of two low‐mode progressive edge waves, generally having different frequencies and wave numbers, traveling in opposite directions along the beach. Standing edge waves, which might form stationary morphologic features with a regular longshore rhythm, are theoretically only excited when the primary surface waves are normally incident. However, edge waves generated by almost normally incident primary waves may be linked to features which slowly migrate along shore. On beaches bounded by headlands or jetties the progressive edge waves excited would be reflected at both ends, forming a complex pattern of standing waves. For beaches bounded at one end, only one of the edge waves would be standing. Regular beach cusps would therefore be expected in the vicinity of barriers. These cusps should decrease in relief with increasing distance from the obstacle as the reflected edge wave, which is not being actively forced, dies away due to viscous dissipation and further nonlinear interactions. Intriguingly, the cusps should have slightly different wavelengths on either side of the obstacl

ISSN:0148-0227    

DOI:10.1029/JC080i033p04529

年代:1975

数据来源: WILEY

摘要:

A first‐order analysis of the skylight scattered from the sea surface for understanding the mechanism of transfer of wave profile to photographic image has been given by Kasevich et al. (1971). The analysis is now extended to second order and numerically evaluated for clear blue and uniform overcast skies. The theoretical results indicate experimental conditions required to obtain a photographic transparency with optical transmittance linearly proportional to sea wave profile. Experimental parameters include sun angle, camera orientation, and maximum wave slope. Fourier analysis of the transparency by coherent optical processing methods will give the directional power density spectrum of the wave field (Stilwell, 1969

ISSN:0148-0227    

DOI:10.1029/JC080i033p04535

年代:1975

数据来源: WILEY

摘要:

A model is presented in which the operation of the terrestrial carbon cycle has been simulated under a set of varying parameters, notably different flux ratios ϕ = Corg/Ccarbin the total rate of carbon transfer to sediments and different ratios κ =kCorg/kCcarbof the recycling constants of both sedimentary carbon species. It can be demonstrated that variations by ±50% of an assumed (and most plausible) value of ϕ = 0.125 (even over time spans of some 108yr) have almost negligible effects on the isotopic composition of carbonate carbon and organic carbon in the sedimentary reservoir, provided the long‐term average of this parameter (i.e., ultimately of the burial rate of organic carbon) remains approximately constant. Accordingly, the standard deviations displayed by the fossil δ13Ccarbrecord would allow for considerable variations of the assumed ϕ over the geologic past. With the Corgreservoir constituting the stoichiometric equivalent of photosynthetically produced oxygen, the evolution of the terrestrial O2budget may be traced through geologic history within certain limits. Moreover, the model proves helpful in elucidating major isotopic anomalies in the sedimentary carbon record as well as in imposing limiting conditions on dating the beginnings of photosynthesis (about 3.7 × 109yr ago according to our calcu

ISSN:0148-0227    

DOI:10.1029/JC080i033p04542

年代:1975

数据来源: WILEY

摘要:

Hydrodynamic and chemical kinetic calculations are used to show that megaton (Mt) nuclear explosions near the ground produce, in the air that is shocked above 2200°K and quickly cooled by expansion, 0.8×1032NO molecules/Mt. Inside this region the air is still so hot that further production or destruction of NO may take place. An upper limit to the production is obtained by assuming that the hot inner air mixes with undisturbed air, producing an additional 0.7×1032NO molecules/Mt, giving a total of 1.5×1032NO molecules/Mt. A lower limit is obtained by assuming that during the fireball rise all of the shocked air containing NO is entrained and mixed into the hotter air, and slow cooling of the mixture reduces the total NO to 0.4×1032molecule

ISSN:0148-0227    

DOI:10.1029/JC080i033p04553

年代:1975

数据来源: WILEY

摘要:

The effect of radial velocity of an ocean wave when viewed by a conventional side‐looking synthetic aperture radar is to position the processed image incorrectly in the cross‐radial direct

ISSN:0148-0227    

DOI:10.1029/JC080i033p04555

年代:1975

数据来源: WILEY

ISSN:0148-0227    

DOI:10.1029/JC080i033p04556

年代:1975

数据来源: WILEY

ISSN:0148-0227    

DOI:10.1029/JC080i033p04557

年代:1975

数据来源: WILEY