摘要:

Shelf break canyons on the west coast of Canada and the United States have been observed to be regions of enhanced upwelling during southward currents compared to the surrounding shelf break. Most shelf break canyons from Oregon north cross only part of the continental shelf cutting from the shelf break toward the coast but end on the continental shelf well below the mixed layer. Juan de Fuca canyon, on the other hand, cuts the continental shelf from the slope to, and actually continues into, the Strait of Juan de Fuca. This difference in geometry has a very strong effect on the subinertial flow around the canyon. Model canyon shapes, which include convergent bathymetric contours, are constructed and motivated for Juan de Fuca canyon and a typical shelf break canyon. Geostrophic analytic solutions show that the in‐canyon flow in Juan de Fuca canyon is generated by first‐order geostrophic dynamics, whereas in the majority of canyons, of which Astoria is an example, in‐canyon flow is generated by higher‐order effects. This difference is postulated to lead to the observed, very deep upwelling over Juan de Fuca canyon compared to more moderate, episodic upwelling over Astoria

ISSN:0148-0227    

DOI:10.1029/1999JC900240

年代:2000

数据来源: WILEY

摘要:

In this paper we describe modifications to a previous theory for the altimeter electromagnetic bias (EM bias) ofSrokosz[1986]. A major correction introduces a scaling of Srokosz's model by nonnegligible dimensionless ratios that depend on the slope variance of both long and short waves. With these modifications the EM bias is no longer simply a function of the cross skewness between surface elevation and slope but now depends on the variance ratios that represent the modulation between short and long waves. Inclusion of these ratios can reduce previous EM bias estimates by as much as 50%. Different directions for the longwave and shortwave field are also accounted for in the two‐dimensional development of our approach. A radar frequency dependence consistent with observation is also predicted by the new model. Derivation extending our development to the next higher order in wave statistics is also presented and discusse

ISSN:0148-0227    

DOI:10.1029/1999JC900277

年代:2000

数据来源: WILEY

摘要:

Observed probability distributions of sea ice thickness are approximately exponential for thick ice. An explanation is given on the basis of simple representations of the thermal and mechanical processes. The argument predicts that the e‐folding scale for the exponential is proportional to the thermal equilibrium thickness. The constant of proportionality depends on the dimensionless ratio of the rates of the thermal and mechanical processe

ISSN:0148-0227    

DOI:10.1029/1999JC900271

年代:2000

数据来源: WILEY