shown that part of this drop may reflect a true change in sea- level due to 

 cooling of the surface waters in the North Pacific over the last 30 years. 



Analyzing steric sea- level records off California it is found that the 

 hydrographic data is quite noisy but that empirical orthogonal function analy- 

 sis is an effective method for extracting the large scale "signal" from the 

 mesoscale "noise." Most of the nonseasonal upper ocean variability is 

 restricted to the upper 200 ms but located subsurface at about the depth of 

 the permanent thermocline. The dominant signal in nonseasonal nearshore 

 oceanic variability is a very large scale low frequency variation in the flow 

 with biological effects off the coast of California similar to those of 

 Southern Hemisphere El Nino events off the coast of Peru and southern Ecuador. 

 Over shorter time scales the wind stress curl appears to be an important 

 aspect of large scale dynamics of the California Current. In addition, 

 another mode of high frequency variability with very short longshore coherence 

 is isolated that resembles the response expected for coastal upwelling driven 

 by the longshore wind stress. (Author). 



051 CHELTON, D. B., and DAVIS, R. E. 1982. "Monthly Mean Sea-Level 

 Variability Along the West Coast of North America," Journal of Physical 

 Oceanography . Vol 12, No. 8, pp 757-784. 



Linear statistical estimators are used to examine 29 years of 

 nonseasonal, monthly-mean, tide gage sea-level data along the west coast of 

 North America. The objective is exploration of the structure and causes of 

 nearshore ocean variability over time scales of months to years at 20 stations 

 from Alaska to Mexico. North of San Francisco, 50-60% of the sea-level 

 variability reflects a simple inverse barometric response to local atmospheric 

 pressure. There inverted barom effects account for only 10-15% of the 

 variance at stations to the south. 



The dominant signal of inverse-barometer-corrected sea-level represents 

 a nearly uniform rise or fall of sea- level everywhere along the eastern rim of 

 the North Pacific. The interannual aspects of this large-scale sea-level 

 variability are closely related to El Nino occurrences in the eastern tropical 

 Pacific which appear to propagate poleward with phase speeds of -40 cm s-'. 

 Higher frequency aspects of this large-scale sea-level variability appear to 

 represent quasi-geostrophic currents driven by basin-wide scales of wind forc- 

 ing over the North Pacific. 



The nature of local (individual station) inverse -barometer corrected 

 sea- level variability is examined through a series of statistical models and 

 the results are compared with existing dynamical models. The longshore 

 component of wind stress generally forces a larger response than the onshore 

 component (except in large semi-enclosed basins) but the important dynamical 

 aspects of the wind field appear to be basin wide rather than local. The 

 response is consistent with that expected from Ekman dynamics. An apparent 

 non-barometric response to local atmospheric pressure is shown to partly 

 represent an influence of sea-level anomalies farther south. Efforts to 

 determine the nature of this indirect coupling between local pressure and 

 sealevel at stations to the south are somewhat limited by the ability of 

 statistical estimators to accurately isolate the responses of sea-level to a 

 number of correlated inputs. However, evidence is presented indicating that 

 part of the apparent non-barometric response is due to longshore wind-stress 



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