Islands, the Pacific high-pressure cell located east of the Hawaiian 

 Islands, and the thermal low-pressure cell located in summer over the 

 western United States. During spring and summer the Aleutian low 

 normally weakens and the Pacific high intensifies and moves north- 

 ward. Winds over the Current during this period are mainly from the 

 northwest and are strongest when the Pacific high and thermal low- 

 pressure cells are closest together and relatively intense. Winds 

 weaken or change direction as this pressure gradient decreases. The 

 seasonal change in strength and location of these pressure cells thus 

 causes seasonal changes in the winds (Reid et al. 1958). 



Skogsberg (1936) described three distinct phases or periods in the 

 seasonal hydrography of Monterey Bay. The calendar year opens in 

 the countercurrent or Davidson Current phase. In late fall and early 

 winter of most years, winds are weak and variable and intermittent 

 southerly winds occur. A northward flowing countercurrent is 

 present at the surface close inshore off central California. The gen- 

 eral north-northwest to south-southeast trend of the coastline and 

 Ekman transport of surface water to the right of the wind cause 

 onshore transport of surface waters and piling up against the coast. 

 Minimal solar radiation and strong vertical mixing of surface waters 

 by winter storms decrease SST's to a seasonal minimum during Janu- 

 ary or February. While SST's decline during the Davidson Current 

 period, temperatures at deeper levels slowly increase due to advec- 

 tion of warm waters from the south. For example, temperatures at 50 

 m depth reach a seasonal maximum during December and January 

 (Skogsberg 1936; Bolin and Abbott 1963). The end of the Davidson 

 Current period is variable and difficult to pinpoint. About March, the 

 offshore high pressure cell intensifies and northwest winds become 

 frequent. The resulting Ekman transport causes offshore transport of 

 surface water and. in the nearshore region, some of this water is 

 replaced by cold, nutrient-rich subsurface water upwelled from the 

 upper hundred or so meters. Upwelling is strongest when northerly 

 winds are strongest, and near Monterey usually reaches a maximum 

 in May or June (Bakun 1975). By August, northerly winds begin to 

 slacken and the strong solar radiation of late spring and summer 

 results in a steady rise in SST that usually continues through Septem- 

 ber. A period of calmer winds that Skogsberg ( 1936) called the oce- 

 anic period occurs in September and October. With a slackening of 

 wind stress, the cool, upwelled water begins to sink and is replaced 

 by warmer surface water from offshore. Coastal SST's rise to their 

 highest seasonal values and strong vertical temperature gradients 

 form (Bolin and Abbott 1963). 



Thus the oceanographic regime off Monterey is marked by three 

 distinct periods: the Davidson Current period, occurring during 

 November through February, has weak northerly winds, strong 

 winter storm events, northward current flow, and onshore transport 

 of surface water. The upwelling period, occurring in March through 

 August, has strong northwest winds, southward current flow, off- 

 shore transport of surface water, and upwelling of cool, nutrient- 

 rich water. The oceanic period, occurring during September and 

 October, is a period of calm between the northerly winds of the 

 upwelling period and the southerly winds of w inter. During this 

 period, highest surface temperatures and strongest vertical temper- 

 ature gradients occur. Although these are the average seasonal char- 

 acteristics in the meteorological and oceanic regimes affecting 

 Monterey Bay. there are marked year-to-year differences in both 

 timing and intensity of the events. 



DESCRIPTION OF DATA 



Recorded tide data from the tide station at Monterey, Calif, were 

 chosen for analysis because the tide gage lies along the biologically 



productive upwelling region off central California and is exposed to 

 open ocean conditions with no nearby river discharge that may affect 

 sea level measurements (such as at San Francisco or Crescent City, 

 Calif.). The Monterey gage is the only primary tide station main- 

 tained by the National Ocean Survey (NOS) between San Francisco 

 and Avila, and thus fills a large data gap along the central California 

 coast. The Monterey station has been operated continuously since 

 1963 by the Naval Postgraduate School (NPS) but the time-series 

 data have not been fully analyzed. The tide station is located along 

 the southern edge of the bay near the end of Monterey Municipal 

 Wharf No. 2 where the water has a depth of approximately 6.8 m. 

 Because of the open shape of the bay and the narrow width of the con- 

 tinental shelf, tide measurements obtained here are presumed to 

 approximate those of the open coast. 



In addition to sea level data, meteorological and oceanographic 

 data representative of the Monterey area, including surface atmo- 

 spheric pressure data, geostrophic wind data, surface salinity and 

 temperature data, and deep hydrocast data were used in this study. 

 The geographic proximity of the various data sources allowed direct 

 comparison of variables with minimal problems resulting from spa- 

 tial distortion. Figure 1 shows the location from which each of the 

 data sources was derived, along with bathymetric contours. 



•■'200 100 so 



H ydrog rap h ic Station 

 Monterey Tide Gage 



Surface Salinity and 



Geostrophic 

 Wind Co tculat tons 



N 



n 



Depths in Meiers 



|_ji 



37'0rf- 



nding 



. Temperature 



36°3lT— 



122-00' 

 J I I I T>~-"i -■.. 



Figure I. — Map of Monterey Ba>. Calif., region showing location of data 

 sources. 



Monterey Sea Level Data 



Tide Gages. — A standard recording tide gage, which traces tide 

 heights continuously on a strip chart, was installed at the Monterey 

 tide station by NPS personnel in June 1963. This analog system is 

 entirely mechanical and is highly dependable when maintained prop- 

 erly. A drum-mounted strip chart is rotated by a spring-driven clock 



