394 



Fishery Bulletin 104(3) 



34.8N- 



34.6- 



34.4- 



34,2- 



34.0- 



100 



90 



80 



O 



70 



60 



50 s 



0) 



-40 m 



=5 

 O 



-30 ^ 



O 



■20 

 10 

 



-120.4W 



Figure 2 



(A) Coverage boundary (indicated by heavy lines around the black square [Platform Irene]) for 1 May-31 August 1999, 

 Numbers and tick marks around boundary identify bins corresponding to x-axis in panel B. (B) Histogram (gray bars, 

 left-hand scale) and cumulative frequency (bold line, right-hand scale) show fraction of trajectories (in percent) intersect- 

 ing bins around coverage boundary. Panel A shows bin locations. Distance around the coverage boundary (Fig. 2A) in 

 kilometers is also shown (bottom scale). Arrow above histogram shows boundary location nearest Platform Irene. 



12% in 2002, and 14% with the 2002 data for the 1999 

 coverage boundary. Here the total possible data were 

 the number of grid points within the coverage bound- 

 ary for either 1999 (45 grid points) or 2002 (291 grid 

 points) multiplied by the number of hours between 1 

 May and 31 August minus the long gaps discussed 

 above (2952 hours-1057 hours in 1999, 2952 hours-104 

 hours in 2002). Examples of 25 EOF-filled trajectories 

 that started every 120 hours and intersected the 2002 

 coverage boundary are shown in Figure IB. 



The principal quantity used in our study to estimate 

 how Platform Irene might affect transport to nearshore 

 habitat was the histogram of points where trajectories 

 crossed the boundaries of the coverage areas. To deter- 

 mine this quantity, coverage boundaries were divided 

 into 4-km-long segments, or bins. The first bin of each 

 histogram was less than 4 km because distances around 

 the coverage boundaries were not exactly divisible by 4. 

 Bin numbers increased counter-clockwise around the 

 boundaries starting from 1 in the southeastern corner 

 (Figs. 2A and 3A). The smallest numbers identified bins 

 lying along the 50-m isobath. 



Results 



Trajectories originating at Platform Irene were suffi- 

 ciently dense to fill in much of the surrounding area. In 

 2002 for example, EOF-filled trajectories spread over an 

 area of about 20 km in the cross-shore direction by 60 

 km in the alongshore direction (Fig. lA). North of Pt. 

 Arguello, several trajectories crossed the 50-m isobath 

 and some ended very near shore. South of Pt. Arguello, 

 only a few trajectories approached the 50-m isobath. 

 Instead, most turned southward or southwestward and 

 moved offshore. A tendency for trajectories to align par- 

 allel to isobaths was evident in the northern end of the 

 ensemble, although in other areas, such as the southeast, 

 many trajectories lay across isobaths. 



A histogram of points where trajectories crossed the 

 coverage boundary for May-August 1999 exhibited a 

 peak in bin 11 on the offshore side along the 500-m 

 isobath (Fig. 2B, left-hand axis). Table 1 and the cu- 

 mulative histogram (Fig. 2B, right-hand axis) showed 

 that 76% of the trajectories crossed the offshore side 

 corresponding to bin numbers 9-13. A second peak oc- 



