were made not only from widely scattered 

 areas in Saginaw Bay but also from many 

 points along the shore of Lake Huron. All 

 10 bottles released from this station on 

 June 7 were recovered from the Tawas Bay 

 area to the northwest within a short dis- 

 tance of one another (fig. 24 B). After 

 release of these bottles, winds were vari- 

 able for 3 days; next the wind was to the 

 northeast for 3 days; the wind to the 

 southwest a week after release ^parently 

 caused the bottles to land in and around 

 Tawas Point. Bottles released on June 29 

 were recovered for the most part on the 

 eastern side of the Michigan Thumb (fig. 

 30 B). The net wind to the southeast most 

 likely caused currents that Ccirried the 

 bottles to this cirea. The widely scattered 

 points of the 7 recoveries from the 10 

 releases on July 18 follow well, with one 

 exception, the wind track (fig. 36 B). The 

 only logical explanation for the recovery 



STATUTE MILE5 



Figure 13. — Location of 60 recoveries from 

 80 drift bottles released at an outer 

 Saginaw Bay station. Ten releases were 

 made at 8 different times from June 

 through October 1956. A triangle shows 

 release point; X's mark recovery points. 



on the Michigan Thumb after 27 days is the 

 influence of a current entering Saginaw Bay 

 from Lake Huron. The recoveries from 

 releases on August 10 (fig. 46 B) and Au- 

 gust 30 (fig. 52 B) indicate that surface 

 currents flowed toward the east in August 

 and September. Westerly winds prevailed 

 these months. Bottles recovered from 

 releases on September 21 (fig. 59 B) and 

 October 12 (fig. 63 A) apparently were car- 

 ried by currents caused by east and south 

 winds, respectively. The recoveries from 

 October 30 releases (fig. 70 A), although 

 scattered widely, correspond well with wind 

 direction. Apparently the bottles drifted 

 into the bay where one was deposited on the 

 west shore. A reversal in wind direction 

 then drove the bottles over to the Michigan 

 Thum where they landed near the mouth of 

 the bay. 



It is evident from the foregoing dis- 

 cussion that the surface currents of Sagi- 

 naw Bay are closely related to the winds 

 cind consequently are highly variable. This 

 dependence of currents on wind wzis closest 

 for the inner reaches of the bay. Near the 

 mouth of the bay a few bottles were found, 

 the movement of which could not be explained 

 by local wind action (fig. 33 B). Wind 

 direction here at the time of release was 

 to the northeast. The 3 bottles that landed 

 within a day of release, however, traveled 

 to the southeast at least 90° to the right 

 of the wind vector. This variation most 

 probably was brought about by a strong 

 current entering the bay from Lake Huron, 

 causing the bottles to drift at right angles 

 to the wind. Additional variations were 

 noted around Tawas Point and the area north- 

 east of Sand Point. 



Surface currents in the bay apparaitly 

 orient to changing winds in a short period 

 of time. For 2 days prior to release and 

 on the day of release of 10 bottles north- 

 east of Point Lookout, winds were from the 

 south (fig. 32 B). The day after release 

 the south winds diminished and chcinged to 

 north. Surface currents had to reorient to 

 the north winds in a very short time in 

 order to cause the bottles to land as indi- 

 cated. For 4 days prior to release of 10 

 bottles south of Point Au Ores on October 30, 

 strong southerly winds blew (fig. 69 A). 

 The day after release the south winds moder- 

 ated and the second day after release 

 changed to north. The surface currents had 

 to reorient rapidly to the north wind to 



15 



