A Note on the Tides in Bass Strait 



by R A Pen i (« k 



Amongst the manners of the 

 Murine Study <3ttjup ot Victoria thftre 



had been considciablc discussion 0(1 

 some apparent anomalies of nines 

 nl low lute n| v;inons localities in 

 Hass Sii.ni, .mil speculation thai the 

 wave caused hy Ihe tnlal torees. swept 

 south around Tasmania, in some way 

 affected the tides in Bass Strait. It 

 was therefore deeided lo analyse the 

 tidal movements in and around Bass 

 Strait hy detailed examination of the 

 tide tables m older in lesi these 

 speculations 



The ha.sie data for ihe analysts 

 were eoniamed in ihe Australian 

 National lute I ahles in I'.iM I loi 

 Predicted Potts unit in Part H lor 

 Seeondary Pons prom these tubles 

 a list ol 21 localities was compiled 

 lor which limes ol high lutes weic 

 available. Of these. Sydney was 

 included lo provide a zero time: Hob- 

 art and Ponland and Warinamhool 

 were to provide information on tide 

 wave travel around Tasmania. five 

 Secondary Ports were available alone 

 the island chain fiom Wilson's 

 Promontory to north-east cornet of 

 Tasmania, two only available ul 

 western entrance lo the Strait; Ihe 

 ten remaining availahle locahhes. 

 were within the atca of H.iss Strait. 



( o-iUlul Ibtei for Hixh 1 Mes in 

 Bum Strait 



Based on the tubulated iiil.uni.i 

 lion co-tidal lines were drawn for 

 localities whose lime of high udc 

 was I. I). Ill and IV hours alter tin 

 time of high lide at Sydney. This was 

 done for several monthly periods 

 Sydney was selected lo provide the 



/cio Imu' base because Ihe lide WMl 

 CKissmjr the I asman Si:a from the 

 ihreclion ol New Zealand approiicrns 

 Australia's east coast on a ncatlv 

 noi lh south hue. T his has iccu, , 

 been dcsu ibed bv P. G. Walton Snjjft 

 (Sea Frontiers 14, 6) in an urticlc 

 on the tides of the Pacific. 



I able I shows co-tidal lines fm 

 selected days ut the lunar month 

 commencing U IVcemher, l%<) jfa 

 hjture in Ihe circle wilhm the inn 

 line ol l.ismiiua tepresents 11* 

 number 61 vlayx nl'lcr new moon 

 Where u occurs, the moon's declina- 

 lion is also shown as "Chid. S." "Decl. 

 zero" of "Heel N". Both the age of 

 the moon and its declination nun 

 dominate the tidal forces and will he 

 lesponsihle for any observed cluing 

 fiom normal. 



Of the 30 days for which calculi., 

 lions weie made only 12 ate sUmn. 

 these being somewhat different from 

 the normal, most Ircciucnt configura- 

 tion of which I I Januaty is a tvpic, 

 example Ihe constant repetition ol 

 this simple pattern is held to he the 

 musi importanl chatacleiistic of the 

 tides in Bass Strait. This simple, most 

 irecjuciiity met with eoufigurauoo 

 consists ol hvo co-lide lines reprt- 

 scnting the same time running norlh- 

 souih at approximately each end of 

 Bass Strait This means lhal localities 

 on these lines, thoush miles apart, 

 all have the same tide times. Qccr 

 the pehod.s studied Ihlv W.ts hy Ut 

 ihe mos» common eon»iguriitii"t 



The breakdown of this partem \*\ 



•M I i AiKlnlm 



I A^llrMiin I rjjtt. Mjrtor Si Cirwii .1 



VJtwili C NUfunu Nhmini >■< VM« - 



14B 



Vict. Nat Vc4 B8 



