Atlas of Tidal Currents for Halifax Harbour

Contents1 Introduction and disclaimer 32 The Model and its limitations 43 Nontidal Currents 54 How to use this atlas 54.1 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6List of Tables1 The amplitude of the major tidal constituents from an analysis of 1973data from the Halifax Harbour tide gauge. The components additionalto are approximately accounted for by scaling the vectors as describedon section 4. . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Extraction from Tide Tables — Halifax Harbour May 14 1999. . . . . 6¢¡List of Figures1 Full Harbour, high tide . . . . . . . . . . . . . . . . . . . . . . . . . 82 Full Harbour, one hour after high tide . . . . . . . . . . . . . . . . . 93 Full Harbour, two hours after high tide . . . . . . . . . . . . . . . . . 104 Full Harbour, three hours after high tide . . . . . . . . . . . . . . . . 115 Full Harbour, two hours before low tide . . . . . . . . . . . . . . . . 126 Full Harbour, one hour before low tide . . . . . . . . . . . . . . . . . 137 Full Harbour, low tide . . . . . . . . . . . . . . . . . . . . . . . . . . 148 Full Harbour, one hour after low tide . . . . . . . . . . . . . . . . . . 159 Full Harbour, two hours after low tide . . . . . . . . . . . . . . . . . 1610 Full Harbour, three hours after low tide . . . . . . . . . . . . . . . . . 1711 Full Harbour, two hours before high tide . . . . . . . . . . . . . . . . 1812 Full Harbour, one hour before high tide . . . . . . . . . . . . . . . . 1913 Inner Harbour, high tide . . . . . . . . . . . . . . . . . . . . . . . . . 2014 Inner Harbour, one hour after high tide . . . . . . . . . . . . . . . . . 2115 Inner Harbour, two hours after high tide . . . . . . . . . . . . . . . . 2216 Inner Harbour, three hours after high tide . . . . . . . . . . . . . . . 2317 Inner Harbour, two hours before low tide . . . . . . . . . . . . . . . . 2418 Inner Harbour, one hour before low tide . . . . . . . . . . . . . . . . 2519 Inner Harbour, low tide . . . . . . . . . . . . . . . . . . . . . . . . . 2620 Inner Harbour, one hour after low tide . . . . . . . . . . . . . . . . . 2721 Inner Harbour, two hours after low tide . . . . . . . . . . . . . . . . . 2822 Inner Harbour, three hours after low tide . . . . . . . . . . . . . . . . 2923 Inner Harbour, two hours before high tide . . . . . . . . . . . . . . . 3024 Inner Harbour, one hour before high tide . . . . . . . . . . . . . . . . 31DRAFT2

1 Introduction and disclaimerThis atlas was created following a request from the Canadian Armed Forces for informationon currents for navigating Halifax Harbour. It is hoped that it will servethe same purpose as the Atlas of Tidal Currents, Bay of Fundy and Gulf of Maine [1],namely to provide hourly snapshots of tidal currents for the purposes of navigation.Note that in Halifax Harbour the tides are not large, and compared to the Bay of Fundyand Gulf of Maine the tidal currents can be dominated and even reversed by other processes(see section 3). In addition, there are limitations of the computer model used tocompute these currents (section 2).THIS ATLAS IS PROVIDED IN THE HOPE THAT IT WILL BE HELP-FUL BUT BE CAUTIONED THAT IT IS TO BE USED AT YOUR OWN RISK.UNDER NO CIRCUMSTANCES IS ANY RESPONSIBILITY ASSUMED FORDAMAGE ARISING FROM THE USE OR THE INABILITY TO USE THIS AT-LAS.We are interested in providing the best information possible. Feedback on the accuracyor inaccuracy of the depicted currents will help establish whether this productis worthwhile and how it might be improved. Comments may be mailed to the authorat the address on the cover page or e-mailed to dgreenbe@georgs.bio.dfo.ca.DRAFT3

3 Nontidal CurrentsThere are many other processes not considered here that give rise to currents that canhave magnitudes of the same order as the tidal currents shown in this atlas. Some ofthese are:Local wind forcing. This will depend on the force, direction and duration of thewind. It is not uncommon to see magnitudes of 5 to 15 s§ cm .Distant meteorological forcing. Even though the Harbour seems calm, distantweather systems can give rise to sea level changes at the mouth of the Harbourinfluencing the inner Harbour currents to the same degree as the local winds forperiods of hours to days .Resonance. Halifax Harbour can be rung like a bell from passing weather systemsor big waves at the Harbour entrance. The period of this resonant ringing isabout 2.1 hours and the currents can be 5 to 10 s cm [5]. The resonance hasbeen observed to be stronger and more frequent in winter.Estuarine circulation. The fresh water flowing out on the surface is compensatedfor by a deeper saltier flow into the harbour. The currents (5 – 15 s cm )are stronger at times of strong runoff, but are seen at all times of the year [6].4 How to use this atlasThis atlas is meant to be used in conjunction with the current annual Tide Tables forHalifax Harbour (e.g. [2]). The general pattern can be obtained directly from one of thediagrams. Two sets of figures are given; the first set (Figures 1 – 12) covers the wholeHarbour, the second set (Figures 13 – 24) covers the central part in greater detail. Thestrength of the current is determined by comparing the length of the current arrow withthe cm§ 5 current scale vector shown. The current magnitudes are derived assuming¢ an tidal range of 1.24 m; however, Tide Tables indicate the tidal range can be ashigh as 2.1 metres, these should be further scaled for more accurate predictions.1. Find the tidal diagram appropriate to your time relative to the tides in the TideTables. (Remember that the times in the Tide Tables are always local standardtime never daylight saving.)2. Determine the range (in metres) of the tide that includes the time of interest bysubtracting the low from the high tide.3. The scale factor for the currents is range .4. In the special case where the time is exactly at high or low tide (see the secondexample) the range should be taken from the rising or falling tide that immediatelyprecedes that time.DRAFT5

4.1 ExamplesThe sea level from the Tide Tables May 14 1999 at Halifax are shown in table 2.May 14 1999 9:00 ADT (the time you want to know the currents).– Convert to AST — 8:00 (this corresponds to about one hour after high tide).– The charts of interest are: Figures 2 and 14.– Currents will first be scaled according to their length relative to the 5 cmscale arrow on the figure.– The tidal range "! #%$'&(!*),+-"! . is so the scale factor to be applied to thecurrents "! .0/1"!*)32+4"! 5 is .May 14 1999 20:05 ADT.– Convert to AST — 19:05 (this corresponds to high tide).– The charts of interest are: Figures 1 and 13.– Currents will first be scaled according to their length relative to the 5 cmscale arrow on the figure.– The tidal range )1! &%$'&(!*),+-"! # is so the scale factor to be applied to thecurrents "! #0/1"!*)32+4"! 5 is .Time Height (m)0100 0.10650 1.81310 0.21905 2.0Table 2: Extraction from Tide Tables — Halifax Harbour May 14 1999.DRAFT6

References[1] Anonymous. Atlas of tidal currents, Bay of Fundy & Gulf of Maine. Technicalreport, Canadian Hydrographic Service, Fisheries and Oceans, Ottawa, 1981.[2] Anonymous. Canadian tide and current tables, volume 1, Atlantic Coast and Bayof Fundy. Technical report, Canadian Hydrographic Service, Fisheries and OceansCanada, 1999.[3] David A. Greenberg, T. S. Murty, and Alan Ruffman. A Numerical Model forthe Tsunami in Halifax Harbour due to the Explosion in December 1917. MarineGeodesy, 16:153–167, 1993.[4] David A. Greenberg, T.S. Murty, and Alan Ruffman. Modelling the tsunami fromthe 1917 Halifax Harbour explosion. Tsunami Hazzards, 11(2):67–80, 1993.[5] D. McGonigal, R. Loucks, and D. Ingraham. Halifax Narrows: sample currentmeter data 1970-71. Data Report BI-D-74-5, Bedford Institute of Oceanography,Dartmouth, N.S., 1974.[6] Brian Petrie and Philip Yeats. Simple models of the circulation, disolved metals,suspended solids and nutrients in Halifax Harbour. Water Poll. Res. J. Canada,25(3):325–349, 1990.[7] Alan Ruffman, David A. Greenberg, and T. S. Murty. The Tsunami from the1917 explosion in Halifax Harbour. In Alan Ruffman and Colin Howell, editors,Ground Zero - A reassessment of the 1917 Explosion in Halifax Harbour, page327. Nimbus Publishing and Gorsebrook Research Institute for Atlantic CanadaStudies, Halifax, Nova Scotia, 1994.DRAFT7

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sHigh TideDRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 1: Full Harbour, high tide844°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sHigh Tide + 1 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 2: Full Harbour, one hour after high tide944°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sHigh Tide + 2 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 3: Full Harbour, two hours after high tide1044°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sHigh Tide + 3 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 4: Full Harbour, three hours after high tide1144°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sLow Tide − 2 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 5: Full Harbour, two hours before low tide1244°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sLow Tide − 1 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 6: Full Harbour, one hour before low tide1344°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sLow TideDRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 7: Full Harbour, low tide1444°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sLow Tide + 1 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 8: Full Harbour, one hour after low tide1544°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sLow Tide + 2 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 9: Full Harbour, two hours after low tide1644°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sLow Tide + 3 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 10: Full Harbour, three hours after low tide1744°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sHigh Tide − 2 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 11: Full Harbour, two hours before high tide1844°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°34’ 44°36’ 44°38’ 44°40’ 44°42’−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’5 cm/sHigh Tide − 1 Hr.DRAFT−63°40’ −63°38’ −63°36’ −63°34’ −63°32’ −63°30’ −63°28’Figure 12: Full Harbour, one hour before high tide1944°34’ 44°36’ 44°38’ 44°40’ 44°42’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/s−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 13: Inner Harbour, high tide20High Tide 44°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sHigh Tide + 1 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 14: Inner Harbour, one hour after high tide2144°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sHigh Tide + 2 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 15: Inner Harbour, two hours after high tide2244°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sHigh Tide + 3 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 16: Inner Harbour, three hours after high tide2344°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sLow Tide − 2 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 17: Inner Harbour, two hours before low tide2444°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sLow Tide − 1 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 18: Inner Harbour, one hour before low tide2544°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/s−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 19: Inner Harbour, low tide26Low Tide44°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sLow Tide + 1 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 20: Inner Harbour, one hour after low tide2744°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sLow Tide + 2 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 21: Inner Harbour, two hours after low tide2844°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sLow Tide + 3 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 22: Inner Harbour, three hours after low tide2944°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sHigh Tide − 2 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 23: Inner Harbour, two hours before high tide3044°37’ 44°38’ 44°39’ 44°40’ 44°41’

44°37’ 44°38’ 44°39’ 44°40’ 44°41’−63°38’ −63°36’ −63°34’ −63°32’5 cm/sHigh Tide − 1 Hr.−63°38’ −63°36’ −63°34’ −63°32’DRAFTFigure 24: Inner Harbour, one hour before high tide3144°37’ 44°38’ 44°39’ 44°40’ 44°41’