A Circulation Model for the Discovery Islands, British Columbia

Figures & data

Fig. 1 Map of the Discovery Islands region showing relevant place names, rivers, bodies of water, weather stations, CTD sites, Tide Table sites and the Barnes Bay fish farm.

Table 1. a) M₂ and b) K₁ model tidal elevation amplitudes (cm) and phases (degrees, gmt) versus values arising from tide gauge analyses. Length (days) is the tide gauge time series length while D (cm) is the difference between modelled and observed values in complex space. Tide gauge numbers are consistent with Fig 2.

No.	site	length	Tide gauge		Model		D
			amplitude	phase	amplitude	phase
a)
1	Little River	365	99.6	33.9	99.2	33.7	0.6
2	Powell River	369	100.7	34.3	100.4	33.7	1.0
3	Lund	224	102.2	35.4	100.8	35.1	1.4
4	Twin Islands	369	101.3	35.4	99.5	35.0	1.9
5	Campbell River	365	76.2	14.4	75.6	20.2	7.7
6	Nymphe Cove	539	61.5	350.4	57.3	351.8	4.4
7	Brown Bay	365	93.5	315.9	91.9	315.5	1.7
8	Seymour Narrows	369	94.6	320.1	95.7	319.6	1.4
9	Maude Island East	368	55.6	7.4	52.1	13.9	7.0
10	Welsford Island	364	99.4	35.1	98.2	38.1	5.4
11	Redonda Bay	339	97.5	36.7	99.4	36.3	2.0
12	Channel Islands	288	102.6	35.9	101.2	36.2	1.5
13	Chatham Point	369	90.3	305.1	90.0	305.0	0.3
14	Okis Islands	366	92.0	312.6	89.6	313.0	2.5
15	Owen Bay	369	85.0	319.9	83.4	319.8	1.6
16	Bodega Anchorage	365	72.9	5.7	72.0	348.7	21.4
17	Big Bay	369	75.5	14.9	71.9	10.6	6.5
18	Turnback Point	365	102.0	37.0	99.4	37.5	2.8
19	Orford Bay	282	101.5	37.2	99.9	37.2	1.5
20	Waddington Harbour	169	103.4	38.0	100.8	37.5	2.7
21	Shoal Bay	387	89.8	307.5	88.2	307.3	1.6
22	Cordero Islands	386	85.8	304.4	85.6	302.4	3.0
23	Kelsey Bay	375	117.0	276.3	112.6	274.3	5.9
24	Yorke Island	362	117.1	271.8	112.1	271.2	5.1
b)
1	Little River	365	90.5	287.5	87.6	288.4	3.3
2	Powell River	369	90.4	286.6	87.3	287.3	3.3
3	Lund	224	88.9	287.9	88.2	288.1	0.8
4	Twin Islands	369	90.4	287.5	87.9	288.3	2.8
5	Campbell River	365	82.6	283.7	82.8	285.8	3.1
6	Nymphe Cove	539	77.0	279.9	75.3	282.4	3.8
7	Brown Bay	365	67.9	270.1	66.5	270.4	1.5
8	Seymour Narrows	369	69.2	272.1	69.1	271.2	1.2
9	Maude Island East	368	81.1	283.9	78.9	286.2	3.9
10	Welsford Island	364	91.1	286.9	88.9	289.1	4.1
11	Redonda Bay	339	87.1	287.4	88.7	288.6	2.4
12	Channel Islands	288	89.9	288.0	88.4	288.6	1.7
13	Chatham Point	369	65.4	270.5	64.5	270.2	1.0
14	Okis Islands	366	67.5	269.8	66.1	271.1	2.0
15	Owen Bay	369	67.8	272.7	67.4	273.3	0.8
16	Bodega Anchorage	365	79.8	281.9	73.1	280.5	7.0
17	Big Bay	369	83.3	283.5	79.5	283.8	3.8
18	Turnback Point	365	91.7	287.6	88.6	288.9	3.7
19	Orford Bay	282	90.3	288.1	88.8	289.0	2.1
20	Waddington Harbour	169	89.2	288.2	88.9	288.9	1.2
21	Shoal Bay	387	66.6	269.6	65.1	270.7	2.0
22	Cordero Islands	386	66.1	269.9	64.2	270.7	2.2
23	Kelsey Bay	375	57.7	261.4	56.7	261.6	1.0
24	Yorke Island	362	55.7	260.0	55.7	261.9	1.9

Fig. 2 Locations of tide gauges (numbered circles) and current meters (red triangles) used to evaluate model accuracy. Colour contours are bathymetry (m). Current meters are Nodales Channel (NC), Discovery Passage (DP) and Cape Mudge (CM).

Fig. 3 Horizontal grid and rivers whose discharges were used for the FVCOM simulations.

Fig. 4 Original and smoothed bathymetry (m) for a) a Discovery Channel transect through mooring DP and b) an along-channel transect from the lower reaches of the Homathko River into Bute Inlet. Δh/h values denote smoothing criteria.

Fig. 5 Initial surface salinity and temperature (°C) interpolated from historical climatology and recent observations at the CTD locations shown in Fig 1.

Fig. 6 Winds on 1–28 April measured at the Sentry Shoal, Cinque Islands and Lee Islands weather stations shown in Fig 1.

Fig. 7 Daily water temperatures taken at 1 and 15 m depth at the Barnes Bay aquaculture site for the period 1 June 2009 to 30 June 2010. The grey strip denotes the 1–28 April model simulation period.

Fig. 8 Discharges for the Homathko, Salmon, Oyster and Campbell rivers (EC, 2010b).

Table 2. Estimated and gauged river discharges for 1 April 2010; e = estimated, g = gauged.

River	Estimated or gauged	Watershed area as fraction of Homathko	Discharge (m^3 s^−1)
Powell	e	0.10	8.0
Toba	e	0.310	24.8
Brem	e	0.046	3.7
Southgate	e	0.385	30.8
Homathko	g	1.0	80.0
Estero	e	0.025	2.0
Phillips	e	0.05	4.0
Apple	e	0.035	2.8
Stafford	e	0.045	3.6
Salmon	g	—	80.0
Campbell	g	—	140.0
Oyster	g	—	20.0

Fig. 9 Model co-amplitudes (cm) for a) M₂ and b) K₁.

Fig. 10 Mean model surface elevations and flows at 1 m depth computed by harmonic analyses for the period 4–28 April 2010. Only vectors at nodes separated by a minimum of 600 m are shown in the larger region; all vectors are shown in the Seymour Narrows insert.

Fig. 11 Maximum surface speeds (m s⁻¹) over the 28-day model simulation period.

Fig. 12 Observed and modelled vertical profiles of M₂ and K₁ tidal speed (semi-major axis, cm s⁻¹) at the current meter moorings (Fig. 2) in a) Nodales Channel (NC), b) Discovery Channel (DP) and c) Cape Mudge (CM).

Fig. 13 Observed and modelled mean, “along-channel”, vertical profiles at current meter moorings a) NC, b) DP and c) CM. For CM, “along-channel” was chosen as 160° counterclockwise from east, the angle of inclination of the M₂ major semi-axis.

Fig. 14 Observed and modelled low-pass filtered, “along-channel,” currents (m s⁻¹) versus depth for a) DP (positive is 116° counterclockwise from east), b) NC (positive is 57° counterclockwise from east) and c) CM (positive is 155° counterclockwise from east).

Fig. 15 Model salinities for transects crossing Discovery Channel through mooring DP at a) hour 0 and b) hour 672; and Nodales Channel through mooring NC at c) hour 0 and d) hour 672.

Table 3. M₂ and K₁ along-channel model velocity amplitudes (cm s⁻¹) and phases (degrees, gmt) versus values used in the Canadian Tide and Current Tables (2010). Locations are shown in Fig 1.

	M2				K1
	Observations		Model		Observations		Model
	amplitude	phase	amplitude	phase	amplitude	phase	amplitude	phase
Arran Rapids	456	267	409	266	99	149	78	152
Beazley Passage	369	85	305	89	78	321	62	327
Gillard Passage	356	91	270	93	82	333	60	334
Hole-in-the-Wall	373	269	407	269	79	142	82	148
Seymour Narrows	466	113	425	111	101	337	99	345

EC (Environment Canada). 2010b. Real-time Hydrometric Data [Data]. Retrieved from http://www.wateroffice.ec.gc.ca/index_e.html

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Canadian Tide and Current Tables . 2010 . Discovery Passage and the west coast of Vancouver Island. Volume 6 , Ottawa : Fisheries and Oceans Canada .

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