Oceanography 101 Cruise Report

Exploring the Tides & Currents of Puget Sound with the Acoustic Doppler Current Profiler (ADCP)

Paul A. McWilliams R/V Clifford A. Barnes Puget Sound, Washington Friday Afternoon May 14, 2004 Introduction...... - 3 - Methods...... - 5 - Secchi Disc...... - 5 - Sediment Grab Sampler...... - 5 - Plankton Nets...... - 6 - CTD...... - 6 - ADCP...... - 7 - ORCA Mooring...... - 7 - Results...... - 8 - Contours...... - 8 - Profiles...... - 9 - Temperature & Salinity...... - 9 - Discussion...... - 10 - Predictions...... - 10 - Direction...... - 11 - Magnitude...... - 11 - Velocity...... - 11 - Temperature & Salinity...... - 12 - Analysis & Interpretation...... - 12 - Direction...... - 12 - Magnitude...... - 12 - Velocity...... - 12 - Temperature & Salinity...... - 13 - Conclusions...... - 14 - Figures & Charts...... - 16 -

2 Introduction

Rapid growth of the residential areas of North King County and South Snohomish County have exceeded the capacity of the existing wastewater treatment and effluent discharge facilities located at West Point in Seattle.

The existing sewage treatment plant and effluent discharge located adjacent to Seattle’s Discovery Park at West Point has been in operation since 1966, and is capable of 133 gallons of sewage per day. Sewage influent is treated through a series of processes that include skimming, settling, and bio-treatment by aerobic bacteria. The treated sewage, known as effluent is then discharged deep into Puget Sound through a pipe and diffuser.

A new wastewater treatment plant will be constructed to meet the demand expected as a result of growth in the North King and South Snohomish County area by 2010. The Brightwater Plant will be located north and east of Woodinville and the effluent will be discharged into Puget Sound from a diffuser located 5200 feet from the shoreline at Point Wells.

The Point Wells location was chosen with careful concern for the circulation patterns of Puget Sound. Even though much of the expected growth is farther north, near Everett, the Point Wells site was chosen with the hope that discharged effluent will be carried to the north and west through Admiralty Inlet and out the Straits of Juan de Fuca to be diffused in the Pacific Ocean. A concern is that circulation patterns may carry the effluent into waters with poor circulation to the north and east including Possession Sound, Port Gardner Bay, Saratoga Passage, and Port Susan.

In order to assess and study conditions at the proposed Brightwater discharge site, a group of University of Washington Oceanography 101 students conducted a

3 week of research cruises aboard the University of Washington research ship R/V Clifford A. Barnes. The students employed a number of tried and true oceanography tools along with state of the art sensors to measure and record conditions Puget Sound between Point Wells, south of Edmonds, and West Point in Seattle at 3 cast stations (See figure 1): 1. West Point—47˚39.31N 122˚26.76W 2. ORCA 1 (Near the Buoy)—47˚45.81N 122˚23.87W 3. ORCA 2 (Offshore)—47˚45.49N 122˚24.86W

The last cruise took place on the afternoon and evening of Saturday, May 14, 2004. The weather for this cruise was calm with a clear sky, bright sunshine, temperatures near 61˚F, and light and variable winds.

This report focuses primarily upon analysis of data Gathered by the Acoustic Doppler Current Profiler, or ADCP, aboard Clifford A. Barnes during the first and last days of the Cruise. Cruises on Saturday May 8, 2004, and Friday May 14, 2004, were chosen because of the wide difference in tide range, tide stage, and weather conditions between the two days. Spring tides were experienced on Saturday, while Friday’s tides were much less pronounced neap tides.

Currents in Puget Sound, like all bodies of water connected to the ocean, depend largely on tides. Wind, geography, and other factors also have their effects on the direction and magnitude of currents, but tidal forces from the Pacific Ocean must also be a major driver of currents. If this is true, then we should be able to make some predictions about the behavior of currents by looking at tide tables for Puget Sound. Once we have made those predictions we can use Data gathered from the ADCP aboard Clifford A. Barnes during the Ocean 101 cruises to test our hypotheses. Conductivity, Temperature, and Depth (CTD) data will also be compared for apparent tidal effects on temperature and salinity.

See the online version of this report including ADCP screen captures at: http://students.washington.edu/paulmcqm/oceanreport.htm

4 Methods

Students aboard R/V Clifford A. Barnes collected data and water, plankton, and benthic organism samples from Puget Sound using the following tools and instruments:

Secchi Disc

The Secchi disc is a device for determining the relative clarity of the water. It consists of a simple white wooden disk on the end of a weighted and measured line marked at intervals with colored tape. The disk is lowered into the water until it is no longer visible. The depth is then read from the marks on the line and recorded. The Secchi disc is very useful because it is simple, fast, reliable, and cheap. Hand tended, it does not require any kind of power. The disadvantage of the Secchi disc is that it can only be used to measure how deeply light penetrates from the surface, it doesn’t indicate the reason that the light is obscured, and the vessel must be stopped to deploy it.

Sediment Grab Sampler

The sediment grab sampler is a device for obtaining samples of sediment material from the very top layer of the seafloor. It consists of two metal scoops mounted together like scissors, which are lowered to the bottom by a steel cable. The sediment grab sampler is designed so that it can be lowered in a fixed open position. After the sampler has reached the bottom the cable is allowed some slack. When the cable is heaved in, the jaws of the metal scoops swing shut grabbing a scoop of the seafloor. The advantages of the Sediment Grab sampler include quick and relatively easy deployment and grabbing fairly large footprint. However, unlike other box and core samplers, the Sediment Grab Sampler does not preserve the stratification of the sediments and only grabs the very top layers of the bottom.

5 Plankton Nets

Plankton nets are used to collect floating plants and animals from the water column. They are deployed over the side and retrieved aboard by steel cable. Nets with different mesh sizes are used to capture different kinds of plankton. The nets are hauled in slow enough that swimming animals are able to escape. Three types of plankton nets were employed during this cruise:  Vertical net  Closing net  Phytoplankton net

CTD stands for Conductivity, Temperature, and Depth. The CTD is a versatile research tool that has recently revolutionized the ability of oceanographers to gain real time measurements of salinity, temperature, and other aspects of the water column. Data from the CTD is delivered to the ship in real-time through a special steel cable with an electrical wire in the center. The CTD unit employed aboard Clifford A. Barnes includes 12 bottles that can be closed at specific depths to sample separate parts of the water column, and a package of 5 sophisticated sensors:  Conductivity—because the amount of electrical current that seawater will carry is related to the amount of dissolved salts present, oceanographers use this to measure salinity.  Temperature—provides a clear picture of the temperature profile of the entire water column.  Depth—water pressure is proportional to depth. The CTD measures the pressure of the water to figure out how deep it is at any given moment.  Transmissometer—measures the relative clarity of the water at given depths by measuring the intensity of a light beam at a senor a known distance from the transmitter. This tells something about the amount of suspended particles in the water.  Fluorescence—measures the levels of chlorophyll in the water column.

6  Irradiance—measures the intensity of light received from the surface.  Dissolved Oxygen—measures the amount of dissolved oxygen present in the water column.

The ADCP or Acoustic Doppler Current Profiler is a device that uses the Doppler effect—the compression or expansion of reflected sound waves—by recording acoustic reflections from suspended particles in the water to determine the direction of water movement throughout much of the water column. It provides information about the direction and velocity averages within the water-column on 10-second intervals. The ADCP employed aboard Clifford A. Barnes is specifically tuned to see the middle section of water column. Accordingly, it cannot provide information about the bottom 15% of the water depth due to backscatter from the bottom and cannot provide information from the near surface layers because of the noise of the ship and the motion of the sea surface. The ADCP measures the movement of water relative to the sensor mounted on the ship. Accordingly, the motion of the ship must be taken into account if the water currents are to be observed correctly. In order to accomplish this, the ADCP receives input from the ships Global Positioning System (GPS) which allows it to account for much of the ships motion. An example of the difference between data corrected for the ships motion and uncorrected data is shown in figure 2.

ORCA Mooring

The ORCA mooring, or Optical Remote Chemical Analyzer, is a buoy moored south of Point Wells, on the east side of Puget Sound, in water with a depth of about 150 meters. The ORCA mooring employs a number of sensors to measure conditions in the water column at its location. The sensor package includes a set similar to those on the CTD, with the addition of total gas and N2, Nutrients, Currents, and meteorological sensors. Data from the ORCA mooring is transmitted by a cell-phone type system so that it is immediately available to researchers at UW.

7 Results

ADCP data is viewed using RD Instruments Win ADCP software. Win ADCP normally displays data in three different windows: the profile, the contour, and detail contour. Profiles will be examined for CTD casts and tidal events.

Contours The contour display diagrams water column movement with a color coded display of any one of six data types: east velocity, north velocity, vertical, error, magnitude, and direction. For each type of graph except for the direction display, millimeter/second velocity or speed values are color coded on a continuum from blue on the zero or negative end to red on the high or positive end. Light blues greens and yellows indicate the middle values. On positive/negative graphs, green represents values close to zero. For example, on a north velocity graph, which shows the velocity of water moving north in mm/s, Red and warm colors indicate strong northward water movement, green indicates water not moving north or south, and blue indicates southward movement. So, a north velocity graph that is “warmer” indicates stronger northward water movement. Similarly the magnitude contour, which does not have negative values, shows the amount of water movement (independent of direction) with warmer colors indicating higher values. Thus a “warmer” magnitude graph indicates faster currents. Table 1: ADCP Contour comparisons for different data types for Saturday May 8 Friday May 14 Cruises. (figures 3-7) Data Type Saturday May 8 Friday May 14 Direction Mostly magenta, purple, & red More greens and blues Magnitude Significant amounts of red Some what cooler, more blue areas North Velocity Strong yellows & reds Green with some blues Strong blue and red trends at Short duration blue and red areas, East Velocity different times mostly green Error Mostly green blue & yellow spots Mostly green blue & yellow spots

Profiles The Profile can provide graphs of 6 data types: east velocity, north velocity, vertical, error, magnitude, and direction. North and east velocities, magnitude

8 and direction graphs were captured for each of the various casts and tidal events. This setting shows three profiles side by side in the Win ADCP window. The left- hand graph shows both the north and east velocities. North velocity is shown in green, so a positive green value indicates northward water movement. Likewise, negative green values indicate southward water movement. East velocity is shown in the same way in red. The magnitude graph, in the center, only gives the speed of the moving water in red, without any direction information. The right- hand graph shows direction of water movement in blue with north on the outside edges and south at the center.

The data entries in Table 1 reflect “best-guess” averages from each profile. Screen captures which correspond to the times of the associated events listed in each row of the table. Table 2: ADCP Profile readings from screen captures coordinated with CTD casts and notable tidal events for Cruise 1 and Cruise 6 AM&PM (figures 8-19) Date Time Tidal Stage Event Velocity Magnitiude Direction (2004) (PDT) (mm/s) (mm/s) (average) 5/8 0912 Ebb Cast 3 S 500 500 S 5/8 1018 Ebb Cast 2 NW 500 750 NW 5/8 1036 Ebb Max Ebb NW 500 500-750 NW 5/8 1039 Ebb Cast 1 NW 250 <500-750(deep) XX 5/14 0818 Ebb Cast 1 SE 250 <500 NE 5/14 0927 Low Slack Cast 2 NW 500 500 NW 5/14 0949 Flood Cast 3 None <250 XX 5/14 1213 Max Flood Max Flood S 500 500 S 5/14 1541 High Slack Cast 3 None 0-500 XX 5/14 1619 Ebb Cast 2 SW 250 250-500 S 5/14 1715 Ebb Cast 1 N 250 250-500 N

Temperature & Salinity See charts 1a-6c in the Figures section at the end of the report to see the temperature and salinity profiles observed using the CTD . Discussion

9 Predictions

A review of tide tables (Table 3) for the Saturday, May 8, and Friday, May 14, cruises will allow us to make some predictions about direction, velocity, and magnitude for currents on those days. These two days are good for comparison because the Saturday cruise occurred during ebb tide, between lower high-water and lower-low water, on a large tidal range, while the Friday cruise occurred mostly during a low tidal range flood with beginnings of ebb at the end of the afternoon cruise. Friday’s lower high-water high tide occurred during the afternoon leg cruise. Consequently, currents for large and small tidal ranges and for ebb and flood tides can be compared. Table 3: Predicted Tides for Saturday and Friday Cruises

Tides Meadow Point, Shilshole Bay: May 2004 Sa 8 Low 2:10 AM 7.2 5:41 AM Rise 12:54 AM 86 8 High 6:53 AM 10.6 8:32 PM Set 8:32 AM 8 Low 2:20 PM -2.9 8 High 10:04 PM 11.8

F 14 High 2:33 AM 11.4 5:32 AM Rise 4:00 AM 24 14 Low 9:13 AM 2.8 8:40 PM Set 4:06 PM 14 High 3:10 PM 8.1 14 Low 8:36 PM 3.5

Tides Edmonds: May 2004

Sa 8 Low 2:07 AM 7.2 5:40 AM Rise 12:55 AM 86 8 High 6:53 AM 10.4 8:32 PM Set 8:31 AM 8 Low 2:17 PM -2.9 8 High 10:04 PM 11.5

F 14 High 2:33 AM 11.1 5:32 AM Rise 4:00 AM 24 14 Low 9:10 AM 2.8 8:40 PM Set 4:06 PM 14 High 3:10 PM 8.0 14 Low 8:33 PM 3.5

Direction The inner part of Puget Sound is, for the most part, a long narrow north-south oriented body of water. The major point of input for tidal influence from the Pacific Ocean is Admiralty Inlet, which joins Puget Sound just to the North and

10 West of the cruise location off Edmonds. During flood, or incoming, tide the primary direction of water currents off Edmonds, Point Wells, and West Point should be toward the south because water passing into the sound from Admiralty Inlet must flow southward to fill the Southern Reaches of Puget Sound. (In contrast, north flowing currents-filling Port Gardner Bay and Port Susan, should be expected to the north of Edmonds.) During Ebb, or outgoing, tides current flow should be primarily in a northward direction between West Point and Point wells, with increasing west flow off Edmonds, as water from the south parts of Puget Sound returns toward Admiralty Inlet. The Saturday cruise occurred during ebb tide, so we would expect to see prevailing north flowing currents. Friday’s ADCP data should indicate southward flow.

Magnitude A larger tidal range means that more water must move into and out of Puget Sound during the same 6-hour period. Therefore fast flowing flood and ebb currents would be expected for days with larger tidal ranges. Because of the larger tidal range for Saturday’s Cruise, 13.5 feet versus 5.3 feet for Friday, the ADCP data for Saturday should show greater magnitude than that for Friday.

Velocity Velocity, a vector quantity, is a combination of direction and magnitude. Accordingly velocity predictions are similar to those for both direction and magnitude. For Saturday’s cruise, strong ebb currents mean that the ADCP should have recorded fairly strong north and west velocities for most of the cruise. Friday’s ADCP data should demonstrate weaker south oriented velocities because of the weaker flood tide.

Temperature & Salinity Flood tides should bring colder, saltier, ocean water into Puget Sound while ebb tides should carry the warmer, fresher, surface waters out of the sound. Thus, Saturday’s strong ebb tide should create a greater stratification at each of the stations as the top layer of fresh surface waters is carried out over the underlying colder and salty layer. A stronger thermocline should also be apparent on

11 Saturday for this reason. The weaker flood tide on Friday should bring cold waters into the sound, and because the tide was in flood with a just the beginnings of an ebb at the end, a shallower thermocline should be expected especially when considering that Friday was bright and sunny and the weather had been that way for several days.

Analysis & Interpretation

Direction The ADCP data show that the currents in central Puget Sound do flow predictably with the tides. The strong pink, purple, and magenta concentration in the direction contour for Saturday (figure 3) shows that during the strong ebb current the primary flow for that cruise was is in a northward direction. Similarly the Direction Contour from Friday cruise shows more blues and greens, which indicate southward and eastward flows, during the middle and later part of the day because of the flood tide that occurred at that time.

Magnitude The magnitude graphs (figure 4) show the expected result that currents flow faster and more energetically on days with larger tide ranges. The Saturday contour does appear to be somewhat “warmer” with more red and orange areas than the Friday contour, as predicted.

Velocity The north and east velocity graphs, which combine direction and velocity, also show strong agreement with the tide based current predictions. The warmer colors in Saturday’s north velocity graph (figure 5) confirm that most of the water movement is northward during the ebb tides of the Saturday cruise. The shades of blue in the Friday contour are not as strong as the warms in the Saturday contour, but this is consistent with prevailing northward currents that are weaker because of the smaller tidal range. Perhaps more important is the east velocity contour for Saturday (figure 6), which shows significant amounts of blue during

12 the peak ebb periods, suggests that strong movement of water to the west occurs from the areas off Point Wells.

The profiles for each of the CTD cast stations show strong northward and, more importantly, westward tendencies during ebb tides (table 2, figures 11, 12, 15 and 18). Likewise, southward velocities are evident in profiles during flood tides (table 2, figures 9 and 19).

Temperature & Salinity Some correlation was found between tides and salinity/temperature profiles and several interesting aspects of the various CTD profiles were observed. Although Saturday’s Cast 1 (Charts 3c and 6c) coincided closely with a maximum ebb tide, the maximum flood on the Friday occurred while R/V Clifford A. Barnes was close to Edmonds Marina for a crew change. As a result, no CTD cast can be closely related to a maximum flood. Fridays AM’s cast 2 (Charts 1b and 4b) is representative of low slack-water and Friday PM’s Cast 3 (Charts 2c and 5c) show high slack-water conditions.

A comparison of cast 1 temperature and salinity profiles for Friday AM and PM seems worthwhile. Friday AM’s cast 1 (Chart 1a and 1b) was taken close to the end of an ebb tide. The top 20 meters or so of the water column are a good deal warmer and a strong thermocline is evident at a depth of approximately 41 meters. This arrangement is consistent with the notion that warmer, fresher surface waters would be drawn out over the colder deep waters.

Friday’s PM cast 1 (chart 2a and 2b) shows very different profiles. The water column is cooler at the surface by about a ¼ degree. This despite the fact that the sun had been shining on the water for many more hours that the it had for the AM cast! In addition the water column appears to have had a much more uniform temperature throughout, falling off gradually but with very little thermocline. The salinity profile is similar. This combination seems to suggest that the flood tide, though weak, has brought colder saltier ocean waters into the

13 sound. Saturday’s Cast 1 (Charts 3a and 6a) taken about three minutes after the predicted maximum ebb is very similar to the Friday AM cast 1.

Cast 3s for Saturday and Friday PM can be contrasted to see the difference between an increasing ebb tide profile and a high slack-water profile. Saturday’s cast 3 (Chart 3c) is remarkable because of the relatively warm waters above a strong thermocline at about 25 meters. Beneath that is a layer of cold water; however, at about 40 meters a warmer layer underlies the cold section. The temperature found at 40 meters is not found again until a depth of about 120 meters. Friday’s PM cast 3 shows a far different profile: water at the immediate surface is comparably warm, but by about 7 meters, the temperature drops by 1 degree. An abrupt ¼ degree thermocline is present at 40 meters. Beneath that the water column seems to be of fairly uniform temperature. Again, this overall homogeneity seems to be a result of the recently completed weak flood tide.

A comparison of profiles for Friday’s AM Casts 2 (charts 1b and 4b) and 3 (charts 3c and 4c) may show how the change from slack to flood begins to erase the thermocline and bring a more uniformly cooler and saltier profile. Caution is warranted however, because the profiles are from different stations. Conclusions

These preliminary investigations seem to suggest that currents in central Puget Sound are driven primarily by the tides as predicted. Indications are that, during strong ebb tides, primary water flow is to the north and west of the proposed Brightwater sewage discharge at Point Wells. During weak flood tides, the currents flow primarily southward. Very little interface between the waters north of Possession Sound and those adjacent to Point wells was apparent in this set of observations. However, more measurements are required to understand the various effects of the full range of possible tides. The implications of small tidal- range (neap) ebb tides and large tidal-range (spring) floods have not yet been explored in this study, and must be understood before the Point Wells effluent discharge begins operation.

14 Additional consideration must also be given to the change that winter storms with prevailing southwesterly winds might have upon the interface between the waters adjacent to Point Wells and those of Possession sound. The long fetch of the north south oriented sound, similar to that which caused the sinking of the Hood Canal Bridge, could push effluent discharge into the poor circulation areas that lie to the northeast near Everett.

At least in terms of wind and tide, the Brightwater discharge site at Point Wells seems acceptable, if the discharge is carefully managed and timed appropriately. More cruises should be conducted to explore the full range of tides, and some effort should be made to look at the full range of tides, and the effects of adverse weather on the current of the central Puget Sound and Admiralty Inlet.

Sophisticated oceanography tools such as the ADCP and CTD can be used to explore and understand the complex forces of moving water at work beneath the waves of Puget Sound. Information gained in such explorations can be of tremendous value to decision makers faced with the needs of a rapidly growing community.

15 Figures & Charts

Figure 1 Chart of the cruise area and cast locations

16 Figure 2 Canceling out the ships motion: ADCP magnitude display (top) versus the processing mode Navigation Mode, for the Friday PM leg. In the raw magnitude display the blue segments represent time that the ship was drifting; Green and warmer sections show when the ship wasin transit between stations.

17 Figure 3 Direction contour comparison of Saturday (top) and Friday Cruises.

18 Figure 4 Magnitude contour comparison of Saturday (top) and Friday Cruises.

19 Figure 5 North velocity contour comparison of Saturday (top) and Friday Cruises.

20 Figure 6 East velocity comparison of Saturday (top) and Friday Cruises.

21 Figure 7 Error contour comparison of Saturday (top) and Friday Cruises.

22 Figure 8 Current profile and contour for the 1036 Saturday maximum ebb.

23 Figure 9 Profile and contour for Friday's 1213 maximum flood.

24 Figure 10 Profile and contour for Friday AM cast 1.

29 Figure 15 Profile and contour for Friday PM cast 2.

30 Figure 16 Profile and contour for Friday PM cast 3.

31 Figure 17 Profile and contour for Saturday cast 1.

Friday AM Cast 1

Tem perature (C) -9.2 9.5 10 10.5 11 11.5 0.8

10.8 )

M 20.8 (

e 30.8 D 40.8

34 Chart 1a. Temperature Depth Profile for Cast 1, Friday AM, West Point, 0818 Ebb Tide.

Friday AM Cast 2

Tem perature (C) -8 9.5 10 10.5 11 11.5

12 ) M (

h 22 t p e D 32

Chart 1b. Temperature Depth Profile for Cast 2, Friday AM, ORCA 1, 0927, Low Slack Water.

Friday AM Cast 3

Tem pe rature (C) 9.5 10 10.5 11 11.5 0 20 40 60 )

M 80 (

t 100 p

e 120 D 140 160 180 200

Chart 1c. Temperature Depth Profile for Cast 3, Friday AM, ORCA 2, 0949, Flood Tide

35 Friday PM Cast 1

Tem pe rature (C) 9.5 10 10.5 11 11.5 0 5 10 15 20 h t

p 25 e

D 30 35 40 45 50

Chart 2a. Temperature Depth Profile for Cast 1, Friday PM, West Point , 1715, Ebb Tide.

Friday PM Cast 2

Tem pe rature (C) 9.5 10 10.5 11 11.5 0

) 20 M (

e 30 D

Chart 2b. Temperature Depth Profile for Cast 2, Friday PM, ORCA 1, 1619, Ebb Tide.

36 Friday PM Cast 3

Tem perature (C) 9 9.5 10 10.5 11 11.5 0

40 ) M (

60 h t

p 80 e D 100

Chart 2c. Temperature Depth Profile for Cast 3, Friday PM, ORCA 2, 1541 High Slack Water.

Saturday Cast 1

Temperature (C) 9.5 10 10.5 11 11.5 0 5 10 15 )

M 20 (

t 25 p

e 30 D 35 40 45 50

Chart 3a. Temperature Depth Profile for Cast 1, Saturday, West Point, 1039, Max Ebb Tide

37 Saturday Cast 2 Temperature

Te m perature (C) 9.5 10 10.5 11 11.5 0

M 20 (

e 30 D

Chart 3b. Temperature Depth Profile for Cast 2, Saturday, ORCA 1, 1018, Ebb Tide.

Saturday Cast 3

Temperature (C) 9.5 10 10.5 11 11.5 0 20 40

) 60 M (

t 80 p e 100 D 120 140 160

Chart 3c. Temperature Depth Profile for Cast 2, Saturday, ORCA 2, 0912, Ebb Tide.

38 Friday AM Cast 1

Salinity (PSU) 29 29.2 29.4 29.6 29.8 30 0

20 ) M (

t 30 e p

Chart 4a. Salinity Depth Profile, for Cast 1, Friday AM, 0818, West Point.

Friday AM Cast 2

Salinity (PSU) 29 29.2 29.4 29.6 29.8 30 0

20 ) M (

t 30 p e

Chart 4b. Salinity Depth profile, for Cast 2, Friday AM, 0927, ORCA 1, Low slack water.

39 Friday AM Cast 3

Salinity (PSU)

-10 29 29.2 29.4 29.6 29.8 30

) 50 M (

h 70 t p e

Chart 4c. Salinity Depth Profile for Cast 3, Friday AM, 0949, ORCA 2, Flood Tide.

Friday PM Cast 1

Salinity (PSU) 29 29.2 29.4 29.6 29.8 30 0

20 ) M (

t 30 p e

Chart 5a. Salinity Depth Profile for Cast 1, Friday PM, 1715, West Point, Ebb tide.

40 Friday PM Cast 2

Salinity (PSU) 29 29.2 29.4 29.6 29.8 30 0 5 10 15 )

M 20 (

t 25 p

e 30 D 35 40 45 50

Chart 5b. Salinity Depth Profile for Cast 2, Friday PM, 1619, ORCA 1, Ebb tide.

Friday PM Cast 3

Salinity (PSU) 29 29.2 29.4 29.6 29.8 30 0 20 40 60 )

M 80 (

t 100 p

e 120 D 140 160 180 200

Chart 5c. Salinity Depth Profile for Cast 3, Friday PM, 1541, ORCA 2 High Slack water.

41 Saturday Cast 1

Salinity (PSU) 28.6 28.8 29 29.2 29.4 29.6 29.8 30 0 10 20 30 )

M 40 (

t 50 p

e 60 D 70 80 90 100

Chart 6a. Salinity Depth Profile for Cast 1, Saturday, 1039, West Point, Max Ebb tide.

Saturday Cast 2

Salinity (PSU) 28.6 28.8 29 29.2 29.4 29.6 29.8 30 0

) 20 M (

t 30 p e

Chart 6b. Salinity Depth Profile for Cast 2, Saturday, 1018, ORCA 1, Ebb tide.

42 Saturday Cast 3

Salinity (PSU) 28.6 28.8 29 29.2 29.4 29.6 29.8 30 0 20 40

) 60 M (

t 80 p e

D 100 120 140 160

Chart 6c. Salinity Depth Profile for Cast 3, Saturday, 0912, ORCA 2, Ebb tide.