Understanding Florida Bay Hypersalinity and Water Understanding Florida Bay Hypersalinity and Water ExchangeExchange

Tom Lee-RSMAS; Nelson Melo-CIMAS; Tom Lee-RSMAS; Nelson Melo-CIMAS; Libby Johns, Ryan Smith and Peter Ortner-AOML;Libby Johns, Ryan Smith and Peter Ortner-AOML;

DeWitt Smith-ENP; and Ned Smith-HBOIDeWitt Smith-ENP; and Ned Smith-HBOI

Aerial view of Florida Bay (FB) and the southern Everglades Aerial view of Florida Bay (FB) and the southern Everglades showing the banks (tan) and basins (blue and green) showing the banks (tan) and basins (blue and green)

configuration, Whipray basin (WB), and river discharge points.configuration, Whipray basin (WB), and river discharge points.

Seasonal cycle of monthly average salinity Seasonal cycle of monthly average salinity for the four regions of Fla Bay, from Nuttle for the four regions of Fla Bay, from Nuttle et et

alal., 2000.., 2000.

Figure 1. Moored instrumentation sites from recent studies of Figure 1. Moored instrumentation sites from recent studies of the inner basin circulation and exchange processes in the inner basin circulation and exchange processes in northeast, north-central, and western basin sub-regions of northeast, north-central, and western basin sub-regions of Florida Bay. Also shown are USGS transport and river Florida Bay. Also shown are USGS transport and river discharge measurement stations.discharge measurement stations.

Location of WB measurement stations: crosses indicate current, temperature and salinity Location of WB measurement stations: crosses indicate current, temperature and salinity stations; diamonds show ENP tide stations; groups of 3 small crosses show drifter release stations; diamonds show ENP tide stations; groups of 3 small crosses show drifter release sites; ADCP transport transects are shown with dashed lines and vessel survey track with sites; ADCP transport transects are shown with dashed lines and vessel survey track with solid bold line, upon which the arrow heads indicate vessel heading. solid bold line, upon which the arrow heads indicate vessel heading.

R/V Virginia KR/V Virginia K

Monthly average fresh water fluxes to Fla Bay Monthly average fresh water fluxes to Fla Bay from long-term measurements. (from Nuttle from long-term measurements. (from Nuttle et et alal., 2005).., 2005).

-20

-10

0

10

20 M

ont

hly

Wat

er F

lux

(cm

)

0 2 4 6 8 10 12

Month

Evaporation

Net

Runoff

Rainfall

Daily average fresh water discharge to Florida Bay for 2001. Data Daily average fresh water discharge to Florida Bay for 2001. Data provided by U.S Geological Survey, South Florida Ecosystem Program, provided by U.S Geological Survey, South Florida Ecosystem Program,

Information Access Site (USGS, 2005).Information Access Site (USGS, 2005).

Florida Bay Florida Bay surface surface salinitysalinity from 2001 from 2001 monthly surveys of the monthly surveys of the R/V R/V Virginia KVirginia K using continuous using continuous underway measurement underway measurement for: A) March 22-23 dry for: A) March 22-23 dry season; B) July 11-12 near season; B) July 11-12 near the end of the dry season; the end of the dry season; and C) October 16-17 wet and C) October 16-17 wet season. Vessel track shown season. Vessel track shown with dotted line. with dotted line.

WB surface salinityWB surface salinity from high-resolution surveys of the from high-resolution surveys of the R/V Virginia KR/V Virginia K using using continuous underway measurement for: A) Mar. 28 dry season; B) Jul. 16 near the end of continuous underway measurement for: A) Mar. 28 dry season; B) Jul. 16 near the end of the dry season; C) Sept. 16 wet season; and D) Oct. 28 near the end of wet season 2001. the dry season; C) Sept. 16 wet season; and D) Oct. 28 near the end of wet season 2001. Vessel track shown with dotted line. Surface drifter trajectories shown with red arrows. Vessel track shown with dotted line. Surface drifter trajectories shown with red arrows.

Time series of basin average salinity for WB during dry and wet seasons Time series of basin average salinity for WB during dry and wet seasons of 2001 of 2001

from from R/V Virginia K R/V Virginia K spatial surveys.spatial surveys.

Terms used in the salt balance model for estimating the fractional rate of volume exchange (Q'i)/mo and water renewal time (T) for WB

during dry and wet seasons 2001. Q’i = Qi/Vol;R = r + P - E; R’ = R/Vol; Vol = Whipray Basin mean volume.

Season ∂SWB/∂t

(mo-1)

R'(mo-1)

Si So Q'i

(mo-1)

T (mo.)

DryDry 2.62.6 -0.078-0.078 42.7 to 41.742.7 to 41.7 44.6944.69 0.44 to 0.30.44 to 0.3 2.3 to 3.42.3 to 3.4

WetWet -5.8-5.8 0.220.22 28.3828.38 32.6532.65 -0.32-0.32 3.13.1

Q'i = (∂SWB/∂t + SoR')/( Si - So)

Linear regression of along-channel currents against volume transportLinear regression of along-channel currents against volume transport measured with shipboard ADCP transects across the current meter sites at Topsy (top) measured with shipboard ADCP transects across the current meter sites at Topsy (top) and Twisty (bottom) transects during the wet season of 2001. Regression relationships and Twisty (bottom) transects during the wet season of 2001. Regression relationships used to convert current to transport and the squared correlation coefficient are shown. used to convert current to transport and the squared correlation coefficient are shown.

Channel Volume Channel Volume TransportsTransports Wet Season Wet Season3 hour low-pass filtered 3 hour low-pass filtered volume transports derived for volume transports derived for the major flow channels to WB the major flow channels to WB for a one month period from for a one month period from the 2.5 month total record of the 2.5 month total record of the wet season 2001. Positive the wet season 2001. Positive values are inflows and values are inflows and negative are outflows. Also negative are outflows. Also shown are east-west and shown are east-west and north-south wind components north-south wind components from the NWFB SeaKeys site. from the NWFB SeaKeys site.

40 hour low-pass filtered40 hour low-pass filtered NWFB NWFB wind components and volume wind components and volume transportstransports through WB flow channels during wet season 2001. Positive values are through WB flow channels during wet season 2001. Positive values are inflows and negative are outflows.inflows and negative are outflows.

Linear regression between subtidal time series of east-west wind Linear regression between subtidal time series of east-west wind and transports through WB flow channels during the wet season and transports through WB flow channels during the wet season 2001.2001.

Location of ENP marine monitoring stations in Florida Bay (triangles), Location of ENP marine monitoring stations in Florida Bay (triangles), CMAN/SeaKeys wind stations (squares), and the location of fresh CMAN/SeaKeys wind stations (squares), and the location of fresh water discharge points (arrows) superimposed on the bays water discharge points (arrows) superimposed on the bays bank/basin configuration (yellow/white) and mangrove islands bank/basin configuration (yellow/white) and mangrove islands (green).(green).

Subtidal sea levelSubtidal sea level time series from selected stations of the ENP monitoring array time series from selected stations of the ENP monitoring array and winds for the NWFB SeaKeys station, rotated 50O into along-bay axis and cross-bay and winds for the NWFB SeaKeys station, rotated 50O into along-bay axis and cross-bay axis components (along-axis winds + toward 50O and cross-axis winds + toward 140O. axis components (along-axis winds + toward 50O and cross-axis winds + toward 140O. Sea level stations were selected to provide coverage of the entire bay. Sea level stations were selected to provide coverage of the entire bay.

Gridded and Contoured Gridded and Contoured Sea Level FieldsSea Level Fields Derived from the ENP Derived from the ENP monitoring array using monitoring array using Golden Software surfer Golden Software surfer interpolation for fall 2001 interpolation for fall 2001 wind events. Winds from the wind events. Winds from the NWFB SeaKeys station are NWFB SeaKeys station are shown with black arrows. shown with black arrows.

Subtidal time series of the total volume transport (QSubtidal time series of the total volume transport (QTT) into (+) and out ) into (+) and out of (-) WB derived from gridded sea level fields, shown with east-west of (-) WB derived from gridded sea level fields, shown with east-west (U) and north-south (V) winds for dry (a) and wet (b) seasons of 2001.(U) and north-south (V) winds for dry (a) and wet (b) seasons of 2001.

Wet season 2001 Wet season 2001 subtidal time series subtidal time series of the total channel of the total channel flow (Qflow (Qcc) and total ) and total bank flow (Qbank flow (Qbb) (top ) (top panel); total bank panel); total bank flow plotted with flow plotted with along-axis winds along-axis winds (middle panel); and (middle panel); and total channel flow total channel flow plotted with winds plotted with winds rotated 80deg rotated 80deg (bottom panel).(bottom panel).

QT = Qc + Qb

Seasonal and annual means of total transport (QT) from WB sea level monitoring data, total measured channel transport (Qc) and residual bank transport (Qb) from Qb = QT - Qc in m3/s

for 2001.

[Mean volume of Whipray Basin is 56.55 x 106 (m3).]

TransportTransport Dry SeasonDry Season Wet SeasonWet Season Annual MeanAnnual Mean

QQTT 0.80.8 -0.1-0.1 0.40.4

QQcc -10.48-10.48 3.23.2 -3.6-3.6

QQbb 11.211.2 -3.3-3.3 3.93.9

Basin RenewalBasin RenewalTime (months)Time (months)

2.12.1 6.86.8 6.16.1

Physical data for Whipray Basin and values for annual water balance model during wet and dry seasons of 2001.

Conversion: 1 m3/s = 2.98 cm/mo.

Mean depth Mean depth (m)(m)

Surface area Surface area (km(km22))

Mean volume Mean volume x 10x 1066 (m (m33))

0.650.65 86.986.9 56.5556.55

Seasonal and Annual Water Balance Model in m3/s

QQww + Q+ Qgg + r+ r + P+ P + E+ E == QQTT

DryDry 0.80.8 1.651.65 - 0.5- 0.5 3.073.07 - 4.25- 4.25 == 0.770.77

WetWet - 0.07- 0.07 - 4.67- 4.67 3.53.5 4.814.81 - 3.64- 3.64 == - 0.07- 0.07

Annual Annual averageaverage

0.360.36 -1.51-1.51 1.51.5 3.943.94 - 3.94- 3.94 == 0.350.35

Annual Mean Volume Transports (m3/s) in Florida Bay and Keys (Annual Mean Volume Transports (m3/s) in Florida Bay and Keys (blue blue arrowsarrows) and Estimated Mean Flow Pathways () and Estimated Mean Flow Pathways (red arrowsred arrows). River ). River Discharge shown by Discharge shown by black arrowsblack arrows. Estimated Bank Flow (. Estimated Bank Flow (pink arrowspink arrows).).

Trout

TaylorMcCormick

Other Rivers

2 5

10 10

44

3

2

1

2

2

4

196

15 Shark

800

25

80110

26050

200

025

15

??

?

ConclusionsConclusions• Water renewal and residence times in Whipray Basin are

controlled by local wind forcing.

• Dry Season - eastward winds produce mean through-flow of 11 m3/s and basin renewal times of 2-3 mo.

• Wet Season – westward winds cause mean through-flow of 3 m3/s and basin renewal times of 6-7 mo.

• Flushing time for complete water renewal ~= 6-12 mo.

• Ground water inflow is weak in dry season = 1-2 m3/s and downwells during the wet season at – 4.7 m3/s.

• Hypersalinity development in north-central Florida Bay results from reduced fresh water inputs during the dry season coupled with poor exchange with surrounding regions.

• Hypersalinity development could be regulated by redirection of a portion of Everglades flow to Whipray Basin via McCormick Creek during the dry season.