• Tool of the Trade

• Rosette with:

• 10-l Niskin bottles

• In situ sensors

• CTD

• Dissolved oxygen sensor

Estuarine Circulation and Chemical Tracers

Sea-Bird 9plus CTD

AccuracyT: 0.001°CC: 0.0003

Siemens/m (<0.005 in

S)P: 0.015% of

fullscale

UnitsTemperature: °C

Salinity: no units; defined by 1978 Practical Salinity Scale (PSU)

Pressure: db (decibars)

DensityDensity (ρ) is a function of T, S, and pρ(4°C, 0, 1 atm) = 1 g cm-3 = 1000 kg m-3

Potential Density of Seawater (corrected for compressibility) ranges from 1022 kg m-3 to 1028 kg m-3

in the open ocean

Sigma Theta (σθ) = ρ(θ, S, 1 atm) - 1000 [kg m-

3]

SBE 43 Dissolved Oxygen SensorPrinciple of Operation:

Oxygen gas diffuses across a membrane, is converted to OH- at the

cathode (Au), 4 electrons are required, and the resulting current is

converted to a voltage proportional to the

number of molecules.

Dissolved Oxygen Units??

Puget Sound Scientific Literature:mg/L, mg-at/L, mL/L, μmol kg-1

Conversion Factors:

1 mole O2 = 32 g O2 = 22.414 L O2 = 2 g-at O

1 L seawater = 1000 cm3 = (0.001 m3)×(density of SW)

Density of SW [kg/m3] = 1000 + sigma theta

Discrete Samples

• Collected from Niskin bottles

• Three main types:

• Dissolved oxygen - for calibration – shipboard titrations

• Chlorophyll – for calibration – shipboard extraction and analysis

• Nutrients (Nitrate, nitrite, ammonium, phosphate, silicate) – seawater collected through a filter and frozen for analysis at the UW Marine Chemistry Laboratory (K. Krogslund)

An estuary is...A place where river(s) meet the ocean that has surrounding land and a limited opening...

Puget Sound is an estuary; it is connected to the Pacific Ocean through the Strait of Juan de Fuca.

Coastal Plain or Drowned River Valley Estuary

Fjord estuaries

• Sill blocks exchange of deep water with ocean

• Little water movement below sill depth

• Strong vertical stratification

Fig 12.35

Fjord Circulation

Deep sill

Shallow sill

thorough mixing of deep water

poor mixing of deep water

Admiralty Inlet

- 30 km long- shallowest depth: 65 m- “double” sill- vigorous mixing results in horizontal gradients- out-going water can be entrained in the incoming layer = reflux

Tidal Currents vs Estuarine Circulation

Tides ≈ 5-10 × Strength of Estuarine Flow

Episodic Intrusions of Deep Water

Main Basin

Numerical Modeling

20 layers350-m resolution in Puget SoundRiver flow - 15 major river, USGSAtmosphere - 6-hour avg from MM5Eight tidal components

Solid = SurfaceDashed =

Deep

Schematic Diagram of the Flow in Puget Sound

Estuarine Circulation:Surface Inflow,Deep Outflow

Driven by river input,mixing, and deep water intrusions

Seasonal Cycle of Properties in the Main Basin

What can affect the amount of freshwater entering the Sound?

20

Rivers and Wind

Stratification

How does it change from rivers to Main Basin?How does change in stratification affect biology?

Currents in the Main Basin

Currents throughout

Puget Sound

14: Saratoga Passage

Level of no motion?

Estimating Residence Times of Basins

Two- Layer Box Models

Knudsen’s Equations

Water Balance:Tin + R = Tout

Salt Balance:SinTin = SoutTout

Solve for Tout:

Tout = R×Sin/[Sin - Sout]

Can add temporal variability, mixing between layers

Whidbey Basin Residence Times

Box Model(1992-2001)

Numerical Model(2006)

Cycles of Phosphorus, Nitrogen, Carbon, Oxygen and Silica in Puget Sound waters

Tracers of Biological Production and Respiration

REDFIELD RATIOS: ∆P : ∆N : ∆C : ∆O2 1 : 16 : 106 : -153

For diatoms: NO3- : Si ratios: ∆N : ∆Si 1 : (1-3)

Dissolved Inorganic Phosphorus, DIP vs Dissolved Inorganic Nitrogen, DINIn the Ocean

REDFIELD STOICHIOMETRY OF LIFE: P : N : C : O2 = 1 : 16 : 106 : 153

Nitrate : Phosphate ratios in Port Susan

Compilation from recent data (Oce 220 , 2010)

AOU (Apparent Oxygen Utilization)

=

[02sat] –[O2]

RATES OF NET BIOLOGICAL OXYGEN PRODUCTION = ∆O2/ ∆C (153/106) X NET CARBON PRODUCTION (NCP)

OXYGEN FLUX TO THE ATMOSPHERE ~ NET BIOLOGICAL O2 PRODUCTION FO2 = - GO2 {[O2]-[O2]sat}

{[O2]-[O2]sat}

The Gas Exchange Mass Transfer Coefficient, G, is a function of wind speed

Rates of Respiration in Rates of Respiration in Waters Below the SurfaceWaters Below the Surface

Oxygen Utilization Rate Oxygen Utilization Rate (OUR) = Respiration Rate = (OUR) = Respiration Rate =

AOU / tAOU / t

t = time since water was t = time since water was at the surfaceat the surface

In Puget Sound deep In Puget Sound deep waterswaters

t = time since water came t = time since water came into the basin from outside into the basin from outside

RATES: NET O2 CONSUMPTION-- RESPIRATION

Sections of Oxygen, Phosphate, and Nitrate in Port Susan, 2010

O2 (μmol kg-1)

PO43-

(μmol kg-1)

NO3- (μmol kg-1)

Temperature and Salinity provide clues that this water has resided behind the sill.

Dissolved Oxygen – Increases behind the sill; Waters with low concentrations displaced to shallower depths

Note: D.O. decreases in water column from July-Aug

Evidence of a “Flushing Event”

Sigma-t – Increases behind the sill

Annual Cycle of Dissolved Oxygen in Hood Canal, as shown in 1954

These vertical sections (Admiralty Inlet to the left, Lynch Cove to the right) of dissolved oxygen show the typical seasonal cycle within Hood Canal.

Low concentrations (dark yellow) dominate during the summer months.

Data Source: Collias et al., UW

In the deep waters, dissolved oxygen is decreased due to respiration by the organisms that are remineralizing organic matter.

Project: Compare April 2010 to previous data sets. Compare Port Susan to Skagit Bay.

RATES: NET OXYGEN PRODUCTION -- PHOTOSYNTHESIS

Oxygen Supersaturation in Puget Sound

Surface waters Oce 220 2010

( Percent Supersaturation)