Post on 11-Jan-2016
• 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)