Quiz 2 Flashcards
physical properties of interest
temperature, salinity, density
chemical properties of interest
oxygen, nutrients, carbon
conservative sw properties
altered only by physical processes: -precipitation and evaporation
- freezing and thawing
- mixing
non-conservative sw properties
altered by biological activities:
- respiration/photosynthesis
- excretion (waster -> nutrients)
- recycling (nutrients)
greatest seasonal variation at _____ latitudes
mid
in the vertical temperature distribution the mixed layer makes up?
roughly 2% (uniform temperature)
in the vertical temperature distribution the thermocline makes up?
roughly 18 % (rapidly changing temperature)
in the vertical temperature distribution in the deep water?
Roughly 80 % (slowly changing temperature)
equatorial ocean has a ___ thermocline
shallow
temperate ocean has a ____ thermocline
deeper
deep (>1000m) ocean temperatures are_____
the same globally
mid-latitude water column may show two thermoclines
- shallower seasonal
2. deeper permanent
how are seasonal thermoclines developed?
- surface cooling and higher winter wind generates deep mixing, increases cooling of the surface ocean
- summer decreased wind and higher heating warms surface
- this process lead to formation of permanent thermocline
the mixed layer depth is ___ in the tropics
relatively constant
there is seasonally variable in ____ regions
subpolar
where is there deep water formation
greenland and iceland
where is there deep MLDs?
Southern Ocean and North Atlantic
In-situ
the temperature we measure (in-place) of a water parcel, at a particular depth (pressure). Not corrected for compressibility (volume change)
Potential Temperature
Temperature the water would have if it was brought adibatically to the surface. Corrected for compression
density of seawater is a ___ function of ___,___,___
- nonlinear
- salinity, temperature, pressure
What is the primary factor that is controlling sw density?
Temperature
what is the equation of state for seawater?
ρ=ρ(S,T,p)
____ is largely determined by temperature
Density
factures controlling density
- pressure (largest but often ignored)
- temperature (most important for circulation)
- salinity (important for deep water formation)
seawater density
1024 kg/m^3
denisty equation
σ (density - 1000) = ρ - ρ ref
ρ ref = 1000 kg m^-3
seawater is ____:
volume ___ with increasing pressure
density ___ with increasing pressure
slightly compressible
decreases
increases
sigma
density of 1027.25 is what in sigma
sigma is density in (kg m^-3) - 1000
1027.25 - 1000 = 27.25
Density and sigma often written like this
σ(s,t,p) = (ρ(s,t,p)) - 1000
Where s is salinity
t is temperature
p is pressure
sigma-t equation
sigma(t) (σt ) = σ(s,t,0) = ρ(s,t,0) - 1000 where ρ(S,T) is density of a sample of seawater of T and S, at a standard atmospheric pressure
what is sigma-t useful for
mapping water properties along density surfaces, without mixing water flows along these density surfaces
Sigma-theta equation
σϴ is σ(s,ϴ,0) = ρ(s,ϴ,0) – 1000
Where ϴ stands for potential temperature
what does sigma-theta consider
adiabatic temperature changes relating to processes in which heat does not enter or leave the system concerned
potential temperature (density)
potential temperature is used to calculate potential density. potential temperature (density) of a parcel of fluid at pressure is the temperature (density) that parcel would have if brought to a standard reference pressure, usually 1 atmos in a way that no energy was exchanged with the surrounding water (adiabatically)
potential temperature is
temp at 1 atm
potential temperature changes are dependent on
thermal expansion coefficients for temperature and salinity
sigma theta for deep water is calculated at
400 dbar σ4
increasing pressure causes the in-situ temperature to ____ and the in situ density to ___
- increase (adiabatic warming)
- increase
potential density
remove effect of pressure on temperature and density. relevant to the dynamics of the circulation
as temperature increases density ____
decreases
as salinity increases density ____
increases
General characteristics of salinity distribution
- surface salinity variable
- deep water generally high salinity
- minimum: temperate & intermediate-depth
surface salinity pattern
strong meridional (n-s) patterns
regional differences in salinity
Highest in N. Atlantic
salinity range in the majority of the ocean
34-35 ppt
temperature range of the majority of the ocean
0-5degC
gases are more soluble in ___ water
colder
02 concentration in surface water mostly dependent upon temperature _____
saturation
oxygen distribution mid water minimum
- relatively rapid respiration
- no gas exchange with atmosphere
oxygen distribution deep water
well-oxygenated
- no gas exchange with atmosphere
- supplied from high latitude
- very slow respiration
oxygen minimum zones
< 0.2 ml o2/liter
where is co2 enriched
the deep sea via biological pump and higher solubility
where is the greatest concentration of carbon
north pacific
how to “age” water
- rates of non-conservative properties changes: production of nitrate and consumption of 02
- tracers (bomb tritium and CFCs)
hyrdographic parameters
temperature, salinity and pressure
temperature and salinity of interest in themselves : define
water masses
CTD
used for hydrographic work , conductivity, temperature and depth (pressure)
salinity
total dissolved g of slats in a kg solution (ppt)
major seawater chemistry is dominated by
Na and Cl
salinity equation
S=(mass of dissolved compounds kg)/(mass of seawater kg) x 1000
units: parts per thousand
salinity is based on _____ assuming the _____
chlorinity, law of constant proportions
chlorinity
grams of Cl- per kilogram of seawater
Salinity (‰) = 1.80655 * Clorinity (‰)
psu
practical salinity unit
absolute salinity
SA = (35.16504 g kg−1/ 35) *SP
+ δSA
(lat,long,p)
SP
is PSU
δSA as a function of latitude, longitude & pressure
current salinity measurements are based on
conductivity measurements matched to seawater samples where chlorinity measured and Marcet’s principle assumed
measuring pressue
least precise of CTD measurements
pressure in decibars (dbar = ~1m)
role of atmosphere/ocean interactions
- forcing of wind-driven ocean circulation
- energy transfer (wind stress)
- albedo and thermal inertia
- heat budget
- radiative equilibrium temperature
ocean-atmosphere interactions
- wind stress (energy transfer)
- atmosphere cools ocean (evaporation)
- ocean cools/warms atmosphere
evaporation ___ the ocean/ ___ the air
cools
warms
precipitation ___ the air / ___ the ocean
cools
warms
mechanisms for air-sea interactions:
Heat exchange and water exchange
- Radiation (wavelength dependent)
- evaporative (exchange of latent heat)
- Precipitation (exchange of latent heat)
- conduction (heat exchange by molecules)
air-sea interaction momentum exchange
friction via wind
rediation
heating from solar radiation (IR spectrum)
flux equation
items/area*time
unit of force
newton N (kg m sec-2)
unit of work
joule N * m (kg m2 sec-2)
unit of power
watt J sec-1
kg m2 sec-3
power equation
power = force x velocity
solar heat flux
342 watts/m^2
(at the top of the atmosphere)
drives wind and photosynthesis
geothermal heat flux
0.0075 watts/m^2 (at Earth surface, bottom of the atmosphere) drives plate tectonics: oceanic ridges
solar / geothermal flux ratio
~3200
concept of black body radiation :
all objects emit
electromagnetic energy (per unit surface area
and time) proportional to their temperature
Thermal radiation equation
Stephan-Boltzman (S-B) relationship Watts / m2 = E = σ * e * k4 σ = S-B constant 5.67 10-8 W m-2 k -4 e = emissivity = 1 in ideal case k4 = Kelvin temperature to fourth power
thermal radiation wein’s displacement law
as temp increases
- total energy increases by the power of 4
- peak energy shifts to higher frequency (smaller wavelength)
what is the S-B constant
5.67 10-8 W m-2 k
what are the three key EM spectrum bands
- ultraviolet
- visible
- infrared radiation
ultraviolet radiation
radiation within band with wavelength from 1 to 400 nm. UV radiation is present in sunlight, and contributes about 10% of electromagnetic radiation output from the sun
visible light
light occurs within the a band rnaging from 400-700 nm
infrared radiation
within band ranging from 700-100,000 nm. IR is not visible EM energy, but is heat
is solar radiation constant
seasonality due to earth’s tilt
sunspot
a cooler and darker, region of the sun’s surface caused by solar magnetic disturbance
solar flare
a violent eruption of plasma from the sun, whipped up by intense magnetic activity
what are milankovitch cycles
cyclical movment related to the Earth’s orbit around Sun.
There are 3: eccentricity, axial tilt and precession
what are the three types of milankovitch cycles
eccentricity, axial tilt, and precession
eccentricity
earth encounters more variation in the energy that is receives from the sun when Earth’s orbit is elongated than it does when earth’s orbit is more circular
3 cycles of periods; 96,125,400 K years
affects variability in solar energy reaching Earth’s surface
Tilt (obliquity)
the tilt of Earth’s axis varies between 22.2 and 24.5 degrees. The greater the tilt angle is, the more solar energy the poles receive.
a cycle of perido: 41 K years
affects variability in solar energy reaching Earth’s surface
precession
a gradual change, or “wobble,” in the orientation of Earth’s axis affects the relationship between Earth’s tilt and eccentricity.
3 cycles of periods: 12, 22, 24 k years
affects relationship of tilt and eccentricity
on average, Earth and atmosphere reflects about
~30% of incoming radiation
reflectivity
proportion of the energy that “bounces off” versus being absorbed
troposphere
<10% height 90% of mass of atmosphere
- inherently unstable
- weather (mixing)
1st law of thermodynamics equation
heath change = internal energy + work done
adiabatic expansion
work done without heat loss or gain, so internal temperature changes
Adiabatic Expansion
∂T/∂Z = -g / Cp
(Note: Z is elevation)
– g = gravitational acceleration on earth surface
(~9.81 m sec-2)
– Cp = specific heat (dry air = 1000.35 J kg-1 k
-1)
• This works out to be ~ 9.8 K km-1
(sign dependent on sign of pressure change)
Higher pressure -> Higher Temperature (+)
Lower pressure -> Lower Temperature (-)
Lapse rate
∂T/∂Z of air an parcel
(water parcels vary in composition)
– Moist air lapse rate = -6.5 K km-1
– Dry air lapse rate = -9.8 oK km-1
Lapse Rate why
- dry air cools as pressure decreases: -9.8 K km^-1
- lapse rate decreases with increasing H20 content due to latent heath release
- as water vapor condenses, it releases heath … which counteracts the parcel’s cooling
centigrade to kelvin
centigrade - 273 = Kelvin
temperature decline with altitude in Troposphere caused by
adiabatic cooling
-typical lapse rate (wet air) ~ 6.5 degree C/km
-adiabatic cooling (dry air) rate 9.8 C /km
~3.3 C/ km increase in potential temperature
is the stratosphere stable?
strongly dense, therefore stable
is the troposphere stable?
No, very weakly density stratified therefore turbulent mixing (weather)
mean earth temp
15 C or 288 K
Global Heath Budget (Energy transfer processes)
- solar radiation (+)
- geothermal heat (minor ~0.03% of solar input) (+)
– Long wave radiation to space (-)
– Conductive heat loss (-)
– Latent heat loss (-)
Earth average albedo 30%
- 20% absorbed the atmosphere
- 50% absorbed by the Earth
- 5% IR directly to space
- 25 of 50 units from Earth are absorbed by the Atmosphere and are then reradiated to space (greenhouse effect)
- most latent heat is found in water vapor
sensible heat
at most temperatures, adding heat to water produces a proportional temperature rise
sensible heat leads to a __ in temperature. Latent heat ____ to a rise in temperaure
rise, does not lead
what equation do you use to calculate the average earth temperature
stephan-boltzmann equation
equation for heat radiated from earth’s surface
(4πR2) * (σ * e * k
4) (σ = constant)
(Remember: e = 1)
(k = temp. in kelvin r=radius
radiative equilibrium temperature
255 K (-18C), with this temperature the Earth radiation will be centered at 11μm, within IR range
average surface temperature of earth
15 C
why is there a temperature discrepancy between the average surface temperature and radiative equilibrium temperature
difference because Earth not true black body
the global heat budget vary with
location (latitude) and earth surface characteristics (albedo)
the greenhouse effect*
the process by which radiation from a planet’s atmosphere warms the planet’s surface to a temperature above what it would be without its atmosphere
trapping of the sun’s warmth in a planet’s lower atmosphere, due to the greater transparency of the atmosphere to visible radiation from the sun than to infrared radiation emitted from the planet’s surface
what are the main gases that absorb and trap IR radiation in the atmosphere
water vapor (36-72%), carbon dioxide (9-26%), Methane (4-9%) and Ozone (3-7%)
earths average temperature
5.12 C
what two parameters are used to measure sea water salinity
conductivity or chlorinity
incoming solar radiation
+324 Wm^-2
incoming solar radiation absorbed by the atmosphere
+67 Wm^-2
incoming solar radiation absorbed by Earth’s surface
+168 Wm^-2
incoming solar radiation total reflected solar radiation
-107 Wm^-2
incoming solar radiation reflected by clouds, aerosols and atmospheric gases
-77 Wm^-2
incoming solar radiation reflected by the Earth’s surface
-30 Wm^-2
total outgoing longwave radiation
-235 Wm^-2
Long wave radiation emitted by the Earth’s surface
-390 Wm^-2
Back longwave radiation reabsorbed by the Earth’s surface
+324 Wm^-2
Latent heat from Earth’s surface
-78 Wm^-2
albedo*
the proportion of the incident light (radiation) that is reflected by a surface, rather than being absorbed. Values are expressed as proportions of the total incident light (or radiation)
latent heat*
latent head is energy released or absorbed by a thermodynamic system during a constant-temperature process (usually a phase transition). Latent heat can be understood as energy in hidden form, which is supplied or extracted to change the state of a substance without changing its temperature
sensible heat*
sensible head is heat exchanged by a thermodynamic system that changes the temperature of the system. As the name implies, sensible heat is the heat that you can feel. The sensible heat possessed by an object is evidenced by its temperature
conservative property*
a water property not affected by biology (temperature and salinity)
albedo values from low to high
ocean, forest, grasslands, soil, desert, ice, fresh snow
ocean heat flux input
solar flux
ocean heat flux output
latent heat, long wave radiation, sensible heat (conduction)
ocean contains ___ times more heat than the atmosphere and about ___ times than the land
1000, 100
Heat capacity of the ocean, lithosphere and atmoshphere
4000 J/kg
800 J/kg
1000 J/kg
exchange volume for ocean in global heat budget
ocean: upper 10-100 m
lithosphere: 1-2m
troposphere: 10 km
conservation of heat energy in the global ocean
Qt = Qsw + Qlw + Qs + Ql \+ Qv • Oceanic heat sources / sinks (from Stewart) – Solar radiation: Qsw (+) – Long wave radiation: Qlw (-) – Conductive (sensible) heat Qs (-) – Latent heat loss Ql (-) – Advective heat loss/gain Qv (+/-)
long wave flux strongly influenced by:
- cloud cover amount and height
- atmospheric water vapor content
mid-depth salinity is the result of what
colder, lower salinity waters from regions of excess rain sinking to depth (thermohaline circulation)
ϴ
potential temperature.
