What is sea water Flashcards
How do satellites show chlorophyll on the globe?
chlorophyll influences the green light reaching satellites
primary production definition
amount of phytoplankton biomass in sea water because of photosynthetic carbon fixation
total
primary productivity
rate of change of phytoplankton biomass is seawater because of photosynthetic carbon fixation
rate
wind field
seasonally averaged near watered winds
strength and direction
what direction do the winds usually come from?
from the NW in the summer
from the south in the winter
surface currents
seasonally averaged direction and relative strength of currents
interested in where they go
are horizontal velocities or vertical velocities faster in the ocean?
horizontal
upwelling
vertical upwards flow
downwelling
vertical downwards flow
what would be the diameter of all the water on earth if it were a sphere?
1384 km
stratification
layers in liquid that separate because of variations in densities with depth
density
mass per unit volume (kg/m^3)
mixing
irreversible mingling of liquids. If liquids don’t separate again after time, they have been mixed
nutrients
chemicals that phytoplankton must acquire from the surrounding water in order to grow
(not mammal nutrients)
what is the standard method for how are physical properties sampled in seawater?
CTD, conductivity-temperature-depth probe
how does a CTD work
electronic instrument that measures salinity (conductivity), temperature, and depth (pressure)
sampling bottles area closed at specific depths
how are ocean profiles viewed because of CTDs?
in vertical profiles since the machine is being lowered into the ocean
salinity
dissolved salt content (g/kg)
what increases density?
increased salinity
decreased temperature (effect is small in cold water)
increased pressure (slightly)
how does salinity change globally
low in polar regions, increases with depth in cold regions
high in tropics because of evaporation, decreases with depth because of warm surface
how does temperature change with depth?
decreases from surface down
increases from a certain point downwards because temperature increases with pressure
(bike pump analogy)
in situ temperature
temperature reading on thermometer sent down into the ocean
potential temperature
temperature you would read if you brought the deep water back to sea surface pressure adiabatically (no heat exchange happens)
benefits of in-situ temperature
life in deep ocean experiences
determines rate of chemical reactions
benefits of potential temperature
track water masses as potential temperature
compare water masses at different depths and determine which would be warmer if they met
direct indication of heat content
what does potential temperature show about deep water temperatures
it’s consistent all the way down
what controls density in polar regions?
salinity
what controls density in tropic regions?
temperature
how does the ocean get salty
weathering run-off
aeolian dust
hydrothermal vents
volcanic volatiles
sediments
gas influx from atmosphere
what elements are found in the ocean?
all 92 naturally occurring elements
from grams to attograms per kg of seawater
what are the sixmain elements in sea water
chloride
sodium
sulfate
magnesium
potassium
calcium
rule of constancy of composition
all conservative elements have constant ratios to each other and salinity in the ocean
what elements are considered conservative elements?
all the major ions except calcium, some of the minor ions
how can we determine salinity?
titration of any of the conservative elements
conductivity measurements
what is ratio of salinity to chlorinity
salinity = 1.815 x chlorinity
how do we get salinity from measuring sea water’s conductivity?
measure the current carried by the salt in the water
what is the salinity of water?
35.00 g/kg (or 35.17)
does the ocean or land store more carbon
the deep ocean
what are the sources of bicarbonate to the ocean?
weathering runoff
CO2 from the atmosphere
how does rain water affect weathering
rain is slightly acidic, interacts with silicate minerals, creates bicarbonate that comes into the ocean from runoff
aka hydrological cycle
what is the chemical equation of weathering?
XSiO3 + H2CO3 + H2O -> X + HCO3 + H3SiO4
silicates + carbonic acid + water -> bicarbonate + other things
what is the chemical equation for atmospheric transfer of CO2 into the ocean?
CO2 + H2O -> H2CO3 carbonic acid
H2CO3 -> H + HCO3 bicarbonate ion
HCO3 -> H +CO3 carbonate ion
CO2 + H2O + CO3 -> 2HCO3
what is the buffer response of the ocean when CO2 is added
H + CO3 -> HCO3
what does DIC stand for
Dissolved Inorganic Carbon
how do you calculate the K constant of Henry’s Law
concentration of products over reactants, not including the solvent
what makes water less soluble?
increased temperature
increased salinity
what changes the value of K in Henry’s Law
decreases with increased temperature and salinity
increases with molecular weight and polarity
what is a mole fraction?
the fraction of atoms in a mixture that are one type of gas (percentage
what is a partial pressure?
the part of the total pressure which is because of a certain gas
what is the equation to calculate partial pressure?
p = PX
partial pressure = total pressure x mole fraction
what is the partial pressure of water when in equilibrium?
the same as the partial pressure of the air above it
what are the three most abundant gases in the air?
Nitrogen, oxygen, argon
why is dry air partial pressures used for calculations?
because water vapour content is much more variable
how much of known CO2 emissions probably ended up in the ocean?
about 40%
what is Henry’s Law
i = Kp
concentration of gas in the water = Gas constant x partial pressure of the gas
what does NAEC stand for?
Normal Atmospheric Equilibrium Concentration
what is the purpose of the NAEC?
to correct for water vapour at the in situ temperature and salinity of the surface ocean
what is the calculation for NAEC
NAEC = K(1 - psw) X
NAEC = gas constant(atmospheric pressure - correction for water vapour) mole fraction
how does adding CO2 affect animals’ ability to make shells?
decreases carbonate in the water, less carbonate available to make shells
how does adding CO2 affect animals’ ability to make shells?
decreases carbonate in the water, less carbonate available to make shells
at what pH do we see maximum buffering capacity?
9
what pH on average is the ocean?
8
what are the most dominant DICs in the ocean in order
bicarbonate
carbonate
carbon dioxide
what effect does biology have on CO2 content in the ocean
takes up CO2 during photosynthesis
releases CO2 during respiration
how does respiration affect seawater chemistry?
increases DIC overall, decreases CO3, doubles HCO3
becomes more acidic
same effect as anthropogenic CO2
how does photosynthesis effect seawater
chemistry
decreases DIC overall, CO3 increases and HCO3 decreases
becomes more basic
how does calcium carbonate formation effect seawater chemistry?
decreases DIC by decreasing CO3
becomes more acidic (removing basic form)
CO2 increases because of lowered pH
opposite for dissolution
what are the main ions found in river water?
bicarbonate
calcium
silicilic acid
sulfate
chloride
sodium
what salts mainly come from volcanic volatiles?
chloride, sulfate
what is the CO2 biological pump?
the CO2 uptake by marine biota into the ocean
what important elements to aeolian dusts bring into the ocean?
iron, aluminum, lead
what influences aeolian dust to enter the ocean?
smaller dust is transported farther
rain brings it down faster
what is hydrothermal circulation?
reaction between seawater and hot magma at mid-ocean ridges
magma alters the chemistry of the ocean water
is hydrothermal circulation a source or a sink?
both, it depends on the element
completely removes magnesium and sulfate
adds in lithium, potassium, Rb, and manganese
what is diagenesis?
chemical reaction in sediment that produces concentration gradients of chemical species in pore water
drives diffusion of released elements into bottom waters
what is pore water?
water between sediment particles
what is an example of a source from pore water?
opal (SiO2) shells increase pore water concentration of silicic acid, which diffuses back into sea water
what are the salt sinks in the ocean?
gas efflux
sea spray
sedimentation
hydrothermal circulation
what is sedimentation?
particle matter settling on the sea floor
main removal of many elements
what is the hydrothermal plume?
the cloud of elements that is reoxidizing outside the hydrothermal vent
what can cause regions of the ocean to degas CO2?
upwellings or deep mixing
how does sea spray remove salts?
spraying on to the land, only significant in some cases (Na and Cl)
non-selective
what are estuaries?
river-sea mixing zones
how is ocean input influenced by estuaries?
modified chemical reactions influence what makes it into the ocean
what is the residence time?
average time that an element stays in the ocean
what is the steady state of the ocean?
that sea water concentrations stay constant, and
inputs = outputs
main inputs and outputs are from the atmosphere and sediments
what is the main equation of the steady state
dX/dt = Ia + Is + R - Oa - Os
Ix = Ox = kX = kVC
any additional inputs/outputs are added into the equation
how do we achieve steady state?
negative feedback mechanisms
rate of removal of X from the ocean is proportional to the amount of X in the ocean
what is the removal rate constant?
k = 1/time (year)
what is the residence time equation?
t = X/I (or O)
what is the relationship between residence time and removal rate constant?
t = 1/k, unit is years
how would you estimate residence time of X?
concentration of X * flux (river flow, sediment acc, etc)
how does the reactivity of elements influence residence times
unreactive = longer
reactive = shorter
major elements = longer
trace elements = vary
essential nutrients = intermediate (recycled)
what is a conservative property
property which varies only with salinity
only effected by processes that effect all salts equally
what influences a non-conservative property?
element-specific processes
