Week 1 Flashcards
ocean biogeochemistry
interactions of processes that control the cycling of key element, like carbon
what are the 3 components of oceanography?
-physical
-chemical
-biological
why does the ocean matter when it comes to global warming?
air-sea exchange of carbon dioxide impacts atmospheric carbon dioxide, modifying the greenhouse effect
key elements in the ocean
carbon, nitrogen, phosphorus, iron, silicon, and oxygen
DIC
dissolved inorganic carbon
CO2 dissolved in the ocean
photosynthesis converts DIC to
POC (particulate organic carbon)
DOC (dissolved organic carbon)
biological pump
Transport of carbon from the
surface to the deep ocean by biological processes
(mainly through sinking organic matter).
solubility pump
Combined influence of physical and chemical processes on ocean concentrations of dissolved CO2 and air-sea exchange (independent of biology).
aerosol effect
when we burn fossil fuels, it releases particles into the atmosphere which helps reflect solar energy away. also affects cloud formation
Pre-industrial atmospheric CO2 concentrations were
quite stable for thousands of years, ~280 ppm
Anthropogenic activities have increased atmospheric
CO2 concentrations by
> 120 ppm since the mid-1800’s, recently exceeding 400ppm.
Atmospheric CO2 concentrations were ~80 ppm lower
during glacial (ice age) periods, much of this
carbon was likely stored
in deep ocean
photosynthesis
plants combine carbon dioxide, water, and
light energy to form plant biomass
respiration
Oxygen is used to break down biomass to
produce carbon dioxide, water and energy
remineralization
The breakdown of organic matter into
elemental and nutrient constituents (aka decomposition)
Gross Primary Production (GPP)
total carbon “fixation“ (photosynthesis), conversion from CO2 to C-biomass
Net Primary Production (NPP)
total carbon fixation by plants - their respiration costs. Organic matter supplied by NPP is available to support heterotrophic organisms.
phytoplankton account for how much total photosynthesis in the ocean?
95%
Euphotic Zone
thin layer at ocean surface (~100m) with enough light to support photosynthesis
the most common growth-limiting nutrients for
phytoplankton in the oceans are
nitrogen, phosphorus, iron, and silicon
nitrogen
nitrate, NO3- and ammonium NH4+
phosphorus
phosphate, HPO42-
silicon
silicate, H3SiO4- (aka H4SiO4 silicic acid)
iron
most dissolved iron ions are bound to organic molecules called ligands (>99%), very small amount as free Fe ions
How does the biological pump effect the concentration of organic matter in the ocean? How are the exported nutrients returned?
It depletes surface concentrations and increases deep ocean concentrations.
Ocean mixing and circulation eventually returns these exported nutrients to surface waters.
How does the biological pump move the organic matter?
Mainly through sinking POM (>90% of export) and through mixing and advection, which can carry POM and DOM produced in surface waters into the ocean interior.
POM
particulate organic matter
DOM
dissolved organic matter
Wind Mixing
direct mixing by winds. pretty shallow, can extend to ~100m
Convective mixing
occurs at higher latitudes, can mix much deeper than wind mixing (»500m)
Surface mixed layer
surface layer where rapid mixing results relatively uniform concentrations of passive tracers (i.e. DIC, nutrients, phytoplankton, etc)
can range from a few meters to hundreds of meters depth, with convective mixing
pycnocline
sharp change in density with depth
thermocline
change in temperature with depth
halocline
change in salinity with depth
typically there is a ____ at the base of the surface mixed layer, may appear only seasonally.
pycnocline
density is a function of
temperature and salinity
Density ____ as temperature _____
increases
decreases
Density ____ as salinity _____
increases
increases
Stable (or stratified) water column
lighter waters over denser waters
weak vertical exchange
Unstable water column
denser waters over lighter waters
convective mixing will result with strong vertical exchange
At _____ the temperature profile ______, with increased stratification during summer months, weakened during winter.
mid-latitudes
varies seasonally
_____ are strongly stratified by _______.
low latitudes
temperature
____ at mid- to high latitudes is a key route for deep ocean _______.
convective mixing
nutrients to return to the surface
The second major return route is through ______________, which brings deeper waters to the surface.
wind-driven upwelling
Vertical mixing largely determines the ______ to surface waters. The depth of the surface mixed layer also controls the _______ experienced by the phytoplankton.
flux of nutrients
light levels
Increased mixing can _______ to surface waters, but may also lead to _______ of phytoplankton growth rates, if they spend too much time at depth.
introduce nutrients
light-limitation
seawater is how much percent pure water (H2O)?
96.5%
3.5% of seawater is dissolved matter. how many ppm is this?
35 parts per thousand
Iron and aluminum are highly ______, resulting in short residence times due to ____________.
particle reactive
particle scavenging
Iron and aluminum are removed from the ocean waters to the sediments by _______ then particle sinking (bio pump), AND _____ onto particles
biological uptake
by adsorption (scavenging)
____ species have a strong tendency to stick (or adsorb) to sinking particles, eventually transferred to sediments.
particle reactive
____ is one of the key nutrients that limits phytoplankton growth and thus NPP in the oceans.
iron
Iron _____ is scavenged more slowly than free Fe irons.
bound to ligands
For our key nutrients (N,P,Si, and Fe) the main sources to the oceans are _____ and _________, and the main sink is __________.
rivers
aerosol deposition
burial in the sediments
Recently is has been shown that the hydrothermal vents (where the heated waters come out of the sediments are also strong ______ to the oceans.
sources of iron
Rivers are a source of ___ to the oceans in the form of bicarbonate ions resulting from the weathering of rocks on the continents.
DIC
The riverine sources of N and P have more than doubled since preindustrial times due to
fertilizer runoff (N and P)
fossil fuel burning
N emissions and subsequent deposition
runoff (N)
