ch 8 Flashcards
what are the three ways gasses can be found in the ocean
in gas phase in a bubble
as true solute surrounded by water molecules
trapped in solid (ice or clathrate hydrates)
what is daltons law
daltons law of partial pressuers
gasses in a mixture exert partial pressures
what is the volume of one more of gas at STP
22.414 L
what are the trends of CO2 in winter versus summer
CO2 trends in N and S hemisphere
mean atmospheric pressure at sea level
1 atm
equilibrium concentration of a gas in water
ingassing and outgassing are equal
K= [Asw]/[Ag]
henrys law
gasses dissolve in seawater in proportion to their partial pressures
has henrys law coefficient
K ,HA
what does K(HA) tell us
how many moles of gas A dissolves in 1 L of seawater at partial pressure of one atm of partial pressure A
what do oceanographers use as thier henrys law coeficient
Bunsent solubility coeficient Ba
asks how many mL of gas can be dissolved per L of seawater Pa of 1 atm
how is gas solubility affected by temperature
decreases with tempertaure
how is solubility affected by salinity, why?
decreases with salinity
due to electrostatic forces exerted by salt ions that cause unfavourable conditions for dissolution
These forces need to be
overcome to make space for gas
between the water molecules
NAEC
normal atmospheric equilibrium concentrations
at equilibrium, seawater is _ saturated
100%
what leads to deviations from equilibrium concentrations
physical effects
chemical/biological effects
what gasses are effected by physical effects and which are affected by chemicall/biological effects
- Non-reactive gases are useful as a reference point - only affected by
physical processes, e.g., by temperature and salinity - Reactive gases (O2, CO2, et al.) influenced by physical processes
plus biological and chemical processes
what are the physical effects that cause deviations in NAEC
- Bubble injection
- Fast changing conditions (ocean or
atmosphere) - Sea surface slicks or surfactants
- Post-equilibrium temperature changes
- Sedimentary or hydrothermal sources
- Nonlinear effects of mixing
explain bubble injection
At high winds, air
can be injected directly into the sea surface
through bubble formation
result of bubble injection
causes supersaturation
fast changing conditions
Also known as kinetic consideration,
occurs when environmental conditions change faster than equilibrium can
be achieved.
For example, when water masses sink before they reach equilibrium or
if pressure or temperature change dramatically
fast changing conditions result
super or under saturation
sea surface obstruction to air sea fluxes
slicks - slow exchange
sufactants- do opposite
sea ice- like slicks but much more- greatly slow or even blocks the
exchanges (depends how complete and how thick is the ice coverage)
post equilibrium changes
Changes in the atmospheric composition of a gas
over time (e.g. increasing CO2,decreasing O2) causes water masses isolated
from the sea surface to deviate from the NAEC
post equilibrium changes result
super or under saturated
subsurface sources
Some gases have minor
sources related to physical phenomena in the deep ocean,
such as hydrothermal vents or release from warming
sediments
subsurface sources result
super or under saturation
what is the benifit of inert gasses
Inert gases are not affected by
biological processes
* So useful as tracers of
physical processes
what kind of gasses does bubble mediated gas exchange effect
Bubbles-mediated gas exchange
affects low solubility gases more
In deeper waters:
* more soluble and more-
temperature dependent gases
- are _
undersaturated
- they formed in high lats after
rapid cooling -> needed more
gas to flow in the ocean to
reach 100% sat. -> might
have sunk before it
Hamme and Severinghaus 2007
28 - less soluble gases are near equilibrium
(reached the 100% equilibrium before sunk)
or supersaturated
what is the surface/ subsurface peak
strongest for most
temperature sensitive gases – as these get warmed
by the sun -> % of saturation increases,
non linear effects of mixing
as seen
before the solubility
curve is nonlinear
(concave upward
mixing line ends up being higher than original solubility curve
non linear effects of mixing result
only super saturation
what controls O2 concentration
Oxygen: horizontal patterns of concentration vs. % saturation
A. Creation or destroying of O2
i. Photosynthesis (+)
ii. Remineralization (-)
B. Water mass mixing (+/-,depending on
[O2] in the other mass)
C. Exchanges with atm.:
* Bubble injection (+)
* Net flow of O2 across the sea surface:
* +/- depending on % saturation
* % saturation depends on A), B)
and changes in temperature
