Chapter 6: climate change and oceans Flashcards
concentration of deissolved salts in water
- NaCl (sodium chloride)
- magnesium
- calsium
- potasium
- sulfate
the average salinity of ocean is
35 ppt (parts per thousand)
35 grams of salt dissolved in 1000g of sea water
properties of water that are changed by
having salt in it
- salt makes sea water more dense than fresh water
- salty water needs to be colder than fresh water before it freezes
- freezing point of fresh water is 0c
- freezing point of sea water is -2 c
ocean salinity change due to climate change:
impacts on anthropogenic CC on ocean
- rise in sst
- sea level rise
- acidification
- salinity variations (indirect impact of CC)
cause of changed salinity
- evaporation (inc)
- precipitation (dec)
- fresh water from river discharge (dec)
- ocean currents
- from less saline oceans (dec)
- from saline oceans (inc)
global salinity is effected by
- hydrological cycle
- evaporation rates
- precipitation rates
- river discharge
- ocean currents
climate change will result in stronger hydrological cycle
how global warming effects salinity
- global warming
- stronger hydrological cycle
- arid regions
- become dryer
- more evaporation
- salinity increase
- more evaporation
- become dryer
- wet regions
- become wetter
- more precipitation
- salinity decrease
- more precipitation
- become wetter
- arid regions
- stronger hydrological cycle
ocean acidification
oceans take up CO2 from the atmosphere (absorb 1/3 of the atmospheric CO2) since the industrial revolution
- reduce global warming
- cause changes in ocean chemistry (carbonate chemistry)
- ocean acidification
- DIC (dissolved inorganic carbons)
Carbonate chemistry of sea water
- atmospheric CO2 dissolve in sea water
- aquous CO2
- carbonic acid
- rapidly dissociate to produce photons and
- bicarbonate ionns
- dissociate into
- carbonate ions and photons
- dissociate into
- carbonic acid
- aquous CO2
- atmospheric CO2 dissolve in sea water
- aquous CO2
- carbonic acid
- aquous CO2
CO2 (aq) + H2O –> H2CO3
carbonic acid
- rapidly dissociate to produce photons and
- bicarbonate ionns
H2CO3 <—> HCO3- + H+
(carbonic acid) <—–> (bicarbonate ions) + (photons)
GIVE RISE TO PHOTONS
- bicarbonate ionns
- dissociate into
- carbonate ions and photons
- dissociate into
HCO3- <——> CO32- + H+
(bicarbonate ions) <—–> carbonate ions + photons
GIVE RISE TO PHOTONS
PH is defined as
PH= -log10 [H+]
the increase in H+ photons will reduce the PH value of the sea water making it more acidic when (PH value <7)
compare the PH values from the past and now
over the past 300 million years = 8.2
current value of PH = 8.1
for a reduction of 0.1 in PH value, what is the corresponding change in [H+] photons
H+ = antilog10 (PH)
H+= 108.1
H+ 8.1 = 125892541.2
H+ 8.2= 158480319.2
( (H8.2 - H8.1)/H8.1 )x 100 = 25.9% (increasing acidity)
this is becaue PH sscale is not linear
the total DIC in sea water is defined as
DIC = [CO2] + [HCO3-] + [CO3 2-]
carbon dioxide + bicarbonate + carbonate
distribution of DIC
the distribution between the three species varies between PH of sea water
for PH = 8.1
[CO2] : [HCO3-] : [CO32-]
1 : 100 : 10
as more CO2 is added to sea water
- PH decreases
- the balance between the three carbonate species also change
- CO2 (aq) and HCO3- increase
- CO32- decrease
(this is an indication of anthropogenic ocean acidification
projected ocean acidification
- anthropogenic CO2 emissions cause
- warming of oceans
- 2 to 4 c by the end of 21st century
- increase in ocean carbon content
- ocean acidification
- reduction in marine carbonate
- reduction of dissolved neutrients in the surface
- ocean acidification
- warming of oceans
sea level rise is caused by
- thermal expansion
- additional water flow from ice melting
sea level rise consequence
due to increase of sea level rise
- low lying areas will have more frequent flooding
- very low lying areas could be submerged campletely
- wil change coastal wet lands and harm coastal ecosystems
- mongroov forests
- coral refs
sea level rise projection
- over the past 100 years average sea level rise in 7 inches
- by the end of 21st century, 7-23 inches additional rise expected