Global Water Cycle
(Water fluxes in 1000 km3/yr)
1
Latitudinal Trends in Global P and E
2
Equilibrium Fractionation between Water Vapor
and Liquid
3
Temperature
Dependence of
Equilibrium
Fractionation
for Water
Phases
e (‰)
d18O
e (‰)
α = R(liq) / R(gas)
dD
4
Rayleigh
Distillation
Prediction
d18O vs
Temp
d18O = -2 ‰
d18O = -5 ‰
dD = -7 ‰
dD = -32 ‰
5
d18O (‰)
d18O vs
Temperature
for
Precipitation
6
dD vs d18O for Global Precipitation
dD (‰)
d18O (‰)
7
dD of Precipitation
Globally
dD of Precipitation
in N. America
8
d18O Precipitation vs Altitude
9
d18O of
Precip vs
Distance
from
Coast
10
Seasonality
of d18O of
Precipitation
11
Deviations from MWL
• Although global pattern of d18O and dD of
precipitation follows MWL, there can be
significant deviations.
• Mainly in arid regions, where evaporation is
important.
• Use Deuterium Excess to quantify departure from
MWL.
• Implication is that evaporation can play a
significant role in the isotopic composition of
precipitation by imposing kinetic, rather than
equilibrium, isotope effects.
12
dD vs d18O in Arid Regions
Rio Grande
(Southwest US)
and Darling
(Central
Australia)
In arid regions, dD vs d18O slope is significantly
13
less than 8 of MWL.
d18O of Precip at Tropical Sites with
Seasonal Cycle in Humidity
14
Deuterium Excess
d-excess (‰) = dD (‰) – 8* d18O (‰)
d-excess of MWL = 10 (‰)
Prediction: d-excess depends
on Relative Humidity
15
Effect of humidity on dD vs d18O slope
MWL
Lakes W. Washington
Lakes E. Washington
16
Isotopic Signatures of the Global Water Cycle
17
Air-Sea Transfer of Water Vapor
18
d18O versus Borehole Paleothermometry
a controversy in Greenland Ice Cores
(DTemp/Dd18O= 1.5 ºC / ‰)
Current Precipitation
DTemp/Dd18O= 3 ºC / ‰
Borehole Temps
Climate scientists favor the borehole temperature changes.
19
Greenland Ice Core d18O and Temperature
Record
Using borehole temperature vs
d18O
20
calibration
Antarctic Ice Core Record of dD and Implied
Temperature
21
Temp
Seasonal
Records of
d18O and dD
in
Precipitation
d18O
dD
22
Five European Rivers
d18O (‰)
d18O and dD
as a Water
Source Tracer
in Steams and
Rivers
dD (‰)
22 = Rhine River
23
Missouri R.
Mississippi R.
d18O and
dD in US
Rivers
L
Meramac R.?
24
d18O and
dD as a
Water
Source
Tracer in
Rivers
25
d-excess of US Rivers
26
d18O in
Ground
Waters
27
d18O and dD as
Groundwater
Tracers in Arid
Regions
28
Surface
Ocean
d18O (‰ vs
SMOW)
(LeGrande, GRL 2006)
29
Surface Salinity
30
d18O vs
Salinity
31
d18O in the Deep Atlantic Ocean
32
dD of
Seawater in
the Deep
Sea
33