1
Global Water Cycle(Water fluxes in 1000 km3/yr)
2
Latitudinal Trends in Global P and E
3
Equilibrium Fractionation between Water Vapor and Liquid
4
Temperature Dependence of Equilibrium
Fractionationfor Water
Phases
(‰)
18O
(‰)
Dα = R(liq) / R(gas)
5
Rayleigh Distillation Prediction18O vs Temp
d18O = -2 ‰
dD = -7 ‰
d18O = -5 ‰
dD = -32 ‰
6
18O vs Temperature
for Precipitation
18O
(
‰)
7D
(‰
)
18O (‰)
D vs 18O for Global Precipitation
8
D of Precipitation Globally
D of Precipitation in N. America
9
18O Precipitation vs Altitude
10
18O of Precip vs Distance
from Coast
11
Seasonality of 18O of
Precipitation
12
Deviations from MWL
• Although global pattern of 18O and D 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.
13
D vs 18O in Arid Regions
Rio Grande (Southwest US)
and Darling (Central
Australia)
In arid regions, D vs 18O slope is significantly less than 8 of MWL.
14
18O of Precip at Tropical Sites with Seasonal Cycle in Humidity
15
Deuterium Excessd-excess (‰) = D (‰) – 8* 18O (‰)
d-excess of MWL = 10 (‰)
Prediction: d-excess depends
on Relative Humidity
16
Effect of humidity on D vs 18O slope
Lakes E. Washington
Lakes W. Washington
MWL
17
Isotopic Signatures of the Global Water Cycle
18
Air-Sea Transfer of Water Vapor
19
18O versus Borehole Paleothermometrya controversy in Greenland Ice Cores
emp/18O= 1.5 ºC / ‰)
Current Precipitation emp/18O= 3 ºC / ‰
Borehole Temps
Climate scientists favor the borehole temperature changes.
20
Greenland Ice Core 18O and Temperature Record
Using borehole temperature vs 18O calibration
21
Antarctic Ice Core Record of D and Implied Temperature
22
SeasonalRecords of 18O and D in
PrecipitationD
18O
Temp
23
18O and D as a Water
Source Tracer in Steams and
Rivers
D (‰)
18O
(
‰)
Five European Rivers
22 = Rhine River
24
18O and D in US
Rivers
Missouri R.
Mississippi R.
Meramac R.?L
25
18O and D as a Water
Source Tracer in
Rivers
26
d-excess of US Rivers
27
18O in Ground Waters
28
18O and D as Groundwater
Tracers in Arid Regions
29
Surface Ocean 18O
(‰ vs SMOW)
(LeGrande, GRL 2006)
30
Surface Salinity
31
18O vs Salinity
32
18O in the Deep Atlantic Ocean
33
D of Seawater in the Deep Sea
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