Water vapor isotope measurements above the Greenland Ice Sheet and importance for interpretation of surface-atmosphere interactions

H. C. Steen-Larsen1 , V. Masson-Delmotte1, E. Brun2,

R. Winkler1, F. Prie1, A. Landais1, C. Risi3, B. Stenni4

1 Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS/IPSL Gif-Sur-Yvette2 Meteo-France/CNRM, Toulouse3 Laboratoire Meteorolgie Dynamic, Paris4 Department of Mathematics and Geosciences, University of Trieste

Water vapor isotope measurements above the Greenland Ice Sheet and importance for interpretation of surface-atmosphere interactions

H. C. Steen-Larsen1 , V. Masson-Delmotte1, E. Brun2,

R. Winkler1, F. Prie1, A. Landais1, C. Risi3, B. Stenni4

- Introduction to stable water isotopes

1 Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS/IPSL Gif-Sur-Yvette2 Meteo-France/CNRM, Toulouse3 Laboratoire Meteorolgie Dynamic, Paris4 Department of Mathematics and Geosciences, University of Trieste

- Introduction to stable water isotopes

- The diurnal water vapor cycle above the

Greenland Ice Sheet

- Tracing Arctic moisture using isotopes

Isotope hydrology

Isotopologues are molecules with an isotope exchanged in

Nomenclature:

1H

16O

1H 2H

16O

1H 1H

18O

1H

Regular water Heavy water Even heavier water

FRACTIONATION is temperature-dependent-Larger at low temperature

Water Vapor Liquid Water

Hot

Heavy

Regular

Cold

Setup of the NEEM isotopic surface

campaign 2009 - 2012

Subsurface temperature

Measurements 0-150cm

With 10 mK resolution

Precipitation samples

Collected as often as

possible

Air temperatures

1, 3, 7, 10, 13 m

above snow surface

d18O and dD of vapor

Continuously from

1, 3, 7, 10, 13 m

above snow surface

Surface snow

samples every

12 hours

Water vapor isotopes on top of the

Greenland Ice Sheet

Water vapor isotopes on top of the

Greenland Ice Sheet

Vertical diurnal structure of the

atmospheric water vapor close to the

surfaceHourly time slices of diurnal cycle

~2h

local~6h ~10h

local~6h

local

~10h

local

~14h

local

~18h

local

~22h

local

The structure of the isotopic profile

with height

-290-12

-10

-8

-6

empe

ratu

re [º

C]

Humidity at ~1 meter Humidity at ~13 meter δD at ~1 meter δD at ~13 meter Temperature at ~1meter

Free troposphere

and boundary

layer interaction

Snow-Air

interaction

4000

3500

3000

2500

2000

Hum

idity

[ppm

]

2015105Time [UTC]

-330

-320

-310

-300

δD [‰

]-16

-14

Te

Snow-pack fluxes

- Humidity and isotopes are linked

- Gradient with height in both humidity and isotopes

Still work in progressModel output (Mass flux and snow

surface temperature) from

CROCUS

4000

3500

3000

2500

2000

Hum

idity

[pp

m]

2015105Time [UTC]

-330

-320

-310

-300

-290

δD [‰

]-16

-14

-12

-10

-8

-6

Tem

pera

ture

[ºC

]

Humidity at ~1 meter Humidity at ~13 meter δD at ~1 meter δD at ~13 meter Temperature at ~1meter

ERA-40 re-

analysis

CROCUS

Snow pack scheme

Boundary layer

model

Free Free

troposphere

isotopes

Interstitial fluxes

Snow-air fluxes

Validate against

observation

Snow surface Snow surface

isotopes

Compare with

atmospheric water

vapor isotopes

δD =8•δ18O+10

αEqδD /αδ18O

Eq ~ 8

d − excess= δD −8•δ18O

Water vapor isotopes as means of

tracking origin of the vapor

Introducing the second order parameter:

Captures kinetic fractionation occurring when a humidity gradient is

present because of different molecular diffusivity of the isotopes.

Introducing the second order parameter:

Captures kinetic fractionation occurring when a humidity gradient is

present because of different molecular diffusivity of the isotopes.

δD =8•δ18O+10

αEqδD /αδ18O

Eq ~ 8

d − excess= δD −8•δ18O

Water vapor isotopes as means of

tracking origin of the vapor

Using back trajectories to find the

moisture source

Using back trajectories to find the

moisture source

Sea Ice

Very dry air

Vapor with

excess

Vapor with

high d-excess

Strong

evaporation

Comparing the observations with

isotope enabled GCM

50

40

30

20

10

Ob

serve

d d-exess [‰

]

20

16

12

MD

Z d

-exc

ess

40x10-3

20

0Frac

Arc

tic m

oist

ure

Bad agreement between

observed and modeled d-

excess

-320

-300

-280

-260

-240

-220

-200

LMD

Z d

D [

‰]

210200190180170160150140Day of 2010

4000

3000

2000

1000

0LM

DZ

Hum

idity

[PP

M]

-360

-320

-280

-240

Observe

d dD[‰

]

6000

4000

2000

0

Observerd H

umdity [P

PM]

8

LM

Good agreement between

observed and modeled

humidity.

OK agreement between

observed and modeled dD

isotopic composition

Water vapor isotopic measurements above the Greenland Ice Sheet and importance for interpretation of surface-atmosphere interactions.

H. C. Steen-Larsen1 , V. Masson-Delmotte1, E. Brun2,

R. Winkler1, F. Prie1, A. Landais1,C. risi3, B. Stenni4

hanschr@gfy.ku.dk

1 Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS/IPSL Gif-Sur-Yvette2 Meteo-France/CNRM, Toulouse3 Laboratoire Meteorolgie Dynamic, Paris4 Department of Mathematics and Geosciences, University of Trieste