Selected Presentation from the INSTAAR Monday Noon Seminar Series.

Institute of Arctic and Alpine Research, University of Colorado at Boulder.http://instaar.colorado.edu

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03 Feb. 2003 Detlev Helmig, INSTAAR and Program in Atmospheric and Oceanic Sciences (PAOS)Email: Detlev@instaar.Colorado.Edu"New insights into snow-photochemical processes and snow-atmosphere gas exchange (if you ever wonder whatmay happen in your freezer if the light stays on)."Seminar given at INSTAAR, University of Colorado. Copyright 2003 Detlev Helmig. All Rights Reserved.Helmig presentation (2.2 Mb PDF).

Selected Presentation from the INSTAAR Monday Noon Seminar Series.

Institute of Arctic and Alpine Research, University of Colorado at Boulder.http://instaar.colorado.edu

http://instaar.colorado.edu/other/seminar_mon_presentations

03 Feb. 2003 Detlev Helmig, INSTAAR and Program in Atmospheric and Oceanic Sciences (PAOS) Email:Detlev@instaar.Colorado.Edu"New insights into snow-photochemical processes and snow-atmosphere gas exchange (if you ever wonder whatmay happen in your freezer if the light stays on)."Seminar given at INSTAAR, University of Colorado. Copyright 2003 Detlev Helmig. All Rights Reserved.Helmig presentation (2.2 Mb PDF).

Abstract

Snowpack has been considered a rather inert substrate that undergoes little chemical interaction with the atmosphere. The conservation of gases in interstitial air and ice cores has been used to decipher records of past atmosphericcomposition and climate. Over the past decade an increasing number of previously unknown snow-photochemicalreactions have been discovered. These processes have been shown to affect the surface-atmosphere exchange of manytrace gases and may have implications on the interpretation of ice core records.

Inert ???

No next day hangover

Deficient in active properties; especially lacking a usual or

anticipated chemical or biological action

Having no or little activity to react

Having no effect

Detlev Helmig

�

"New Insights into Snow-Photochemical Processes and Snow-Atmosphere Gas Exchange“

(if you ever wondered what may happen in your freezer in case the light stays on)

Carina in the freezer

Ice Core Measurements

CO2

Methane

Nitrous Oxide (N2O)

CO

Hydrogen Peroxide (H2O2)

Formaldehyde (H2CO)

Methyl Bromide (CH3Br)

Chlorofluorocarbons (CFC)

Methanesulfonate (MSA)

Oxygen

Nitrogen

Argon

Anions: Cl-, NO3-, SO4

2-,

Cations: Ca2+, K+, Mg2+, Na+, NH4+

Others: Fe, S, Al, Si, Ti, Mg

18O in H2O14C in CO14C in CO215N in N236Cl10Be

Primary Aerosol

Electrical Conductivity (balance of acids and bases)

Minerals (Silicates, Clay, Mirca, Feldspars, etc.)

Microparticles, Dust

Pristine Arctic?

Pollution in the Arctic

• Lead Records in Greenland Ice Cores

• Heavy Metals (Lead, Hg) in Fish, Mammals

• Pesticides (DDT, Lindan) in Birds, Mammals

• Environmental Pollutants (PCB, PCP) in Wildlife

• Antarctic (Arctic) Ozone Hole

• Hg in Arctic Environment

• Polar Sunrise Ozone Depletion

• ??? Nitrogen Photochemistry ???

Front Cover AE

Polar Springtime Ozone Depletion (Alert)

Bottenheim et al., Atmos Environ. 36, 2535 (2002)

X Barrow

Polar Ozone Depletion Chemistry

1. Formation of Br2

(HOBr)g -> (HOBr)aq

(HOBr)aq + H+

aq + Br-aq -> (Br2)aq + H2O

(Br2)aq -> (Br2)g

2. Ozone Destruction

Br2 + hn -> 2 Br

2 Br + 2 O3 -> 2 BrO + 2 O2

3. Recycling of BrO

a) BrO + BrO -> 2 Br + O2

b) OH + CO (or VOC) -> HO2 + CO2 (or VOC products)

BrO + HO2 -> HOBr + O2

HOBr + hn -> Br + OH

BrO/Ozone

Honninger and Platt, Atmos. Environ. 36, 2481 (2002)

Ozone Depletion in Arctic Snowpack

Diurnal Ozone and NOx at 30 cm depth

Peterson and Honrath, GRL 28, 511, 2001

Ozone in Firn Air

NOx in Firn Air

Solar Actinic Flux

NOx in Ambient Air

Sun/Shading Experiments

Actinic Flux into Snowpack

Shepson et al., AGU, 2000

CH3CO-O-O-NO2

CO production in snow

Chemical Fluxes out of the Snow at Summit

NO at South Pole

Photochemical Cycles

Photochemical Ozone Production

Photochemical Ozone Production

Summit Diurnal Photochemical Ozone Production: 1.8 – 2.6 ppb/day

South Pole Diurnal Photochemical Ozone Production: 3 - 5 ppb/day (Crawford et al., GRL 28, 3641 (2001)

OH at South Pole

Photochemical Ozone Production

Ambient Ozone at South Pole

Ozone Depletion in Arctic Snowpack

Peterson and Honrath, GRL 28, 511, 2001

Ozone in Firn Air

NOx in Firn Air

Solar Actinic Flux

NOx in Ambient Air

Ozone Fluxes out of Seasonal Snow

Zeller, 2000

Table 1

Literature with ozone deposition measurements over snow-covered surfaces.

Reference Location Landscape Measurement Dep. Velo- Comments

Technique city (cm s-1)

Aldaz, 1969 New Mexico BE 0.02

Galbally & Allison, 1972

Mt Buller, Australia

1.3 m Snow Depth

TG -3.3 - 1.7 Ozone release from snow observed.

Galbally and Roy, 1980a,b

Australia TG, BE 0.06 Deposition velocity increased with snow age.

Wesely et al., 1981

Illinois Plowed Field ECM*, CL 0.03 (mean)

Colbeck & Harrison, 1985

Lancaster/England

Grass Field TG, CL 0.08

Padro et al. 1992 Canada Deciduous Forest

ECM 0.3

Stocker et al., 1995

Colorado Grassland ECM, CL 0.04-0.1 Deposition velocity decreased with snow age.

Zeller & Hehn, 1996

Wyoming Coniferous Forest

ECM, CL Consistent upwards ozone fluxes observed.

Gong et al., 1997 Camp Narwahl

Ice Camp TB 0.006 – 0.3 Data for ozone depletion events (Polar Sunrise)

Zeller, 2000 Wyoming Coniferous Forest

ECM, CL Upwards ozone fluxes from

surface (mean 0.2 mg m-2

s-1

)

*BE: Box Enclosure; ECM :Eddy Correl. Method; CL: Chemiluminescence; TG: Tower Gradient; TB: Teth. Balloon

Ozone in the Arctic Boundary Layer at Summit, Greenland

Instrumentation for Tethered Balloon Vertical Profiling

Summit Surface Ozone Measurements

Ozone Diurnal Trends at Summit

52.5

53.5

54.5

55.5

0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00

Time (hrs)

Diu

rnal M

ean

Ozo

ne (

pp

b)

5

6

7

8

0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00

Time (hrs)

Sta

nd

. D

ev

. o

f D

iura

l M

ea

ns

(p

pb

)

Summit June 10, 2000 Profiling Data

Summit Potential Temperature Profile June 10, 2000

0

100

200

300

400

500

600

700

288 289 290 291 292 293 294 295 296

Potential Temperature (K)

Heig

ht

(m)

Up, 16:14

Down, 16:38

Boundary Layer

Height

Summit Ozone/RH Profile June 18, 2000

Profile Mixing Temp Temp WS WS ozone Ozone Richardson Stability Ozone Ozone

Layer Height 2/3 MLH 1/3 MLH 2/3 MLH 1/3 MLH 2/3 MLH 1/3 MLH Number Function Flux Dep. Vel.

m K K m/s m/s ppb ppb kg/(s m2) cm/s

8up 70 259.70 259.90 7.30 6.00 50.80 50.40 -0.10 2.09 -5.58E-10 0.77

42up 75 258.50 258.70 4.20 4.10 53.20 51.00 -18.97 72.89 -8.19E-09 11.08

43up 74 259.43 259.66 3.90 3.80 56.80 56.30 -21.44 79.89 -2.04E-09 2.54

Flight #43up TS Potential

Temperature

0

10

20

30

40

50

60

70

80

90

100

290 291 292 293

Flight #43up TS Temperature

0

10

20

30

40

50

60

70

80

90

100

259 259.5 260

Flight #43up TS Wind Speed

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5

Flight # 43up - ECC Ozone

0

10

20

30

40

50

60

70

80

90

100

54 56 58 60

Surface Data/Balloon Sonde Comparison

Summit 3D Potential Temperature

Summit 3D Wind Speed

Summary

NO HONO Cl, F CO Alkenes HCHO H2O2 PAN?

NO2 HNO2 H3CCHO

HNO3

Aerosols

NO3-, Organics

Ozone

???

Mechanisms? Seasonality? Magnitude of Fluxes? Seasonal Snow <-> Year-Round Snow?

Summit 2000

Niwot Ridge

Summit

Coastal Greenland?

2003-2006Future Flux

Research

South Pole

2003/2004

Future Balloon Research

ANTCI

Antarctic Tropospheric Chemistry Investigation

Contributors

Jim Boulter

Florence Bocquet

Don David

Nancy Rivera Garymar Rivera

Doug Hultstrand

Scott Peckham