Iodine Monoxide and the Relations to Sea Ice - Congrex

Iodine monoxide 

and the relations to sea ice, biological 

activity and tropospheric composition 

SOLAS – ESA – EGU joint conference 

Frascati, Italy 

29 Nov – 2 Dec 2011 

Anja Schönhardt, A. Richter, M. Begoin, F. Wittrock, J. P. Burrows 

IUP Bremen

The importance of iodine compounds 

Iodine radicals in the atmosphere 

� Change of tropospheric composition / oxodizing capacity 

- destruction of ozone 

- partitioning of HO x and NO x 

� Formation of fine new particles � growth to CCN 

Iodine 

Precursors 

(mainly 

biogenic?) 

I 2 

CH 3I 

CH 2I 2 

CH 2ICl 

hn 

O 2 

I . O3 IO 

different branches 

IO observed in coastal areas, marine boundary layer, Polar sites 

Anja.Schoenhardt@iup.physik.uni-bremen.de 

SOLAS-ESA-EGU conference 

Frascati, 29 Nov – 2 Dec 2011 

2 

I xO y 

Halogens 

Fluorine 

Chlorine 

Bromine 

Iodine 

Astatine 

McFiggans et al, 

ACP, 2004. 

with typical amounts 0-10 pptv (>20 pptv only sporadically)

Halogens in the Polar Regions 

Ozone depletion in the Arctic 

(Barrie et al, 1988) 

• anti-correlation of Bromine and Ozone 

• similar evolution of BrO and IO at Halley Station 

• strong temporal variability 

Br 

O 3 

� ozone depletion, mercury oxidation, particle formation 

� importance of halogens for Polar atmospheres 

IO/BrO observed in Antarctica 

(Saiz-Lopez et al, 2007) 




3

Iodine monoxide in the MBL 

IO maxima during low tide & day time 

Fine particle bursts coninciding with IO maxima 

G. McFiggans, 2010. 

K. L. Furneaux, 2010. 




4

Important questions and aspects 

Impact of gaseous iodine 

• Ozone destruction – what is the relevance? 

• Particle formation – what is the relative contribution? 

(cp. sulfate aerosol, sea salt aerosol, SOA etc) 

Main release pathways / connections of iodine to the biosphere 

From phytoplankton / different groups / inorganic sources 

Required information 

• Column amounts / volume mixing ratios of iodine compounds 

(IO, I 2, OIO, precursors) …globally and long term 

• Altitude profiles of iodine compounds 




5

Overview 

Introduction: 

The SCIAMACHY instrument and the IO retrieval by DOAS 

Observations: 

• IO above Antarctica 

+ comparisons to sea ice cover 

• IO above oceanic regions 

+ comparisons to Chlorophyll-a content 




6

The satellite instrument 

SCIAMACHY: SCanning Imaging Absorption spectroMeter 

for Atmospheric CHartographY 

• UV-Vis-NIR spectrometer (214 – 2400 nm) 

• sun-synchronous orbit, 10:00 am equator crossing 

Geometry: 

960 km 

800 km 

30x60 km² 

ENVISAT: 

Foto: ESA 




7

IO retrieval by Differential Optical Absorption Spectroscopy 

I 0 

I 

� I0 

( �) 

� 

k 

ln�� i 

( s) 

� i '( 

�, 

s) 

ds � ak� 

� r( 

�) 

I( 

�) 

�� 

� � S i 

k 

Retrieval settings 

• Spectral range: 416 – 430 nm 


absorption term: 

• trace gases 

• Ring effect 

• Trace gases: IO, NO 2 (223K), O 3 (223K) 

• Ring effect, quadratic polynomial 

• Earthshine reference spectrum I 0 

polynomial: 

broad-band 

effects 

Result: Slant Column � i 

residual 

SC � � ( s) 

ds 



S 

i 

fitting 

window 

8

Results: IO from SCIAMACHY 




9

Global observations of IO slant columns 

IO present only in small amounts 

� Temporal averaging necessary 




10

Global observations of IO slant columns 

• IO above Antarctica 

• IO in East Pacific upwelling region 




11

180° 

IO over Antarctica – multi year composites 

Ross 

Ice Shelf 

Ross Sea 

(Max. sea ice extent) 

90°W 

Antarctic Circle 

Filchner-Ronne 

Halley Ice Shelf 

Neumayer 0° 

Amery 

Ice Shelf 

90°E 

Weddell Sea 

AMF for: 

90% reflecting ground 

1 km box profile 




12

IO above Antarctica 

Sep/Oct 

Dec/Jan 

Oct Oct/Nov Nov Nov/Dec Dec 

Jan Jan/Feb Feb Feb/Mar Mar 

6 year composites 




13

BrO above Antarctica 

Oct Nov Dec Jan Feb Mar 

• Appearance of IO and BrO both in Antarctic spring 

• Different spatial-temporal evolutions 

• IO above sea ice in spring time later than BrO 

=> different release pathways 

BrO data: Mathias Begoin and Andreas Richter 

6 year composites 




14

IO in Antarctica: relation to sea ice concentrations 

Sea ice influence 

• Sea ice reduces in late 

spring time 

• Phytoplankton habitat 

beneath/within the sea ice 

• Contact to atmosphere 

facilitated when ice cover 

breaks open / melts 

Ice data: 

AMSR-E sensor 

L. Kaleschke, G. Spreen, 

Klima Campus, Hamburg. 

Oct Nov 




15

IO in Antarctica: relation to sea ice concentrations 

Science 282, 2238 (1998), K. M. Golden, et al. : 

The Percolation Phase Transition in Sea Ice 

“For temperatures warmer than Tc [about -5°C], 

brine carrying heat and nutrients can move 

through the ice, whereas for colder temperatures 

the ice is impermeable.” 

• Biogenic release of iodine species is probable 

• Sea ice more porous in later spring time: contact 

between species below sea ice and air above 

• Strong biological productivity in cold Antarctic waters 




16

Connection of iodine to the biosphere (chlorophyll-a) 

• Long-term observations of 

IO and Chlorophyll-a 

• IO from SCIAMACHY 

• Chl-a from SeaWiFS 

• Care needed for IO absolute 

amounts over ocean regions 

• Enhanced IO at some 

biologically active regions 

• No clear correlation 

SeaWiFS data from NASA: 

http://oceancolor.gsfc.nasa.gov/cgi/l3 




17

Comparison: IO columns and chlorophyll-a content 

Observations: 

• Enhanced IO columns above the 

Eastern Pacific 

• Spatial coincidence with enhanced 

Chlorophyll-a 

• No strong spatial correlation 

apparent at some other locations 

Thoughts: 

• Surfacing of the cold Humboldt 

current from the Antarctic 

• Connection of the specific 

biospheres? 




18

Comparison: IO columns and chlorophyll-a content 

Observations: 

• Slightly enhanced IO at some coasts 

• IO amounts partly correlated with 

Chl-a concentrations 

• No clear relationship: 

some regions with no relation 

between Chl-a and IO 

• no IO above the inland lakes 

Implications: 

� no spectral interference 

� possibly better relation of IO with 

specific phytoplankton groups 

(diatoms?) 




19

Summary 

IO retrieval from SCIAMACHY 

• Multi year data set of IO columns (up to 2003 - 2010) 

• Conversion of IO slant columns to vertical columns 

IO above Sea Ice / Polar Regions 

• Strong detailed spatial and temporal variation 

• Striking differences in comparison to BrO 

• Enhanced IO above sea ice in late spring time 

• Link between IO enhancement and reduced ice concentration (still within the sea 

ice area, relation to phytoplankton habitat, importance of ice temperature?) 

IO and Chlorophyll-a / Oceanic Regions 

• Some regions with correlation between IO and Chl-a, other regions with no relation 

• Importance of specific types of phytoplankton is possible 




20

Outlook 

Next steps 

• Detailed correlation studies with the data presented 

(esp. IO – ice concentration) 

• Correlation studies with biospheric parameters 

(e.g. biogenic VOCs, Chl-a, diatoms) 

� Determine conditions related to the presence of IO 

� Improve the understanding of the importance of atmospheric iodine 

• Potential for IO retrieval from further instruments (GOME, GOME-2) 

Related posters: 

no.01 Itziar Alonso-Cañas (#57 Cook) 

no.05 Astrid Bracher (#28 Magellan) 

no.60 Rainer Volkamer (#22 Magellan) 




21

Acknowledgements 

• ESA, Changing Earth Science Network SciNet – funding of TIBAGS 

• Diego Fernández & Roberto Sabia 

• University Bremen 

• SeaWiFS data (NASA, National Aeronautics and Space Administration, USA) 

(available at the Ocean-Color webpage http://oceancolor.gsfc.nasa.gov) 

• AMSR-E sea ice data (L. Kaleschke & G. Spreen) 

(available at the Integrated Climate Data Center, Klima Campus, Uni Hamburg) 

Thank you for listening! 




22

The End 




23

The End 




24

transfer 

to land/ice 

precipitation 

deposition 

? 

Why should we care about iodine compounds? 

aerosol particles 

inorganic 

Recycling/ 

Re-emission 

? 

ice algae 

McFiggans et al, 

ACP, 2004. 

phytoplankton/algae 

? 

iodine oxides 

I xO y 

different 

pathways 

I 2 

CH 3I CH 2I 2 




25 

? 

IO 

I 

O 2 ozone depletion 

O 3 

hn 

CH2ICl CH3I HX, XO 

soils 

rice paddies 

salt lakes 

vulcanoes 

biomass 

burning 

Small drawings from: 

www.vskrems.lerchenfeld.ac.at

Iodine monoxide in the MBL 

(L. Carpenter et al, 2001) 

• anti-correlation of IO and tidal height 

• presence of macro algae (oxidation 

processes during low tide) 

• correlation of IO with solar irradiance 

(photochemistry) 

� importance of halogens for the 

marine boundary layer 




26

180° 


3. Iodine monoxide above Antarctica 

90°W 

Antarctic Circle 

Halley 

Neumayer 

90°E 




27 

0° 

• ~10 14 molec/cm²dSCD of IO 

• several ppb IO in snow pack? 

(Friess et al 2001, 2009) 

(Saiz-Lopez et al, 2007) 

organic iodocarbons in sea water 

CH 2I 2, CH 2IBr, CH 2ICl 

(Carpenter et al, 2007)

90°W 

Hudson 

Bay 


3. Iodine monoxide above Antarctica 

Alert 

180° 

Arctic 

Ocean 

Ny-Ålesund 

0° 

Bremen 


Arctic Circle 

90°E 

(Barrie et al, 1988) 

Br 

O 3 

• BrO up to 20 ppt 

• IO below the detection limit 

(Hönninger et al, 2004) 

• IO ~3 ppt on two occasions 

(Oetjen, 2009, Mahajan pers. comm.) 

Update! 

• IO dSCD ~10 13 molec/cm²< 1ppt 

(Wittrock et al, 2000; Oetjen 2009) 



28

Vertical columns of iodine monoxide 

Retrieval method: Differential Optical Absorption Spectroscopy 

Result from DOAS retrieval: slant column amounts SC 

Meaningful quantity 

for investigations: vertical columns VC 

Geometry Air Mass Factor AMF 

• calculated via radiative transfer model SCIATRAN 

• correction factor to account for the relative path 

length through the absorber layer 

SC( 

�, 

SZA, 

�,...) 

AMF ( �, SZA, 

�,...) 

� 

VC 

SC( 

�, 

SZA, 

�,...) 

VC � 

AMF ( �, 

SZA, 

�,...) 




29 

� 

SC � � ( l) 

dl 

VC 

i 

i 

L 

� 

z�0 

L �L( 

�, SZA, 

�,...) 

i 

TOA 

� � ( z) 

dz 

i

Vertical columns of IO – AMF studies 

Influencing parameters (examples): 

• Ground reflectance 

• Solar Zenith Angle 

• Absorber altitude profile 

• Aerosol scenario 

Results from sensitivity studies 

� Sensitivity for IO detection much better above 

bright surfaces 

� Dependency on altitude profile small for bright 

surfaces, larger for dark surfaces 

� Influence from aerosol amount smaller above 

bright surfaces 

� More detailed AMF studies including aerosoles 

and measured IO altitude profiles necessary 

90 % reflecting surface 

5 % reflecting surface 




30

Vertical columns of IO – AMF studies 

Sensitivity to ground layers: 

• Reduced sensitivity for darker sufaces 

• Enhanced visibility of IO above bright 

surfaces 

• For precise quantitative studies, the 

ground reflectance needs to be taken 

into account 




31

Improving the basic satellite data set 

NRT data set Consolidated data set 

Consolidated data set 

• Consistent amounts with inital product 

• Improved quality (less noise) due to improved background consideration 

• Extended, consistent time series now processed and ready to use (2003-2010 ongoing) 




32

The very End 

(Lizotte, 2001) 

Primary productivity in the Antarctic sea ice surface communities by 

month as modeled by Arrigo et al. (1998b). Symbols: multi-year ice 

(triangles); first-year ice (squares); and total sea ice (circles). 




33

The very End 

(Lizotte, 2001) 

Primary productivity in the Antarctic sea ice zone (SIZ) by month as 

modeled by Arrigo et al. (1998b,c). Symbols: SIZ total (triangles); 

MIZ water (diamonds); shelf water (squares); and sea ice (circles). 




34

Iodine Monoxide and the Relations to Sea Ice - Congrex

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