Halocarbons from the Peruvian

Halocarbons from the Peruvian upwelling system

H. Hepach

, B. Quack

, S. Fuhlbrügge

, S. Raimund

, E. L. Atlas

, A.

Engel

, A. Bracher

, S. Flöter

and K. Krüger

1 – GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Germany

2 – Rosenstiel School of Marine and Atmospheric Science (RSMAS), University of Miami, USA

3 – Helmholtz-University Young Investigators Group PHYTOOPTICS, Alfred-Wegener-Institute (AWI) Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany

4 – Institute of Environmental Physics, University of Bremen, Germany 5 – Department of Geosciences, University of Oslo, Oslo, Norway

SOPRAN 2015 Annual Meeting Mainz

Halocarbons in the tropical ocean

Biological processes Photolysis of

CH₂I₂

Air-sea gas exchange

Photoproduction of CH₃I

CHBr₃, CH₂Br₂, CH₂I₂, CH₃I, CH₂BrI CH₂ClI

Br, I

IO BrO

O₃ O₃

Aerosol, ultra- fine Particles, HO_x and NO_x

Chemistry

The M91 cruise

M91 (RV Meteor)

Callao, Peru to Callao, Peru (December 1 – December 26 2012)

(MODIS Aqua data from December 2012)

Environmental conditions during M91

Wind speed

Air and water temperature, DT

Halocarbons during M91

• Elevated atmospheric halocarbons above the upwelling

• Bromocarbons in surface water in comparison to other upwelling regions in moderate concentrations

• Higher CH

I than CHBr

Iodocarbon surface

concentrations

Iodocarbon sources –

upwelling and phytoplankton

r_s = 0.73 r_s = 0.79 r_s = 0.72

• Relationship with cooler water  sources are in upwelling

• Iodocarbons correlate significantly with diatoms (dominant species in the surface)  potential source organisms

r_s = -0.57

r_s = -0.38

r_s = -0.65 r_s = -0.64

Temperature anomaly [°C]

Iodocarbons and SML parameters

• Enhanced DOM concentrations

such as sugars in the south where iodocarbons are elevated

• DOM constitutents may be important halocarbon

precursers  indirect biological production

SML Data from Engel et al.

Iodocarbon sea-to-air fluxes

Origin of atmospheric iodocarbons

4 days

• CH

I

2.4 h

• CH

ClI

4.3 min

• CH

I

Tropical lifetime (WMO, 2011)

CH₃I

CH₂ClI

CH₂I₂

Summary and conclusions

• Peruvian upwelling is a source for halocarbons

• Only a moderate source for bromocarbons, but a strong source for iodocarbons

• Probably direct and indirect biological production as source for iodocarbons

• Very high iodocarbon sea-to-air fluxes despite low wind speeds

• Large oceanic concentrations contribute significantly to

tropospheric iodine loading in the tropical East Pacific  high

atmospheric mixing ratios of CH

I, CH

ClI and CH

I

despite

their very short tropical lifetimes

Iodocarbon depth profiles

CH₃I

CH₂I₂

• Two types of profiles:

subsurface maxima and surface maxima ( upwelling)

• Largest

concentrations in profiles with surface maxima

• Surface usually depleted in

CH₂I₂