Delivery of halogenated very short-lived substances from the west Indian Ocean to the stratosphere during the Asian summer monsoon

Alina Fiehn, Birgit Quack, Helmke Hepach, Steffen Fuhlbrügge, Susann Tegtmeier, Matthew Toohey, Elliot L Atlas, Kirstin Krüger

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Halogenated very short-lived substances (VSLSs) are naturally produced in the ocean and emitted to the atmosphere. When transported to the stratosphere, these compounds can have a significant influence on the ozone layer and climate. During a research cruise on RV Sonne in the subtropical and tropical west Indian Ocean in July and August 2014, we measured the VSLSs, methyl iodide (CH3I) and for the first time bromoform (CHBr3/ and dibromomethane (CH2Br2/, in surface seawater and the marine atmosphere to derive their emission strengths. Using the Lagrangian particle dispersion model FLEXPART with ERAInterim meteorological fields, we calculated the direct contribution of observed VSLS emissions to the stratospheric halogen burden during the Asian summer monsoon. Furthermore, we compare the in situ calculations with the interannual variability of transport from a larger area of the west Indian Ocean surface to the stratosphere for July 2000- 2015. We found that the west Indian Ocean is a strong source for CHBr3 (910 pmolm-2h-1), very strong source for CH2Br2 (930 pmolm-2h-1), and an average source for CH3I (460 pmolm-2h-1). The atmospheric transport from the tropical west Indian Ocean surface to the stratosphere experiences two main pathways. On very short timescales, especially relevant for the shortest-lived compound CH3I (3.5 days lifetime), convection above the Indian Ocean lifts oceanic air masses and VSLSs towards the tropopause. On a longer timescale, the Asian summer monsoon circulation transports oceanic VSLSs towards India and the Bay of Bengal, where they are lifted with the monsoon convection and reach stratospheric levels in the southeastern part of the Asian monsoon anticyclone. This transport pathway is more important for the longer-lived brominated compounds (17 and 150 days lifetime for CHBr3 and CH2Br2. The entrainment of CHBr3 and CH3I from the west Indian Ocean to the stratosphere during the Asian summer monsoon is lower than from previous cruises in the tropical west Pacific Ocean during boreal autumn and early winter but higher than from the tropical Atlantic during boreal summer. In contrast, the projected CH2Br2 entrainment was very high because of the high emissions during the west Indian Ocean cruise. The 16- year July time series shows highest interannual variability for the shortest-lived CH3I and lowest for the longest-lived CH2Br2. During this time period, a small increase in VSLS entrainment from the west Indian Ocean through the Asian monsoon to the stratosphere is found. Overall, this study confirms that the subtropical and tropical west Indian Ocean is an important source region of halogenated VSLSs, especially CH2Br2, to the troposphere and stratosphere during the Asian summer monsoon.

Original languageEnglish (US)
Pages (from-to)6723-6741
Number of pages19
JournalAtmospheric Chemistry and Physics
Volume17
Issue number11
DOIs
StatePublished - Jun 8 2017

Fingerprint

stratosphere
monsoon
summer
entrainment
sea surface
convection
marine atmosphere
timescale
Indian Ocean
anticyclone
atmospheric transport
iodide
halogen
ocean
tropopause
air mass
troposphere
autumn
time series
seawater

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Delivery of halogenated very short-lived substances from the west Indian Ocean to the stratosphere during the Asian summer monsoon. / Fiehn, Alina; Quack, Birgit; Hepach, Helmke; Fuhlbrügge, Steffen; Tegtmeier, Susann; Toohey, Matthew; Atlas, Elliot L; Krüger, Kirstin.

In: Atmospheric Chemistry and Physics, Vol. 17, No. 11, 08.06.2017, p. 6723-6741.

Research output: Contribution to journalArticle

Fiehn, Alina ; Quack, Birgit ; Hepach, Helmke ; Fuhlbrügge, Steffen ; Tegtmeier, Susann ; Toohey, Matthew ; Atlas, Elliot L ; Krüger, Kirstin. / Delivery of halogenated very short-lived substances from the west Indian Ocean to the stratosphere during the Asian summer monsoon. In: Atmospheric Chemistry and Physics. 2017 ; Vol. 17, No. 11. pp. 6723-6741.
@article{aa608a0d9db8415c9d17907558b62710,
title = "Delivery of halogenated very short-lived substances from the west Indian Ocean to the stratosphere during the Asian summer monsoon",
abstract = "Halogenated very short-lived substances (VSLSs) are naturally produced in the ocean and emitted to the atmosphere. When transported to the stratosphere, these compounds can have a significant influence on the ozone layer and climate. During a research cruise on RV Sonne in the subtropical and tropical west Indian Ocean in July and August 2014, we measured the VSLSs, methyl iodide (CH3I) and for the first time bromoform (CHBr3/ and dibromomethane (CH2Br2/, in surface seawater and the marine atmosphere to derive their emission strengths. Using the Lagrangian particle dispersion model FLEXPART with ERAInterim meteorological fields, we calculated the direct contribution of observed VSLS emissions to the stratospheric halogen burden during the Asian summer monsoon. Furthermore, we compare the in situ calculations with the interannual variability of transport from a larger area of the west Indian Ocean surface to the stratosphere for July 2000- 2015. We found that the west Indian Ocean is a strong source for CHBr3 (910 pmolm-2h-1), very strong source for CH2Br2 (930 pmolm-2h-1), and an average source for CH3I (460 pmolm-2h-1). The atmospheric transport from the tropical west Indian Ocean surface to the stratosphere experiences two main pathways. On very short timescales, especially relevant for the shortest-lived compound CH3I (3.5 days lifetime), convection above the Indian Ocean lifts oceanic air masses and VSLSs towards the tropopause. On a longer timescale, the Asian summer monsoon circulation transports oceanic VSLSs towards India and the Bay of Bengal, where they are lifted with the monsoon convection and reach stratospheric levels in the southeastern part of the Asian monsoon anticyclone. This transport pathway is more important for the longer-lived brominated compounds (17 and 150 days lifetime for CHBr3 and CH2Br2. The entrainment of CHBr3 and CH3I from the west Indian Ocean to the stratosphere during the Asian summer monsoon is lower than from previous cruises in the tropical west Pacific Ocean during boreal autumn and early winter but higher than from the tropical Atlantic during boreal summer. In contrast, the projected CH2Br2 entrainment was very high because of the high emissions during the west Indian Ocean cruise. The 16- year July time series shows highest interannual variability for the shortest-lived CH3I and lowest for the longest-lived CH2Br2. During this time period, a small increase in VSLS entrainment from the west Indian Ocean through the Asian monsoon to the stratosphere is found. Overall, this study confirms that the subtropical and tropical west Indian Ocean is an important source region of halogenated VSLSs, especially CH2Br2, to the troposphere and stratosphere during the Asian summer monsoon.",
author = "Alina Fiehn and Birgit Quack and Helmke Hepach and Steffen Fuhlbr{\"u}gge and Susann Tegtmeier and Matthew Toohey and Atlas, {Elliot L} and Kirstin Kr{\"u}ger",
year = "2017",
month = "6",
day = "8",
doi = "10.5194/acp-17-6723-2017",
language = "English (US)",
volume = "17",
pages = "6723--6741",
journal = "Atmospheric Chemistry and Physics",
issn = "1680-7316",
publisher = "European Geosciences Union",
number = "11",

}

TY - JOUR

T1 - Delivery of halogenated very short-lived substances from the west Indian Ocean to the stratosphere during the Asian summer monsoon

AU - Fiehn, Alina

AU - Quack, Birgit

AU - Hepach, Helmke

AU - Fuhlbrügge, Steffen

AU - Tegtmeier, Susann

AU - Toohey, Matthew

AU - Atlas, Elliot L

AU - Krüger, Kirstin

PY - 2017/6/8

Y1 - 2017/6/8

N2 - Halogenated very short-lived substances (VSLSs) are naturally produced in the ocean and emitted to the atmosphere. When transported to the stratosphere, these compounds can have a significant influence on the ozone layer and climate. During a research cruise on RV Sonne in the subtropical and tropical west Indian Ocean in July and August 2014, we measured the VSLSs, methyl iodide (CH3I) and for the first time bromoform (CHBr3/ and dibromomethane (CH2Br2/, in surface seawater and the marine atmosphere to derive their emission strengths. Using the Lagrangian particle dispersion model FLEXPART with ERAInterim meteorological fields, we calculated the direct contribution of observed VSLS emissions to the stratospheric halogen burden during the Asian summer monsoon. Furthermore, we compare the in situ calculations with the interannual variability of transport from a larger area of the west Indian Ocean surface to the stratosphere for July 2000- 2015. We found that the west Indian Ocean is a strong source for CHBr3 (910 pmolm-2h-1), very strong source for CH2Br2 (930 pmolm-2h-1), and an average source for CH3I (460 pmolm-2h-1). The atmospheric transport from the tropical west Indian Ocean surface to the stratosphere experiences two main pathways. On very short timescales, especially relevant for the shortest-lived compound CH3I (3.5 days lifetime), convection above the Indian Ocean lifts oceanic air masses and VSLSs towards the tropopause. On a longer timescale, the Asian summer monsoon circulation transports oceanic VSLSs towards India and the Bay of Bengal, where they are lifted with the monsoon convection and reach stratospheric levels in the southeastern part of the Asian monsoon anticyclone. This transport pathway is more important for the longer-lived brominated compounds (17 and 150 days lifetime for CHBr3 and CH2Br2. The entrainment of CHBr3 and CH3I from the west Indian Ocean to the stratosphere during the Asian summer monsoon is lower than from previous cruises in the tropical west Pacific Ocean during boreal autumn and early winter but higher than from the tropical Atlantic during boreal summer. In contrast, the projected CH2Br2 entrainment was very high because of the high emissions during the west Indian Ocean cruise. The 16- year July time series shows highest interannual variability for the shortest-lived CH3I and lowest for the longest-lived CH2Br2. During this time period, a small increase in VSLS entrainment from the west Indian Ocean through the Asian monsoon to the stratosphere is found. Overall, this study confirms that the subtropical and tropical west Indian Ocean is an important source region of halogenated VSLSs, especially CH2Br2, to the troposphere and stratosphere during the Asian summer monsoon.

AB - Halogenated very short-lived substances (VSLSs) are naturally produced in the ocean and emitted to the atmosphere. When transported to the stratosphere, these compounds can have a significant influence on the ozone layer and climate. During a research cruise on RV Sonne in the subtropical and tropical west Indian Ocean in July and August 2014, we measured the VSLSs, methyl iodide (CH3I) and for the first time bromoform (CHBr3/ and dibromomethane (CH2Br2/, in surface seawater and the marine atmosphere to derive their emission strengths. Using the Lagrangian particle dispersion model FLEXPART with ERAInterim meteorological fields, we calculated the direct contribution of observed VSLS emissions to the stratospheric halogen burden during the Asian summer monsoon. Furthermore, we compare the in situ calculations with the interannual variability of transport from a larger area of the west Indian Ocean surface to the stratosphere for July 2000- 2015. We found that the west Indian Ocean is a strong source for CHBr3 (910 pmolm-2h-1), very strong source for CH2Br2 (930 pmolm-2h-1), and an average source for CH3I (460 pmolm-2h-1). The atmospheric transport from the tropical west Indian Ocean surface to the stratosphere experiences two main pathways. On very short timescales, especially relevant for the shortest-lived compound CH3I (3.5 days lifetime), convection above the Indian Ocean lifts oceanic air masses and VSLSs towards the tropopause. On a longer timescale, the Asian summer monsoon circulation transports oceanic VSLSs towards India and the Bay of Bengal, where they are lifted with the monsoon convection and reach stratospheric levels in the southeastern part of the Asian monsoon anticyclone. This transport pathway is more important for the longer-lived brominated compounds (17 and 150 days lifetime for CHBr3 and CH2Br2. The entrainment of CHBr3 and CH3I from the west Indian Ocean to the stratosphere during the Asian summer monsoon is lower than from previous cruises in the tropical west Pacific Ocean during boreal autumn and early winter but higher than from the tropical Atlantic during boreal summer. In contrast, the projected CH2Br2 entrainment was very high because of the high emissions during the west Indian Ocean cruise. The 16- year July time series shows highest interannual variability for the shortest-lived CH3I and lowest for the longest-lived CH2Br2. During this time period, a small increase in VSLS entrainment from the west Indian Ocean through the Asian monsoon to the stratosphere is found. Overall, this study confirms that the subtropical and tropical west Indian Ocean is an important source region of halogenated VSLSs, especially CH2Br2, to the troposphere and stratosphere during the Asian summer monsoon.

UR - http://www.scopus.com/inward/record.url?scp=85020479721&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85020479721&partnerID=8YFLogxK

U2 - 10.5194/acp-17-6723-2017

DO - 10.5194/acp-17-6723-2017

M3 - Article

AN - SCOPUS:85020479721

VL - 17

SP - 6723

EP - 6741

JO - Atmospheric Chemistry and Physics

JF - Atmospheric Chemistry and Physics

SN - 1680-7316

IS - 11

ER -