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Atmospheric DMS in the High Arctic
Stockholm University, Faculty of Science, Department of Meteorology .
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During the Arctic summer when the anthropogenic influence is limited, the natural marine source of sulfur in the form of gas-phase dimethyl sulfide viz. DMS(g), is of great importance for cloud formation. The harsh environment of the Arctic makes it difficult to perform in situ measurements of DMS(g) and hence regional model simulations can serve as a complement to increase our understanding of DMS related processes in the Arctic. In this thesis a regional scale meteorological forecast model, extended with DMS(g) calculations, is used to provide a consistent three-dimensional time evolving picture of DMS(g) over the pack-ice region. The analysis focus on meteorological aspects on the horizontal and vertical distribution of DMS(g). Our results show that the amount of DMS(g) over an oceanic source region alone does not determine concentration found over the pack-ice, the prevailing wind also exerts a large influence on the horizontal DMS(g) distribution.

The modeled DMS(g) concentrations are advected in plumes in over the pack-ice, which, in combination with the photo-chemical decay, explain the large observed temporal variability of DMS(g) over the pack-ice. The modeled vertical structure show episodes with DMS(g) maxima well above the local boundary layer. Also shown is that DMS(g) maxima can be formed adjacent to frontal zones. In the presence of turbulence DMS(g) can be mixed downwards into the local boundary layer and aid growth to local particles and hence contribute to cloud formation in the boundary layer.

 

Place, publisher, year, edition, pages
Stockholm: Department of Meteorology, Stockholm University , 2010. , 47 p.
Keyword [en]
DMS, Modelling, Arctic
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
URN: urn:nbn:se:su:diva-38178ISBN: 978-91-7447-043-7 (print)OAI: oai:DiVA.org:su-38178DiVA: diva2:306740
Public defence
2010-04-29, sal G, Arrheniuslaboratorierna, Svante Arrhenius väg 20 C, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript. Paper 4: Manuscript.Available from: 2010-04-07 Created: 2010-03-30 Last updated: 2010-04-06Bibliographically approved
List of papers
1. The horizontal distribution of atmospheric DMS in the high Arctic summer
Open this publication in new window or tab >>The horizontal distribution of atmospheric DMS in the high Arctic summer
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The horizontal distribution of gas--phase dimethyl sulfide, DMS(g), in the Arctic atmosphere north of 70N is investigated during a summer season using the three--dimensional numerical model COAMPS©. The highest modeled median DMS(g) concentration over the ocean is found in the Kara and Greenland Seas. The simulated DMS(g) concentration is the result of the interaction between factors such as the local DMS flux, wind speed and direction as well as adjacent areas of open ocean. Over the pack—ice, around the North Pole (north of 88N), DMS(g) concentrations are generally lower. The horizontal distribution of atmospheric DMS over the pack--ice is determined by transports associated with synoptical weather systems together with the source strength of DMS(g) taking into account photochemical decay. Trajectory analysis shows that in July and August, 2001, the Greenland--Sea sector was the dominating source region for DMS(g) found in the North--Pole region due to the prevailing winds from this region. Averaging DMS(g) over the lowest atmospheric layer (below 200 m) for time periods from a few days to a month shows a gradual decrease northwards of the concentration over the pack--ice resulting from DMS(g) being continuously advected in well-defined plumes. In contrast to the narrow DMS(g) plume with its source over the Chukchi Sea in July, a wide plume originating from the Kara, Barents and Greenland Seas was present in August 2001. Both plumes extended more than 100 km in over the pack--ice.

 

Keyword
Arctic DMS modellering
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
urn:nbn:se:su:diva-38173 (URN)
Available from: 2010-03-30 Created: 2010-03-30 Last updated: 2010-12-27Bibliographically approved
2. The inter-annual variability of atmospheric DMS in the high Arctic summer
Open this publication in new window or tab >>The inter-annual variability of atmospheric DMS in the high Arctic summer
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Meteorological aspects on the DMS(g) dispersion in the high Arctic atmosphere during the summer season are studied with a regional model that is applied over the pan-Arctic region. Four individual years, 1991, 1996, 2001 and 2007 with variable seasonal ice-melt are studied. The model results show that the Kara, Barents and Greenland Seas are the dominating source regions for DMS(g) found around the North-Pole region in three of the four years. The situation is quite different in 2007 where the concentration mainly originates from the East Siberian Sea. This due to the meteorological conditions as well as the extensive ice-melt in August which increase the source region as well as reduce the distance to the North-Pole. The modeled temporal variability is large in near-surface DMS(g) concentration over the pack-ice region, where the highest concentrations are found in the Atlantic sector. The prescribed seasonal decline is overshadowed by the increase in DMS(g) concentration due to decreased ice extent. Our results show that DMS(g) concentrations are reaching the North-Pole region in well defined plumes originating from different source regions. In 2007 the plumes are more frequent and have high concentration compared to 1996 where only a few plumes reach the area early in the season. The horizontal and vertical distribution of DMS(g) over the pack-ice is determined by the transport associated to individual low-pressure systems entering the pack-ice region. This variability both in time and space illustrates the difficulty to generalize observations taken at specific locations and times over larger areas and time periods.

 

Keyword
Arctic DMS modelling
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
urn:nbn:se:su:diva-38174 (URN)
Available from: 2010-03-30 Created: 2010-03-30 Last updated: 2010-12-27Bibliographically approved
3. Influence of meteorological processes on the spatial and temporal variability of atmospheric dimethyl sulfide in the high Arctic summer
Open this publication in new window or tab >>Influence of meteorological processes on the spatial and temporal variability of atmospheric dimethyl sulfide in the high Arctic summer
2007 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 112, no D13308Article in journal (Refereed) Published
Abstract [en]

Near-surface observations of gas phase dimethyl sulfide, DMS(g), over the central Arctic Ocean display large temporal variability. By using a three-dimensional numerical model, the atmospheric part of COAMPS2.0®, we show that meteorological processes such as transport and mixing cause variability in DMS(g) of the same order as in the observations. The observations used in this study were taken on board the icebreaker Oden that cruised the high Arctic during the following three expeditions: the International Arctic Ocean Expedition 1991, the Arctic Ocean Expedition 1996, and the Arctic Ocean Experiment 2001. Calculation of air-sea flux and photochemical decay of DMS(g) was added to COAMPS2.0®. A 10-day period in August 2001 was modeled. The time development of observed DMS(g) is captured by the model, correlation coefficient 0.76, in spite of a simplified treatment of DMS processes. Also, the model results clearly show that DMS(g) is advected over the pack ice in plumes originating from different source areas around the pack ice.

Place, publisher, year, edition, pages
American Geophysical Union, 2007
Keyword
Arktis
National Category
Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-20233 (URN)10.1029/2006JD008183 (DOI)000248029700003 ()
Available from: 2007-11-26 Created: 2007-11-26 Last updated: 2017-12-13Bibliographically approved
4. The vertical distribution of atmospheric DMS in the high Arctic summer
Open this publication in new window or tab >>The vertical distribution of atmospheric DMS in the high Arctic summer
Show others...
2010 (English)In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 62, no 3, 160-171 p.Article in journal (Refereed) Published
Abstract [en]

The vertical structure of gas-phase dimethyl sulfide, DMS(g), in the high Arctic atmosphere is investigated during a summer season. The model results show that the near-surface DMS(g) concentration over open ocean is very variable both in time and space, depending on the local atmospheric conditions. Profiles over ocean have typically highest concentration near the surface and decrease exponentially with height. Over the pack-ice, the concentrations are typically lower and the vertical structure changes as the air is advected northward. Modeled DMS(g) maxima above the local boundary layer were present in about 3\% of the profiles found over the pack-ice. These maxima were found in association to frontal zones. Our results also show that DMS(g) can be mixed downward by turbulence into the local boundary layer and act as a local near--surface DMS(g) source over the pack-ice and may hence influence the growth of cloud condensation nuclei and cloud formation in the boundary layer. Profile observations are presented in support to the model results. They show that significant DMS(g) concentrations exist in the Arctic atmosphere at altitudes not to be expected when only considering vertical mixing in the boundary layer.

 

Keyword
Arctic DMS modelling
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
urn:nbn:se:su:diva-38175 (URN)10.1111/j.1600-0889.2010.00458.x (DOI)
Available from: 2010-03-30 Created: 2010-03-30 Last updated: 2017-12-12Bibliographically approved

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