Assessing the potential for dimethylsulfide enrichment at the sea surface and its influence on air–sea flux
The flux of dimethylsulfide (DMS) to the atmosphere is generally inferred using water sampled at or below 2 m depth, thereby excluding any concentration anomalies at the air–sea interface. Two independent techniques were used to assess the potential for near-surface DMS enrichment to influence DMS e...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-09-01
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| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/12/1033/2016/os-12-1033-2016.pdf |
| Summary: | The flux of dimethylsulfide (DMS) to the atmosphere is generally inferred
using water sampled at or below 2 m depth, thereby excluding any
concentration anomalies at the air–sea interface. Two independent techniques
were used to assess the potential for near-surface DMS enrichment to
influence DMS emissions and also identify the factors influencing enrichment.
DMS measurements in productive frontal waters over the Chatham Rise, east of
New Zealand, did not identify any significant gradients between 0.01 and 6 m
in sub-surface seawater, whereas DMS enrichment in the sea-surface microlayer
was variable, with a mean enrichment factor (EF; the concentration ratio
between DMS in the sea-surface microlayer and in sub-surface water) of 1.7.
Physical and biological factors influenced sea-surface microlayer DMS
concentration, with high enrichment (EF > 1.3) only recorded in
a dinoflagellate-dominated bloom, and associated with low to medium wind
speeds and near-surface temperature gradients. On occasion, high DMS
enrichment preceded periods when the air–sea DMS flux, measured by eddy
covariance, exceeded the flux calculated using National Oceanic and
Atmospheric Administration (NOAA) Coupled-Ocean Atmospheric Response
Experiment (COARE) parameterized gas transfer velocities and measured
sub-surface seawater DMS concentrations. The results of these two independent
approaches suggest that air–sea emissions may be influenced by near-surface
DMS production under certain conditions, and highlight the need for further
study to constrain the magnitude and mechanisms of DMS production in the
sea-surface microlayer. |
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| ISSN: | 1812-0784 1812-0792 |