In:
Biogeosciences, Copernicus GmbH, Vol. 19, No. 4 ( 2022-02-17), p. 1021-1045
Abstract:
Abstract. The marginal sea ice zone has been identified as a source
of different climate-active gases to the atmosphere due to its unique
biogeochemistry. However, it remains highly undersampled, and the impact of
summertime changes in sea ice concentration on the distributions of these
gases is poorly understood. To address this, we present measurements of
dissolved methanol, acetone, acetaldehyde, dimethyl sulfide, and isoprene in
the sea ice zone of the Canadian Arctic from the surface down to 60 m. The
measurements were made using a segmented flow coil equilibrator coupled to a
proton-transfer-reaction mass spectrometer. These gases varied in
concentrations with depth, with the highest concentrations generally
observed near the surface. Underway (3–4 m) measurements showed higher
concentrations in partial sea ice cover compared to ice-free waters for
most compounds. The large number of depth profiles at different sea ice
concentrations enables the proposition of the likely dominant production
processes of these compounds in this area. Methanol concentrations appear to
be controlled by specific biological consumption processes. Acetone and
acetaldehyde concentrations are influenced by the penetration depth of light
and stratification, implying dominant photochemical sources in this area.
Dimethyl sulfide and isoprene both display higher surface concentrations in
partial sea ice cover compared to ice-free waters due to ice edge blooms.
Differences in underway concentrations based on sampling region suggest that
water masses moving away from the ice edge influences dissolved gas
concentrations. Dimethyl sulfide concentrations sometimes display a
subsurface maximum in ice -free conditions, while isoprene more
reliably displays a subsurface maximum. Surface gas concentrations were used to
estimate their air–sea fluxes. Despite obvious in situ production, we
estimate that the sea ice zone is absorbing methanol and acetone from the
atmosphere. In contrast, dimethyl sulfide and isoprene are consistently emitted from the
ocean, with marked episodes of high emissions during ice-free conditions,
suggesting that these gases are produced in ice-covered areas and emitted
once the ice has melted. Our measurements show that the seawater
concentrations and air–sea fluxes of these gases are clearly impacted by sea
ice concentration. These novel measurements and insights will allow us to
better constrain the cycling of these gases in the polar regions and their
effect on the oxidative capacity and aerosol budget in the Arctic
atmosphere.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-19-1021-2022
DOI:
10.5194/bg-19-1021-2022-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2158181-2
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