Preprints
https://doi.org/10.5194/bg-2021-252
https://doi.org/10.5194/bg-2021-252

  13 Oct 2021

13 Oct 2021

Review status: this preprint is currently under review for the journal BG.

Sea ice concentration impacts dissolved organic gases in the Canadian Arctic

Charel Wohl1,2,3,a, Anna E. Jones3, William T. Sturges2, Philip D. Nightingale1,2,4, Brent Else5, Brian J. Butterworth6,7, and Mingxi Yang1 Charel Wohl et al.
  • 1Plymouth Marine Laboratory, Plymouth, PL1 3DH, United Kingdom
  • 2School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom
  • 3British Antarctic Survey, Cambridge, High Cross, Madingley Road, CB3 0ET, United Kingdom
  • 4Sustainable Agriculture Systems, Rothamsted Research, North Wyke, Devon, EX20 2SB, United Kingdom
  • 5University of Calgary, Calgary, Alberta, T2N 1N4, Canada
  • 6Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
  • 7NOAA Physical Sciences Laboratory, Boulder, Colorado, USA
  • anow at : Institut de Ciències del Mar, Barcelona, 08003, Spain

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 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 broadly higher concentrations in partial sea ice cover compared to ice-free waters. The large number of depth profiles at different sea ice coverages enables 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 the mixed layer depth, implying dominant photochemical sources in this area. Dimethyl sulfide and isoprene both display higher surface concentrations in partial sea ice coverage compared to ice-free waters due to ice edge blooms. Dimethyl sulfide concentrations sometimes display a subsurface maximum in ice -free conditions, while isoprene displays more reliably 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, DMS 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.

Charel Wohl et al.

Status: open (until 24 Nov 2021)

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Charel Wohl et al.

Data sets

Shipborne Dissolved Organic Gas Measurements in Depth Profiles and Underway Seawater (Methanol, Acetone, Acetaldehyde, DMS, Isoprene) Amundsen 2017 Charel Wohl, Anna E. Jones, William T. Sturges, Philip D. Nightingale, Brent Else, Brian J. Butterworth, Mingxi Yang1 https://www.polardata.ca/pdcsearch/

Charel Wohl et al.

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Short summary
We measured concentrations of five different organic gases in seawater in the high Arctic during summer. We found higher concentrations near the surface of the water column (top 5–10 m) and in areas of partial ice cover. This suggests that the sea ice influences the concentrations of these gases. These gases indirectly exert a slight cooling effect on the climate and it is therefore important to measure the levels accurately for future climate predictions.
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