Surface Ocean Geochemistry and Air-Sea Exchange
The IOS microlayer skimmer (AKA Princess Bob) deployed from the CCGS Amundsen in the Canadian Archipealgo, summer 2016.
Photo: Vickie Irish
As part of our efforts to understand the chemistry of air-sea exchange, we've naturally gravitated towards the sea-surface microlayer, the upper 50-200 micrometers of the ocean that's in direct contact with the atmosphere. Collecting such samples by hand is tedious, and therefore the Institute of Ocean Sciences (namely former post-doc Magnus Wendeberg, Lucius Perrault, and Svein Vagle) developed an automated sampler based on 10 rotating glass plates that are able to collect 3 L of microlayer sample a minute. With the skimmer, we are able to collect enough material not only for chemical analyses to characterize the composition of the microlayer, but we can also run experiments. Don't try this at home, but if you do, be sure to first consult the definitive manual of sea-surface microlayer measurements prepared by another of our former post-docs, Oliver Wurl.
​
Our ability to collect large quantities of sea-surface microlayer material has led to some exciting opportunities to collaborate with atmospheric chemists, who are desperately trying to figure out from where aerosols in the atmosphere come and of what they're made. Under the fearless leadership of Jon Abbatt, of the University of Toronto, the NETCARE project brought together ocean and atmosphere scientists to try to tease apart the role of the ocean in Arctic atmospheric chemistry. Interestingly, despite confirmation that the sea-surface microlayer is rich in material that makes good aerosols, it seems that bulk surface waters, not the microlayer, may be a larger source of aerosol particles. This makes some sense, since there's very little microlayer and a LOT of bulk surface waters to get blown into the atmosphere from breaking waves. However, it's still not clear whether it's the bulk water or microlayer material that actually contributes the most the climatic activity of the aerosol loading....
​
UofT student Emma Mungall, discovered that reactions (maybe photochemical?) occurring in the sea-surface microlayer release organic gases that can further react in the atmosphere to form aerosols. Most interestingly, Emma's measurements indicated that river waters might have been the source of the reactive material in the microlayer, but at the location of her measurements, the most direct source of river waters is the coast of Siberia. Thus, that reactive organic matter had survived a journey all the way across the central Arctic basin, before emerging from beneath the sea ice in northern Baffin Bay.
​
At the same time, UBC student Vickie Irish discovered that the surface waters of the Canadian Arctic Archipelago have higher concentrations of ice nucleating particles (i.e., particles that facilitate the formation of clouds in the atmosphere) when there's a larger proportion of river waters in the mix.
We've clearly underestimated the importance of river waters to the atmosphere over the Arctic Ocean. Now, the question is: how is that changing with climate?