Atmosphere-Ocean Exchange of Volatile Compounds in the Canadian Arctic | Charel Wohl

This article was co-written by Charel Wohl and his supervisor Mingxi Yang (miya@pml.ac.uk) in acknowledgement of their BEIS funded research project.

This project, in collaboration with Professors Brent Else (University of Calgary) and Tim Papakyriakou (University of Manitoba), seeks to determine the abundance and atmosphere-ocean exchange of a large number of volatile organic compounds in the Canadian Arctic. These organic compounds can affect the cycling of aerosols (which control cloud formation) and also ozone (a major air pollutant) in the Arctic atmosphere. The concentrations of these organic compounds are measured in the ocean as well as in the atmosphere of the Arctic on board of the Canadian icebreaker CCGS Amundsen. Professor Jon Abbatt (University of Toronto) and Dr. Anna Jones (British Antarctic Survey) also accepted my invitation to collaborate on this project. They are contributing instrumentation and additional measurement expertise towards this expedition.

My PhD student (Mr. Charel Wohl) and I installed a highly sensitive mass spectrometer (proton-transfer-reaction mass spectrometer) on the CCGS Amundsen in May 2017 when the ship was in port in Quebec City, Canada. Charel joined the expedition on board of the Amundsen in early July 2017 for Leg 2b, which will finish in mid August 2017. He has been able to successfully detect several organic compounds in the Arctic waters as well as in the atmosphere, including alcohols, acetone, acetaldehyde, dimethyl sulfide, and isoprene. Charel has also been helping Profs’ Else and Papakyriakou’s teams with collections of seawater samples for carbonate chemistry analysis, as well as assisting their measurements of air-sea carbon dioxide fluxes by the eddy covariance method

Charel’s main task on this expedition is to operate a PTR-MS (proton-transfer-reaction mass spectrometer, pictured above), which is coupled to a segmented-flow coil equilibrator to measure the dissolved concentrations of a large number of organic compounds in seawater. Charel is also measuring their atmospheric concentrations in order to understand how the Arctic Ocean is emitting/absorbing these organic compounds.

In addition, Charel is measuring the size distribution of aerosols and abundance of ozone in the Arctic atmosphere. This is in collaboration with University of Toronto and the British Antarctic Survey, respectively. Aerosols are seeds upon which clouds form and they affect the radiative balance (e.g. heating/cooling) of the Arctic. Ozone is a principal air pollutant and greenhouse gas. Both aerosols and ozone in the Arctic are affected by the abundance of organic gases.

A CTD (conductivity temperature density) rosette is regularly cast to obtain seawater samples from the upper few metres to several hundred metres below. These seawater samples are analysed for a number of different chemical, biological, and physical parameters. Charel is measuring the concentrations of dissolved organic gases at different depths in order to understand their production and removal.

Charel Wohl (right) and Tonya Burgers (left, a student from University of Manitoba) hauling a niskin bottle over board to sample the surface ocean (upper 1 to 2 m). Because of the smaller profile of the niskin, this method of sampling does not stir up the surface ocean as much as the CTD rosette and thus better preserves the near-surface profile.

Charel (left) and Tonya (right) then transfer seawater from the niskin bottle (3 litre capacity) to small sampling bottles for analyses.

Leg 2a of the ArcticNet expedition aboard the Amundsen (6-13 July) hosted Schools on Board, an experiential learning program for high school students.  Four high schools students from Canada (including 2 participants from Inuit towns) travelled with the expedition, touring instrument installations and participating in research activities.  The PTR-MS was operational during this time period, and one of the postdoc fellows involved in our Canada-UK Bursary research program gave the students a tour of the equipment our research team is using aboard the Amundsen.  Students were able to learn about basics of meteorology, trace gas exchange between the atmosphere and ocean, and atmospheric chemistry.