NAAMES-III Expedition: September 4, 2017

September 8th, 2017 by Kristina Mojica

Sampling at the bow: measuring ocean-atmosphere exchange

One of the main objectives in the NAAMES mission is to understand what gases and particles present in the surface ocean get into the atmosphere and influence clouds and climate. To help answer this question, our group measures gases present in both the ocean and atmosphere, as well as the rate at which the gases are exchanged- that is, how quickly they go into or go out of the ocean.

To do this, we need to observe the natural wind motions and gas concentrations with as small an influence from the ship as possible. The ship disturbs the natural wind field and can also be a source of gases and particles (especially from its exhaust stack). So we go up and out! We install the inlet on the forward mast, which minimizes these impacts from the ship itself. This is where we can get the air most representative of the North Atlantic environment while on board.

So before leaving the dock we lower the forward mast, climb on, and install long sampling inlet tubes. Then, before departing, we raise the mast and run the other end of the tubes back to a mass spectrometer which is running in a container van just aft of the mast. Then (assuming everything is working!) we continuously draw in air and measure two gases (dimethylsulfide and acetone). By simultaneously monitoring the 3D wind direction, we can find out how much of these two gases are entering the atmosphere from the ocean.

Jack Porter on top of the forward mast installing aerosol sampling inlet. Photo credit: Brian VerWey

Group leader Tom Bell cranking up the mast before departure
as the Martha’s Vineyard ferry passes. The spiny line leading to the left
is a bundle of thoroughly cable-tied inlet tubes and electrical cables
that go from the mast back to the instrument van.

Written by Mike Lawler

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2 Responses to “NAAMES-III Expedition: September 4, 2017”

  1. Rob says:

    Interesting method Mike hope all goes to plan will be a world game changer if it enables us to understand clouds etc better cheers rob

  2. Marta porter says:

    Be careful up there Jack Porter.

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Notes from the Field