Southern Ocean GasEx Blog

Dispatches from the Southern Ocean Gas Exchange Experiment

Ocean Essence

Posted by sogasex on March 3, 2008

By Steve Archer, Plymouth Marine Laboratory

I can watch albatross for hours; they are the ultimate ’surfers’ of ocean swell and wind. It’s a challenge for them today and certainly was yesterday; the conditions in this part of the South Atlantic are almost too calm; every now and then the albatross have to give an undignified flap or two to keep airborne. It is excellent weather for scientists who are getting equipment set-up as the ship makes good time towards our study site.

Albatross and our work are not completely disconnected. I’m part of a collaborative effort between the University of Hawaii and Plymouth Marine Laboratory in the UK. This collaboration builds on similar work we carried out last summer in the North Atlantic. We’re interested in quantifying the emission of a sulphur gas, dimethyl sulphide (DMS for short) from the ocean to the atmosphere. Humans can detect this gas at comparatively low concentration; it is part of the smell you associate with seaweed-covered beaches. Research suggests that seabirds, like albatross, are much better DMS detectors than we are and may use the gas to identify different regions of the ocean as they navigate to and from feeding areas. DMS is a product of the photosynthetic microbes, the phytoplankton, that inhabit the surface waters of the oceans (see the blog on 29th February). Once in the atmosphere, DMS has an impact on aerosol and cloud formation and so, like CO2, there is another intriguing link between ocean biology, atmospheric chemistry and our changing climate.

I’m trying to measure DMS concentrations in the seawater as often as I can to tie-in with the air-side measurements that Byron Blomquist (Uni of Hawaii) will measure to generate estimates of sea-to-air flux of DMS. In combination, this information will help to explain what controls how much of the gas produced by the ocean biology, finds its way into the atmosphere. What is more, like you and I, our instruments are pretty accurate at ’smelling’ DMS compared to CO2 and so this information will hopefully help to explain some of the controls on CO2 flux to and from the ocean.

The DMS concentrations in the seawater are gradually increasing as we move away from the land masses and into more oceanic water, probably as a result of changes in composition of the phytoplankton. As you can see from the two photographs, the dolphins were taken yesterday evening and the albatross earlier this morning, that we’ve cruised into bluer, more oceanic water today. Different species of phytoplankton produce different amounts of the precursor to DMS, a compound that abbreviates to DMSP. For reasons that we are still unclear about, phytoplankton that inhabit more oceanic waters generally produce relatively more DMSP and DMS and it is in the remote oceanic atmosphere that this gas is likely to have most impact on climate.

albatross.jpg

Wandering albatross surfing a mini ocean swell in the South Atlantic today.

dolphins.jpg

One of the pairs of dolphins that visited the Ronald H. Brown yesterday.

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