Southern Ocean GasEx Blog

Dispatches from the Southern Ocean Gas Exchange Experiment

ASIS – The Return of Big Bird

Posted by sogasex on March 31, 2008

By Will Drennan, University of Miami

ASIS, the University of Miami’s “Air-Sea Interaction Spar” buoy, was recovered by the Ronald H Brown over a week ago, after a week at sea. The comment most people make when seeing ASIS for the first time is “Wow, that’s big”. At 6 x 2 x 2 m (36 x 6 x 6 ft), and weighing close to a ton, it is indeed one on the larger pieces of kit on the deck. As Mike Rebozo can tell you, it can also be difficult to deploy and recover. While he’s likely lost count of how many times ASIS has gone over the side of various ships over the past decade, the real question is how many of Mike’s grey hairs are a result of ASIS ?

The role of ASIS in SO GasEx is to make measurements at, and close to, the ocean surface. Above the surface, we measure basic meteorological parameters, as well as the air-sea fluxes of CO2, water vapour, heat and momentum. In collaboration with Ian Brooks and Sarah Norris of the University of Leeds, we are also measuring aerosol fluxes and concentrations. At the surface, we measure surface waves and wave slopes at various scales. This is particularly important for gas transfer work, as small scale waves are thought to be significant control on gas transfer rates. Below the water, we measure temperature, salinity and energy dissipation rates (a measure of surface mixing, which acts as a control on gas transfer). There is also one of Mike DeGrandpre’s SAMIs (see Mike’s blog) measuring carbon dioxide, dissolved oxygen, and light (PAR). Finally we also measure how ASIS moves in the water. Equipped with three ARGOS beacons giving position, we wanted to make sure to find it again.

While many of these atmospheric measurements are also made on board the Brown, a ship disturbs the near surface too much to measure many air-sea processes, such as small scale waves. ASIS was designed precisely to fill the need for a platform for such high resolution near-surface measurements. On its previous cruise on the Brown, during Gasex-2001, ASIS was christened “Big Bird”, after its less than graceful flight over the deck during deployments. The bird is still big, but hopefully the flights are becoming more graceful.

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ASIS being deployed

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ASIS in the water

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