Keeping your world up and running.®

Q&A with Oceanographers Dr. Burke Hales and Dr. Dave Herbert

May 2013

FlukePlus learned that several Fluke tools had been spotted aboard a NOAA science vessel near Antarctica. While the ship withstood yet-another storm, mission scientists Dr. Burke Hales and Dr. Dave Hebert graciously traded emails explaining their experiments and measurements. They are on the Ronald H Brown in the South Atlantic Ocean (50oS, 40oW), approximately 100 km north of South Georgia Island. A group of approximately 30 scientists are onboard the ship to study gas exchange between the atmosphere and ocean under high wind conditions. The experiment is known as "Southern Ocean Gas Exchange". The goals of the experiment, what different type of studies are being conducted and a daily blog of what is happening on the ship can be found at so-gasex.or. This program is funded by the National Oceanic and Atmospheric Administration (NOAA), who are supporting our work, the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA).

Q. FlukePlus

Can you describe your mission for us?

A. Dr. Dave Hebert

I'll let Dr. Hales explain what we are doing out here in the middle of the South Atlantic. I have enclosed a screen from the oscilloscope that I am using to help debug my equipment (fig 1). This one was an example of the transceiver not working properly. I send screens to the developer of my instrument and he provides suggestions of things to check. He commented that I should not send any blurry ones - it is a bit hard to get a close-up of the screen on a rolling ship.

1924 Crosley model 50 radio

Example #1

A. Dr. Burke Hales

The mission is intended to study exchange of CO2 between the ocean and atmosphere at high wind speeds and in high sea-states. The reason for doing this is that in global carbon budgets, it appears that the oceans are taking up somewhere between 1/3 and 1/2 of the CO2 emitted by man every year. This is based on measurements of CO2 in ocean waters, and gas-transfer rates based on wind-speed relationships.

The problem is that the wind-speed relationships have been developed based on study of low wind-speed conditions. Most of these suggest that the dependence is on the square of the wind speed, but recently some researchers have suggested that the dependence should be on the cube of the wind speed. The difference between these two relationships is very large at high wind speeds, and there isn't much data to back things up in those conditions. But the oceans do experience these high winds fairly often.

If it turns out that we've been using the wrong wind speed dependence, that means that the estimates of ocean uptake of CO2 are wrong, and the difference will have to be accounted for elsewhere in the global CO2 budget. So that's why we're down here in the Southern Ocean with (austral) winter approaching looking for lousy weather.

The general approach is to inject an inert chemical tracer in the water, follow it around as it moves and spreads, and study the gas exchange while we do that.

Testing the CTD instrument

The project that Dave and I are working on was intended to make comprehensive, high-resolution measurements of the carbon in the water in dissolved and particulate, organic and inorganic forms (my part), in conjunction with detailed measurements of the physical transport (mixing and currents; Dave's part). From these we were going to construct a mass-balance for carbon that would tell us about how much was going across the air-sea interface.

For my part, we use a towed vehicle that looks like a cross between an airplane and a submarine. The 'SuperSoar' glides up and down through the water as it's towed by the ship, and carries a suite of electronic instruments and a high-pressure pump. The pump sends water back up to the ship via a tube in the core of the towing cable, where we do high-speed chemical analyses. Dave's instrument measures turbulent mixing, and I'll let him describe it for you.

Unfortunately, we've been having some trouble…after towing for about 7 hours early in the cruise, we hit something underwater that pretty well finished us. So we've been spending a lot of time troubleshooting…