I8S Podcast (6.7 MB)

By Pien Huang

One of the major improvements to the 4th report of the Intergovernmental Panel on Climate Change, is the use of better predictive models. In the six years since the publication of the third report, they’ve cleared up some uncertainty by scoring the performance of their models to real observations.

We’ll take you aboard the Roger Revelle, a research vessel of the Scripps Institution of Oceanography, to look at one of the first steps in climate change prediction – collecting real-time data on which models are based.

In the first of a four-part series, we’ll look one cruise, I8S, as part of a larger data collection program.

[waves; birds]

In February and March 2007, the R/V Roger Revelle spent six weeks sampling water from Antarctica to the west coast of Australia, under the direction of Captain David Murline and Chief Scientist James Swift. This transect is one of about sixteen that are monitored every ten years in the Climate Variability – CO2 Repeat Hydrography program, or CLIVAR for short.

CLIVAR was born out of the World Ocean Circulation Experiment, a one-time research project in the 1990’s that trolled the oceans and created a vertical profile of water properties throughout the oceans, such as temperature, density, and carbon and oxygen content. CLIVAR was developed to continue and to improve on the measurements of the World Ocean Circulation Experiment, to create an ongoing record of the oceans on a decadal scale. It is the start of a modern oceanographic record akin to the measurements taken by Charles Keeling, who put a sensor on a tower in Mauna Loa, and first alerted us to the rising levels of CO2 in the atmosphere in the early ’60’s.

Measuring the oceans is more involved. To do it right, you have to take a boat out, drop an array of bottles and sensors overboard, and haul them back up, processing water samples on-site. And then you repeat this, in our case, over 80 times. Each of these steps takes time, technology, and manpower, as well as a lot of money and planning. CLIVAR is an international program, and in the United States, it’s funded by the National Science Foundation and the National Oceanographic and Atmospheric Association (NOAA).

In the planning stages of CLIVAR, scientists at a convention took a beach-ball of the Earth, and drew in lines which they felt represented the world’s oceans. These lines have since been debated and pared down, but there is a randomness to their names. Chief Scientist Jim Swift, who was present at the meeting, has this to say:

Why, for instance, is this called 8South and 9N? There’s some – we’ll call it goofiness to the WOCE line numbers. I9 comes over here, and I9 south over her, I9N comes up here…it’s just scientists, you know, doing their thing.

All of these transects have a common purpose, but each individual cruise requires months of planning by the Chief Scientist, who tailors the trip to a particular region, and also accommodates add-on programs from other scientists. A day of shiptime on the Roger Revelle costs a minimum of $29,000. So whenever possible, the scientists collaborate to save on operational costs like shiptime, fuel, and labor.

What really sets I8S apart from other CLIVAR cruises is location. Because the transect starts in Antarctica, the trip departs from New Zealand and requires two weeks of travel time to its first sampling station. Chief Scientist Jim Swift discusses the planning:

So I got some historical ice information; well, there’s a lot of ice there in December, so December’s too early to start the cruise. But if I look at January, we’re getting a big reduction in the ice, and by February, that’s the ice minimum. And oh, by March, it’s starting to grow in again. So the sea ice minimum in this region was in approximately overall February, so I told the ship scheduling people that the ideal for us was to reach this point at the ice minimum in early February.

Our cruise track, if transcribed on the opposite side of the world, would start with a two week steam across the North Atlantic, from the coast of France to Hudson Bay, and then a sampling route that runs south, down through the Great Lakes to Alabama, and then out to Bermuda.

In early February, we left port in Dunedin, New Zealand on a southwestern course, our ship laden with food and lab equipment for the next six weeks. We plunged through the Roaring ‘40’s which are followed by the Roaring ‘50’s, latitude zones that are located in the only place in the world where there is infinite fetch. Fetch refers to the distance a wave can travel before it breaks; the further a wave has traveled, the more energy it has. The waves in the Roaring 40’s and 50’s are caught in the Antarctic Circumpolar Current, and can theoretically travel in a circle around Antarctica forever. The waves don’t break, but they produce colossal swells. Luckily, Captain Murline’s steady course keeps seasickness to a minimum, and cribbage tournaments keep us occupied through the worst of it. We are well-rewarded when we cross over the Circumpolar Current.

Josh Green reads from the blog of Joe Ferris, second-mate:

When you get so far south the wind dies down and the clouds part and you have beautiful days from the high pressure system that always sits over the continent. Also great long sunsets and sunrises. Getting here we haven’t seen the sun for two weeks, and lots of fog. [But] now [that] we are here and its amazing, we…turn around and starting working our way back north.

Along with the sun, the proximity to Antarctica brought icebergs in all shapes and sizes, from those you could net with a fishing net, to entire islands that dwarfed our ship. It was a treat for the passengers, but a strain on the crew.

Second mate Joe Ferris, whose responsibilities include navigating the night watch, writes:

Today rates as one of the most intense 4 hour watches of my 8 year career at Scripps Institution. While driving a north-westerly line…we again ran into the ice edge. From the satellite maps we knew to expect it somewhere in the vicinity…but the ice edge today was blown and dispersed seaward from southerly winds… we approached the ice edge trying to see how close we could get and looking for a safe spot for a station. There was none, small bergs were everywhere…[and] we spent a good three hours maneuvering around icebergs at close quarters to get out. Pretty spectacular stuff, except I really didn't have much time to enjoy it since I was the one on the helm.

Still, manning the controls on the night watch has its perks:

Last night I was treated to a once in a lifetime display of Aurora Australis, otherwise known as the Southern Lights. We had a big storm all afternoon, but by midnight the sky cleared and off on the horizon a blank of clouds started glowing green. Suddenly the Aurora Australis developed into a wide band arcing and dancing across the entire sky. The bands were shifting between purple, pink, and green, and it all seemed so…close that it [felt like] we were in it…

I tried calling the labs but everyone was asleep, so I woke the chief scientist up and when he saw the show he called everyone else. Ten minutes later I had about 20 scientists on the bridge, they didnt see the best of show, but they got to view some bands develop and dance around for a hour before it completely died out.

For I8S Outreach, this is Pien Huang. Tune in next, when we explore the machines and robots of data collection, on-board I8S.

This broadcast has been supported by the National Science Foundation, the National Oceanographic and Atmospheric Association, and the Scripps Institution of Oceanography.