Jim Swift standing on sea ice by the ice camp for a project called SHEBA. The icebreaker Louis S. St-Laurent broke through the ice to deliver supplies to this camp. The SHEBA camp was one end of the ocean ‘section’.

Jim Swift examining CTD (conductivity, temperature, density) data on a computer in the ship's laboratory. Conductivity measures the salinity.

One interesting expedition was on the large Canadian icebreaker Louis S. St-Laurent [Fig. 1] as part of a US-Canada project to study the way the Arctic Ocean, ice, and atmosphere exchange heat. This program is called SHEBA (Surface Heat Budget of the Arctic Ocean--see the web site http://sheba.apl.washington.edu for more about that experiment). My part of the project was to measure temperature, salinity, oxygen and nutrients at 36 depths about every 6-40 miles along an imaginary line from Alaska to the central Arctic Ocean near where the SHEBA ice camp was located. We use a piece of equipment called a rosette to obtain water samples [Fig. 2]. With these measurements we have detailed data along a line which we call an oceanographic section. We call them sections because it’s like examining a slice across the ocean [Figs. 3 & 4]. It was very exciting for us because it was the first section ever made across this part of the Arctic Ocean. There have been very few ship passages in this area because the ocean is covered with ice about 4-9 feet thick and only heavy icebreakers can get through the ice.

Figure 1. The Canadian icebreaker Louis S. St-Laurent in transit through the Arctic Ocean.

The Arctic Ocean actually receives the tail end of warm, shallow Gulf Stream waters which have traveled from the south, northwards across the entire Atlantic Ocean. We have learned how processes in the Arctic make these waters colder and fresher, add gasses such as oxygen, carbon dioxide, and freons, and then deliver them back into the Atlantic Ocean at great depths. Over the rest of the World Ocean these deep waters very slowly rise and eventually - hundreds of years later - head back north, completing what some scientists have called a great conveyor belt of ocean circulation on the grandest scale [Fig. 5]. I began analyzing the Arctic section data [Fig. 6] in 1998 - but there is always more work to do!

Figure 2. The rosette about to go into the sea to collect water samples.

I really enjoy my work because I like discovering new facts about the ocean and I enjoy being on the ocean, collecting data and then working to understand how the data fit into a pattern. Check out the site http://odf.ucsd.edu/joa/ where you will find out how you can actually USE our data on your computer!

Figure 3. Graph showing variations in salinity with depth for the Arctic section. Salinity is measured in parts per thousand. The black area is the ocean bottom and the biggest spike is an underwater mountan range called the Lomonosov ridge that runs for hundreds of miles across the Arctic Ocean. It can be seen to act as a dam for the very saline water. The fresher water is found near the coast. Can you find the reason for this?

Figure 4. Graph showing variations in potential temperature with depth for the Arctic section.

Figure 5. The Global Conveyor Belt The Arctic serves to cool the tail end of the warm waters that have come from the south.

Figure 6. Map showing the locations of the 1997 section and other recent sections. A section is an imaginary line in the ocean along which measurements are made at locations 6-40 miles apart. The lines are called 'sections' because it's like examining a slice across the ocean.

Water sampling equipment (a rosette) being lowered into the ocean.

Jim Swift removing a seawater sample from a rosette, which is a piece of equipment that is lowered into the water and used to obtain many water samples, often at a variety of depths.

Polar bears on Arctic sea ice. The bears live on the ice in the summer and their main source of food is seals. Scientists have to watch out for bears when working on the ice especially if there is open water nearby.