BioEd Online

For decades, US nuclear-powered submarines have crept under the Arctic ice, mapping and projecting power in one of the world's most disputed and environmentally sensitive regions. But when this year's vessels set out, some of them will have an additional task: collecting scientific data.

Submarine data on the Arctic Ocean have been invaluable to researchers working on the geology, biology and chemistry of these waters. In the second half of the 1990s, as part of the Science Ice Exercise (SCICEX), the US Navy allowed scientists aboard its Sturgeon-class nuclear submarines for special, unclassified science cruises. But the project ended when the boats were decommissioned.

Now SCICEX is being resurrected – this time, classified missions are being asked to collect research data. Nature talked to two of the researchers involved in the next phase of the project, biologist Raymond Sambrotto and chemist Bill Smethie, both of the Lamont-Doherty Earth Observatory at Columbia University in New York.

Was it hard to get the Navy to restart this programme?

BS: The Navy seems to be quite interested in the changes that are occurring in the Arctic. They're interested because they need to know what capabilities they'll need to operate in the Arctic in the future, and what US assets need to be protected, such as shipping, which may become more prevalent.

The plan here is to take advantage of transits across the Arctic Ocean. Submarines have to go from one side to the other, and the Navy is willing to add two or three days to that transit time to allow for the collection of scientific data and samples. But they won't allow civilian scientists to go, so a research plan has been developed in which Navy personnel and a civilian arm of the Navy called the Arctic Submarine Laboratory, based in San Diego, California, will collect the data and samples.

RS: This will be catch as catch can. The Navy has specified a geographical area — as long as the sub is in that area and is operating within certain depth limits and speed limits, it will release the data to us immediately upon the sub's return.

How important are these data to researchers such as yourselves?

BS: It is hard to get to many regions of the Arctic Ocean to sample. A submarine can do this quite readily. We need to develop time series to see how things are changing in the Arctic, and things are changing quite rapidly now.

As the ice is melting back, it's changing the freshwater content. And it's changing the biology as more water becomes open during the summer. So it's very important to document how this change is occurring and to understand it.

What kinds of measurements are you hoping to obtain?

BS: Temperature and salinity data will be collected on these cruises by launching devices called expendable CTDs (conductivity, temperature, depth sensors). These are probes that are launched from the submarine and fall through the water column measuring temperature and salinity, which are recorded on the sub.

The water samples we'll collect will be for salinity, for nutrients, for certain trace components such as helium, tritium, chlorofluorocarbons and various chemicals for determining the biological parameters. One other chemical parameter to be studied are oxygen isotopes: from these, we can determine a freshwater budget for the Arctic. We can find out how much of the water comes from rivers, how much from sea-ice melt and how much from the Pacific Ocean.

RS: For the biology, we'll be looking at levels of chlorophyll in the water and levels of particulate material — some of which is living and some detrital. We'll also be collecting water samples to look at the bacterial and plankton composition of the water. Some of the samples will be brought back for investigation and some work will be done right on the sub.

How many cruises will this work involve?

RS: One or two per year, hopefully. This March, there is the ice camp – every two years the Navy sets up a research camp off the coast of Alaska. They do a variety of things there for military purposes, but it's an opportunity for science as well.

We're using the camp to calibrate the samples coming off the submarines. These are different submarines from those we've worked with before. We need to make sure that there's no contamination or impact from sampling from the submarine. So we're going to be sampling from the ice camp by standard methods of lowering bottles and collecting water and comparing that with the samples collected by the submarine. Then we can calibrate how accurate the submarine samples will be in future.