Robots under ice

Josh Kohut with one of Rutgers' gliders.

My name is Josh Kohut, I’m an assistant professor of oceanography at Rutgers University.

What makes the Ross Sea special is it’s an area where we have a lot of nutrients but not much phytoplankton growth. Phytoplankton are very small-celled plants in the ocean. They provide a tremendous amount of oxygen to the planet and in the Ross Sea they bloom, provide a food source for zooplankton and other animals in the ecosystem up in the upper parts of the ocean. Once they are consumed or die they fall down to the deeper parts of the ocean. And that’s a way to take carbon and move it down to the depths before it settles on the bottom in the sediments.

Phytoplankton are plants, so they need nutrients to grow. Instead of getting those nutrients from the soil they get them from the ocean around them. They also need sunlight, so in order for a phytoplankton to grow it needs to be up in the upper parts that can feel the sun and they also need that Miracle-gro of the ocean, which is the nutrients, nitrate, phosphate, those different things that allow the phytoplankton to grow.

The analogy that we like to use is that they are like vitamins that we would take to supplement the energy that we get from our food. In the same way, phytoplankton need iron to build some of the tools that they have to photosynthesize. In the area of the Ross Sea, we have plenty of nutrients and when the phytoplankton are up near the surface of the ocean they have plenty of light in the summer months. What they don’t have often are nutrients like iron.

One of the big questions we are looking to understand and address is where is that iron coming from, is it coming from the sediments, is it coming from the bottom of the Ross Sea, is it coming from this deep water that comes from the circumpolar current, comes up and actually enters the Ross Sea from offshore. Where is this iron coming from?

One of the questions that we have raised and that we are going to answer with this is what role the deep water that comes to the Ross Sea has on the iron and on the phytoplankton productivity on the shelf. We need to find that deep water. What we’re going to do in December is we’re going to send a glider out. This is about a month and a half before the cruise even starts. We’re going to send a glider out to basically serve as a scout and it’s going to go out into the Ross Sea and it’s going to tell us where that deep water is.

The biggest challenge is we are taking a six-foot long robot and we’re putting it in off the edge of the ice into the Ross Sea. And the Ross Sea is a very rough place. And there is a lot of ice and a lot of conditions—it’s not a benign place to put a robot like that. So there’s challenges with that. But we have to push that envelope, we want to get out there, we need that information, and the robot is perfect way to do it. But I’m definitely nervous about that deployment. Whenever you put oceanographic equipment in the water you’re never completely confident you’re going to get it back. When you put a robot in the Ross Sea you’re even less so.