Chelle Gentemann studies the living ocean from space

Chelle Gentemann: Satellite data is really helping us avoid endangered species.

Satellite researcher Chelle Gentemann works with the California-based company Remote Sensing Systems. Gentemann works with the AMSR-E sensor, an instrument on board NASA’s Aqua satellite, its data is used to map temperatures and wind speeds in Earth’s oceans. That information, she said, can help protect marine life.

Chelle Gentemann: One example is loggerhead turtles that get caught in drift and gill nets. The distribution of ocean temperature can actually be used to define regions for the fishing industry to avoid.

That’s because loggerhead turtles prefer cooler waters. Dr. Gentemann provides data for an environmental program that maps ocean temperatures. It’s called TurtleWatch.

Chelle Gentemann: Turtlewatch looks at temperatures around Hawaii, and they put regions for fisherman to avoid putting their drift nets in so that they’ll mitigate the by-catch of loggerheads. And this has just started, and looks to be successful.

In addition to protecting turtles, satellite data can help in sustainable fishing of salmon, said Gentemann. She explained that the U.S. government regulates how much – and when – salmon can be caught in national waters each year.

Chelle Gentemann:
Some of the satellite data and little sensors that we track salmon with, we know that salmon actually prefer specific temperatures. Since the temperatures along the coast vary from year to year, the government can actually fine-tune the open season to get closer to their desired total catch.

Dr. Gentemann talked more about how the AMSR-E instrument on NASA’s Aqua satellite works.

Chelle Gentemann: The Aqua satellite is a NASA satellite and it carries the Advanced Scanning Radiometer for the Earth Observing System, or AMSR-E instrument and this was built and supplied by the Japanese Aerospace Exploration Agency, which is called JAXA. AMSR-E was modeled after a series of instruments called SSMI, which is the special sensing microwave imager. And the SSMI series of satellites have been continually in orbit since 1987, which is almost 22 years. So AMSR-E observes the Earth. It is a passive microwave radiometer. And what that means is that there’s both active and passive. And an active scatterometer actually sends a signal down and measures its reflection. A passive microwave radiometer simply measures emitted radiation at specific frequencies, or wavelengths.

So, over the ocean, AMSR-E measures ocean temperature, wind speed, water vapor, cloud water, rain rate, and sea ice. These measurements are then used for research, weather prediction, and climate monitoring. Satellite measurements of sea ice also form an important part of the work of AMSR-E onboard the Aqua satellite.

Chelle Gentemann:
AMSR provides important measurements of both sea ice concentration, meaning how much ice is in a given region. And obviously, some of it is completely solid in pack ice, so that would be 100 percent. And near the edges, it starts to diminish, and it’s sort of ‘mixed-pancake’ ice and water. Those would be 50 percent, or 20 percent sea ice. It also measures the sea ice age. So it’s able to tell the difference between first-year sea ice as well as multi-year sea ice.

One reason it’s important to study sea, says Gentemann, is because it has an effect on our food supply.

Chelle Gentemann:
One example of that is the Eastern Bering Sea, which is one of the areas where sea ice has been dramatically retreating in the summer and almost disappearing. It supports extraordinarily rich marine resources. And, what I mean by that is that it supports fisheries, birds, and mammals. Many of these are federally-protected species. But also, many of these are very productive commercial stocks. So, 50 percent of all of the fish and shellfish landings in the US, crab, salmon, they’re all up in the Bering Sea. This is a very key food source for the United States. But these fisheries also, they employ fishers, processors, and distributors. So it’s important for our economy and it’s important for our food supply. But, as the Bering sea responds to variations in climate, its ability to support these resources can change.

How does it do that?

Chelle Gentemann: One example is the spring bloom of phytoplankton that can support the fisheries. What happens is that the sea ice expands in the winter, and then in the summer, as the sea ice is pulling back, there’s these large algae mats underneath the sea ice. And the timing of when the sea ice retreats actually affects the timing of this primary production bloom.

The primary production bloom is important because it’s the basis of the food chain, says Gentemann.

Chelle Gentemann: So we move up, and actually, all of this nutrient is going to go up and support all commercial fisheries. But if the retreat of the sea ice happens to early, or too late, the temperature that this happens in really affects what part of the food chain it supports. And so we’ve seen that there’s been collapse of some fisheries in that area, because it’s been happening too late. And we’ve also seen that fish are starting to go to different regions or shift migratory patterns, because there’s not enough nutrients there, when there used to be. it’s coming later and later. So, with AMSR-E data, we’re able to look at these correlations between the sea ice retreat and the ocean temperature, and we combine that with fish tracking data to try and understand how this diminishing sea ice is going to affect our fisheries and our food sources.

Our thanks today to NASA’s Aqua Mission, improving our knowledge of our home planet through satellite observations.

December 14, 2009

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