Sydney: Earth’s oceans are incredibly vast. Some parts of it are so remote that the nearest human habitation is the International Space Station.
As the world warms, what happens in the ocean – and what happens to the ocean – will matter to all of our lives. But to monitor what’s happening in distant waters, we need to study the ocean from space.
Late last year, NASA and the French space agency CNES launched a satellite that promises to give scientists a better view of the ocean surface than ever before. The Surface Water and Ocean Topography (SWOT) mission will explore ocean currents that play an important role in weather and climate.
To get the most out of satellite observations, we need to compare them with measurements made at surface level. That’s why we’re taking to the sea on board the state-of-the-art CSIRO research vessel RV Investigator to gather essential marine data under the path of satellites in Earth’s orbit.
current affairs
Climate change is disrupting the global network of currents that connect the oceans. Researchers have detected the slowdown of the deep “upturn circulation” that carries carbon, heat, oxygen and nutrients from Antarctica around the world. Meanwhile, at the surface, ocean currents are becoming more energetic.
We have also seen dramatic changes in fast, narrow rivers of ocean water called Western Boundary Currents, such as the Gulf Stream and the East Australian Current.
These currents spread heat from the tropics toward the poles, and in recent decades they have become hotspots of ocean warming. In the Southern Hemisphere, they are warming two to three times faster than the global average.
As these currents become unstable, they change the way heat is distributed throughout the ocean. This would result in major changes to local weather and marine ecosystems that could affect the lives of millions of people.
playground physics
The SWOT satellite mission will give researchers a powerful new tool to monitor changes in ocean currents using precise satellite measurements of the ocean surface – as well as a little playground physics.
The satellite carries an instrument that will map changes in sea surface height in unprecedented detail. These variations can range from less than a meter in height over horizontal distances of hundreds of kilometers. But oceanographers can use the measurements to estimate ocean currents flowing beneath.
Small changes in sea surface elevation create horizontal pressure differences that tend to push water away from areas of higher sea level and toward areas of lower sea level. That pressure difference is balanced by the Coriolis force, which gently deflects ocean currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
You can experience the Coriolis force in the playground. Step onto the carousel-go-round and ask a friend to stand on the opposite side of you. Toss a ball to your friend as you start spinning. You will notice that the ball appears to be deflected away from the direction of rotation.
In reality, the ball has moved in a straight line; Your friend has moved away from the spot you were aiming at. But, to both of you, it appears that the ball has been deflected by an invisible “pseudo force” – the Coriolis force.
Now imagine that the carousel is the Earth, and the ball is an ocean current. The Coriolis deflection is sufficient to balance pressure differences across hundreds of kilometers and cause seawater to flow into ocean currents.
science at sea
By carefully measuring ocean surface height and using our knowledge of the Coriolis force, oceanographers will be able to reveal ocean currents in greater detail than ever before using data from a NASA satellite. But to make sense of that data, researchers need to compare satellite measurements to observations made on Earth.
That’s why we’re leading the journey of more than 60 scientists, support staff and crew aboard the RV Investigator, Australia’s national flagship for blue water ocean research.
Our 24-day voyage will study ocean dynamics off the south-east coast of Australia using the investigator’s world-class scientific instruments, including satellite-tracked floating buoys and drifters used to measure real-time currents on the ocean surface. Will be used to measure the speed of.
The trip is part of a huge collaboration by scientists around the world to gather observational data under the satellite’s path in Earth’s orbit.
This data will help validate satellite measurements and improve weather forecasts, including those from the Australian Bureau of Meteorology, and assist in climate risk assessment and prediction.
Using what we see in space, in the ocean and on the playground, we hope to better understand how our oceans are changing. (Conversation)