The Argo Evolution

Updated: May 31, 2019

Floating robots are changing our understanding of the ocean's role in climate

by Grace Greenwald and Shannon Switzer Swanson

Every second, humanity pumps an average of two and a half million pounds of carbon dioxide into the atmosphere, according to scientists’ best estimates. But where does all that carbon end up once it’s set free?

Climate scientists say that the world’s oceans are one major destination, as a global ‘carbon sink’. Day by day, oceans have been thought to sop up 50 percent of the carbon dioxide emissions we release by burning fossil-fuels, manufacturing cement, and converting forest into farmland, among many other activities.

While oceans absorb a large amount of carbon, they don’t soak it up at the same pace or volume across the planet. In fact, there’s one ocean that scientists have identified as the grand carbon ‘hoover’. It happens to be one few have heard of and even fewer have visited due to its remoteness and treacherous conditions. For years, it was widely estimated that 90 percent of CO2 absorbed by our seas is consumed by the ring of water that surrounds Antarctica: the ‘Southern Ocean’.

But what if that’s wrong? What if, in fact, the southern ocean is actually emitting carbon dioxide? And how did a crucial part of the carbon cycle get flipped on its head? This new theory about the Southern Ocean comes from data collected by an army of ocean-going robots, a floating armada of sensor buoys that have been launched into the seas of Antarctica. These buoys are the first to collect robust data in previously untraceable waters, and the people who developed them and tend to their care are dedicated to leveraging what they find to uncover the reality of ocean health and function. Their army of robotic buoys has put the remote Southern ocean, and its contributions to the carbon cycle, back in sight, and mind, with their discoveries.

‘People would often ask me: “You’re an oceanographer, how’s the ocean doing?” And my answer was always: “We don’t look”,’ Dr. Ken Johnson says as he stares from his desk out over a grey and choppy Pacific Ocean.

Johnson, a senior scientist in biogeochemical oceanography at the Monterey Bay Aquarium Research Institute (MBARI), has spent his life trying to change that. He is one of hundreds of scientists around the globe who tend to the buoys as part of the Argo Project, an international collaboration to explore large swaths of the ocean in minute detail.


The Argo program launched in 1999, and in its first decade, released 3,200 buoys into our oceans to collect a baseline of oceanic data – namely temperature and salinity. Around 2008, Johnson, who specializes in developing biogeochemical sensors, teamed up with other oceanographers to test the limits of sensor technology. Together they ushered in this new chapter in the Argo program, in which scientists and government agencies across the globe are now using sensors to study the chemistry, biology, and physical patterns of our oceans.


‘Our contribution has been inventing and adding chemical sensors that don’t need to be calibrated every second. You calibrate it once and then throw it in the ocean for five years,’ explains Johnson. These small steps in improving sensor technology leave researchers with more hours (and sanity) to focus on the real work.


After tinkering with his lab’s calibration methods and troubleshooting the sensor hardware, Johnson and his team at MBARI – which includes chemists, engineers, and machinists who develop and test all of the technology in-house – have turned their sensors on the Southern Ocean.  His lab’s latest efforts are part of the Southern Ocean Carbon and Climate Observations and Modeling project (SOCCOM). Housed at Princeton University, SOCCOM has been working with sensor specialists like Johnson to deploy buoys outfitted with biogeochemical sensors in order to more accurately measure the amount of CO2 the Southern Ocean absorbs and releases as part of our global carbon cycle.


In the Antarctic summer of 2018, a team of scientists, including Johnson, departed from the southernmost tip of South America – Ushuaia, Argentina – and sailed for two weeks dead south to reach the Southern Ocean and deploy 100 buoys fitted with the biogeochemical sensors developed by Johnson’s team. The data has been rolling in since, and it wasn’t what anyone was expecting: Instead of absorbing carbon dioxide from the atmosphere, in winter the Southern Ocean appears to be releasing it.