A rogue robotic oceanographic instrument that drifted away from the Totten Glacier accidentally collected data on one of Antarctica’s most inaccessible regions, offering researchers an unexpected trove of new insights.
The Totten Glacier, located in eastern Antarctica, has long kept its mysteries. After two and a half years, the lost robot—an autonomous device known as an Argo ocean float—began an unplanned journey that led it beneath the Denman and Shackleton ice shelves, which had never been measured before.
With its temperature and salinity sensors, the float collected new data over a period of nine months under the ice, providing rare insight into Antarctic ice melt and sea-level rise.
The Argo float’s remarkable journey was recently documented by scientists involved in the research, who detailed the new findings at The Conversation.
Argo Floats and Ice Shelves
Reaching depths of up to two kilometers, Argo floats are essential tools for understanding the Antarctic region. These devices are free-floating robots that drift through the ocean, rising and falling, until they surface roughly every 10 days to send their data to satellites.
Ocean data is also essential for tracking global warming, as 90% of the heat increase over the last 50 years has been stored in the ocean. The difficult-to-measure regions beneath ice shelves provide some of the most critical data for calculating sea-level rise. These temperature and salinity readings, collected at five-day intervals, are the first of their kind ever collected beneath the East Antarctic ice shelf.
Ice shelves are floating glaciers that mark where Antarctica’s ice mass meets the sea, departing from the frozen continent’s solid bedrock. They prevent continental ice from entering the sea, yet remain vulnerable to warm water flowing beneath them, which melts the ice shelves.
The collapse of these ice shelves hastens sea level rise, and as such, scientists are very interested in monitoring them. Yet, one of the most critical factors, the warm water entering the ice shelves from below, is notoriously difficult to observe directly. In the past, scientists have at times relied on drilling holes and lowering sensors into them to obtain data, though this is costly and is therefore rarely done.
A Journey Through Antarctica
The Totten Glacier, which the researchers originally studied, contains enough ice to raise the global sea level by 3.5 meters if it were to melt completely. Their previous investigation of Totten suggested that sufficient warm water lay beneath the ice shelf, placing it at significant risk of rapid melting. Given the global ecosystem’s obvious concern, the team was displeased when their Argo float drifted away from its target.
Fortunately, they did not have long to wait before the Argo ran into another suitable target: the Denman glacier, capable of producing a 1.5-meter sea-level rise if completely melted. Previous analyses of radar data suggest that Denman may be unstable, but collecting corroborating oceanic data has proven challenging. The wayward Argo, however, discovered that warm water can indeed penetrate beneath the shelf.
After nine months lost beneath the ice, the team began to suspect that their Argo float may have ended beneath a glacial mass, never to transmit again. But then, most unexpectedly, there Argo emerged from beneath Denman and Shackleton, sending the researchers data from never-before-visited regions beneath the Antarctic ice.
Analyzing the Antarctic Data
One major snag for the researchers was that without the Argo float regularly surfacing, the data could not be tagged with GPS locations. Still, the team managed to overcome this hurdle in their analysis. Each time the robot approached the surface and encountered ice, it recorded an essential measurement of ice thickness at the point of contact. By collating those readings with known ice thickness measurements obtained from satellites, the team could then chart the Argo floats ‘path beneath the ice shelf.
Fortunately, the data indicates that warm water is not currently penetrating the Shackleton Ice Shelf, meaning that at least the ice in this area is relatively stable, for now. However, the discovery of warm water beneath Denman remains a serious concern, as even a slight increase in the amount of warm water there could accelerate melt, and thereby drive further instability.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.