Peter Harmsen
Argo probes are autonomous buoys used in an international program to measure ocean conditions, such as temperature and salinity.
A robotic oceanographic instrument, which “fled out of sight” of scientists after drifting away from the Totten Glacier, accidentally collected data in one of the most inaccessible regions of Antarctica, offering researchers an unexpected wealth of new clues.
Sometimes we get lucky in science. This was the case of an oceanographic probe, which was launched by scientists to carry out a certain task, but ended up deviating and doing something wrong. something completely different.
Equipped with temperature and salinity sensors, the Argo floating platform should be carrying out ocean surveys around the Totten Glacier in East Antarctica.
To the scientists’ initial disappointment, the robot probe quickly moved away from this region, but ended up reappearing further west, near ice shelves where no measurements had ever been taken oceanic.
Adrift in remote and wild seas for two and a half yearsthe floating platform spent about nine months under the gigantic Denman and Shackleton ice shelves. survived to send new data from parts of the ocean that are generally difficult to samplewhich provided a rare insight into Antarctic melting and rising sea levels.
A Argo’s extraordinary journey was recently described by the scientists involved in the research, who presented the data collected in a published in the journal Science Advancesand detailed their conclusions in .
Argo floats and ice platforms
Capable of reaching depths of up to two kilometers, Argo floats are tools essential to understanding the Antarctic region.
These devices are drifting robots that move freely in the ocean, rising and falling in water columnsuntil they emerge to the surface, as a rule, every 10 days, to send their data to satellites, explains .
Ocean data is also crucial for tracking global warming, as 90% of the heat increase recorded over the last 50 years was stored in the ocean.
The regions beneath ice shelves, which are difficult to measure, provide some of the most critical data for calculate sea level rise. These temperature and salinity readings, taken at five-day intervals, are the first of their kind ever collected under an East Antarctic ice shelf.
Ice shelves are floating glaciers that mark the point where the Antarctic ice mass meets the sea, far from the solid bedrock of the frozen continent. They function as “brakes”preventing continental ice from flowing into the ocean, but they remain vulnerable to the entry of warmer water from below — a mechanism that melts the shelves from the base.
The collapse of these platforms accelerates sea level risere, therefore, scientists have a great interest in monitoring them.
However, one of the most critical factors, the hot water that penetrates from belowis notoriously difficult to observe directly. In the past, researchers have sometimes resorted to drilling holes in the ice and lowering sensors, a expensive method and therefore rarely used.
A trip through Antarctica
The Totten Glacier, which was the initial target of the study, contains enough ice to raise global average sea levels by 3.5 meters if it melted completely.
Previous work on Totten suggested the existence of water sufficiently warm under the platformplacing it at significant risk of rapid melting. Faced with a threat with potential impact on the global ecosystem, the team was not satisfied when the Argo float moved away from the predicted location.
Happily, I didn’t have to wait long until Argo “found” another target of enormous relevance: or Denman Glacierwhich, if it melted completely, could contribute to a sea level rise of 1.5 meters.
Previous analysis of radar data indicated that Denman may be unstable, but obtaining ocean data to confirm this has been difficult. Argo, however, found that hot water can actually penetrate under the platform.
After nine months missing under the ice, the team began to suspect that the float could have been trapped under a glacial mass and would never broadcast again.
But, completely unexpectedly, or Argo re-emerged beneath Denman and Shackleton, sending researchers data from regions under the Antarctic ice never before visited.
Analysis of Antarctic data
One of the main obstacles for researchers was that, without the float surfacing regularly, data could not be associated with locations GPS. Still, the team managed to overcome this limitation.
Whenever the robot approached the surface and encountered ice, it recorded a Essential measurement: the thickness of the ice at the point of contact.
By cross-referencing these readings with known satellite measurements of ice thickness, the team managed to reconstruct the route of the Argo float under the ice shelf.
The data collected by the vagabond probe indicates, fortunately, that, at this moment, hot water is not penetrating under the Shackleton Ice Shelf, which means that, at least for now, the ice in this area is relatively stable.
The detection of hot water under Denman continues to be a cause for serious concern: even a small increase in the amount of hot water entering there could accelerate defrosting and, therefore, worsen instability.
