The study shows that there are just enough “cracks and holes” around Antarctica to allow enough daylight through the sea ice.” (NASA) A team of researchers recently observed evidence of potentially large blooms beneath the sea ice around Antarctica. This discovery confirms the conclusions of an underwater scientific expedition that took place ten years ago, which already reported a massive population of phytoplankton in the region.
The study reporting this discovery was published in the journal Frontiers. Scientists believed that due to the lack of light, the ice sheet prevented the growth of phytoplankton in the ocean around Antarctica for most of the year.
However, the document shows that there are just enough “cracks and holes” in the area to allow enough daylight through the sea ice.
“In wide views from most satellites, the ice sheet can appear uniform and sheet-like, reinforcing the idea that light would be too scarce and weak to support plant life underneath,” says Chris Horvat, a sea ice scientist at Brown University and First author of the study.
But observed from and below the ocean’s surface — and using a latest-generation NASA satellite — Antarctica’s sea ice is actually riddled with fractures and openings, the study says. “Sunlight penetrates through the cracks and fuels blooms under the ice in the Southern Ocean. »
Enough light under the ice
Experts point out that phytoplankton is to the ocean what grass is to land: these floating, plant-like organisms absorb the sun, ingest mineral nutrients, and create their own food (energy) through photosynthesis. “Phytoplankton is an essential food source for other life forms in the ocean and plays a key role in recycling and removing carbon for the planet,” specifies the specialist, adding that it develops roughly wherever there are open, sunny areas of the ocean there,” Horvat points out.
When conditions are right, these microscopic cells can grow to scales visible from space.Chris Horvat, lead author of the study
In addition to satellite imagery, Horvat and his colleagues have collected multiple data sources, such as those collected from swimmers. These instruments can detect the presence of chlorophyll and carbon particles. These can indicate the presence of phytoplankton.
“By reviewing data from more than 2,000 ice dives over a seven-year period, the science team found that almost all measurements showed phytoplankton accumulation even before spring and summer sea ice retreated in the southern hemisphere,” reads in the study .
Experts also relied on ice cover models to estimate the location, thickness, and movement of the Southern Ocean ice cover. They then found that 3 to 5 million square kilometers – an area larger than India – of the ice-covered Southern Ocean could let in enough light to support some blooms beneath the ice.
“Scientists have talked about the potential of these blooms before, but this is the first time we’ve seen them under the ice in Antarctic waters,” Horvat said. “This discovery opens the way to a whole new way of looking at life around and beneath the ice. Sea ice is more interesting and diverse than you might think, and it can support a variety of ecosystems. »
With information from Michael Carlowicz of NASA