Imagine an invisible river stretching for hundreds of kilometers, flowing through the atmosphere from the tropics to the polar regions. This river doesn't appear on any map; it has no channel or banks, yet it carries enough water vapor to alter the mass balance of the Antarctic ice sheet and influence sea levels.
This is what a study recently published in the scientific journal "Geophysical Research Letters" concluded, conducted by a team of Japanese researchers who developed a tool capable of "seeing" these atmospheric rivers in an unprecedented way.
What are atmospheric rivers and what is their effect on the polar climate?
Atmospheric rivers are narrow, extended pathways of water vapor that sweep across the atmosphere from the tropics to the poles, and have been known to scientists for decades. However, their true extent has remained shrouded in mystery because they are difficult to observe over Antarctica due to the rugged terrain and dry air that hinder traditional observation methods.
Kazuo Takahashi, a doctoral student at Japan’s Sokendai University of Advanced Studies and the lead author of the study, summarizes the mechanism of these phenomena by saying, “They transport moisture from the tropics and mid-latitude regions to the poles.”
In an email interview with Al Jazeera Net, he explains: "When this moisture reaches Antarctica, it can condense to form clouds and then snow, making it one of the main sources of snowfall on the continent."
The other interesting aspect of this phenomenon is its size and significant impact. A recent study revealed that it is responsible for between 30 and 60% of the total annual rainfall in the interior regions of Antarctica, and this percentage rises to 90% in some coastal areas of West Antarctica.
Takahashi explained that "most of the Antarctic Plateau is an extremely arid environment and only a small amount of snow falls on normal days. Atmospheric rivers can bring many times more snow than usual in a single event."
To unravel this mystery, the research team, led by Kazuo Takahashi and colleagues at the National Institute of Polar Research in Japan, reinvented the detection tool itself. Traditional algorithms previously used to study this phenomenon reduced the atmosphere to a single, flat image by summing the movement of water vapor through the entire air column; this method proved ineffective in detecting atmospheric rivers over a rugged continent like Antarctica.
The innovative method, called the three-dimensional method, takes a completely different approach by analyzing the atmosphere layer by layer.
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