Antarctica’s Weddell Sea in the Southern Hemisphere is usually an uninterrupted sheet of ice during the frigid winter months of June, July and August. That is why the appearance of a massive area of open water, or polynya, in the middle of the sea is baffling scientists worldwide. First observed as a small hole in the winter of 2016, the polynya now extends an astounding 80,000 square kilometers, or about as big as the US state of Maine.
Polynyas are fairly common near the Arctic and Antarctic coasts, thanks to the persistent katabatic winds that blow the ice away from the coastline. However, one in the middle of the open ocean, like the Weddell polynya, are rare and occur only under certain conditions.
“The Southern Ocean is strongly stratified. An icy but relatively fresh water layer covers a much warmer and saltier water mass, thus acting as an insulating layer,” says Professor Dr. Mojib Latif, head of the Research Division at GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany. “This (polynya) is like opening a pressure relief valve — the ocean then releases a surplus of heat to the atmosphere for several consecutive winters until the heat reservoir is exhausted.”
The Weddell polynya was first observed by satellites in the austral winters of 1974 and 1975. Measuring about 250,000 square kilometers, or about the size of the US state of Oregon, it was much larger than the current polynya. However, since satellite imagery was still in its nascent stages little research was conducted into the cause of this mysterious phenomenon. By 1976, the hole patched up and did not reappear again for 40 years, until 2016.
This time around, researchers from the University of Toronto and the Southern Ocean Carbon and Climate Observations and Modeling project are determined to find out the cause of this “enigma.” In early September, the team sent robotic floats, that can withstand the negative 20 degrees Celsius water temperatures, to investigate. Able to operate under sea ice, the buoys can collect data and potentially provide critical information about the hole’s formation.
Though the researchers have yet to analyze the data collected, there are some that believe the polynya is a result of climate change. However, Torge Martin, a meteorologist and climate modeler at the Helmholtz Centre, thinks the phenomenon might be cyclical, rather than a result of the climate. The expert says, “Its recurrence supports our hypothesis . . . that the Weddell Polynya was not a one-time event but possibly occurred regularly in the past.”
While scientists work to unravel the hole’s mysteries, and the impacts of climate change on our planet, some Antarctic dwellers are making the most of the open water. “It literally is a hotspot,” said Kent Moore, professor of physics at the University of Toronto. “There are seals using it, predators, leopard seals — they’ll be exploiting this region. It’s like an oasis to them.