BEIJING, Jan. 29 (Xinhua) -- Amidst the drifting ice and fog of Antarctica's Amundsen Sea, scientists aboard China's polar research icebreaker Xuelong, or Snow Dragon, spotted a mysterious phenomenon -- large, persistent openings in the sea ice known as polynyas -- which are far more than oddities and serve as crucial engines for both Earth's climate and marine life.
The mission reached a tense climax before dawn on Jan. 25 during China's ongoing 42nd Antarctic expedition.
"Got it!" a shout rang out as a drone-deployed anchor hook successfully snagged the cable of a submerged mooring system. Members of the expedition team on the ship rushed to the stern, hauling the heavy, instrument-laden line aboard with the precision and determination of a seasoned tug-of-war team.
This recovered system, a 2,900-meter-long vertical chain of sensors anchored to the seafloor, had spent an entire year silently recording the ocean's secrets.
Unlike surface buoys vulnerable to Antarctic icebergs, these fully submerged moorings are a "key tool for continuous deep-sea observation," said He Jianfeng, deputy chief engineer at the Polar Research Institute of China. They act as submerged sentinels, continuously "taking the pulse" of the deep by recording temperature, salinity, currents and even collecting sinking biological particles, He explained.
The data retrieved is invaluable for understanding the role of polynyas, which are primary factories for the world's deepest, coldest water.
In winter, exposed to blistering winds, the ocean here loses heat rapidly. The surface water becomes so cold and salty that it sinks violently to the seafloor, forming a dense body called Antarctic Bottom Water. This sinking process is a fundamental driver of the global ocean conveyor belt, a massive circulation that redistributes heat and nutrients around the globe and regulates climate.
Today, Chinese scientists have accumulated a wealth of long-term monitoring data, which is being used to track changes in the formation rate of Antarctic Bottom Water, understand the processes behind ice shelf melting, and study how the region's complex ecosystems respond to global warming.
Zhang Haifeng, leader of the expedition's ocean team, highlighted a key success from a previous voyage. During the 2025 expedition, the team captured strong signals of intense vertical convection, observing a critical stage in the formation of Antarctic Bottom Water, he said.
With the return of spring sunlight, the open polynya transforms. Freed from ice cover and nourished by nutrients from deeper waters, it bursts into life with immense blooms of microscopic algae.
"This explosion of algae feeds Antarctic krill, which in turn draws in fish, penguins and whales, forging the unique and rich ecosystem of Antarctica," He said.
Crucially, as these algae die, they sink, carrying carbon into the deep sea, a process known as the biological carbon pump.
Polynyas have a remarkable ability to lock away carbon, functioning like a "giant oceanic carbon pump," Zhang said.
Since 2003, Chinese scientists have used specialized tools like sediment traps, which collect sinking particles, to measure this carbon export. Their long-term data is now helping to reveal how these icy ecosystems regulate the global carbon cycle.
"Every piece of data we collect and analyze adds new knowledge to Earth's climate archives and helps us predict the future," Zhang said.
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