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Following the World Meteorological Organization El Nino reappearance, on July 5, the National Oceanic and Atmospheric Administration (NOAA) showed that the global average temperature for two consecutive days (July 3 and July 4) broke the record, with July 4 being the hottest day on record globally.

Scientists are starting to ask a scary question: With El Nino, has the global climate entered a more unstable and dangerous phase?

NOAA physicist and oceanographer Boyin Huang said in an interview with NBD that the reduction of sea ice is the “gray rhino” of our time, “which will cause sea levels to rise, slow and change the direction of the North Atlantic circulation, and greatly change the global climate, especially in Europe.”

Antarctic sea ice at record low

In Antarctica, the continuing decline in sea ice is alarming, and scientists are urgently searching for answers. On February 21 of this year, Antarctic sea ice reached its lowest level since satellite records began in 1979, raising serious concerns about changes in the state of Antarctic sea ice within the broader Earth system.

Two visualizations created recently by Princeton University and NOAA climate scientist Zachary Labe show a frightening reality: Antarctic sea ice continues to melt after reaching a record-low extent in February.

Image credit: Zachary Labe

In the image below, the Antarctic sea ice extent, taken on June 28 this year, is significantly smaller than the average since records began in 1981.

Photograph: The Guardian

The data show that on June 28, the Antarctic sea ice extent was only 11.7 million square kilometers, which is about 2.6 million square kilometers less than the average from 1981 to 2010, and about 1.2 million square kilometers less than the record low set on June 27, 2022.

"Based on more than 40 years of satellite sea ice extent data over Antarctica, this is the most unusual thing we"ve ever seen, said Dr. Holly Ayres, doctoral research assistant of the Department of Meteorology of the University of Reading in the United Kingdom pointed to NBD.

"I think that the reduction of Antarctic sea ice and rising sea surface temperature result mostly from global warming that further results from increasing green-house-gases, partly from natural phenomena such as El Nino and La Nina events.," Dr. Holly Ayres explained.

Sea ice condensing much more slowly than average this year

Sea ice in the Arctic is also declining, even more so than in the Antarctic - according to the United Nations, the Arctic Ocean"s extremely low sea ice will continue through 2023, and The last 16 years (2007-2022) are the lowest 16 years in the 44-year satellite record. 

The northernmost part of the planet is experiencing temperature increases two to four times higher than anywhere else, and Arctic sea ice has been declining at a rate of about 12% per decade since satellite records began. Since 1979, Arctic sea ice has lost about 548,000 square miles of sea ice. Moreover, the loss of Arctic sea ice has accelerated since 2000.

To make matters worse, early last month, the latest assessment report of the United Nations Intergovernmental Panel on Climate Change concluded that the Arctic Ocean is expected to be "ice-free in summer" as early as mid-century. However, an international research team published a paper in the British journal Nature Communications on June 6, suggesting that "ice-free summer" may appear as early as the 2030s, reminding relevant parties to prepare as early as possible.

Image credit: Zachary Labe

The analysis suggests that the Arctic will remain ice-free in September for decades to come, even if global greenhouse gas emissions are drastically reduced.

In fact, in July 2022, a significant "ice-free area" appeared near the North Pole and lasted for several weeks. Over the past few years, thinner, looser sea ice has been replacing older, thicker ice in the Arctic.

Dr. Holly Ayres noted that "global sea ice extent in the Arctic and Antarctic is at very low levels for this time of year, and [this year"s extreme phenomenon] is mainly due to the current rate of ice condensation being much slower than average." In 2016, global sea ice extent reached the smallest level ever recorded, but recovered in the following years. However, in 2022 and again this summer, the global sea ice extent set two consecutive records for minimum sea ice extent."

"What makes this year different from previous years with less sea ice is that the growth rate of sea ice is much slower during the fall and early winter months from March to June. Moving into winter, the extent of sea ice did not recover as normally, causing this to form a clear anomaly compared to the average." Dr. Holly Ayres explained to the reporter.

Melting sea ice will exacerbate global warming

Antarctic sea ice is an important part of the polar climate system and one of the most sensitive elements of global climate change. The World Meteorological Organization said it was too early to say whether the new record low was part of normal, natural weather fluctuations or a new long-term melting trend caused by climate change. Because sea ice and ice shelves "support" the ice on landing grounds, melting sea ice could have a major indirect ripple effect on sea levels.

Sea ice is also vital to the Antarctic ecosystem, as it is not only a refuge for penguins and other animals, it is also key to the life of creatures lower down the food chain, such as Antarctic krill. Sea ice is also important for heat because it is more reflective than seawater and therefore reflects more sunlight than the ocean. Sea ice also acts as a physical barrier, affecting the exchange of gases between the ocean and the atmosphere and protecting continental ice shelves.

Dr. Holly Ayres told NBD that the large-scale melting of Antarctic sea ice will bring many effects. The role of Antarctic sea ice is to protect the Antarctic ice shelf from the warm ocean, however, as the ice shelf melts, the global sea level will rise, and the melting ice shelf will flow into the ocean, which will have a major impact on the global ocean circulation, which can disrupt normal global climate patterns, she said.

"In winter, sea ice acts as an insulating barrier between the ocean and the atmosphere above it. When this insulating barrier is reduced at the current rate, heat is released from the ocean into the atmosphere that would not normally be released in the presence of sea ice. This additional atmospheric warming may interact with the global climate through changes in wind and pressure systems. In addition, sea ice is highly reflective, which means that if the sea ice melts over a large area, the ocean surface absorbs more solar radiation, and any change in the net radiation balance further contributes to global warming, a process known as polar amplification." Dr. Holly Ayres added.

Huang pointed out that in the regions where ice disappears, the water temperature will increase rapidly since ice-melting usually regulates water temperature by absorbing heat. This will activate marine heatwaves even in the Arctic and northern North Atlantic, bring catastrophic damage to the ecosystem, biodiversity, and fisheries, and further affect human beings since the melting ice will further accelerate global warming.

So is the massive loss of sea ice in Antarctica, the North Atlantic, and the Arctic reversible?

According to Huang, it depends on the time scale. At a seasonal time scale, the melted ice can mostly be reversible from summer to winter. From year to year, it is possible that ice may be reversible or even increase. But for a long-term time scale (>10 yr), the tendency of decreasing ice is clear, and the ice reduction appears irreversible; or it needs a long time to recover in the future. In either case, the damage due to the ice reduction is serious.