全球海冰量降至歷史最低水平

Recent satellite data reveals that the world's sea-ice levels have reached an unprecedented low, marking a significant environmental concern. The sea-ice, which exists in the Arctic and Antarctic regions, plays a crucial role in regulating the Earth's temperature by reflecting sunlight back into space. However, as global temperatures continue to rise, this vital layer of ice is diminishing, allowing the darker ocean waters beneath to absorb more heat, which exacerbates global warming. The latest data indicates that the decline in sea-ice is attributed to a combination of warm air, elevated sea temperatures, and winds that disrupt the ice formation. Between February 8 and February 13, the total area of sea-ice in both the Arctic and Antarctic was recorded at 15. 76 million square kilometers, a drop from the previous record low of 15. 93 million square kilometers set in early 2023. This decline is particularly alarming as the Arctic sea-ice is currently at its smallest extent for this time of year, while the Antarctic sea-ice is nearing a record low that has been monitored since the late 1970s. The trend of diminishing Arctic sea-ice has been well-documented over the years. In the 1980s, the average extent of Arctic sea-ice at the end of summer was approximately 7 million square kilometers, but by the 2010s, this figure had plummeted to around 4. 5 million square kilometers. In contrast, the Antarctic sea-ice had shown remarkable resilience until the mid-2010s, defying earlier predictions of decline. However, recent years have seen a series of notably low sea-ice extents in Antarctica, although natural variability still plays a role. Walter Meier, a senior research scientist at the National Snow and Ice Data Center (NSIDC), emphasized that the data collected suggests this is not merely a temporary fluctuation but rather a more permanent shift, akin to the changes observed in the Arctic. The Antarctic sea-ice is relatively thin and mobile, being surrounded by ocean rather than land, which makes it particularly susceptible to winds that can break the ice apart. The influence of warmer air and ocean temperatures has been significant in driving the current low sea-ice levels, especially as the southern hemisphere summer comes to a close. The ice-shelves in Antarctica, which are formed from ice flowing off the continent, have also been impacted by high air temperatures. Tom Bracegirdle, a research scientist at the British Antarctic Survey, noted that the atmospheric conditions in December and January were conducive to surface melting on the ice-shelves, which likely contributed to the observed decline in Antarctic sea-ice. Without the influence of climate change, the record low of sea-ice in 2023 would have been an extremely rare occurrence, estimated to happen only once in 2,000 years. Yet, the data for 2025 is on track to potentially surpass this record. Meanwhile, in the Arctic, the sea-ice is expected to reach its annual maximum during the winter months, aided by cold temperatures that promote ice formation. However, current sea-ice levels are nearly 0. 2 million square kilometers below any previous records for this time of year, and this trend has been evident since late 2024. This situation has been exacerbated by a delayed freeze-up of ice around Hudson Bay, where unusually warm ocean waters have taken longer to cool. Additionally, storms have disrupted ice formation in the Barents and Bering Seas, with the long-term reduction in sea-ice thickness amplifying these effects. Julienne Stroeve, a professor of polar observation and modeling at University College London, explained that thinner ice is more responsive to weather patterns, meaning that weather events can have a more pronounced impact than they did in the past. In recent weeks, Arctic sea-ice levels have fallen even further below average. In early February, temperatures around the North Pole were approximately 20 degrees Celsius above normal, leading to melting conditions in areas such as Svalbard. This phenomenon is quite surprising for this time of year. While the current low winter sea-ice extent does not guarantee that the Arctic will experience record low conditions throughout 2025, it is important to note that conditions can change rapidly in polar regions. However, with the Arctic warming nearly four times faster than the global average, further declines in sea-ice are almost certain in the coming decades. The United Nations' Intergovernmental Panel on Climate Change predicts that the Arctic could be nearly free of sea-ice at the end of summer at least once before 2050, with some studies suggesting it could occur even sooner. The reduction of sea-ice at both poles has significant implications not only for local wildlife, such as polar bears and penguins, but also for the Earth's climate as a whole. Since the early 1980s, polar sea-ice has lost around 14% of its natural cooling effect due to the decrease in bright, reflective ice. Simon Josey, a professor at the National Oceanography Centre, warned that altering the distribution of sea-ice around Antarctica could have serious consequences for the planet's ability to combat climate change. Sea-ice also plays a vital role in the ocean's circulation, which helps distribute heat across the globe and maintains relatively mild temperatures in regions like the UK and north-west Europe. If there is another significant winter loss of Antarctic sea-ice, it could raise concerns about the impact on ocean circulation patterns.