This story is an update to the Arctic sea ice feature in our World of Change series, which tracks long-term change on Earth’s surface through satellite imagery.
这个故事是我们的“变化世界”系列中北极海冰专题的更新，该系列通过卫星图像跟踪地球表面的长期变化。
A layer of frozen seawater caps the Arctic Ocean. This sea ice grows through the long polar winter, usually peaking in March, then melts through the summer to its annual low in September. It is a natural fluctuation that has persisted for millennia. But satellite records show the ice now covers less of the Arctic Ocean at its annual maximum and minimum than it did a few decades ago.
北冰洋上覆盖着一层冰冻海水。这些海冰在漫长的极地冬季生长，通常在三月达到顶峰，然后在夏季融化，在九月达到年度最低点。这是一种持续了数千年的自然波动。但卫星记录显示，与几十年前相比，现在北冰洋在年度最大值和最小值时所覆盖的面积有所减少。
Sea ice in 2026 reached its annual minimum extent on September 12 (above), when it covered an estimated 4.6 million square kilometers (1.78 million square miles), according to NASA and the National Snow and Ice Data Center (NSIDC). That ties 2008, 2010, and 2025 for the 10th-lowest minimum in the satellite record.
根据 NASA 和国家冰雪数据中心 (NSIDC) 的数据，2026 年海冰在 9 月 12 日（上图）达到了年度最小范围，当时海冰覆盖面积估计为 460 万平方公里（178 万平方英里）。这与 2008 年、2010 年和 2025 年并列，是卫星记录中第十低的最低值。
The maps below pair each September since 1990 (left), around the ice’s annual minimum, with the following March (right), near its annual maximum, through March 2026.
下面的地图将自 1990 年以来的每年 9 月（左）和随后的 3 月（右）配对，在冰层年度最小值附近，直到 2026 年 3 月，接近年度最大值。
Scientists have used satellites to observe the annual growth and retreat of Arctic sea ice continuously since late 1978. While sea ice extent has declined overall during that time, the downward trend steepened in the 2000s and set off a run of record and near-record lows. Each of the past 20 summers, from 2007 through 2026, ranks among the 20 lowest minimum extents in the satellite record. The lowest occurred in September 2012.
自 1978 年底以来，科学家们利用卫星连续观测北极海冰的每年增长和消退。虽然海冰范围在此期间总体有所下降，但下降趋势在 2000 年代更加陡峭，并创下了一系列历史新低和接近历史低点。从 2007 年到 2026 年，过去 20 个夏天的每个夏天都位列卫星记录中最低范围的 20 个之内。最低值出现在 2012 年 9 月。
More recently, the September sea ice extent has been relatively steady. Weather can make a big difference in how much ice melts from one summer to the next. For example, over the past decade, increased cloud cover has prevented sunlight from accelerating the melt , according to NASA scientists . Despite this recent plateau, the summer minimum remains well below the long-term average.
最近，九月海冰范围相对稳定。天气会对一个夏天和下一个夏天的冰融化量产生很大影响。例如，根据美国宇航局科学家的说法，在过去的十年中，云层的增加阻止了阳光加速融化。尽管最近出现了平台期，但夏季最低值仍远低于长期平均水平。
Across the Arctic, the ice that remains is younger and thinner . Observations show a decline in multiyear ice—that which survives at least one melt season—leaving an Arctic dominated by thinner first-year ice . Winter ice is also shrinking. The March 2026 maximum statistically tied the 2025 maximum for the lowest in the satellite record.
在整个北极，残留的冰层更年轻、更薄。观测显示，多年冰（至少在一个融化季节中幸存下来的冰）减少了，使得北极以更薄的第一年冰为主。冬季冰层也在缩小。从统计数据来看，2026 年 3 月的最高值与 2025 年的最高值并列卫星记录的最低值。
Cycles of natural variability such as the Arctic Oscillation are known to play a role in Arctic sea ice extent, but the decline observed throughout the satellite record cannot be explained by natural variability alone. Natural variability and rising global temperatures have worked together to melt greater amounts of Arctic sea ice. Scientists have projected an essentially ice-free Arctic could occur at least once before the middle of the 21st century.
已知北极涛动等自然变率周期在北极海冰范围中发挥着作用，但整个卫星记录中观察到的下降不能仅用自然变率来解释。自然变化和全球气温上升共同作用，融化了更多的北极海冰。科学家预测，在 21 世纪中叶之前，北极可能至少出现一次基本无冰的情况。
To determine sea ice extent, scientists rely on satellites with passive microwave sensors that measure the microwave energy Earth naturally emits. Sea ice emits more of this energy than open water, so it stands out in microwave images. Because microwaves pass through clouds, the satellites can observe sea ice regularly, regardless of weather.
为了确定海冰的范围，科学家依靠带有无源微波传感器的卫星来测量地球自然发射的微波能量。海冰比开放水域释放更多的能量，因此它在微波图像中脱颖而出。由于微波穿过云层，因此无论天气如何，卫星都可以定期观测海冰。
The record began in 1978 with data collected by NASA’s Nimbus-7 , followed by Defense Meteorological Satellite Program (DMSP) satellites starting in 1987 and NASA’s Aqua satellite between 2002 and 2011. Starting in 2025, scientists began using observations from the Japan Aerospace Exploration Agency’s GCOM-W satellite . The white circle at the center of each image is the “pole hole,” north of which satellite sensors have historically been unable to collect data. The sea ice estimates assume that this hole is ice-filled.
该记录始于 1978 年，由 NASA 的 Nimbus-7 收集数据，随后是 1987 年开始的国防气象卫星计划 (DMSP) 卫星以及 2002 年至 2011 年间 NASA 的 Aqua 卫星收集的数据。从 2025 年开始，科学家开始使用日本宇宙航空研究开发机构的 GCOM-W 卫星的观测数据。每张图像中心的白色圆圈是“极洞”，其以北的卫星传感器历来无法收集数据。海冰估计假设这个洞充满了冰。
NASA Earth Observatory images by Michala Garrison, using data from the National Snow and Ice Data Center .
美国宇航局地球观测站的图像由 Michala Garrison 使用国家冰雪数据中心的数据拍摄。