Arctic death spiral
The Arctic Ocean occupies 14.1 million square kilometers (5.4 million sq mi) around Earth's North Pole. Historically, most of the surface of the Arctic Ocean stayed ice-covered year-round. Close this core of year-round ice was an edge of seasonal ice that froze each winter and melted each summer. The Arctic ice mass gets its maximum extent in March and its minimum extent in September.
According to a preliminary report from the National Snow and Ice Data Center on September 16, 2021, sea ice cover seemed to get its annual summer minimum. The extent of the Arctic Ocean where sea ice concentration was at least 15% was 4.72 million square kilometers (1.82 million sq mi). That's the twelfth-smallest summer minimum on record and 1.5 million square kilometers (579 thousand sq mi) below the 1981-2010 average.
arcticdeathspiral.org created amazing visualization of how to dissolve ice sheet in the Arctic ocean.
As Arctic sea ice vanishes, the following feedback effects have already begun and presumably clarify why the Arctic is warming at about twice the global average rate:
- less sunlight is reflected; as a result, the Arctic warms more rapid
- methane locked in the Arctic seabed and neighboring tundra for thousands of years is fleeing: just a tiny fraction of the evaluated deposits would cause 0.5°C of extra warming; a more significant release could lead to a rise of 6-8°C
- more open ocean means more huge waves, slowing and decreasing the formation of the following year's ice
- the sea channels out of the Arctic spend less of the year blocked by ice, letting more ice float away
- shrinking Arctic ice weakens a pivotal driver for ocean currents and restricts the rate at which dissolved CO₂ is pulled into the deep ocean
Even if we prevent further greenhouse gas emissions and stabilize atmospheric CO₂ at present levels, this feedbacks mean Arctic sea ice will continue to retreat, and the global climate will continue to warm.