Rising temperatures mean that Arctic sea ice isn’t spreading nearly as widely as it used to in the winter, NASA has revealed.
According to the space agency’s National Snow and Ice Data Center, Arctic sea ice peaked at 5.75 million square miles (14.88 million square km) on February 25.
This is roughly 297,300 square miles (770,000 square km) below the 1981-2010 average maximum – and is equivalent to missing an area of ice slightly larger than Texas and Maine combined, or nearly 40 times the size of Wales.
At 5.75 million square miles, this year’s Arctic ice maximum extent is also the 10th-lowest in the National Snow and Ice Data Center’s record.
The news follows reports earlier this week that Earth’s poles are both undergoing ‘freakish’ heatwaves – with parts of the Arctic more than 50°F (30°C) warmer than average.
NASA has also confirmed that Antarctic sea ice reached its lowest extent on record on February 25, following preliminary analysis last month.
This image shows the average concentration of Arctic sea ice on February 25, 2022. The yellow outline shows the median sea ice extent for the month of March, when the ice generally reaches its maximum extent, as observed by satellites from 1981 to 2010
10 LOWEST ARCTIC SEA ICE RECORDS
1. 2017 (March 7)
2. 2018 (March 17)
3. 2016 (March 23), 2015 (February 25)
5. 2011 (March 9), 2006 (March 12)
7. 2007 (March 12), 2021 (March 21)
9. 2019 (March 13)
10. 2022 (February 25)
Usually, Arctic sea ice spreads to its furthest extent in March and recedes around September – and vice versa in the Antarctic.
The fact that ice isn’t spreading as far suggests global warming is making waters too warm for ice to properly form and spread.
Sea ice at the poles keeps the polar regions cool, helps moderate global climate and provides a habitat for wildlife.
‘We’re losing the older ice, the multiyear ice,’ said Mark Serreze, director of the National Snow and Ice Data Center.
‘There used to be stuff out there that was 10 to 12 years old. That’s gone. So there’s no secret here, you’re losing multiyear ice.’
Sea ice at both poles advances and then retreats annually, following a pattern with the seasons every year.
In the Arctic, it tends to reach its maximum extent around March after growing through the colder months, and shrinks to its minimum extent in September after melting through the warmer months.
In the Southern Hemisphere, Antarctic sea ice follows an opposite cycle – it’s at its greatest extent around September and its minimum extent usually in March.
This NASA Blue Marble image shows Arctic sea ice on February 25, 2022, when sea ice reached its maximum extent for the year. Sea ice extent for February 25 averaged 14.88 million square kilometers (5.75 million square miles), the tenth lowest in the satellite record
This graph shows Arctic daily sea ice extent in 2022, 2021, and 2012 compared to the 1981-2010 average. This year’s annual maximum extent was reached on February 25 – earlier than usual
According to NASA, the fact that the Arctic ice reached its maximum extent in February this year is unusual.
In fact, NASA says February 25 ties with 2015 as the third earliest Arctic maximum extent on record (in 2015, Arctic maximum extent also occurred on February 25).
In the south pole, meanwhile, Antarctic sea ice dropped to a record-low minimum extent – 741,000 square miles (1.92 million square km), on the same day (February 25).
This year’s minimum extent in the Antarctic was 73,400 square miles (190,000 square km) below the previous record set on March 3, 2017.
It was also 359,000 square miles (930,000 square km) below the 1981 to 2010 average minimum of 1.10 million square miles (2.85 million square kilometers).
Antarctic sea ice extent for February 25, 2022, was 1.92 million square kilometers (741,000 square miles). The orange line shows the 1981 to 2010 average extent for that day
THE SPREAD OF SEA ICE
Sea ice forms as seawater freezes and, because it loses density, floats on the surface of the water.
It is estimated to cover around 7 per cent of Earth’s surface and about 12 per cent of the world’s oceans.
The lion’s share of sea ice is contained within the polar ice packs in the Arctic and Southern oceans.
These ice packs undergo season variations and are also affected locally on smaller time scales by wind, current and temperature fluctuations.
NASA says winds and ocean currents specifically linked to the Southern Ocean and Antarctica have a strong influence on sea ice extent.
Sea ice in the Arctic is surrounded by land, whereas sea ice in the Antarctic is surrounded only by ocean and can thus spread out more freely.
To estimate sea ice extent, satellite sensors gather sea ice data that are processed into daily images, each image grid cell spanning an area of roughly 15 miles by 15 miles (25 km by 25 km).
Scientists then use these images to estimate the extent of the ocean where sea ice covers at least 15 per cent of the water.
Since satellites began reliably tracking sea ice in 1979, maximum extents in the Arctic have declined at a pace of about 13 per cent each decade, NASA says.
Minimum extents, meanwhile, are declining at about 2.7 per cent per decade.
NASA says: ‘These trends are linked to warming caused by human activities such as emitting carbon dioxide, which traps heat in the atmosphere and causes temperatures to rise.
NASA’s analysis also shows the Arctic is warming about three times faster than other regions.
Last September, NASA revealed that Arctic sea ice was at its 12th lowest extent since records began.
Sea ice in the Arctic dropped to an area of just 1.82 million square miles on September 16, 2021.
According to NASA, September Arctic sea ice minimum extents are currently declining at a rate of 13.1 per cent each decade, relative to the 1981–2010 average.
MELTING OF POLAR ICE ISN’T JUST CAUSING SEA LEVELS TO RISE — IT’S ALSO WARPING EARTH’S CRUST, STUDY WARNS
The melting of polar ice from Antarctica, the Arctic and Greenland is warping the Earth’s crust — with the effect felt thousands of miles away, a 2021 study found.
When ice sheets build up on the land, their weight causes the crust beneath the ice to sink a bit to compensate, much like how a laden boat sits lower in the water.
As the ice melts, this weight is removed, and so the crust rises up again in response in a process that scientists call ‘isostatic rebound’.
While this up-and-down movement has long been understood, researchers led from Harvard University wanted to explore whether the crust might also shift sideways.
The team analysed satellite data on polar ice losses from 2003–2018 to model the resulting impact on crustal motions.
They found that melting Arctic and Greenland glaciers caused the ground to shift horizontally in much of the Northern hemisphere, and by up to 0.3mm in the US.
Read more: Melting polar ice is warping Earth’s CRUST, study warns