Arctic News: Antartica

Showing posts with label Antartica. Show all posts

Monday, February 3, 2025

Sea ice loss

Global sea ice area was 13.07 million km² on February 5, 2025, the lowest area on record, as illustrated by the image below, adapted from seaice.visuals.earth.

What is the difference between sea ice area and extent? Extent is the total region with at least 15% sea ice cover. Extent can include holes or cracks in the sea ice and melt ponds on top of the ice, all having a darker color than ice. Sea ice area is the total region covered by ice alone.

Therefore, sea ice area is a critical measure in regard to albedo. Loss of sea ice area is a self-reinforcing feedback that causes the temperature to rise, resulting in further melting of sea ice, thus accelerating the temperature rise.

A Blue Ocean Event is often defined as crossing a tipping point that is crossed when sea ice falls below 1 million km² in extent. Doesn't it make more sense to look at sea ice area, rather than at sea ice extent?

Loss of albedo as a result of loss in sea ice is only one out of many feedbacks that come with rising temperatures, as described at the Threat.

Antarctic sea ice

There are many mechanisms that are driving up, if not accelerating the temperature rise and loss of sea ice.

As illustrated by the above image, Antarctic sea ice area was 1.05 million km² on Feb 22, 2023, and was 1.55 million km² on Feb 5, 2025. Will there be a Double Blue Ocean Event 2025?

The image below shows Antarctic sea ice thickness on four different dates, including February 4, 2025, from the University of Bremen.

For a comparison of Antarctic sea ice thickness at earlier dates, have a look at this earlier post.

Arctic sea ice

Warmer water flowing into the Arctic Ocean causes Arctic sea ice to lose volume, diminishing its capacity to act as a buffer that consumes ocean heat entering the Arctic Ocean from the North Atlantic.

This means that a lot of incoming ocean heat can no longer be consumed by melting the sea ice from below, and the heat will therefore contribute to higher temperatures of the water of the Arctic Ocean.

[ from earlier post ]

[ Arctic sea ice volume, click images to enlarge ]

The image on the right shows Arctic sea ice volume up to February 5, 2025. Arctic sea ice volume in 2024 and 2025 has been much lower than in previous years.

More incoming heat therefore threatens to reach the seafloor of the Arctic Ocean and destabilize methane hydrates contained in sediments at the seafloor, resulting in eruptions of huge amounts of methane, as illustrated by the above image.

The image below shows that the temperature at latitudes higher than 80°N on February 5, 2025, was much higher than the mean temperature 1959-2002.

As said, rising temperatures come with many feedbacks, and they can contribute strongly to the further acceleration of the temperature rise. Another feedback is more water vapor ending up in the atmosphere, as illustrated by the image below.

[ from earlier post ]

The above image shows the average daily precipitable water anomaly on February 2, 2025. More water vapor is another self-reinforcing feedback, since water vapor is a potent greenhouse gas that further accelerates the temperature rise.

The image below shows Arctic sea ice extent up to February 3, 2025. During the first few months of the year, Arctic sea ice is still growing in extent. The red line and red marker shows 2025 sea ice. Dots mark Arctic sea ice extent on February 3 for the respective year and Arctic sea ice extent was at a record low for the time of year on February 3, 2025, despite La Niña conditions.

A new El Niño may emerge in the course of 2025, while Arctic sea ice extent, area and volume are all at record low, while numerous self-reinforcing feedbacks are kicking in with accelerating ferocity and while temperatures are driven up by further mechanisms, e.g. high sunspots. Such a combination of mechanisms could result in a huge temperature rise and in a Blue Ocean Event in 2025, threatening huge amounts of methane to erupt from the seafloor.

[ Arctic sea ice extent, click on images to enlarge ]

Climate Emergency Declaration

The situation is dire and the precautionary principle calls for rapid, comprehensive and effective action to reduce the damage and to improve the situation, as described in this 2022 post, where needed in combination with a Climate Emergency Declaration, as discussed at this group.