Arctic News: Ractic

Showing posts with label Ractic. Show all posts

Monday, February 3, 2025

Sea ice loss

Global sea ice area was 13.43 million km² on February 2, 2025, the lowest area on record, as illustrated by the image below, adapted from seaice.visuals.earth.

What is the difference between sea ice are 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 and further sea ice to melt, thus accelerating the temperature rise.

Loss in albedo as a result of loss in sea ice is only one out of many feedbacks that come with rising temperatures. As warmer water flows into the Arctic Ocean, Arctic sea ice loses volume, which diminishes 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 ]

The image on the right shows Arctic sea ice volume up to February 3, 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.

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.

There are many further mechanisms that are driving up, if not 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? Antarctic sea ice area was 1.05 million km² on Feb 22, 2023, and was 1.72 million km² on Feb 2, 2025. Will there be a Double Blue Ocean Event 2025?

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.