Arctic sea ice volume
In September 2024, Arctic sea ice reached a new record low volume, as illustrated by the image below, adapted from the Danish Meteorological Institute, with markers for September (red) and April (blue) corresponding with the year's minimum- and maximum volume.
Trends could be added pointing at Arctic sea ice approaching zero volume soon; even more worrying, tipping points could be crossed and speed up the temperature rise beyond a smooth curve. Feedbacks are typically seen as increasing the temperature gradually and smoothly, either in a linear or non-linear way. Feedbacks are mechanisms, but there are also mechanisms that act more abruptly.
Indeed, some mechanisms can have a more abrupt impact. Sea ice could shrink strongly and rapidly as a (tipping) point is reached where the latent heat buffer disappears abruptly and as further incoming ocean heat suddenly can no longer be consumed by melting of what once was thick sea ice that extended meters below the surface. Arctic sea ice typically reached its annual low about half September, but an abrupt decline of Arctic sea ice may well occur earlier than that. Sea ice may melt strongly, and large pieces of sea ice may additionally get pushed out of the Arctic Basin by strong winds. Large and rapid loss of Arctic sea ice may therefore well occur in July 2025 or even earlier, as the latent heat tipping point gets crossed and additional mechanisms further contribute to increase the temperature.
Indeed, some mechanisms can have a more abrupt impact. Sea ice could shrink strongly and rapidly as a (tipping) point is reached where the latent heat buffer disappears abruptly and as further incoming ocean heat suddenly can no longer be consumed by melting of what once was thick sea ice that extended meters below the surface. Arctic sea ice typically reached its annual low about half September, but an abrupt decline of Arctic sea ice may well occur earlier than that. Sea ice may melt strongly, and large pieces of sea ice may additionally get pushed out of the Arctic Basin by strong winds. Large and rapid loss of Arctic sea ice may therefore well occur in July 2025 or even earlier, as the latent heat tipping point gets crossed and additional mechanisms further contribute to increase the temperature.
Antarctic Sea ice extent
Antarctic sea ice extent has passed its maximum for the year, and looks set for a steep decline, in line with seasonal changes.
On October 11, 2024, Antarctic sea ice was more than 1 million km² lower in extent than on October 11, 2022, and almost 3 million km² lower in extent than a decade ago, as illustrated by the image below.
On October 11, 2024, Antarctic sea ice was more than 1 million km² lower in extent than on October 11, 2022, and almost 3 million km² lower in extent than a decade ago, as illustrated by the image below.
Antarctic sea ice extent was
16.757 million km² on October 11, 2024
17.926 million km² on October 11, 2022
19.412 million km² on October 11, 2014
This difference indicates that extent may fall below 1 million km² in February 2025.
As illustrated by the image below, Antarctic sea ice extent was 1.976 million on February 25, 2022, so 1 million km² less extent than that would result in a Blue Ocean Event early next year. A Blue Ocean Event is deemed to occur when the sea ice extent falls to 1 million km² or less.
Low Antarctic sea ice extent is a tipping point, as sea ice thickness by February 2025 can be expected to be minimal, resulting in no further ocean heat getting consumed by sea ice below the surface. So, there would be less sunlight getting reflected back into space for months and by February 2025 there would no longer be thicker sea ice that previously consumed incoming ocean heat, and both of these mechanisms are further increasing temperatures.
Note also that Antarctic sea ice extent looks set for a steep decline, the more so as the impact of less sunlight getting reflected will increase over the coming months as more sunlight reaches the Southern Hemisphere, in line with seasonal changes. Albedo changes hit Antarctic sea ice in particular, as it is located at higher latitudes than Arctic sea ice, which is located mostly around the North Pole.
The image below, based on ERA5 data from early 2023 through October 8, 2024, indicates that temperature anomalies have been rising since the start of El Niño, a rise that has continued during ENSO-neutral conditions into La Niña.
Oceans are still absorbing an estimated 91% of the excess heat energy trapped in the Earth's climate system due to human-caused global warming. If just a small part of that heat instead remains in the atmosphere, this could constitute a huge rise in temperature.
Polar amplification of the temperature rise causes a relative slowing down of the speed at which heat flows from the Equator to the poles. This impacts ocean currents and wind patterns, resulting in slowing down of the Atlantic meridional overturning circulation (AMOC) and of ocean currents around Antarctica that carry heat to the deep ocean, as well as in deformation of the Jet Stream.
A recent study warns about intensification of global warming due to the slowdown of the overturning circulation. The overturning circulation carries carbon dioxide and heat to the deep ocean, where it is stored and hidden from the atmosphere. As the ocean storage capacity is reduced, more carbon dioxide and heat are left in the atmosphere. This feedback accelerates global warming.
Furthermore, the combined impact of aerosols and nitrogen fertilizers has been underestimated; a recent study concludes that when ammonia, nitric acid and sulfuric acid are present together, they contribute strongly to the formation of cirrus clouds.
The IPCC image below shows how much temperatures are currently suppressed in the Arctic due to aerosols and thus also shows how much temperatures in the Arctic look set to rise as the aerosol masking effect falls away.
A huge temperature rise could occur soon
A huge temperature rise could occur soon, as the impact of these mechanisms keeps growing, as the latent heat tipping point gets crossed in a Double Blue Ocean Event and the seafloor methane tipping point subsequently gets crossed.
As temperatures keep rising in the Arctic, changes to the Jet Stream look set to intensify, resulting in loss of terrestrial albedo in the Arctic that could equal the albedo loss resulting from sea ice decline.
Further feedbacks include permafrost degradation, both terrestrial and on the seafloor of the Arctic Ocean, which looks set to cause huge releases of greenhouse gases (particularly CO₂, CH₄ and N₂O).
This would in turn also cause more water vapor to enter the atmosphere, further speeding up the temperature rise.
As the image below illustrates, the Antarctic Sea ice extent minimum was well below 2 million km² on each of the past three years.
Temperatures did catch up with 2023 temperatures again, as illustrated by the image below, adapted from Copernicus, showing a temperature of 15.62°C on October 6, 2024, an anomaly of 0.8°C from 1991-2022, the highest anomaly on record for the time of the year.
Minimum annual Antarctic sea ice extent was:
1.976 million km² on February 25, 2022
1.788 million km² on February 21, 2023
1.985 million km² on February 20, 2024
Global sea ice extent at record low for time of year
Low global sea ice is driving up global temperatures at the moment, in multiple ways, as discussed further below.
On October 17, 2024, global sea ice extent was 22.03 million km², a record low for the time of year. Global sea ice extent is now several million km² lower than it was decades ago, i.e. more than 2.5 million km² lower than the 2010's average extent and more than 5 million km² lower than the 1980's average extent.
On October 17, 2024, global sea ice extent was 22.03 million km², a record low for the time of year. Global sea ice extent is now several million km² lower than it was decades ago, i.e. more than 2.5 million km² lower than the 2010's average extent and more than 5 million km² lower than the 1980's average extent.
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| [ click on images to enlarge ] |
Antarctic Sea ice thickness and volume
There are indications that Antarctic sea ice volume is already decreasing. The images by University of Bremen below show sea ice thickness on August 27, 2024 (left), September 29, 2024 (center) and October 5, 2024 (right).
Temperatures keep rising
Temperature anomalies were high in September 2024, while there have been ENSO-neutral conditions since May 2024 through September 2024. Parts of Antarctic sea ice were hit by very high anomalies, of over 10°C, while very little sunlight is yet reaching Antarctic sea ice in September.
The image below, based on ERA5 data from early 2023 through October 8, 2024, indicates that temperature anomalies have been rising since the start of El Niño, a rise that has continued during ENSO-neutral conditions into La Niña.
Note that the above anomalies are calculated from 1991-2020, which isn't pre-industrial. When using a pre-industrial base, temperature anomalies would be a lot higher.
Higher sea surface temperatures come with greater stratification.
Mechanisms accelerating the temperature rise
As illustrated by the image below, there are at least seven mechanisms that are accelerating the surface temperatures rise, and therefore are accelerating sea ice decline.
These seven mechanisms all relate to changes in snow and ice cover, wind patterns and ocean currents, as follows:
1. latent heat buffer loss ➭ less heat gets consumed by melting
Sea ice constitutes a buffer that consumes ocean heat; the temperature of the water will not rise as long as there is ice, but once all ice has melted, further heat will raise the temperature of the water. The amount of energy absorbed by melting ice is as much as it takes to heat an equivalent mass of water from zero to 80°C.
2. sea ice changing into dark ocean ➭ less sunlight is reflected
Water covered by snow and ice can reflect as much as 90% of the sunlight back into space, absorbing only 10%. By contrast, water without snow and ice can absorb as much as 94% of sunlight, with as little as 6% reflected back into space.
A recent study found that global sea ice has lost 13%–15% of its planetary cooling effect since the early/mid 1980s, and the implied global sea ice albedo feedback is 0.24–0.38 W m⁻² K⁻¹.
3. less sea ice ➭ less outward radiation
A 2014 study finds significantly lower values of far-IR emissivity for ocean surfaces than for sea ice and snow, leading to a decrease in surface emission at far-IR wavelengths, reduced cooling to space, and warmer radiative surface temperatures.
4. ocean warming ➭ less lower clouds ➭ less sunlight reflected
A 2021 study finds that warming oceans cause fewer bright clouds to reflect sunlight into space, admitting even more energy into earth's climate system.
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| [ Earthshine annual albedo anomaly expressed as reflected flux in W/m². CERES data. ] |
5. ocean warming ➭ stratification ➭ less heat reaches deeper waters
Higher sea surface temperatures come with greater stratification.
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| [ from earlier post ] |
6. ocean currents and wind patterns change ➭ less heat reaches deeper waters
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[ from earlier post ] |
Polar amplification of the temperature rise causes a relative slowing down of the speed at which heat flows from the Equator to the poles. This impacts ocean currents and wind patterns, resulting in slowing down of the Atlantic meridional overturning circulation (AMOC) and of ocean currents around Antarctica that carry heat to the deep ocean, as well as in deformation of the Jet Stream.
7. freshwater lid forms at ocean surface ➭ more heat reaches Arctic Ocean
Greater stratification, meltwater and rain can contribute to the formation of a freshwater lid that expands at the surface of the North Atlantic, enabling more ocean heat to travel underneath this lid from the North Atlantic into the Arctic Ocean, which can occur abruptly at times when a deformed Jet Stream causes storms that speed up ocean currents along this path.
Further mechanisms
Further mechanisms that could accelerate the temperature rise include a new El Niño in 2025, coinciding with a peak in sunspots that is higher than expected. The black dashed line in the image below, adapted from NOAA, indicates a transition to La Niña in October 2024, persisting through Jan-Mar 2025.
A new El Niño is about to emerge and this may occur in the course of 2025, while Earth's Energy Imbalance is high (and rising, image below), while feedbacks and further mechanisms contribute to accelerate the temperature rise and while sunspots reach a peak in this cycle (expected to occur in July 2025), adding further heat.
A further mechanism that could strongly accelerate the temperature rise is the falling away of the masking effect of aerosols currently emitted jointly with the greenhouse gases produced in the process of burning fossil fuel and biofuel. Blunt measures may be taken to reduce burning of fossil fuel and biofuel, which will reduce greenhouse gas emissions and emission of cooling aerosols, while such measures can at the same time encourage many to use more wood burners, causing more emissions of warming aerosols. Sadly, few people are calling for more sophisticated measures.
The IPCC image below shows how much temperatures are currently suppressed in the Arctic due to aerosols and thus also shows how much temperatures in the Arctic look set to rise as the aerosol masking effect falls away.
The water feedback is also getting stronger. The image below, created with NOAA data, shows surface precipitable water through September 2024. Note that values in 2024 are higher than in 2023.
The image below, adapted from Climate Reanalyzer, shows the spread of the September 2024 anomaly in precipitable water, with less over the Amazon, but more over the Sahara, while more also shows up at higher northern latitudes, i.e. over the Barents Sea and the Canadian Arctic Archipelago.
The water vapor feedback roughly follows the temperature rise (7% more water vapor for every 1°C warming). Given the strength of such feedbacks, it is important to highlight feedbacks when assessing the rise since pre-industrial and the rise to come (over the next few years).
As temperatures keep rising, this could cause a second Blue Ocean Event to occur in 2025, i.e. in the Arctic. Subsequently, as the oceans keep heating up, the seafloor methane tipping point could be crossed. The danger is that a cascade of events will unfold like a domino effect, leading to extinction of most species, including humans, as the image below warns, listing 14 mechanisms that could further accelerate the temperature rise.
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| [ from earlier post - click on images to enlarge ] |
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| [ for more background, also view the Extinction page ] |
A huge temperature rise could occur soon, as the impact of these mechanisms keeps growing, as the latent heat tipping point gets crossed in a Double Blue Ocean Event and the seafloor methane tipping point subsequently gets crossed.
As temperatures keep rising in the Arctic, changes to the Jet Stream look set to intensify, resulting in loss of terrestrial albedo in the Arctic that could equal the albedo loss resulting from sea ice decline.
Further feedbacks include permafrost degradation, both terrestrial and on the seafloor of the Arctic Ocean, which looks set to cause huge releases of greenhouse gases (particularly CO₂, CH₄ and N₂O).
This would in turn also cause more water vapor to enter the atmosphere, further speeding up the temperature rise.
The danger of a huge temperature rise is very large in the Arctic, where vast amounts of methane are held in sediments at the seafloor and in permafrost on land, and where there is very little hydroxyl in the air to break down the methane.
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.
• Arctic Data archive System - National Institute of Polar Research - Japan
https://ads.nipr.ac.jp/vishop
• Danish Meteorological Institute - Arctic sea ice volume and thickness
https://ocean.dmi.dk/arctic/icethickness/thk.uk.php
• University of Bremen - Arctic sea ice
https://seaice.uni-bremen.de/start
• NSIDC - Interactive sea ice chart
https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph
• Earth's Sea Ice Radiative Effect From 1980 to 2023 - by Duspayev et al. (2024)
• NOAA - Climate Prediction Center - ENSO: Recent Evolution, Current Status and Predictions
https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf
• NOAA - Physical Sciences Laboratory
https://psl.noaa.gov
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.
Links
• Arctic Data archive System - National Institute of Polar Research - Japan
https://ads.nipr.ac.jp/vishop
https://ocean.dmi.dk/arctic/icethickness/thk.uk.php
• University of Bremen - Arctic sea ice
https://seaice.uni-bremen.de/start
• NSIDC - Interactive sea ice chart
https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph
Discussed on facebook at:
https://www.facebook.com/groups/arcticnews/posts/10161543138459679
https://www.facebook.com/groups/arcticnews/posts/10161543138459679
• NOAA - Climate Prediction Center - ENSO: Recent Evolution, Current Status and Predictions
https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf
• NOAA - Physical Sciences Laboratory
https://psl.noaa.gov
• Feedbacks
https://arctic-news.blogspot.com/p/feedbacks.html
• Jet Stream
https://arctic-news.blogspot.com/p/jet-stream.html
• Freshwater lid on the North Atlantic
https://arctic-news.blogspot.com/p/cold-freshwater-lid-on-north-atlantic.html
• Latent Heat
https://arctic-news.blogspot.com/p/latent-heat.html
• Sunspots
https://arctic-news.blogspot.com/p/sunspots.html
• Indicators of Global Climate Change 2023: annual update of key indicators of the state of the climate system and human influence - by Piers Forster et al.
https://arctic-news.blogspot.com/p/feedbacks.html
• Jet Stream
https://arctic-news.blogspot.com/p/jet-stream.html
• Freshwater lid on the North Atlantic
https://arctic-news.blogspot.com/p/cold-freshwater-lid-on-north-atlantic.html
• Latent Heat
https://arctic-news.blogspot.com/p/latent-heat.html
• Sunspots
https://arctic-news.blogspot.com/p/sunspots.html
• Indicators of Global Climate Change 2023: annual update of key indicators of the state of the climate system and human influence - by Piers Forster et al.
https://essd.copernicus.org/articles/16/2625/2024
• Pre-industrial
https://arctic-news.blogspot.com/p/pre-industrial.html
• Transforming Society
https://arctic-news.blogspot.com/2022/10/transforming-society.html
• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html
• Climate Emergency Declaration
https://arctic-news.blogspot.com/p/climate-emergency-declaration.html
• Pre-industrial
https://arctic-news.blogspot.com/p/pre-industrial.html
• Transforming Society
https://arctic-news.blogspot.com/2022/10/transforming-society.html
• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html
• Climate Emergency Declaration
https://arctic-news.blogspot.com/p/climate-emergency-declaration.html