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Dangerously large Arctic sea ice extent

Arctic sea ice extent was 5.88 million km² on August 21, 2022, larger in extent than in any of the years from 2010 through 2021 at this time of year, as illustrated by the image below. 

At first glance, one might think that this relatively large extent was a sign of healthy sea ice. After all, the larger the sea ice, the more sunlight gets reflected back into space. At the same time, however, the situation is very dangerous, as there is a growing risk that large eruptions of methane will occur from the seafloor of the Arctic Ocean.

Why is the situation so dangerous? There are many contributors to the danger, three of them are:
1. Sea ice acts as a seal
Temperatures in the Arctic are rising faster than in the rest of the world. As temperatures rise in the Arctic, increased precipitation, meltwater and runoff from land, and flow of freshwater from rivers all decrease salinity of the water in the Arctic Ocean. Lower salinity makes it harder for sea ice to melt. 
Furthermore, we’re currently in the depth of a persistent La Niña (NOAA image on the right), and the associated lower air temperatures further contribute to a relatively larger extent of the sea ice. 
More extensive sea ice in turn makes it harder for ocean heat to be transferred to the atmosphere, thus instead raising the temperature of the water of the Arctic Ocean.
Sea ice acts as a seal that impedes transfer of ocean heat from the Arctic Ocean to the atmosphere. 
The larger the sea ice is in extent, the less ocean heat can be transferred from the Arctic Ocean to the atmosphere, which means that more heat will remain in the Arctic Ocean.
2. Lid on North Atlantic

Ocean stratification is increasing globally, as ocean warming is stronger for upper layers versus the deep ocean. Stratification increased from 1960 to 2018 by 5.3% for the upper 2000m and by as much as 18% for the upper 150m, while salinity changes also play an important role locally, a 2020 study finds.

As temperatures in the Arctic are rising faster than in the rest of the world, the Jet stream is getting deformed, and this can, at times strongly, increase precipitation over the North Atlantic and increase runoff from land (including from melting glaciers) that both contribute to growth of a relatively cold, freshwater lid at the surface of the North Atlantic.

This lid on the North Atlantic reduces transfer of ocean heat to the atmosphere and enables large amounts of salty, warm water to enter the Arctic Ocean, diving under the sea ice. 
This lid also increases the risk of a sudden, large influx of hot, salty water. Slowdown of the Atlantic meridional overturning circulation (AMOC) causes ocean heat to accumulate, while more warm water travels underneath this lid (instead of at the sea surface) toward the Arctic Ocean. As the Jet Stream gets more deformed, strong winds along the path of AMOC can at times speed up the flow of water that travels underneath this cold freshwater lid over the North Atlantic, suddenly pushing large amounts of salty, warm water into the Arctic Ocean. 
3. Latent heat buffer loss

The navy.mil combination image below has three panels. The left panel shows the sea ice on August 30, 2012, the center panel shows the sea ice on August 30, 201, and the right panel shows a forecast for the sea ice for August 21, 2022, run on August 20, 2022.

The image illustrates that Arctic sea ice is currently larger in extent than it was in 2012 and 2014 around this time of year, and that there has been a dramatic reduction in thickness of the sea ice over time.

Sea ice acts as a buffer that absorbs heat, while keeping the temperature at zero degrees Celsius. As long as there is sea ice in the water, this sea ice will keep absorbing heat, so the temperature doesn’t rise at the sea surface. 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.

This ice has meanwhile all but disappeared, so without this latent heat buffer further incoming heat must go elsewhere, i.e. the heat will further raise the temperature of the water of the Arctic Ocean.

Compound impact

The danger is that, as more salty, warm water keeps arriving in the Arctic Ocean while the latent heat buffer has largely disappeared and while sea ice extent is relatively large, this will raise the temperatures and salinity levels at the bottom of the Arctic Ocean enough to destabilize hydrates in sediment at the seafloor of the Arctic Ocean, resulting in methane eruptions both from these hydrates and from free gas underneath these hydrates.

High methane concentrations
The possibility of large releases of methane from the seafloor of the Arctic Ocean is the more dangerous given the already very high methane concentrations in the atmosphere. The annual growth in methane in 2021 was the highest on the NOAA record
The image on the right shows a methane peak of 2622 (marked by the red oval), recorded by the N20 satellite on August 20, 2022 am at 399.1 mb. Note the high methane concentrations north of Siberia. 
Another N20 satellite image is added underneath showing high methane concentrations over the Arctic on August 20, 2022 am at 695.1 mb, which is much closer to sea level.  
The MetOp satellite image underneath also shows high methane concentrations over the Arctic at 695.1 mb on August 20, 2022 am. 

Methane releases from the seafloor of the Arctic Ocean are very dangerous because there is very little hydroxyl in the atmosphere over the Arctic to break down the methane.  

The MetOp satellite image underneath shows a mean for methane of 1971 ppb (marked by the red oval) at 293 mb on the morning of August 18, 2022 am. An abrupt release as large as the methane currently in the atmosphere could raise the mean twice as high, to 3942 ppb and when using a 1-year GWP of 200, this translates into 788.4 ppm CO₂e.

Average daily carbon dioxide (CO₂) concentration at Mauna Loa, Hawaii, was 417.05 ppm on August 18, 2022 (next image on the right). When adding that 417.05 ppm for CO₂ to the above 788.4 ppm CO₂e for methane, that gives a total of 1205.45 ppm CO₂e. 

In other words, a large eruption of methane from the seafloor of the Arctic Ocean could abruptly cause the joint CO₂e of just two greenhouse gases, i.e. methane and CO₂, to cross the 1200 ppm clouds tipping point globally and trigger a further 8°C global temperature rise, due to the clouds feedback alone. 

When adding further forcers, a huge temperature rise could be triggered with far less methane. 

Conclusion

In conclusion, there is a growing risk that methane will erupt from the seafloor of the Arctic Ocean and cause a dramatic rise in temperature.

Even without such eruption of methane from the seafloor of the Arctic Ocean, temperatures look set to rise strongly soon, as we move into an El Niño and face a peak in sunspots. 

Either way, the resulting temperature rise could drive humans extinct as early as in 2025 with temperatures continuing to skyrocket in 2026

This makes it in many respects rather futile to speculate about what will happen beyond 2026. At the same time, the right thing to do now is to help avoid the worst things from happening, through comprehensive and effective action as described in the Climate Plan.

• Arctic sea ice August 2022
Further links

• Increasing ocean stratification over the past half-century – by Guancheng Li et al. 
https://www.nature.com/articles/s41558-020-00918-2• The ocean has become more stratified with global warming – news release

• IPCC AR6 WG1 SPM
• NOAA – Globally averaged marine surface annual mean methane growth rates.
• NOAA – Trends in Atmospheric Carbon Dioxide
• NOAA – MetOp satellite 
• NOAA – N20 satellite

• Jet Stream
https://arctic-news.blogspot.com/p/jet-stream.html

• Cold freshwater lid on North Atlantic
https://arctic-news.blogspot.com/p/cold-freshwater-lid-on-north-atlantic.html

• NOAA – Monthly Temperature Anomalies Versus El Niño
https://www.ncei.noaa.gov/access/monitoring/monthly-report/global/202207/supplemental/page-4

• University of Bremen
https://seaice.uni-bremen.de/databrowser

• NSIDC – Arctic sea ice concentration
https://nsidc.org/arcticseaicenews

• NSIDC – Chartic, interactive sea ice graph
https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph

• NOAA – Trends in Atmospheric Methane
https://gml.noaa.gov/ccgg/trends_ch4

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