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.
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.
|[ SSTA and SST, August 23, 2022 ]
Deformation of the Jet Stream can a times strongly increase evaporation over the North Atlantic with more precipitation further down the path of the Atlantic meridional overturning circulation (AMOC).
Deformation of the Jet Stream can also increase runoff from land (including from melting glaciers).
In both these cases, this can contribute to the formation and growth of a relatively cold, freshwater lid at the surface of the North Atlantic.
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, 2015, and the right panel shows a forecast for the sea ice for August 30, 2022, run on August 22, 2022.
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.
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.
|[ The Buffer has gone, feedback #14 on the Feedbacks page ]|
Methane levels are already at record high and growth is accelerating, even without an extra burst of seafloor methane. The NOAA record shows that methane grew by 18.31 ppb in 2021, the highest annual growth on record.
NOAA’s data are for marine surface measurements. More methane tends to accumulate at higher altitudes, as illustrated by the two data images on the right.
The top data image on the right shows methane recorded by the MetOp satellite on August 22, 2022 am. The image shows means of 1972 ppb at five pressure levels (of 280 mb and less), with a peak level of 2543 ppb, the highest that day, occurring at 218 mb.
The second data image on the right shows methane means recorded by the MetOp satellite on August 25, 2022 pm of 1975 ppb at four pressure levels (at 254 mb, 266 mb, 280 mb and 283 mb).
Another N20 satellite image is added underneath showing high methane concentrations over the Arctic, also on August 20, 2022 am, but at 695.1 mb, which is much closer to sea level. This confirms that much of the methane may have originated in the Arctic.
An image is added underneath from another satellite, the MetOp satellite, also showing high methane concentrations over the Arctic, also on August 20, 2022 am, this time at 586 mb, further confirming that much of the methane may have originated in the Arctic.
A large abrupt methane release could double the methane in the atmosphere. 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.
A level twice as high as that 1975 ppb mean is a mean of 3950 ppb, and when using a 1-year GWP of 200, this translates into 790 ppm CO₂e, i.e. only 410 ppm away from the 1200 ppm clouds tipping point.
The average monthly CO₂ at Mauna Loa, Hawaii, was 420.99 ppm both in May and in June 2022. As illustrated by the image on the right, average daily CO₂ hasn’t been below 416 ppm in July and August 2022, while some hourly measurements were around 425 ppm CO₂.
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 even with far less methane erupting from the seafloor.
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.
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 (earlier posts in 2022)
• Arctic sea ice June 2022 – why the situation is so dangerous
• Arctic sea ice July 2022
• Increasing ocean stratification over the past half-century – by Guancheng Li et al.
• The ocean has become more stratified with global warming – news release
• Jet Stream
• Cold freshwater lid on North Atlantic
• NOAA – Monthly Temperature Anomalies Versus El Niño
• University of Bremen
• NSIDC – Arctic sea ice concentration
• NSIDC – Chartic, interactive sea ice graph
• NOAA – Trends in Atmospheric Methane
https://earth.nullschool.net• Naval Research Laboratory
https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/arctic.html• Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf – by Natalia Shakhova et al. (2019)
https://arctic-news.blogspot.com/p/cold-freshwater-lid-on-north-atlantic.html• Albedo, latent heat, insolation and more
https://arctic-news.blogspot.com/p/albedo.html• Latent Heat Buffer
• Feedbacks in the Arctic
• Clouds feedback
• How much time is there left to act?
• Cataclysmic Alignment
• Human Extinction by 2025?
• Climate Plan