Showing posts with label Southern Ocean. Show all posts
Showing posts with label Southern Ocean. Show all posts

Tuesday, June 30, 2026

Water Vapor Worries

The Ozone Layer

[CC image, credit: nptel.ac.in ]
The Atmosphere can be divided into layers. The Troposphere is the layer that is closest to the surface. When rising up in the Atmosphere, the next layer up is the Stratosphere. The next layer up is the Mesosphere and the fourth layer from the bottom is the Thermosphere.

The temperature rises or falls in a different way in each of these layers, as illustrated by the red line in the image CC from archive.nptel.ac.in on the right and the scale on the bottom.

The ozone layer is located in the lower stratosphere at an altitude of 15 to 35 km or 9 to 22 miles above the Earth's surface, with the highest concentrations usually peaking around 25 km. This altitude corresponds with a pressure level of 100 to 10 mb or hPa.

The ozone layer absorbs 97% to 99% of the Sun's medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which otherwise could cause severe damage to life on Earth.

Water vapor rising over Antarctica

The image below shows a temperature anomaly forecast for July 3, 2026. At this time of year very little sunlight is reaching Antarctica, so the temperature over Antarctica can get very low. At the same time, global warming has increased sea surface temperatures and this also keeps air temperatures over water relatively warm. The difference in temperature strengthens wind patterns from the Southern Ocean to Antarctica, which can lead to atmospheric rivers moving toward Antarctica, carrying water vapor and heat from the Southern Ocean to Antarctica.


The red color on the above image indicates high temperature anomalies over Antarctica. The dark blue areas indicate where snow has fallen over the sea ice around Antarctica and over the interior of Antarctica. 


As temperatures rise, the water vapor in the air increases. The amount of water vapor that the air can hold rises by 7% for each 1°C temperature rise (Clausius-Clapeyron relation). While much of the water vapor will fall out of the air as precipitation, in the form of rain or snow, some of the water vapor will remain in the air. This extra water vapor increases temperatures, since water vapor is a strong greenhouse gas. The IPCC adds: Water vapor feedback acting alone approximately doubles the warming from what it would be for fixed water vapor. Furthermore, water vapor feedback acts to amplify other feedbacks in models, such as cloud feedback and ice albedo feedback. If cloud feedback is strongly positive, the water vapor feedback can lead to 3.5 times as much warming as would be the case if water vapor concentration were held fixed.

Part of the precipitation will fall over Antarctica in the form of snow, thickening the snow cover there, without returning to the surface of the Southern Ocean. The net result is that the salinity of the Southern Ocean surface increases, facilitating increased melting of Antarctic sea ice, further speeding up the temperature rise, as also discussed in earlier posts such as this one.

The threat is further illustrated by the image below, which shows a forecast of precipitable water standardized anomalies on June 30, 2026. 


Damage to the Ozone Layer

Furthermore, part of the extra water vapor can rise up and moisten the atmosphere up to and above the ozone layer. The combination image below shows relative humidity on June 30, 2026 at 01:00 UTC, with relative humidity reaching up to 100% at surface level (left), up to 100% at 70 mb or hPa (center), and up to 23% at 10 mb or hPa (right).


[ from earlier post ]
Increases in stratospheric water vapor are bad news, as they not only speed up global warming but also lead to loss of stratospheric ozone, as Drew Shindell pointed out back in 2001.

It has long been known that deterioration of the ozone shield increases ultraviolet-B irradiation, in turn causing skin cancer.

Research (box right) suggests that, millions of years ago, it could also have led to loss of fertility and consequent extinction in plants and animals.

Water vapor reaching stratospheric altitudes causes ozone depletion, as James Anderson describes in a 2017 paper and discusses in the short 2016 video below.

[ from earlier post ]

Conclusion

The image below shows annual maximum daily precipitation change with a temperature versus 1850-1900 rise of 1.5°C, 2°C, and 4°C, from the IPCC AR6. 


The situation looks set to deteriorate further. More water vapor causes more warming, since water vapor is a potent greenhouse gas. As more snow falls over Antarctica, the sea surface of the Southern Ocean increases in salinity, which speeds up melting of sea ice. The extra water vapor and increased melting of sea ice can both strongly accelerate the temperature rise, while water vapor that reaches the stratosphere also causes damage to the ozone layer.

The situation is dire and unacceptably dangerous, and the precautionary principle necessitates the danger to be acknowledged, while facilitating rapid, comprehensive and effective action to reduce the damage and to improve the outlook, where needed in combination with a Climate Emergency Declaration, as described in posts such as in this 2022 post and this 2025 post, and as discussed in the Climate Plan group.


Links

• Moistening Atmosphere
https://arctic-news.blogspot.com/p/moistening-atmosphere.html

• Care for the Ozone Layer
https://arctic-news.blogspot.com/2019/01/care-for-the-ozone-layer.html

• Double Blue Ocean Event 2026-2027? - update 




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Wednesday, July 2, 2025

Saltier water, less sea ice

The Southern Meriodinal Ocean Circulation (SMOC) used to be driven by a cold freshwater layer resulting from melting Antarctic sea ice, enabling circumpolar waters to cool off and freshen, making them more dense and sink to the bottom. 
[ Antarctic waters sinking to the bottom, click on images to enlarge ]
This is illustrated by the above image, from a study led by Violaine Pellichero (2018), showing water-mass transformation within the Southern Ocean mixed-layer under sea-ice. Schematic cross-section illustrating the main water-masses in the Southern Ocean (Antarctic Intermediate and Mode Waters in red, Circumpolar Deep Waters in gray, and Dense Shelf Waters and Antarctic Bottom Waters in blue) and their interaction with ice and the surface. The water-masses are denoted by their neutral density values and the arrows corresponding to each water-masses indicate subduction (downward) or upwelling (upwards). The violet arrows illustrate the effect of northward sea-ice extent and freshwater transport. The green line is the mixed-layer.

A study led by Alessandro Silvano (2025) finds that, over the years, surface waters have become more salty.
By combining satellite observations with data from underwater robots, researchers built a 15-year picture of changes in ocean salinity, temperature and sea ice, as illustrated by the above image. Around 2015, surface salinity in the Southern Ocean began rising sharply – just as sea ice extent started to crash. 
When surface waters become saltier, they sink more readily, stirring the ocean’s layers and allowing heat from the deep to rise. This upward heat flux can melt sea ice from below, even during winter, making it harder for ice to reform. This vertical circulation also draws up more salt from deeper layers, reinforcing the cycle.

In addition to heat rising up from the deep, there is the danger that increasing amounts of both heat and carbon dioxide (CO₂), previously stored in the deep ocean by sinking circumpolar waters, will instead remain at the surface and cause both atmospheric temperatures and CO₂ concentrations to rise.

In the video below, Paul Beckwith discusses the recent study. 


The video below by @JustHaveaThink also discusses the recent study. 


Saltier water, less sea ice

   [ Saltier water, less sea ice ]
The higher the water's salt content, the lower its melting point. Seawater typically has a salinity of about 3.5% (35 grams of salt per liter of water). Sea ice starts melting when the temperature rises to about -2°C (28.4°F). By contrast, freshwater remains frozen as long as the temperature remains below 0°C (32°F).

What is causing the Southern Ocean surface to become more salty? Higher temperatures come with feedbacks, such as stronger wind and stronger evaporation resulting in both a lot more water vapor and a lot more heat getting transferred from the surface to the atmosphere. 

Much of the water vapor will return to the surface in the form of precipitation such as rain and snow, but part of this precipitation will fall over Antarctica, with the net result of an increase in salinity of the surface of the Southern Ocean. Increased snowfall over Antarctica can be attributed to rising air temperatures and stronger evaporation, changes in atmospheric circulation and the effects of ozone depletion. 

Furthermore, 7% more water vapor will remain in the atmosphere for every degree Celsius rise in temperature. Since water vapor is a potent greenhouse gas, this will further increase temperatures, making it a self-amplifying feedback that can significantly contribute to further acceleration of the temperature rise. 

Accumulating feedbacks

Warmer oceans result in stronger stratification (feedback #29), further contributing to make it harder for heat to reach the deeper parts of oceans. As a result, a larger proportion of the heat that was previously entering oceans will instead remain in the atmosphere or accumulate at the ocean surface, and slowing down of the Atlantic Meriodinal Overturning Circulation (AMOC) further contributes to this. 
[ from earlier post ]
More evaporation typically makes the sea surface more salty, while more precipitation, melting of sea ice and run-off from rivers and glaciers typically make the ocean surface fresher. As the recent study shows, the Southern Ocean surface is becoming more salty, which contributes to higher sea surface temperatures and in more melting of the sea ice. It's a self-amplifying feedback, in that saltier water at the ocean surface draws up more heat from the deep ocean, making it harder for sea ice to regrow. Increasing amounts of heat and CO₂ that were previously stored in the deep ocean by sinking circumpolar waters, threaten to instead remain at the surface and cause both atmospheric temperatures and CO₂ concentrations to rise. 

Less sea ice also comes with loss of albedo (water is less reflective than ice, feedback #1), loss of the latent heat buffer (as sea ice disappears, heat can no longer be consumed by the process of melting, and the heat will instead go into increasing the temperature, feedback #14) and loss of emissivity (water is less efficient than ice in emitting in the far-infrared region of the spectrum, feedback #23), while warmer water result in more water vapor and less low-level clouds that reflect sunlight back into space (feedback #25). 

The image below, from an earlier post, illustrates that higher temperatures come with feedbacks and the impact of one feedback can amplify the impact of other feedbacks.


The above image depicts some of the dangers of feedbacks for the Arctic. Many feedbacks also apply to the Antarctic, but the bottom part of the image on the right may be particularly applicable to the Southern Hemisphere, which has more ocean surface and Antarctica constitutes a huge land mass on and around the South Pole. 

Covering more than 70% of Earth’s surface, our global ocean has absorbed about 90% of the warming that has occurred in recent decades due to increasing greenhouse gases, and the top few meters of the ocean store as much heat as Earth's entire atmosphere, as described by a NASA post. 

Even a small change could therefore result in a huge rise in the global air temperature.

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.



Links

• The southern ocean meridional overturning in the sea-ice sector is driven by freshwater fluxes - by Violaine Pellichero (2018) 

• Rising surface salinity and declining sea ice: A new Southern Ocean state revealed by satellites - by Alessandro Silvano et al. (2025)
https://www.pnas.org/doi/full/10.1073/pnas.2500440122
discussed on facebook at: 
https://www.facebook.com/groups/arcticnews/posts/10162876582119679

• Abrupt Antarctic Ocean Regime Shift: Reversed SMOC - Southern Meridional Overturning Circulation - video by Paul Beckwith 
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