Showing posts with label salt. Show all posts
Showing posts with label salt. Show all posts

Friday, August 8, 2025

Extreme Heat Risk

High temperatures on land


The above image, adapted from NOAA National Weather Service, shows extreme heat risk for multiple areas in the U.S. for August 9, 2025, with a location near Imperial, California highlighted with details.
Details for the forecast for this location are: 
- Wet bulb globe temperature: 93°F or 34°C
- Temperature: 102°F or 39°C
- Apparent Temperature: 117°F or 47°C
- Dew Point: 77°F or 25°C
- Relative Humidity: 46%
- Forecast for: August 9, 2025 21:00 UTC

On the above image, this extreme risk area is located at a latitude of 33.22° North. What is remarkable is that on the map there is also a high risk area that extends all the way from the southern border of the U.S. with Mexico to the northern border of the U.S. with Canada, with extreme risk areas showing up at latitudes North higher than for Toronto, Canada. 

The image below, again adapted from NOAA National Weather Service, shows a wet bulb globe temperature forecast for August 11, 2025, with an extreme heat warning highlighted (inset) for a location near Imperial, California.
Details for the forecast for this location are: 
- Wet bulb globe temperature: 95°F or 35°C
- Temperature: 109°F or 43°C
- Apparent Temperature: 121°F or 49°C
- Dew Point: 73°F or 23°C
- Relative Humidity: 32%
- Forecast for: August 11, 2025 21:00 UTC


[ from earlier post ]

The image below, adapted from the heat risk page at the NOAA National Weather Service, shows a forecast for August 9, 2025, updated 10.49 AM EST. The map shows high and extreme risk areas, including an extreme risk area centered around Grand Rapid, Michigan, which is located at a latitude of about 43° North.

The image below shows a heat stress forecast for August 11, 2025, with areas with extreme heat risk showing up in Michigan, while areas with major heat risk are showing up at latitudes as high as in Maine. 


The image below, adapted from Climate Reanalyzer, shows a three-day forecast of maximum temperatures run on August 8, 2025.


The above images illustrate that extreme weather events that come with very high, even fatal heat stress conditions can now increasingly occur almost anywhere in the U.S.

Friederike Otto, climatologist at Imperial College London concludes: “Even relatively cold Scandinavian countries are facing dangerous heatwaves today – no country is safe from climate change". 

High sea surface temperatures

In 2023, sea surface temperature anomalies first rose strongly (from 0.15°C on January 7, 2023, to 0.73°C on January 10, 2024). Then, sea surface temperature anomalies came down, in line with ENSO fluctuations (El Niño/La Niña). ENSO fluctuations and forecasts are also discussed in more detail further below. 

Yet, over the past few months, sea surface temperature anomalies have been rising again, reaching an anomaly of 0.44°C from 1991-2020 on August 14, 2025, as illustrated by the image on the right, adapted from Copernicus and based on ERA5 data.

The image below, adapted from ClimateReanalyzer and based on NOAA OISST v2.1 data, shows sea surface temperatures through August 14, 2025. Sea surface temperatures have risen recently to very high levels, reaching 20.96°C on August 14, 2024, an anomaly from 1982-2010 of 0.72°C.


The image below, adapted from Climate Reanalyzer, shows the one-day average sea surface temperature anomaly (from 1971-2000) on August 7, 2025.


[ click on images to enlarge ]
Speeding up Arctic sea ice demise

Arctic sea ice declines due to rising ocean heat. The above image shows very high sea surface temperature anomalies around and inside the Arctic Ocean. These anomalies go up and down with the change in seasons, but they are getting higher over time due to rising Earth Energy Imbalance.

The image on the right, from an earlier post, illustrates the huge amounts of heat that have accumulated in the ocean, showing equivalent ocean heat content on August 9, 2025.

The image on the right underneath shows North Atlantic sea surface temperatures as high as 32.8°C on August 5, 2025. The image shows heat moving up along the path of the Gulf Stream toward the Arctic, threatening to cause more loss of sea ice and permafrost.

    [ from earlier post, click to enlarge ]
Arctic sea ice also declines due to the sunlight heating up the sea ice. Where sea ice disappears, the water heats up rapidly. Arctic sea ice decline comes with feedbacks such as the albedo feedback, i.e. less sunlight getting reflected by sea ice means more heat is getting absorbed, further accelerating the temperature rise. More algae and soot settling on the sea ice can further contribute to albedo loss. 

Feedbacks of the temperature rise can manifest as changes in heat sinks and buffers, with rapid impact on the temperature rise. Oceans constitute a huge buffer that has taken up huge amounts of heat. The capacity of oceans to take up heat threatens to diminish, e,g, due to stratification and changes in ocean currents, as discussed in earlier post such as this one. 

Another buffer is the latent heat buffer that consumes heat in the process of melting snow and ice. Arctic sea ice is getting thinner over the years, and the amount of heat that can be absorbed in the process of melting is getting smaller over time. As the latent heat buffer diminishes, heat that was previously absorbed by the phase change from snow and ice to water, will therefore instead get absorbed by the water, further raising the temperature of the water. As sea ice thickness decreases over the years, less incoming ocean heat can be consumed by melting the remaining sea ice. 

More freshwater temporarily slows down melting of Arctic sea ice

   [ Bering Strait ]
Furthermore, Arctic sea ice decline is due to heat that is moving with the flow of rivers into the Arctic Ocean. The image on the right shows sea surface temperatures as high as 20.3°C in the Bering Strait on August 7, 2025.

Extreme weather events are getting more severe and are occurring more frequently, including heatwaves and thunderstorms on land that can extend over the Arctic Ocean. Rain falling on sea ice can speed up its demise. Heatwaves and storms over land can furthermore heat up the water of rivers and increase their flow, thus increasing the heat flowing into the Arctic Ocean. 

Also, more evaporation of sea water takes place over the North Atlantic, with more precipitation falling further down the track of the Gulf Stream and its extension north. This also adds more freshwater in the Arctic. 

Water from melting sea ice, from rivers and from precipitation is all freshwater, i.e. it contains no salt. The increase in freshwater at the surface of the Arctic Ocean has resulted in a temporary slowdown in the retreat of Arctic sea ice extent, due to a buffer that spans a maximum of 2°C (as depicted by image below on the right). 

Freshwater buffer looks set to be overwhelmed soon

    [ Saltier water, less sea ice, from earlier post ]
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).

As said, the increase in freshwater at the surface of the Arctic Ocean slows down the retreat of Arctic sea ice extent, but this is only a temporary slowdown. Given the speed at which the temperature of the water of the Arctic Ocean keeps rising, this temporary slowdown looks set to be overwhelmed soon and rapid melting of sea ice looks set to return with a vengeance. 


The above image shows Arctic sea ice concentration on August 14, 2025. 

Arctic and Antarctic - two different situations

The image below, by Eliot Jacobson, illustrates the rise of precipitable water (total column) over the years. 


Over the past two months (June-July 2025), the temperature over the Arctic Ocean has been slightly lower than 1951-1980, as illustrated by the image below. By contrast, areas with very high anomalies are visible between 60°S and 90°S. What's happening?


The image below shows that the precipitable water anomaly can be very high at both the North Pole and the South Pole. The image depicts the situation on August 9, 2025 18Z.  


In the Northern Hemisphere, water evaporates from the sea surface of the North Atlantic and the North Pacific. Prevailing winds carry much water vapor in the direction of the Arctic. Precipitation over the Arctic Ocean freshens the surface, forming a buffer that temporarily slows down the decline of the sea ice extent. Similarly, much of the precipitation over land is carried by rivers into the Arctic Ocean, also freshening the surface of the Arctic Ocean. And of course, heavy melting of Arctic sea ice in June and July 2025 has added further freshwater to the surface of the Arctic Ocean.

The slowdown of AMOC can also create a buffer by delaying the transport of ocean heat toward the Arctic Ocean, but given the increase of Earth's Energy Imbalance and the additional heat that is instead accumulating in the north Pacific and the North Atlantic, more heat looks set to eventually reach the Arctic Ocean, overwhelming such buffers. 

[ Precipitable water anomalies over Antarctica ]
In the Southern Hemisphere, water evaporates from the Southern Ocean and part of it falls on the Antarctic ice sheet, thickening the snow layer, as illustrated by the image on the right, showing a forecast of high precipitable water anomalies over Antarctica on August 20, 2025.

As a result, the Southern Ocean surface is getting more salty. As discussed in an earlier post, saltier surface waters sink more readily, allowing heat from the deep to rise, which can melt Antarctic 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 conclusion, geographic differences result in different precipitation outcomes and this in turn causes salinity differences that are behind these temperature anomaly differences. 

As said, the slowdown in the decline of Arctic sea ice extent that results from the increase in freshwater is temporary. Given the speed at which the temperature of the water of the Arctic Ocean keeps rising, this temporary slowdown looks set to be overwhelmed soon and rapid melting of sea ice looks set to return with a vengeance.

By contrast, the dramatic decrease in sea ice around Antarctica looks set to continue long-term, as a feedback that is amplified by albedo loss, lower emissivity, loss of the sea ice's latent heat buffer, ocean current changes and salinity changes. 

Dire state of sea ice

The net result is illustrated by the image below. The global sea ice area anomaly was 2.62 million km² below the 1981-2010 mean on August 13, 2025, a standard deviation of -4.13σ from 1981-2010. The image shows that the global sea ice area anomaly was well below 1981-2010 in the years 2023, 2024 and 2025, which is remarkable, since there was a La Niña early in 2025. The year 2016 is also marked, since 2016 was a strong El Niño year.
The image below shows Arctic sea ice volume through August 11, 2025, when volume was at a record daily low, as it has been for more than a year. 

High temperatures and dire state of sea ice despite borderline La Niña

What makes these high temperatures on land and the dire state of the sea ice even more significant is that there currently are no El Niño conditions. As illustrated by the image on the right, adapted from NOAA, the ENSO outlook (CFSv2 ensemble mean, black dashed line) favors borderline La Niña conditions during the Northern Hemisphere fall and early winter 2025-2026, which suppresses temperatures.

Over the past few months, there's been a zigzag pattern of rises and falls in sea surface temperatures in Niño 3.4, an area in the Pacific (inset) that is critical to the development of El Niño, as illustrated by the image below.


On August 11, 2025, the temperature in Niño 3.4 reached 26.51°C, an anomaly of 0.36°C vs 1991-2020. An El Niño event is defined by NOAA as an episode of at least five consecutive 3-month running mean sea surface temperature anomalies vs 1971-2000 surpassing the threshold of 0.5°C in the Niño 3.4 area, as illustrated by the image below.


The image on the right, adapted from ECMWF, shows the El Niño forecast through August 2026. The next El Niño may emerge soon, and it may continue to grow in strength in the course of 2026. 

The temperature rise is accelerating and the rise could accelerate even more due to decreases in buffers (as described above), due to strengthening feedbacks, especially during an El Niño, and due to further reduction of the aerosol masking effect, which are all developments that could rapidly speed up existing feedbacks and trigger new feedbacks. 

Seafloor methane

One of the most dangerous feedbacks is methane erupting from the seafloor of the Arctic Ocean. The image below shows hourly methane average recorded at the Barrow Atmospheric Baseline Observatory (BRW), a NOAA facility located near Utqiaġvik (formerly Barrow), Alaska, at 71.32 degrees North. 


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

• NOAA (National Oceanic and Atmospheric Administration), National Weather Service
https://digital.weather.gov

• NOAA - heat risk graphics
https://www.wpc.ncep.noaa.gov/heatrisk/graphics

• Climate Reanalyzer
https://climatereanalyzer.org

• Heat Stress in the US
https://arctic-news.blogspot.com/2025/07/heat-stress-in-the-us.html

• High feels like temperature forecast (2024)
https://arctic-news.blogspot.com/2024/08/high-feels-like-temperature-forecast.html

• Wet Bulb Globe Temperature Tipping Point (2023)
https://arctic-news.blogspot.com/2023/07/wet-bulb-globe-temperature-tipping-point.html

• ‘No country is safe’: deadly Nordic heatwave supercharged by climate crisis, scientists say 

• Eliot Jacobson - Total Column Precipitable Water 1943 through July 2025
https://www.facebook.com/photo/?fbid=122244827390164489

• Kevin Pluck - sea ice visuals
https://seaice.visuals.earth

• Danish Meteorological Institute - Arctic sea ice thickness and volume

• NOAA - Oceanic Niño Index (ONI)

• ECMWF - El Niño forecast

• NOAA - Global Monitoring Laboratory
https://gml.noaa.gov/dv/iadv



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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 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. 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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Monday, October 8, 2018

What Does Runaway Warming Look Like?

The forcing caused by the rapid rise in the levels of greenhouse gases is far out of line with current temperatures. A 10°C higher temperature is more in line with these levels, as illustrated by the image below.


Carbon dioxide levels have been above 400 ppm for years. Methane levels above 1900 ppb were recorded in September 2018. Such high levels are more in line with a 10°C higher temperature, as illustrated by the above graph based on 420,000 years of ice core data from Vostok, Antarctica, research station.

How fast could such a 10°C temperature rise eventuate? The image below gives an idea.


Such runaway warming would first of all and most prominently become manifest in the Arctic. In many ways, such a rise is already underway, as the remainder of this post will show.

High Arctic Temperatures

Why are Arctic temperatures currently so high for the time of year?


As warmer water enters the Arctic Ocean from the Atlantic and Pacific Oceans, there is no thick sea ice left to consume this heat. Some of this heat will escape from the Arctic Ocean to the atmosphere, as illustrated by above dmi.dk  image showing very high temperatures for the time of the year over the Arctic (higher than 80°C latitude).


Above dmi.dk image shows that Arctic temperatures are increasingly getting higher during Winter in the Northern Hemisphere.


Similarly, above NASA image shows that Arctic temperatures are increasingly getting higher during Winter in the Northern Hemisphere.


As the Arctic warms up faster than the rest of the world, the Jet Stream is becoming more wavy, allowing more hot air to move into the Arctic, while at the same time allowing more cold air to move south.

Above image shows that the air over the Beaufort Sea was as warm as 12.8°C or 55°F (circle, at 850 mb) on October 2, 2018. The image also illustrates that a warmer world comes with increasingly stronger cyclonic winds.


The images above and below shows that on October 2 and 7, 2018, the sea surface in the Bering Strait was as much as 6°C or 10.7°F, respectively 6.4°C or 11.6°F warmer than 1981-2011 (at the green circle).


As temperatures on the continent are coming down in line with the change in seasons, the air temperature difference is increasing between - on the one hand - the air over continents on the Northern Hemisphere and - on the one hand - air over oceans on the Northern Hemisphere. This growing difference is speeding up winds accordingly, which in turn can also speed up the influx of water into the Arctic Ocean.

[ The Buffer has gone, feedback #14 on the Feedbacks page ]
Start of freezing period

Here's the danger. In October, Arctic sea ice is widening its extent, in line with the change of seasons. This means that less heat can escape from the Arctic Ocean to the atmosphere. Sealed off from the atmosphere by sea ice, greater mixing of heat in the water will occur down to the seafloor of the Arctic Ocean, while there is little or no ice buffer left to consume an influx of heat from the Atlantic and Pacific Oceans, increasing the danger that warm water will reach the seafloor of the Arctic Ocean and destabilize methane hydrates. 

Rising salt content of Arctic Ocean

It's not just the influx of heat that is the problem. There's also the salt. Ice will stay frozen and will not melt in freshwater until the temperature reaches 0°C (or 32°F). Ice in saltwater on the other hand will already have melted away at -2°C (or 28.4°F).

The animation of the right shows salty water rapidly flowing through the Bering Strait.

With the change of seasons, there is less rain over the Arctic Ocean. The sea ice also seals the water of the Arctic Ocean off from precipitation, so no more fresh water will be added to the Arctic Ocean due to rain falling or snow melting on the water.

In October, temperatures on land around the Arctic Ocean will have fallen below freezing point, so less fresh water will flow from glaciers and rivers into the Arctic Ocean. At that time of year, melting of sea ice has also stopped, so fresh water from melting sea ice is no longer added to the Arctic Ocean either.

Pingos and conduits. Hovland et al. (2006)
So, the Arctic Ocean is receiving less freshwater, while the influx of water from the Atlantic and Pacific Oceans is very salty. This higher salt content of the water makes it easier for ice to melt at the seafloor of the Arctic Ocean. Saltier warm water is causing ice in cracks and passages in sediments at the seafloor of the Arctic Ocean to melt, allowing methane contained in the sediment to escape.

[ click on images to enlarge ]
The image on the right, from a study by Hovland et al., shows that hydrates can exist at the end of conduits in the sediment, formed when methane did escape from such hydrates in the past. Heat can travel down such conduits relatively fast, warming up the hydrates and destabilizing them in the process, which can result in huge abrupt releases of methane.

Heat can penetrate cracks and conduits in the seafloor, destabilizing methane held in hydrates and in the form of free gas in the sediments.

Methane

peak methane levels as high as 2859 ppb
On October 2 and 7, 2018, peak methane levels were as high as 2838 ppb, respectively 2859 ppb, as the images on the right shows. Methane levels over the Beaufort Sea have been high for some time, and have remained high at very high altitudes.

The threat is that a number of tipping points are going to be crossed, including the buffer of latent heat, loss of albedo as Arctic sea ice disappears, methane releases from the seafloor and rapid melting of permafrost on land and associated decomposition of soils, resulting in additional greenhouse gases (CO₂, CH₄, N₂O and water vapor) entering the Arctic atmosphere, in a vicious self-reinforcing cycle of runaway warming.

A 10°C rise in temperature by 2026?


Above image shows how a 10°C or 18°F temperature rise from preindustrial could eventuate by 2026 (from earlier post).

The situation is dire and calls for comprehensive and effective action, as described at the Climate Plan.


Links

• Temperature Rise
https://arctic-news.blogspot.com/2017/08/temperature-rise.html

• Mean Methane Levels reach 1800 ppb
https://arctic-news.blogspot.com/2013/06/mean-methane-levels-reach-1800-ppb.html

• Why are methane levels over the Arctic Ocean high from October to March?
https://arctic-news.blogspot.com/2015/01/why-are-methane-levels-over-the-arctic-ocean-high-from-october-to-march.html

• Blue Ocean Event
https://arctic-news.blogspot.com/2018/09/blue-ocean-event.html

• Feedbacks
https://arctic-news.blogspot.com/p/feedbacks.html

• The Threat
https://arctic-news.blogspot.com/p/threat.html

• Extinction
https://arctic-news.blogspot.com/p/extinction.html

• Aerosols
https://arctic-news.blogspot.com/p/aerosols.html

• How extreme will it get?
https://arctic-news.blogspot.com/2012/07/how-extreme-will-it-get.html

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html



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Wednesday, February 19, 2014

High methane levels over the Arctic Ocean on February 17, 2014



Above image shows IASI methane readings over the last day or so, when levels as high as 2223 ppb were recorded.

Where does the methane come from?

On above image, methane shows up prominently along the faultline that crosses the Arctic Ocean from the northern tip of Greenland to the Laptev Sea. This indicates that the methane originated from the depths of the Arctic Ocean, where sediments contain large amounts of methane in the form of free gas and hydrates, which have become destabilized.

High methane concentrations have persistently shown up over the Arctic Ocean since October 1, 2013. On January 19, 2014, levels as high as 2363 ppb were recorded over the Arctic Ocean, as illustrated by the image below, from an earlier post.

[ from earlier post, click on image to enlarge ]
Below is a comparison of methane readings for the week from February 9 to 16, 2014, compared to the same period in 2013.

[ from earlier post, click on image to enlarge ]
The above comparison shows that there is a lot of methane over the Arctic Ocean that wasn't there last year. 

Furthermore, high methane readings show up where currents move the sea ice out of the Arctic Ocean, in areas such as Baffin Bay. This indicates that methane that is released from the seafloor of the Arctic Ocean appears to be moving underneath the ice along with exit currents and entering the atmosphere where the sea ice is fractured or thin enough to allow the methane to pass through. 

Also note that more orange areas show up on the southern hemisphere in 2014, indicating that more methane from the northern hemisphere is now spreading south beyond the equator. This in addition to indications that more methane is rising and building up at higher altitudes, as discussed in an earlier post.

Causes

What made these high releases from the seafloor of the Arctic Ocean persist for so long? At this time of year, one might have thought that the water in the Arctic Ocean would be much colder than it was, say, on October 1, 2013.

Actually, as the combination image below shows, sea surface temperatures have not fallen much at the center of the Arctic Ocean between early October, 2013 (left) and February 17, 2014 (right). In the area where these high methane concentrations occured, sea surface temperatures have remained the same, at about zero degrees Celsius.

[ click on image to enlarge ]
The above comparison image shows that, while surface temperatures in the Atlantic Ocean may have fallen strongly with the change of seasons, surface temperatures in the Arctic Ocean have changed only little.

In this case of course, what matters more than surface temperatures are water temperatures at greater depth. Yet, even here temperatures in the Arctic Ocean will have decreased only slightly (if at all) compared to early October 2013, since the Gulf Stream has continued to push warmer water into the Arctic, i.e. water warmer than the water in the Arctic Ocean, so the heating impact of the Gulf Stream continues. Also, sea surface temperature anomalies along the path of the Gulf Stream continue to be anomalously high, as the image below shows.


The situation looks even more grim on the Climate Reanalyzer image below, showing sea surface temperature anomalies that are far more profound in the Arctic Ocean.


Note also that, as the sea ice extent increased, there have been less opportunities for the heat to evaporate on the surface and for heat to be transferred from the Arctic Ocean to the air.

Finally, what matters a lot is salinity. The combination image below compares salinity levels between October 1, 2013 (left), and February 17, 2014 (right).

[ click on image to enlarge ]
Salinity levels were low on October 1, 2013, as a lot of ice and snow had melted in the northern summer and rivers had carried a lot of fresh water into the Arctic Ocean. After October 1, 2013, little or no melting took place, yet the Gulf Stream continued to carry waters with higher salt levels from the Atlantic Ocean into the Arctic Ocean.

Annual mean sea surface salinity
Seawater typically has a salinity level of over 3%; it freezes and melts at about −2°C (28°F). Where more saline water from the Atlantic Ocean flows into the Arctic Ocean, the water in the Arctic Ocean becomes more saline. The freezing and melting point of fresh water (i.e. zero salinity) is 0°C (or 32°F). More salinity makes frozen water more prone to melting, i.e. at temperatures lower than 0°C, or as low as −2°C.

As the salinity levels of the water on the seafloor of the Arctic Ocean increased, the ice that had until then held the methane captive in hydrates on the seafloor of the Arctic Ocean started to melt. Indeed, the areas in the Arctic Ocean where the high methane releases occurred on January 14, 2014 (top image) show several practical salinity units (psu) increase since October 1, 2013.

Higher salinity levels are showing up closer to the faultline that runs through the Arctic Ocean from the top of Greenland to the Laptev Sea.

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