Arctic News: latent heat

Showing posts with label latent heat. Show all posts

Friday, July 13, 2018

Disappearance of Arctic Sea Ice

The image on the right shows sea surface temperatures on July 6 for the years 2014 to 2018 at a location near Svalbard (at 77.958°N, 5.545°E), with an exponential trend added based on the data.

The combination image below shows sea surface temperatures on July 6 for each of these years, with the location highlighted by a green circle:
2014: -0.8°C or 30.6°F
2015: 6.2°C or 43.2°F
2016: 8.3°C or 47.0°F
2017: 14.4°C or 57.9°F
2018: 16.6°C or 61.9°F

The situation reflects the rapid decline of Arctic sea ice over the years and constitutes a stark warning of imminent sea ice collapse and its consequences for the world at large.

[ click on images to enlarge ]

The image on the right shows the sea surface temperature on July 18, 2018, at that location. It was as warm as 17.2°C or 63°F near Svalbard. This compares to a sea surface temperature of 5°C or 41.1°F in 1981-2011 at that location (at the green circle). For more background on the warm water near Svalbard, also see the earlier post Accelerating Warming of the Arctic Ocean.

The images illustrate why sea ice has fallen dramatically in volume, especially so where sea currents push warm water from the Atlantic Ocean underneath the sea ice.

The decline of Arctic sea ice volume over the years is illustrated by the Jim Pettit graph below.

As the Wipneus image below shows, Arctic sea ice volume on July 9, 2018, was at a record low for the time of the year.

The animation on the right shows a fall in volume of some 1 meter over most of the sea ice, over the period from June 21 through July 12, 2018, with a further eight days of forecasts added.

The animation illustrates the huge amount of melting taking place from underneath, due to an inflow of heat from the Atlantic Ocean and the Pacific Ocean, and from warm water from rivers that end in the Arctic Ocean. Meanwhile, sea ice extent doesn't fall very much at all.

When only looking at sea ice extent, the dramatic fall in sea ice volume may be overlooked.

Complete disappearance of Arctic sea ice in September 2018 is within the margins of a trend based on yearly annual minimum volume, as illustrated by the image on the right.

Latent heat can make such disappearance come abruptly and - for people who only look at changes in extent - rather unexpectedly.

Latent heat is energy associated with a phase change, such as the energy absorbed by solid ice when it changes into water (melting). During a phase change, the temperature remains constant.

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.

Oceans take up over 90% of global warming, as illustrated by the image below. Ocean currents make that huge amounts of this heat keep entering the Arctic Ocean from the Pacific Ocean and the Atlantic Ocean.

Once the sea ice is gone, further ocean heat must go elsewhere, i.e. it will typically raise the temperature of the water. The atmosphere will also warm up faster. More evaporation will also occur once the sea ice is gone, which will cool the sea surface and warm up the atmosphere (technically know as latent heat of vaporization).

As temperatures in the Arctic are rising faster than at the Equator, the Jet Stream will change, making it easier for warm air to enter the Arctic. More clouds will form over the Arctic, which will reflect more sunlight into space, but which will also make that less outward IR radiation can escape into space over the Arctic, with a net warming effect.

Meanwhile, El Niño is getting stronger, as illustrated by above image on the right. A warmer Arctic comes with stronger heat waves, forest fires and associated emissions, and rapid warming of water in rivers that end in the Arctic Ocean, all of which will further warm up the Arctic Ocean. Forest fires have already been burning strongly in Siberia over the past few months and methane recently reached levels as high as 2817 ppb (on July 8, 2018, pm).

One huge danger is that, as the buffer disappears that until now has consumed huge amounts of ocean heat, and the Arctic Ocean keeps warming, further heat will reach methane hydrates at the seafloor of the Arctic Ocean, causing them to get destabilized and release methane.

[ The Buffer has gone, feedback #14 on the Feedbacks page ]

Additionally, disappearance of the sea ice will come with albedo changes that mean that a lot more sunlight will be absorbed, instead of getting reflected back into space as occurred previously.

Similar albedo changes are likely to take place over land in the Arctic soon thereafter. Adding up all warming elements associated with disappearance of the sea ice can result in an additional global warming of several degrees Celsius.

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

Links

• Can we weather the Danger Zone?
https://arctic-news.blogspot.com/2018/07/can-we-weather-the-danger-zone.html

• How much warmer is it now?
https://arctic-news.blogspot.com/2018/04/how-much-warmer-is-it-now.html

• Accelerating Warming of the Arctic Ocean
https://arctic-news.blogspot.com/2016/12/accelerating-warming-of-the-arctic-ocean.html

• High Temperatures Over Arctic Ocean In June 2018
https://arctic-news.blogspot.com/2018/06/high-temperatures-over-arctic-ocean-in-june-2018.html

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

• Latent Heat
https://arctic-news.blogspot.com/p/latent-heat.html

• How much warming have humans caused?
https://arctic-news.blogspot.com/2016/05/how-much-warming-have-humans-caused.html

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

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

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

Monday, June 16, 2014

Warming of the Arctic Fueling Extreme Weather

Extreme weather

Heavy rains and floods hit Serbia and Bosnia in May 2014, as discussed in an earlier post.

Later in May, further flooding hit central Europe. From May 30 to June 1, 2014, parts of Austria received the amount of rain that normally falls in two-and-half months: 150 to 200 mm (5.9 to 7.9"), with some parts experiencing 250 mm (9.8").

What is fueling this extreme weather? Have a look at the image below.

The image shows a number of feedbacks that are accelerating warming in the Arctic. Feedback #14 refers to (latent) heat that previously went into melting. With the demise of the snow and ice cover, an increasing proportion of this heat gets absorbed and contributes to accelerated warming in the Arctic.

As the sea ice heats up, 2.06 J/g of heat goes into every degree Celsius that the temperature of the ice rises. While the ice is melting, all energy (at 334J/g) goes into changing ice into water and the temperature remains at 0°C (273.15K, 32°F).

Once all ice has turned into water, all subsequent heat goes into heating up the water, at 4.18 J/g for every degree Celsius that the temperature of water rises.

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. The energy required to melt a volume of ice can raise the temperature of the same volume of rock by 150º C.

Currently, the energy equivalent of 1.5 million Hiroshima bombs goes into melting of the Arctic sea ice each year, according to calculations by Sam Carana.

As the ice disappears, this energy will instead be absorbed elsewhere and cause temperatures in the Arctic to rise further, indicated as feedback #14.

This comes on top of the albedo feedback #1 that can on its own more than double the net radiative forcing resulting from the emissions caused by all people of the world, according to calculations by Prof. Peter Wadhams.

Further feedbacks include changes to the polar vortex and jet stream that are in turn causing more extreme weather, as also described in the earlier post Feedbacks in the Arctic.

Global Warming

Higher levels of greenhouse gases are trapping more heat in the atmosphere, resulting in more intense heatwaves in some places, while stronger winds and greater evaporation of water from the sea lead to stronger rainfall in other places. Global warming thus contributes to more extreme weather around the globe.

The Arctic is hit not only by the warming resulting from greenhouse gas emissions, but also by emissions of soot, dust and other compounds that settle on the snow and ice cover and speed up its demise.

As illustrated by the image below, by Nuccitelli et al., most heat goes into the oceans. A substantial amount of heat also goes into the melting of ice.

A lot of ocean heat is transported by the Gulf Stream into the Arctic Ocean. The North Atlantic is hit particularly strongly by pollution from North America, as illustrated by the image below.

[ screenshot from Perdue University's Vulcan animation ]

Heat carried by the Gulf Stream into the Arctic Ocean contributes to high sea surface anomalies in the Arctic, as illustrated by the image below. Arctic sea ice is under threat from heat from the North Atlantic, while heat from the Pacific Ocean that was in part caused by pollution from east-Asia is now threatening to enter the Arctic Ocean through the Bering Strait, as illustrated by the image below that shows areas with sea surface temperature anomalies well over 8 degrees Celsius.

[ click on image to enlarge ]

Warmer water in the Arctic Ocean in turn causes methane to be released from the seafloor of the Arctic Ocean, as discussed further below.

Accelerated Warming in the Arctic

As said, warming hits the Arctic particularly strongly due to feedbacks such as albedo changes caused by the demise of the snow and ice cover in the Arctic. Another feedback is a changing jet stream. The jet stream used to circumnavigate the globe at high speed, separating climate systems that used to be vastly different above and below the jet stream. Accelerated warming in the Arctic is decreasing the temperature difference between the Arctic and the Equator, in turn causing the jet stream to slow down and become wavier. As a result, air can more easily move north to south and visa versa, especially when the jet stream's waves expand vertically and take a long time to move from west to east (i.e. a blocking pattern).

These changes to the jet stream are fueling extreme weather events. In the May/June event, a large loop had developed in the jet stream over Europe and got stuck in place, making a strong southerly wind carry moisture-laden air from the Mediterranean Sea over Central Europe, clashing with colder air flowing down from the north as the jet stream was stuck in such a blocking pattern.

Record May heat hit northern Finland and surrounding regions of Russia and Sweden. Earlier in May (on May 19) an all-time national heat record was set of 91.4°F (33.0°C) in St. Petersburg, Russia, slashing the previous record by a wide margin. This temperature was unprecedented in records in St. Petersburg that started in 1881 and show a previous May record set in 1958 of 87.6°F (30.9°C).

The compilation below shows the jet stream on three days (May 24, 25 and 27), on top of surface temperature anomalies for those days.

[ click on image to enlarge ]

Further illustrating the event is the animation below, showing the jet stream from May 26 to June 11, 2014. Note that this is a 14.5 MB file that may take some time to fully load.

[ click on image to enlarge ]

Methane

Huge methane emissions took place from the seafloor of the Arctic Ocean from September 2013 to March 2014. These emissions have meanwhile risen up higher in the atmosphere and have moved closer to the equator.

Compared to June 2013, mean methane levels at higher altitudes are now well over 10 ppb higher at higher altitudes while there has been only little change closer to the ground. Since these mean levels are global means, the difference is even more pronounced at specific locations on the Northern hemisphere, where clouds of methane originating from the Arctic are contributing to the occurence of heat waves.

The contribution of methane to such heatwaves depends on the density of the methane at the time in the atmosphere over the location during such events.

Highest global mean methane levels varied from 1907 ppb to 1812 ppb for the period June 6 to 15, 2014, as illustrated by the image on the right, and peak methane concentration varied a lot from day to day. On June 6, 2014, peak readings as high as 2516 ppb were recorded.

Indicative for what can be the result is the temperature anomaly on May 19, when temperatures went up as high as 91.4°F (33.0°C) in St. Petersburg, Russia, slashing the previous record by a wide margin, of more than 2°C, as described above

Conclusion

The situation is the Arctic is threatening to escalate into runaway warming and urgently requires comprehensive and effective action as discussed at the Climate Plan blog.

References

- May 2014 Global Weather Extremes Summary

http://www.wunderground.com/blog/weatherhistorian/comment.html?entrynum=281

Post by Sam Carana.