Why are methane levels over the Arctic Ocean high from October to March?

Water temperatures at different depth

Why are methane concentrations in the atmosphere over the Arctic Ocean so high from October through to March?

The image below, replotted by Leonid Yurganov from a study by Chepurin et al, shows sea water temperature at different depths in the Barents Sea.

Above image illustrates that, while Arctic sea water at the surface reaches its highest temperatures in the months from July to September, water at greater depth reaches its highest temperature in the months from October to March. Accordingly, huge amounts of methane are starting to get released from the Arctic Ocean's seafloor in October.

Surface temperatures in October

As the image below shows, temperature at 2 meters was below 0°C (32°F, i.e. the temperature at which water freezes) over most of the Arctic Ocean on October 26, 2014. The Arctic was over 6°F (3.34°C) warmer than average, and at places was up to 20°C (36°F) warmer than average.

  

Image from 'Ocean temperature rise'

At the same time, continents around the Arctic Ocean are frozen. Surface temperatures over the Arctic Ocean were higher than temperatures on land at the end of October, due to the enormous amounts of heat being transferred from the waters of the Arctic Ocean to the atmosphere. This was the result of ocean heat content, which in 2014 was the highest on record, especially in the Arctic Ocean, which also made that at that time of year the sea ice extent was still minimal in extent and especially in volume. 

Start of freezing period

In October, the Arctic Ocean typically freezes over, so less heat will from then on be able to escape 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.

Less fresh water added to 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. 

Rising salt content

As addition of fresh water ends, the salt content of the water in the Arctic Ocean starts to rise accordingly, while the Gulf Stream continues to push salty water into the Arctic Ocean. The higher salt content of the water makes it easier for ice to melt at the seafloor of the Arctic Ocean. Saltier water causes ice in cracks and passages in sediments at the seafloor of the Arctic Ocean to melt, allowing methane contained in the sediment to escape. 

Pingos and conduits. Hovland et al. (2006)

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.

Less hydroxyl in atmosphere

Besides heat, open water also transfers more moisture to the air. The greater presence of sea ice from October onward acts as a seal, making that less moisture will evaporate from the water. Less moisture evaporating, together with the change of seasons (i.e. less sunshine) results in lower hydroxyl levels in the atmosphere at the higher latitudes of the Northern Hemisphere, in turn resulting in less methane being broken down in the atmosphere over the Arctic.

Gulf Stream

Malcolm Light writes in this and this earlier posts that the volume transport of the Gulf Stream has increased by three times since the 1940's, due to the rising atmospheric pressure difference set up between the polluted, greenhouse gas rich air above North America and the marine Atlantic Air. 

The increasingly heated Gulf Stream with its associated high winds and energy rich weather systems then flows NE to Europe where it is increasingly pummeling Great Britain with catastrophic storms, as also described in this earlier post, which adds that faster winds means more water evaporation, and warmer air holds more water vapor, so this can result in huge rainstorms that can rapidly devastate the integrity of the ice. The image below further illustrates the danger of strong winds over the North Atlantic reaching the Arctic.

Branches of the Gulf Stream then enter the Arctic and disassociate the subsea Arctic methane hydrate seals on subsea and deep high - pressure mantle methane reservoirs below the Eurasian Basin - Laptev Sea transition. This is releasing increasing amounts of methane into the atmosphere where they contribute to anomalously high local temperatures, greater than 20°C above average.

From: The Biggest Story of 2013

Emissions from North America are - due to the Coriolis effect - moving over areas off the North American coast in the path of the Gulf Stream (see animation on the right).

The Gulf Stream reaches its maximum temperatures off the North American coast in July. It can take almost four months for this heat to travel along the Gulf Coast and reach the Arctic Ocean, i.e. water warmed up off Florida in early July may only reach waters beyond Svalbard by the end of October.

Waters close to Svalbard reached temperatures as high as 63.5°F (17.5°C) on September 1, 2014 (green circle). The image below shows sea surface temperatures only - at greater depths (say about 300 m), the Gulf Stream can push even warmer water through the Greenland Sea than temperatures at the sea surface.

Since the passage west of Svalbard is rather shallow, a lot of this very warm water comes to the surface at that spot, resulting in an anomaly of 11.9°C. The high sea surface temperatures west of Svalbard thus show that the Gulf Stream can carry very warm water (warmer than 17°C) at greater depths and is pushing this underneath the sea ice north of Svalbard.

from: Causes of high methane levels over Arctic Ocean 

Through to March the following year, salty and warm water (i.e. warmer than water that is present in the Arctic Ocean) will continue to be carried by the Gulf Stream into the Arctic Ocean, while the sea ice will keep the water sealed off from the atmosphere, so little heat and moisture will be able to be transferred to the atmosphere. 

Start of melting period

This situation continues until March, when the sea ice starts to retreat and more hydroxyl starts getting produced in the atmosphere. Increased sea ice melt and glaciers melt, the latter resulting in warmer water flowing into the Arctic Ocean from rivers, will cause salinity levels in the Arctic Ocean to fall, in turn causing methane levels to fall in the atmosphere over the Arctic Ocean. Furthermore, the water traveling along the Gulf Stream and arriving in the Arctic Ocean in March will be relatively cold.  

References


- Chepurin, G.A., and J.A. Carton, 2012: Sub-arctic and Arctic sea surface temperature and its relation to ocean heat content 1982-2010, J. Geophys. Res.-Oceans., 117, C06019, DOI: 10.1029/2011JC007770. http://onlinelibrary.wiley.com/doi/10.1029/2011JC007770/abstract 

- Combination image created by Sam Carana with Climate Reanalyzer, from: Temperature Rise, http://arctic-news.blogspot.com/2014/10/ocean-temperature-rise.html 

- Submarine pingoes: Indicators of shallow gas hydrates in a pockmark at Nyegga, Norwegian Sea, by Martin Hovland and Henrik Svensen (2006) http://www.sciencedirect.com/science/article/pii/S0025322705003968

- Sea surface temperature west of Svalbard,
created by Sam Carana with
http://earth.nullschool.net

Post by Sam Carana.

Causes of high methane levels over Arctic Ocean

Methane levels in the atmosphere over the Arctic Ocean are very high, as illustrated by the image below, by Leonid Yurganov, showing IASI methane readings for October 11-20, 2013.

Previous posts have discussed these high levels of methane, pointing at links between high methane levels over Arctic Ocean and earthquakes and volcanic activity.

Malcolm Light points at another factor that is contributing to the high methane levels observed over the Arctic Ocean in October 2013.

Malcolm says: The massive methane release in the Arctic this October is partly because the Gulf Stream waters got massive heating in the Atlantic off the North American coast in July. It takes the Gulf Stream currents almost 4 months to reach the emission sites along the southern side and end of the Eurasian Basin. This combined with the earthquake activity along the Gakkel Ridge and deep pyroclastic eruptions is escalating the rate of methane release by destabilizing the submarine Arctic methane hydrates at increasing rates.

The NOAA image below shows temperature anomalies for July 2013. NOAA adds that in July 2013 many regions were much warmer than average, with part of the northeastern Atlantic off the coast of North America observing record warmth.

The image below shows how water traveling along the Gulf Stream ends up in the Arctic Ocean. Water in the Gulf Stream travels at 4 miles per hour, but slows down to less than 1 mile per hour in the North-Atlantic Current. This means that water warmed up off Florida in July will start reaching waters beyond Svalbard in October.

The image below, from Malcolm Light's September 2012 post Further Confirmation of a Probable Arctic Sea Ice Loss by Late 2015, shows how warm water flows into the Arctic Ocean and warms up methane hydrates and free gas held in sediments under the Arctic Ocean.

 The image below shows the methane readings over the past few days on the Northern Hemisphere.

More on Wildfires

Previous posts have highlighted the huge amounts of carbon dioxide, methane and soot being emitted as a result of wildfires. Apart from this, there are further important pollutants to consider in regard to their potential to contribute to warming, especially at high latitudes.

The image below, dated August 7, 2013, and kindly supplied by Leonid Yurganov, shows high levels of carbon monoxide as a result of wildfires in Siberia, reaching high up into the Arctic all the way to Greenland. 

[ click on image to enlarge ]

Formation of tropospheric ozone mostly occurs when nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds (VOCs) react in the atmosphere in the presence of sunlight. NOx, CO, and VOCs are therefore called ozone precursors. Apart from a health hazard, tropospheric ozone is an important greenhouse gas. Furthermore, carbon monoxide emissions contribute to hydroxyl depletion, thus extending the lifetime of methane.

While there appears to be little or no carbon dioxide from wildfires over North America on the above August 7 image, there are many recent wildfires raging over the North American continent, as illustrated by the August 12 map below, from Wunderground. 

[ click on image to enlarge ]

This point is illustrated even better on the image below [added later, ed.] showing a composite image with carbon monoxide over July 3-13, 2013. Carbon monoxide resulting from wildfires in Canada is seen crossing the Atlantic Ocean, due to the Coriolis effect, as well as reaching Greenland in large amounts.

[ click on image to enlarge ]

Related

- Wildfires even more damaging
http://arctic-news.blogspot.com/2013/07/wildfires-even-more-damaging.html

- The Threat of Wildfires in the North
http://arctic-news.blogspot.com/2013/06/the-threat-of-wildfires-in-the-north.html

- Wildfires in Canada affect the Arctic
http://arctic-news.blogspot.com/2013/07/wildfires-in-canada-affect-the-arctic.html

Arctic satellite thermal infrared CH4 data compared to surface in-situ and total column measurements

Leonid Yurganov, Senior Research Scientist,
Joint Center for Earth Systems Technology,
University of Maryland Baltimore County

Below an abstract of a paper written by Leonid Yurganov, Xiaozhen Xiong and Ira Liefer, and submitted for presentation at the AGU-Fall meeting 2013.

ABSTRACT: The trace gas sensitivity of Thermal InfraRed (TIR) sounders (AIRS, IASI, TANSO) is greatest in the middle and upper troposphere; though, lower troposphere (1-2 km of altitude) sensitivity is less but not negligible. As a result, where methane largely is constrained to the lower troposphere, as is common in the Arctic particularly the marine Arctic, retrievals from these instruments provides important synoptic data on high latitude methane sources. Low Arctic water vapor content favors a better sensitivity to methane as well: H2O is the main absorber in the 7.8 micrometers spectral region.

Both AIRS/Aqua v6 (NASA) and IASI/Metop-A (NOAA/NESDIS/CLASS retrievals) methane data averaged over 0-4 km altitude clearly demonstrate increased methane concentrations over the Barents and Norwegian Seas (BNS) with seasonal maximum in December - March. Similar increases are observed over the Kara, Laptev, and Chukchi Seas for September-November, i.e. during the period of minimum ice cover over the Arctic (Figures 1 and 2). Comparison of a long series of AIRS data with in situ methane concentrations at the Zeppelin NILU observatory (Svalbard) show good agreement both in amplitude and phase of seasonal variations. Agreement with Barrow NOAA continuous methane in situ data is much worse, which likely results from lower thermal contrast in winter over the cold and icy surfaces of the Eastern Arctic. Further surface validation is by a comparison of total methane columns with the Sun-Tracking FTIR at Ny-Alesund, Svalbard (TCCON network).

These analyses demonstrate that TIR satellites are capable of detecting Arctic methane enhancements from space, particularly over relatively warm year-round water surfaces such as the BNS. Ongoing research is addressing further verification of retrieved methane columns by collecting data with a cavity ring-down spectroscopy analyzer for methane and carbon dioxide on board of the Russian Research Vessel Akademik Fedorov during the expedition NABOS-2013. Data will be collected to measure marine methane concentrations and vertical fluxes between Norway and the Eastern Arctic (New Siberian Islands) between 20 August and 23 September, 2013.

Figure 1

Figure 2. methane concentrations over the Barents and Norwegian Seas (BNS), over the Kara, Laptev, and East Siberian Seas, and over Eurasia (between 50 and 70 degrees North)

Record Methane in Arctic early March 2013

The image below, produced by Dr. Leonid Yurganov, shows methane levels for the first ten days of March 2013.

Methane levels for this period are at record highs in the Barents and Norwegian Seas, i.e. the highest levels ever recorded by IASI, which is is short for Infrared Atmospheric Sounding Interferometer, a Fourier transform spectrometer on board the European EUMETSAT Metop satellite that has supplied data since 2007.

The record levels are indicated on the image below at the top right, while the geographical location of the four domains distinguished in the image are illustrated on the image further below.

The image at the top of this post displays average methane levels for the period March 1 to 10, 2013, at 600 mb. On individual days and on specific locations, methane levels could be much higher, as illustrated by the NOAA image below showing methane levels reaching a high of 2237 ppb on March 6, 2013, at 742 mb. The empty image further below is added to help distinguish land contours.

The earlier post Dramatic increase in methane in the Arctic in January 2013 showed that high methane levels lined up closely with the contours of land and sea ice. The same is the case for the record levels of methane in early March, as illustrated by the animation below.

Overview of IASI methane levels

Dr. Leonid Yurganov kindly shared an overview of his analysis of IASI methane levels over the years.

The overview shows a marked difference between methane levels in the Arctic and methane levels at lower altitudes, i.e. between 40 and 50 degrees North. Furthermore, the overview shows a steady increase in methane levels over the years, both at high latitudes and at lower latitudes. Over the Arctic, mean levels of well over 1900 ppb are now common.

The overview gives the mean values for methane levels. Peaks can be much higher. Levels of up to 2241 ppb were registered above the Arctic at 742 mb on January 23, 2013 (see earlier post). Moreover, high levels are registered over a wide area, particularly over the Barents Sea and the Norwegian Sea, which are currently free of sea ice (see earlier post), indicating worrying releases of methane from the seabed in that area.

How much extra methane is released to account for this rise in methane levels? Dr. Yurganov explains: “this may be a relatively slow process, 7 ppb per month for the area between Norway and Svalbard means only 0.3 Tg per month. But in a longer time scale (at least several years) and inclusion of the autumn Kara/Laptev emissions it might be very important both for the methane cycle and for the climate. Further discussion promises to be fruitful”.

Dr. Yurganov plans to update his overview on completion of further analysis of existing data of IASI methane levels for earlier periods, and complemented with further periods in future as the data come along.

Meanwhile, we'll keep a close eye on methane levels in the Arctic, particularly given the prospect that large areas of the Arctic Ocean (Kara Sea, Laptev Sea and East Siberian Sea) will soon become free of sea ice. Further people analyzing methane levels are invited to also comment on the situation in the Arctic.

Dramatic increase in methane in the Arctic in January 2013

Below a combination of images produced by Dr. Leonid Yurganov, showing methane levels January 1-10, 2013 (below left), January 11-20, 2013 (below center) and January 21-31, 2013 (below right).

Click on image to enlarge

Above image shows dramatic increases of methane levels above the Arctic Ocean in the course of January 2013 in a large area north of Norway.

Why are these high levels of methane showing up there? To further examine this, let's have a look at where the highest sea ice concentrations are. The image below shows sea ice concentrations for January 2013, from the National Snow and Ice data Center (NSIDC).

Overlaying methane measurements with sea ice concentrations shows that the highest levels of methane coincide with areas in the Arctic Ocean without sea ice. This is shown on the animation below, which is a 1.84 MB file that may take some time to fully load.

High methane levels persist in January 2013

Below a combination of images produced by Dr. Leonid Yurganov, comparing methane levels between January 1-10, 2012 (below left), and January 1-10, 2013 (below right).

The 2013 image shows worryingly high levels of methane between Norway and Svalbard, an area where hydrate destabilization is known to have occurred over the past few years. Even more worrying is the combination of images below. Methane levels came down January 11-20, 2012, but for the same period in 2013, they have risen. 

On January 21, 2013, as shown on the image below, methane levels of up to 2234 ppb were recorded at 892 mb. Further examination indicated that this was caused by large releases of methane above North-Africa, apparently associated with the terrorist attack on the natural gas plant in Algeria.  An image without data is added underneath, to better distinguish locations on the map. 

It didn't take long for even higher methane levels to be reached above the Arctic. The NOAA image below shows methane levels of up to 2241 ppb above the Arctic at 742 mb on January 23, 2013. 

Below a NOAA image with temperature anomalies for January 7, 2013, when a huge area of the Arctic experienced anomalies of over 20 degrees Celsius, including a large area close to Svalbard. 

Temperatures change daily, as the wind changes direction and as sea currents keep the water moving around the Arctic Ocean. For an area close to Svalbard, the recent 30-day temperature anomalies is over 20 degrees Celsius, as shown on the NOAA image below, and this indicates persistently high temperature anomalies for that area. 

Below, a NOAA image showing sea surface temperature anomalies up to 5 degrees Celsius close to Svalbard.

Related

- High methane levels persist in December 2012
- Methane contributes to accelerated warming in the Arctic

High methane levels persist in December 2012

The image below was posted earlier at Methane contributes to accelerated warming in the Arctic. As mentioned there, this is a compilation of images produced by Dr. Leonid Yurganov, comparing methane levels between November 21-30, 2008 (below left), and November 21-30, 2012 (below right).

Dr. Yurganov has released two further images this year, i.e. for December 1-10, 2012 (below left), and for December 11-20, 2012 (below right).

The images show that the highest methane levels show up above the water, as opposed to above land, indicating that methane is being released from the seabed across the Arctic. The images further show that high levels of methane persist in December 2012.

Apart from comparing 10-day periods, we can also look at methane levels for individual days. The NOAA image below shows methane levels up to 2167 ppb on December 27, 2012, for the morning set of measurements.

To better see where the high (yellow) levels of methane were measured, a map with empty data is added below, showing the location of the continents more clearly on the map.

Pressure levels at which measurements are taken are displayed in hectopascals (symbol hPa) which are numerically equivalent to millibars (mb). A pressure of 600 mb (or hPa) corresponds with an altitude of 13794.9 ft (4204.7 m). By comparison, air pressure at mean sea level is 1013.25 hPa (millibar), or 29.92 inches of mercury.

The map below, from apocalypse4realmethane2012, shows methane measurements taken on the same day (December 27, 2012, morning set), but at 718 mb, which corresponds with an altitude that is a bit closer down to sea level. The map focuses on the Arctic and shows geographic names. If you like, click on the map to enlarge it.

Methane measurements were taken with the IASI (Infrared Atmospheric Sounding Interferometer) instrument, fitted onto the European Space Agencys (ESA) MetOp series of polar orbiting satellites.

For further analysis, the NOAA image with surface temperature anomalies for December 28, 2012, is added above, showing anomalies up to 20 degrees Celsius. Furthermore, the NOAA image with sea surface temperature anomalies for December 27, 2012, is added below, showing anomalies up to 5 degrees Celsius.

Methane contributes to accelerated warming in the Arctic

Above combination image featured earlier in the post Striking increase of methane in the Arctic. The images were produced by Dr. Leonid Yurganov, Senior Research Scientist, JCET, UMBC, who presented his findings at the AGU Fall Meeting 2012. The image below gives an update for 2012, showing an image with methane levels at 600 hPa.

Temperature anomalies on the inset on above image are averages for the full month November, whereas the methane levels displayed on the left are for the first ten days of November only. Using temperature maps for the same periods in such comparisons may result in even more striking simularities between methane levels and temperatures. For a more complete picture, further comparisons between November 2008 and November 2012 are added, for days 11-20 (below),

and for days 21-30 (below).

The images show that the highest methane levels show up above the water, as opposed to above land, indicating that methane is being released from the seabed across the Arctic.

Temperatures have meanwhile changed. In November 2012, there were high temperature anomalies in east Siberia. There now are very low temperatures throughout Siberia, as illustrated by the Wunderground map below, which shows high temperatures. Temperatures as low as -60.5°F (-51.4°C) were recorded in Susuman, east Siberia, both on December 13th and 17th, 2012.

The now hugely deformed polar jet stream and high levels of methane in the Arctic are only two out of numerous feedbacks that contribute to accelerate warming in the Arctic. Without rapid action, we can expect such wild swings in temperature to get even worse, making more extreme weather the new norm.

Striking increase of methane in the Arctic

Click on image to enlarge

Dr. Leonid Yurganov, Senior Research Scientist, JCET, UMBC, and member of AMEG, produced the above images with IASI/METOP satellite data (EUMETSAT).

The images show methane levels for 2008, 1-10 November, and for 2011, 1-10 November.

The images show a striking increase of methane over the shelf areas of the Arctic Ocean.

For reference, the image on the right is added, showing predicted methane hydrates, as published by WWF with surface temperature hotspots added.

Dr. Yurganov points at the threat of large emissions of methane from clathrates (methane hydrates) in the Arctic, and urges others to support his proposals for further satellite methane monitoring.

Current growth of methane is being monitored by the Atmospheric Infrared Sounder (AIRS) facility on NASA's Aqua satellite.

Dr. Yurganov has been using AIRS data for years and points at an image he produced using AIRS data. The image shows that, during the autumn of 2011, the anomaly in the Northern Hemisphere was substantially larger than the anomaly in the Southern Hemisphere.
ftp://asl.umbc.edu/pub/yurganov/methane/AIRS_CH4_2002-2012.pdf

Monthly mean maps of methane are available at Dr. Yurganov's website. The maps have been produced using AIRS data since 2002 up to now, for both the Northern Hemisphere and the Southern Hemisphere. The maps are at:
ftp://asl.umbc.edu/pub/yurganov/methane/MAPS/

Comparisons with other instruments for the Arctic are still few or lacking. Examples are for TANSO, May-November, 2010:
ftp://asl.umbc.edu/pub/yurganov/methane/MAPS/TANSO_2010day&night.jpg

Methane levels for March 2012 are highest above ESAS

NASA has made available the monthly methane levels for March 2012. As the polar projection below shows, extremely high levels of methane are concentrated above the East Siberian Arctic Shelf (ESAS).

The image below further shows how the anomalies have increased over the years, especially on the Northern Hemisphere; note the wide gaps between anomalies on the Northern Hemisphere (blue) and the Southern Hemisphere (green) over the past few months. 

The images, based on AIRS NASA data, were produced by Dr. Leonid Yurganov, Senior Research Scientist, JCET, at University of Maryland - Baltimore County. For further images, see Dr. Yurganov's archive at asl.umbc.edu/pub/yurganov/methane