Methane levels in the Arctic

High methane levels over the 

Arctic Ocean on February 17, 

2014

Arctic News,

19 February, 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. 

Furthermore, 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.


Quantities

These high levels of methane showing up over the Arctic Ocean constitute only part of the methane that did escape from the seafloor of the Arctic Ocean. Where these high concentrations did show up, the ocean can be thousands of meters deep, giving microbes plenty of opportunity to decompose methane rising through the water first. Furthermore, the methane has to pass through sea ice that is now getting more than one meter thick in the area where these high levels of methane showed up on satellite records. In conclusion, the quantities of methane that were actually released from the seafloor must have been huge.

Importantly, these are not one-off releases, such as could be the case when hydrates get destabilized by an earthquake. As the Arctic-news blog has documented, high releases from the seafloor of the Arctic Ocean have been showing up persistently since early October 2013, i.e. 4½ months ago. This blog has warned about the threat for years. This blog has also described in detail the mechanisms that are causing these releases and the unfolding climate catastrophe that looks set to become more devastating every year. The poster below illustrates the danger.

[ click on image to enlarge - note that this is a 4.9 MB file that may take some time to fully load ]

Impacts and Response

Huge releases from the seafloor of the Arctic Ocean have occurred persistently since early October 2013, even when releases like this may show up for one day in one area without showing up in that same area the next day on satellite images.

This apparent 'disappearance' can be due to the Coriolis effect that appears to move the methane, whereas it is in fact the Earth that is spinning underneath the methane. This doesn't mean that the methane had disappeared. Actually, much of this methane will persist over the Arctic for many years to come and will continue to exercize its very high initial warming potential over the Arctic for years.

Furthermore, even if less methane may show up on satellite images the next day, that doesn't necessarily mean that releases from the seafloor has stopped. Instead, it looks like methane is being released continuously from destabilizing hydrates. The methane may accumulate underneath the sea ice for some time, to burst through at a moment when fractures or ruptures occur in the sea ice, due to changes in wind and wave height.

Methane released from the Arctic Ocean seafloor has contributed to high surface temperature anomalies over the Arctic Ocean in a number of ways. As a potent greenhouse gas, methane is trapping heat that would otherwise radiate into space. Furthermore, methane rising through the sea ice reduces growth of the sea ice.

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The danger is that methane will further warm up the air over the Arctic, causing further weakening of the Jet Stream and further extreme weather events, particularly extreme warming of water all the way along the path of the Gulf Stream from the Atlantic Ocean into the Arctic Ocean, in turn triggering further releases from hydrates at the seafloor of the Arctic Ocean and escalating into runaway global warming. This threat calls for comprehensive and effective action, such as described at theClimatePlan blog