Saturday, August 30, 2014

Warming waters threaten to trigger methane eruptions from Arctic Ocean seafloor

K. Tung / Univ. of Washington. (Top) Global
average surface temperatures, where black dots
are yearly averages. Two flat periods (hiatus)
are separated by rapid warming from 1976-1999.
(Middle) Observations of heat content, compared
to the average, in the north Atlantic Ocean.
(Bottom) Salinity of the seawater in the same
part of the Atlantic. Higher salinity is seen
to coincide with more ocean heat storage.
A new study looks at how, in the 21st century, surface warming slowed as more heat moved deeper into the oceans, specifically the North Atlantic.

Sun-warmed salty water travels north along ocean currents in the Atlantic. When this saltier water reaches the North Atlantic, its greater density causes it to sink. From about 1999, this current began to speed up and draw heat deeper into the ocean.

These huge amounts of heat moving deeper into the Atlantic Ocean are very worrying.

The image below shows that sea surface temperatures have reached extremely high levels on the Northern Hemisphere, where sea surface temperature anomalies as high as 1.78 degrees Celsius were recorded on August 19, 2014.

As discussed in an earlier post, water carried by the Gulf Stream below the surface can be even warmer than surface waters. As the post discusses, high sea surface temperatures west of Svalbard indicate that the Gulf Stream can carry very warm water (warmer than 16°C) at greater depths and is pushing this underneath the sea ice north of Svalbard. Similarly, warm water from greater depth comes to the surface where the Gulf Stream pushes it against the west coast of Novaya Zemlya.

Very warm water is now invading the Arctic Ocean through the Bering Strait from the Pacific Ocean, while very warm water is also traveling on the back of the Gulf Stream from the North Atlantic into the Arctic Ocean.

The danger is that this warm water will destabilize hydrates contained in sediments under the Arctic Ocean and trigger huge methane eruptions.

Rising methane levels over the past few years are ominous in this respect. The image below shows very high mean global methane levels on August 28, 2014, while methane readings as high as 2561 ppb were recorded on that day.

Methane Levels -  see earlier post for a discussion of IPCC/NOAA data

In conclusion, the situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog.

References and Related Links

- Varying planetary heat sink led to global-warming slowdown and acceleration
by Xianyao Chen and Ka-Kit Tung.

- Cause of global warming hiatus found deep in the Atlantic Ocean
University of Washington News Release

- Horrific Methane Eruptions in East Siberian Sea

- Methane Buildup in the Atmosphere

- Climate Plan blog

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