Arctic News: isostatic

Showing posts with label isostatic. Show all posts

Sunday, May 14, 2017

Earthquake east of Greenland triggers methane releases

An earthquake with a magnitude of M 4.5 on the Richter scale hit the seafloor 204 km East of Nord, Greenland, on May 8, 2017 at 04:48:53 (UTC). Location: 81.684°N 5.076°W. Depth: 10.0 km.

The inset shows that methane levels over 1950 ppb (magenta color) were recorded on the morning of May 8, 2017, by two satellites.

This is a reminder that earthquakes can destabilize methane hydrates, which can hold huge amounts of methane in sediments at the seafloor of the Arctic Ocean. As temperatures keep rising, snow and ice on Greenland and Svalbard keeps melting, taking away weight from the surface, making that isostatic rebound can increasingly trigger earthquakes on the faultline that crosses the Arctic Ocean.

Methane releases have followed earthquakes in the Arctic before, e.g. see this 2016 post, illustrating the danger of potentially huge methane releases in case of larger earthquakes in the Arctic.

Why is methane so important again? Below follow some images from the methane page.

Over a 10-year timescale, methane emissions cause more warming than carbon dioxide emissions, as illustrated by the graph in the left-hand panel of above image.

Methane levels fluctuate with the time of year, higher mean levels are typically reached in September.

On September 14, 2016, methane levels at 367 mb were as high as 2697 ppb (locally), while global mean methane level was as high as 1865 ppb (above image).

On May 13, 2017, am, global mean methane levels were as high as 1844 ppb at altitudes corresponding to 383mb to 469 mb (MetOp-1 satellite), while local levels as high as 2485 ppb were recorded.

Methane levels have risen 256% from 1750 to 2015, as illustrated by the image on the right.

Growth in methane levels has been accelerating recently. Contained in existing data is a trend indicating that methane levels could increase by a third by 2030 and could almost double by 2040, as illustrated by the image below.

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

Links

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

• High Methane Levels Follow Earthquake in Arctic Ocean
https://arctic-news.blogspot.com/2016/07/high-methane-levels-follow-earthquake-in-arctic-ocean.html

• Methane
https://arctic-news.blogspot.com/p/methane.html

Monday, January 9, 2017

Canadian Arctic Archipelago Hit By M5.8 Earthquake

An earthquake with a magnitude of 5.8 on the Richter scale hit the Canadian Arctic Archipelago on January 8, 2017.

Above image was created with USGS (United States Geological Survey) content. The image shows the epicenter of the quake (gold star). The earthquake hit Barrow Strait on January 8, 2017 at 23:47:12 (UTC), at 74.320°N - 92.305°W and at a depth of 18.9 km.

Another earthquake hit Barrow Strait on January 9, 2017, this time with a magnitude of 5.2 on the Richter scale, within a day of the earlier M5.8 quake (both in orange on map below). These two earthquakes are among the largest quakes to hit the area in the past five years (map area shows all M1+ quakes since January 9, 2012).

These earthquakes are important, given their magnitude and given that they hit an area without large faultlines (though earthquakes are not uncommon here, also see this discussion). Importantly, these earthquakes occurred in an area prone to glacial isostatic adjustment, as illustrated by the image below.

From "http://grace.jpl.nasa.gov", (unfiltered version). Credit: A, G., J. Wahr, and S. Zhong (2013) "Computations
of the viscoelastic response of a 3-D compressible Earth to surface loading: an application to Glacial Isostatic
Adjustment in Antarctica and Canada", Geophys. J. Int., 192, 557–572, doi: 10.1093/gji/ggs030

Glacial isostatic adjustment as a phenomenon typically takes place over relatively long periods. Yet, extreme weather events can trigger earthquakes in areas that are already on the edge.

The extreme weather situation is depicted by the combination image below.

Similar to the M4.6 earthquake that hit Baffin Island on February 12, 2015, this earthquake occurred at a time when surface temperature anomalies over parts of North America and Greenland were at the bottom end of the scale. At the same time, temperature anomalies over the Arctic Ocean are at the top end of the scale, as illustrated by the left panel in above image. The right panel in above image shows pressure differences reaching the top and bottom ends of the scale.

Earthquakes in the Arctic Ocean are dangerous as they can destabilize methane hydrates. Huge amounts of methane are present in sediments under the Arctic Ocean in the form of free gas and hydrates. Earthquakes can send out strong tremors through the sediment and shockwaves through the water, which can trigger further earthquakes, landslides and destabilization of methane hydrates. The situation is especially dangerous when combined with extreme weather events that can cause cracks and movement in sediments.

Above map, from an earlier post, shows the location of fault lines on the Northern Hemisphere.

The combination image below shows methane levels on January 9, 2017, am, at two different altitudes.