MOSCOW INSTITUTE OF PHYSICS AND TECHNOLOGY
PICTURE: ALEUTIAN ISLANDS ARE AN ARCHIPELAGO INCLUDING DOZEN OF ISLANDS WITH 40 ACTIVE AND 17 DORMANT VOLCANOES. More CREDIT: SHUTTERSTOCK
A researcher from the MIPT has suggested a new explanation for the rapid warming of the Arctic. In his recent paper in Geosciences, he suggests that the warming could have been caused by a series of large earthquakes.
Global warming is one of the pressing problems facing civilization. It is widely believed to be caused by human activities that increase the concentration of greenhouse gases in the atmosphere. However, this view does not explain why temperatures sometimes rise quite abruptly.
In the Arctic, one of the factors driving global warming is the release of methane from permafrost and metastable gas hydrates in the shelf zone. Since researchers began monitoring temperatures in the Arctic, the region has seen two periods of abrupt warming: first in the 1920s and 1930s, then from 1980 and until today.
Leopold Lobkovsky, author of the study described in this story, is a member of the Russian Academy of Sciences and director of the MIPT laboratory for geophysical research on the arctic and continental edges of the world ocean. In his work, the scientist hypothesized that the unexplained abrupt temperature changes could have been triggered by geodynamic factors. In particular, he pointed to a number of major earthquakes in the Aleutian arc, which is the closest to the Arctic.
To test his hypothesis, Lobkovsky had to answer three questions. First, did the dates of the great earthquakes coincide with temperature jumps? Second, what mechanism enables the lithospheric faults to spread more than 2,000 kilometers from the Aleutian Islands to the Arctic shelf region? Third, how do these disturbances amplify methane emissions?
The answer to the first question came from analyzing historical data. It turns out that the Aleutian Arc was actually the site of two major earthquakes in the 20th century (more details under the text). Each of them preceded a sudden increase in temperature by about 15 to 20 years.
To answer the second question, a model of the excitation dynamics of the lithosphere was required. The model used by the researcher describes the propagation of so-called tectonic waves and predicts that they should travel at around 100 kilometers per year. This coincides with the delay between each of the large series of earthquakes and the subsequent rise in temperature, as it took the disturbances 15 to 20 years to travel over 2,000 kilometers.
To answer the third question, the researcher suggested the following explanation: The deformation waves arriving in the shelf zone create slight additional stresses in the lithosphere sufficient to perturb the internal structure of the metastable gas hydrates and permafrost that stores trapped methane . This releases methane into the water of the shelf and into the atmosphere, causing global warming in the region due to the greenhouse effect.
“There is a clear correlation between the great earthquakes in the Aleutian arc and the phases of global warming. There is a mechanism for the physical transfer of the stresses in the lithosphere at the appropriate speeds. And these additional tensions can destroy metastable gas hydrates and permafrost, and release methane. Each of the three components in this scheme is logical and suitable for mathematical and physical explanation. What is important is that this explains a known fact – the sudden rise in temperature anomalies in the Arctic – that was not accounted for by previous models, ”commented Lobkovsky.
According to the researcher, his model will benefit from the discussion and likely to be improved, and there is much work to be done to confirm or rule out the proposed mechanism.
The research reported in this story was carried out at the MIPT with support from the Russian Science Foundation (Grant No. 20-17-00140).
Two major series of earthquakes. The first started with an earthquake of magnitude 8 in 1899 in the eastern part of the Aleutian Arc, followed by two other large earthquakes in the western part of the islands with a magnitude of 8.3 and 8.4. The second series began with an 8.6 magnitude earthquake in 1957, followed by the 9.3 magnitude earthquake in Alaska in 1964. The following year, an 8.7 magnitude earthquake struck the western portion of the arc. Each of these devastating seismic events had subterranean sources that stretched for hundreds of kilometers.