Some of the deepest parts of the Black Sea are still responding to the climate change demanded by the last ice age, scientists have discovered – a period that officially ended about 12,000 years ago.
Analysis of gas hydrate deposits – in this case methane trapped by water molecules, in a solid substance that looks like ice – has revealed a knocking reaction in the northwestern part of the Black Sea called the Danube Fan.
With temperature measurements and other data, the drill core of gas hydrate deposits reveals something surprising: the level of free methane gas under the coast has not adapted to the already hot conditions on the surface for thousands of years.
“This shows that the gas hydrate system among fans of the Danube deep ocean is still responding to climate change that began at the end of the last glacial maximum,” the researchers wrote in their paper.
Attempts by scientists to determine the basis of Gas Hydrate Stability Zone (GHSZ) – Central to these findings, is the lowest point that gas hydrates naturally form due to temperature, pressure and some other factors. Above and below that zone, you will not be trapped in ‘free’ methane gas hydrates.
To find the basis of this zone, researchers turn to seismic reflection measures of sedimentation, commonly referred to as bottom-simulating reflectors or BSR for short. However, previous work has found that in this part of the Black Sea, there is a discrepancy between the bases of the BSR and the gas hydrate stabilization zone.
By coastal drilling and temperature measurements, researchers have now concluded that the gas hydrate stabilization zone has adapted to warmer conditions than in the last millennium – as suggested at higher levels – but free methane gas and the associated BSR are still holding. .
“From our point of view, the gas-hydrate stability boundary has already been exposed to warmer conditions in the suburbs, but the lower methane gas, which is always found on this lower shore, has not yet managed to grow with it,” says the geophysicist. Michael Rydell, from GOMAR Helmholtz-Center for Ocean Research in Germany.
That may be the response behind it, as BSR should not be where it should be. The team thinks sediment permeability may also play a role, and their measurements show that methane has managed to grow in certain areas, but not in others.
“In summary, we have found a very dynamic situation in the region, which also seems to be related to the development of the Black Sea since the last ice time,” Riddle says.
About 20,000 years ago, the water level in the Black Sea was about 100 meters (328 feet) lower, meaning less pressure on the ocean floor. The water was also significantly colder. As far as free methane gas is concerned, those conditions have not changed.
As with any study of the effects of climate change, this research is intended to be helpful in future weather modeling. For example, there are currently huge amounts of gas hydrate deposits beneath the Arctic, and it is important to know how they may react to rising temperatures in the coming years.
Scientists have insisted that their findings should be carefully interpreted, along with the many different factors of the game and more abundance for study – but they also emphasize the importance of intrinsic-parameters and quality data for such analysis.
“For our investigation we used our drilling device Meram-Mebo 200 and broke all previous depth records with a maximum depth of about 145 meters. [476 feet], ”Says Gerhard Bohrmann, a geologist from the University of Bremen in Germany.
Research has been published in Earth and Planetary Science Letters.