Băng mê-tan là gì & ảnh hưởng thay đổi khí hậu ra sao Phỏng vấn Tiến sĩ Roy Hyndman
Hallo, Earth-friendly viewers! Today on Planet Earth: Our Loving Home, we will explore methane hydrate, which is also called flammable ice, methane ice or gas hydrate.
Methane hydrate is a compound of methane and water. It exists mainly under the ocean floor and the permafrost in enormous quantities. Scientists estimate that there could be 500- 2500 gigatons of carbon under the sea floor. The reservoir just in permafrost has about 400 gigatons of carbon, while the total carbon in the atmosphere is around 700 gigatons.
As methane is a strong greenhouse gas, scientists are concerned that global warming could lead to huge amounts of methane being released from methane hydrate into Earth’s atmosphere, resulting in catastrophic consequences for both humanity and our animal co-inhabitants.
In order to understand more about methane hydrate and its influence on the earth, Supreme Master Television interviewed Dr. Roy Hyndman of the Pacific Geoscience Center and the Geological Survey of Canada, in Sydney, British Columbia.
Dr. Hyndman is a Canadian geophysicist and a professor in the School of Earth and Ocean Sciences, the University of Victoria. One of his major research areas is marine methane hydrate.
He has published 200 scientific journal and volume articles on a wide range of marine and land geoscience research.
He has been involved in numerous international collaborative programs, and has participated and organized research cruises in the Atlantic, Pacific, Indian and Arctic oceans.
Dr. Hyndman is former President of the Canadian Geophysical Union.
He is a Fellow of the Royal Society of Canada, a Fellow of the American Geophysical Union, an Honorary member of the Canadian Society of Exploration Geophysicists, and a recipient of the J. Tuzo Wilson medal for contributions to geophysics in Canada.
Now let’s meet Dr. Hyndman.
Methane’s a very strong greenhouse gas, so if you put it into the atmosphere it contributes to warming the global system. The methane doesn’t last very long in the atmosphere; it oxidizes and converts to carbon dioxide.
Dr. Roy Hyndman: The carbon dioxide we’re putting in now will be around for a long time.
Dr. Roy Hyndman: Hydrates are a kind of chemical composition that we’ve known about for a long time in the laboratory, but only quite recently were they appreciated in nature.
So perhaps thirty years ago they were recognized on the deep sea floor. And the reason it took so long is if you bring them to the surface they melt immediately, so rarely could they be preserved.
When people brought sea floor samples up, they’re gone. They look like ice, perhaps a little more like dry ice, carbon dioxide ice, but similar physical properties, similar densities, speed of sound and so on.
There are some special differences, but mostly they are like water. They occur when the pressure is high and temperatures are low, so they will not occur under normal surface conditions.
They occur primarily beneath the deep sea floor, not beneath the continental shelf; it’s too shallow, the pressure’s not high enough and the temperature’s too high.
Most commonly on the continental slopes around the world, that’s the transition between the continental shelf and the deep sea floor; it’s on the way down most of them occur.
They’re not very common in deep sea basins.
Supreme Master TV: So, that is about a few hundred meters?
Dr. Roy Hyndman: They need at least about 600 metres. The very deep sea basins are 2000 to 4000 meters (6500 to 13000 feet), so it’s between the continental shelf where it’s shallow and the deep sea floor, that slope between the two.
They also occur under land in the Arctic where permafrost occurs, but only in the far North where, as I say, permafrost is sufficiently cold and you get down deep enough; they also can occur there. They don’t occur under land at normal, temperate, middle latitudes like here.
Supreme Master TV: And how much of those deposits are at the bottom of the sea or in the sea? Is it as big as coal or petroleum?
Dr. Roy Hyndman: There have been some estimates that there’s much more than our conventional hydrocarbons. I think in recent years the estimates are getting smaller, so the amount is still very large, but probably not as large as once thought.
However we know rather little about how common they are. We only have the necessary surveys in very small areas in a few places around the world. And only in very few places have we drilled into them.
Supreme Master TV: So what are scientists trying to learn from those samples from the drilling of methane hydrate? Is it about the history of Earth or the history of the ocean?
Dr. Roy Hyndman: Part of it’s to get bigger pictures of what is at the bottom of the ocean that records past geological history.
A lot of what we know about the past climate change comes from the bottom; mud and sand get older as you go down and you get a picture of what conditions were. You have to go down and actually see whether that’s correct calibration or testing of the methods.
And there’s a lot of things you cannot do with geophysical measurements; we measure the chemistry and state of the material, and the muds and sands that it is deposited in.
So a lot of things you cannot get remotely; you have to actually go down and get samples.
We make measurements in the bore holes as well, in the drill holes, not just bring samples up. We run special geophysical tools down the bore holes.
Dr. Roy Hyndman: That’s the best we can do.
Supreme Master TV: So there is a lot of research going on?
Dr. Roy Hyndman: A lot of research going on.
Supreme Master TV: What about technology? Is there also technology for exploration in preparation, and how advanced are we in that field?
Dr. Roy Hyndman: No gas has been produced from the deep-sea floor from this material, none.
Dr. Roy Hyndman: Most work that has been done to produce gas from it has been in the Arctic, because there you can work on land. It’s very cold, but at least you’re on land.
Supreme Master TV: I see.
Dr. Roy Hyndman: The biggest project has been in Northern Canada, called the Mallik Project, where I think that they are just now in their fourth year trying to. They started with drilling to tell how much was there and are now at this stage of seeing whether you can get gas out of it.
So, I think a long way from doing it economically but they are getting closer.
HOST: In order to further study methane hydrate, ocean floor exploration is an important means of scientists’ research.
HOST: Welcome back to today’s Planet Earth: Our Loving Home on methane hydrate and its relation to climate change. How did methane hydrate come into being?
Although scientists do not know all the details; they know that it is a result of the collaborative work by micro-organisms, a certain temperature and pressure.
Dr. Roy Hyndman: They’re a little like conventional oil and gas; they come from organic material in the muds and sands beneath the sea floor.
The difference is that they’re low temperature; they’re produced by bacterial action on the organic material that’s buried.
Supreme Master TV: The process starts from the bottom not from the top?
Dr. Roy Hyndman: It starts from the bottom, it starts at some depth, and it releases the methane gas as this reaction takes place.
You break down this plankton or it can be woody material from rivers, and when it breaks down it produces this gas.
It’s similar to swamp gas, sewer gas; all these things that we know about on land, it’s a similar process.
And at low temperature, in contrast to conventional gas, which is mainly made at high temperature, with the chemical cracking, breaking down things at high temperature, this is done at low temperature.
So it’s the material that’s in the mud and sand on the sea floor steadily making this gas and it’s rising.
Dr. Roy Hyndman: So the gas is steadily rising continuously, or we always in the ocean have a continuous release of methane all the time?
Dr. Roy Hyndman: We do, but as it comes up, as it gets near the sea floor, it gets to the condition where you can form this ice. Ice is not stable, it’s too hot when you get deeper, and as the gas comes up it gets cooler, it combines with the water in the mud and sand, because it’s high porosity to produce gas hydrate, usually in the porous spaces of the mud and sand.
So normally it doesn’t reach the sea floor; it gets trapped in this frozen ice material. Where it’s too hot you can collect some gases, greenhouse gases. That could be released. In some of our sea-marine surveys, yes we have seen methane coming out of the sea floor in kind of plumes of gas.
They’re not very common, but yes, we definitely do see them and we do map them.
HOST: With the help of modern techniques, scientists are now gradually uncovering methane hydrate’s secret beneath the ocean floor.
Dr. Roy Hyndman: Until ten-twenty years ago, most of the expeditions were done with real submarines with people in them. We had one here, we had a research submarine; it can go to quite deep waters.
They were very expensive, they were dangerous, required so much safety precautions, they could not work for very long, they would go down for one hour, and you spend a day or two preparing and finishing and you stay down at the bottom for an hour.
Since that time, most work is done by remote vehicles on a cable, with a lot of different instruments, including TV cameras and video and acoustic seismic systems and electrical systems, and currently there’s chemistry, there is a large number of things that are put on these vehicles.
So they’re actually much better. You can sit in the laboratory on a ship or sometimes you can sit in your laboratory here and look what’s going on.
Supreme Master TV: And they can measure the hydrate inside the water?
Dr. Roy Hyndman: There are a few places where you actually see hydrate on the sea floor; I can show you pictures of them.
Supreme Master TV: That would be very interesting to see.
Dr. Roy Hyndman: That does happen in very few places. The TV camera, which you can look at in the laboratory; while it’s happening, while it’s swimming around, you can see the gas hydrate. You can see the types of animals and bacteria living on the methane itself that’s coming out, they can use this as a food source.
So you get more animals and plants in the areas where there is some methane coming out of the sea floor.
Dr. Roy Hyndman: They are specialized, making use of this energy.
HOST: The stability of the frozen methane hydrate under the ocean floor or permafrost is vital for keeping the balance of our global carbon cycle and eco-system.
With the continuous temperature increase in the Arctic area, it has become a concern of ecologists and climatologists.
Do we have a basic understanding at what conditions such gas can be released, and pose some kind of ecological danger?
Dr. Roy Hyndman: Quite a lot of work has been done on that question.
People were particularly concerned whether this is a positive feedback, that if we warm the global atmosphere and oceans that will cause methane release and that will produce more warming, that will go round and round until we get very rapid warming.
Abrupt warming periods back in geological history have been suggested to have come from this process.
HOST: The process, Dr. Hyndman mentioned, is actually a new theory called the “hydrate hypothesis” regarding climate change, which asserts that a feedback loop of methane hydrate has caused global warming in Earth’s history.
Then this leads us to ask, how is the present situation of the methane ice in the Arctic area?
Dr. Roy Hyndman: The gas hydrate is usually below the permafrost, so actually quite deep under the land; it can be 500, (to) 800 meters down, so the time of that to warm is very slow, but that’s under the land.
But under the sea it is a little different; it can be shallower. It is possible that there could be…
Dr. Roy Hyndman: Even shallower than 100 meters.
Supreme Master TV: So that would be subjected to the sunshine-caused temperature change.
Dr. Roy Hyndman: There are definitely places around the world where changes in the water temperature could produce gas release.
Dr. Roy Hyndman: We can see it bubbling up from the ocean, places like the Mackenzie Delta in the Arctic, where you see a gas coming out of the ground, out of the water channels bubbling continuously.
HOST: At the 2008 annual conference of the European Geosciences Union in April 2008 in Vienna, Russian polar scientist Natalia Shakhova along with her colleagues presented their latest research results.
According to their observations, the methane concentration in the sea water near the Siberian coast has been highly saturated, while high concentrations of methane can also be found in the air over the sea.
In some places, the methane concentration even reached five times normal values. At the same time, measurements conducted by helicopter also showed the presence of higher methane concentrations at altitudes as high as 1,800 meters.
These results clearly show that the methane is being released in some places in the Arctic area. The release of methane in the Arctic area is a severe warning to all humanity. It is the time now for all of us to change our lifestyles. Let’s go veg, be green and save the planet.