3 ms·

Maybe I'm wrong, but I thought that at a fairly shallow depth the seawater is at a constant temperature of 4 degrees Celsius, because that's the temperature whe

Maybe I'm wrong, but I thought that at a fairly shallow depth the seawater is at a constant temperature of 4 degrees Celsius, because that's the temperature where the water is at its densest. Global warming may push this depth a bit lower, but I can't see how it can impact the seabed.

defrost 3y ago
The article opens: Buried beneath the oceans surrounding continents is a naturally occurring frozen form of methane and water. Sometimes dubbed “fire-ice” as you can literally set light to it, marine methane hydrate can melt as the climate warms, uncontrollably releasing methane – a potent greenhouse gas – into the ocean and possibly the atmosphere. The oceans surrounding continents are, for the majority, shallow waters not deep ocean. It's somewhat worse than that in practice, studies indicate that when methane hydrates melt and are released at the land|ocean edges where the bottom waters have warmed ... more methane ice hydrates slowly migrate under pressure to the melting zone, replacing lost methane ice hydrates and then melting itself. Long-distance migration and venting of methane from the base of the hydrate stability zone https://www.nature.com/articles/s41561-023-01333-w https://www.nature.com/articles/s41561-023-01333-w Some of the methane containment zone warming enough to melt and release methane is akin to taking the cap off the toothpaste when the tube is under pressure.
- credit_guy 3y ago
  The link you posted starts with this: > Marine methane hydrate is an ice-like substance that is stable in sediment around marine continental margins where water depths are greater than ~450–700 m. The continental shelves are the areas close to the continents that are shallow, with an average depth of 200 m. They constitute 7.5% of the total ocean area [1]. All the water below 200 m depth is virtually at the same temperature of about 4 degrees Celsius [2]. So, the methane hydrate is well below the surface layer that gets heated by the sun and affected by the climate change. [1] https://onlinelibrary.wiley.com/doi/abs/10.1038/npg.els.0003193 https://onlinelibrary.wiley.com/doi/abs/10.1038/npg.els.0003... [2]https://rwu.pressbooks.pub/webboceanography/chapter/6-2-temperature/ https://rwu.pressbooks.pub/webboceanography/chapter/6-2-temp...
  - defrost 3y ago
    So we agree that it is unstable in shallow depths of less than 450m? Such as depths of 200m where the pressure is less and tempreture greater? Good. You read onwards, I trust ... The potential for methane from hydrate in deeper water to reach the atmosphere was considered negligible. was considered negligible .. not any more. Increases in bottom-water temperature at the landward limit of marine hydrate around continental margins, where vulnerable hydrate exists at or below the seabed, cause methane to vent into the ocean. The shallower less stable hydrates in the twilight zone are capable of gassing out and causing the migration upwards of the formerly deeper more stable stuff. The punchline on the article I linked that you quoted is: We demonstrate that, under suitable circumstances, some of the 96.5% of methane bound in deeper water distal hydrates can reach the seafloor and vent into the ocean beyond the landward limit of marine hydrate. This reservoir should therefore be considered for estimating climate change-induced methane release during a warming world. So while you may not believe this, it is the case that a bunch of petroleum exploration marine hydrologists and geophysicists are asserting that this can happen for this one specific reservoir on the Mauritanian passive margin. There are multiple reasons for this to happen, one in particular that you overlooked is: But frozen methane in the deep ocean may vulnerable after all. In oceans and seas where the water is deeper than around 450 metres to 700 metres are layer upon layer of sediment that contains the hydrate. And some of it is deeply buried and warmed geothermally by the Earth so, despite being hundreds of metres below the seafloor, it is right at the point of instability. That's right, the sun isn't the only source of heat - there's still life left in the old ball of once molten rock after all.

defrost 3y ago

The article opens: Buried beneath the oceans surrounding continents is a naturally occurring frozen form of methane and water. Sometimes dubbed “fire-ice” as you can literally set light to it, marine methane hydrate can melt as the climate warms, uncontrollably releasing methane – a potent greenhouse gas – into the ocean and possibly the atmosphere. The oceans surrounding continents are, for the majority, shallow waters not deep ocean. It's somewhat worse than that in practice, studies indicate that when methane hydrates melt and are released at the land|ocean edges where the bottom waters have warmed ... more methane ice hydrates slowly migrate under pressure to the melting zone, replacing lost methane ice hydrates and then melting itself. Long-distance migration and venting of methane from the base of the hydrate stability zone https://www.nature.com/articles/s41561-023-01333-w https://www.nature.com/articles/s41561-023-01333-w Some of the methane containment zone warming enough to melt and release methane is akin to taking the cap off the toothpaste when the tube is under pressure.

credit_guy 3y ago
The link you posted starts with this: > Marine methane hydrate is an ice-like substance that is stable in sediment around marine continental margins where water depths are greater than ~450–700 m. The continental shelves are the areas close to the continents that are shallow, with an average depth of 200 m. They constitute 7.5% of the total ocean area [1]. All the water below 200 m depth is virtually at the same temperature of about 4 degrees Celsius [2]. So, the methane hydrate is well below the surface layer that gets heated by the sun and affected by the climate change. [1] https://onlinelibrary.wiley.com/doi/abs/10.1038/npg.els.0003193 https://onlinelibrary.wiley.com/doi/abs/10.1038/npg.els.0003... [2]https://rwu.pressbooks.pub/webboceanography/chapter/6-2-temperature/ https://rwu.pressbooks.pub/webboceanography/chapter/6-2-temp...
- defrost 3y ago
  So we agree that it is unstable in shallow depths of less than 450m? Such as depths of 200m where the pressure is less and tempreture greater? Good. You read onwards, I trust ... The potential for methane from hydrate in deeper water to reach the atmosphere was considered negligible. was considered negligible .. not any more. Increases in bottom-water temperature at the landward limit of marine hydrate around continental margins, where vulnerable hydrate exists at or below the seabed, cause methane to vent into the ocean. The shallower less stable hydrates in the twilight zone are capable of gassing out and causing the migration upwards of the formerly deeper more stable stuff. The punchline on the article I linked that you quoted is: We demonstrate that, under suitable circumstances, some of the 96.5% of methane bound in deeper water distal hydrates can reach the seafloor and vent into the ocean beyond the landward limit of marine hydrate. This reservoir should therefore be considered for estimating climate change-induced methane release during a warming world. So while you may not believe this, it is the case that a bunch of petroleum exploration marine hydrologists and geophysicists are asserting that this can happen for this one specific reservoir on the Mauritanian passive margin. There are multiple reasons for this to happen, one in particular that you overlooked is: But frozen methane in the deep ocean may vulnerable after all. In oceans and seas where the water is deeper than around 450 metres to 700 metres are layer upon layer of sediment that contains the hydrate. And some of it is deeply buried and warmed geothermally by the Earth so, despite being hundreds of metres below the seafloor, it is right at the point of instability. That's right, the sun isn't the only source of heat - there's still life left in the old ball of once molten rock after all.