Thursday, June 17, 2021

Can mining Australian coal slow sea level rise?

Disclaimer. I am stuck at home waiting for a child’s COVID test result, and desperately looking for a distraction from some personal admin. I am taking a sick day. This has nothing to do with my work, my employer, or anything else and is entirely me falling down an internet rabbit hole in order to avoid making a phone call.

Second disclaimer. I am not a climatologist, or an oceanographer, or a bulk commodity logistics manager. If I have drastically screwed up any of these fields, please correct me. Here we go:

Here on planet Earth, the surface is looking a bit grim. The recent and continuing increase in CO2 from burning carbonaceous materials has resulted in the planet warming up, and this warming is threatening to melt various ice sheets, which will raise sea level enough to inundate low lying coastal properties.

Of particular concern are the Thwaites and Pine Island glaciers, in West Antarctica, both of which discharge into the Amundsen Sea. One of the problems with these glaciers is that warmish (a few degrees C, so well above the freeing point of -2 for salty water) salty water, which circulates around the continental shelf of Antarctica, is melting these glaciers from below. During the last ice age, the glaciers were thicker, the sea level was lower, and as a result, these glaciers flowed all the way to the edge of the continental shelf. They carved enormous canyons in it was they went, and today these submarine canyons allow the warm salty water to flow inland and erode the current glaciers from underneath. Both glaciers are also prone to collapse, which would cause rapid sea level rise, as they drain a large portion of West Antarctica.

If the planet continues to warm, these glaciers could start melting from above as well as below, but even if warming were to stop tomorrow, the basal melting is happening right now, with current CO2 levels.

As a result, there have been studies (like Kimura et al.2017) of how this warm water actually interacts with the seabed and glacier, and over the past few years, several authors have proposed various technological solutions to keep the glaciers from melting. Many of these (e.g. Lockley et al. 2020) seem like science fiction. Others (Wolovick et al. 2018) imagine and model action beginning a hundred years from now.

At the same time, action to reduce CO2 emissions here in Australia has been sluggish at best. The coal industry is large, influential, well funded, and provides thousands of well paying unionized jobs. It is also a very successful industry, which, every year, exports close to 400 million metric tons of coal, mostly to East Asia. Roughly half of this is burned to produce electricity; the other half is used in steel production. Both eventually end up being turned into heat-trapping CO2, which is released into the atmosphere.

So, in the interest of solving both of these problems together, perhaps we should consider reducing the flow of deep warm water to the Amundsen Sea glaciers by filling the submarine canyons up with coal.

Let’s start by looking at the scale of the problem. Most of the Pine Island Trough is about 50 km wide, and 500-800 meters deep, with deeper areas and more complex topography near the ice edge.

Luckily, Australia has tens of cubic kilometres of coal reserves, depending on which definition one uses. And if the trough doesn’t need to be completely filled because the warm water doesn’t reach within 250m of the surface, than there is plenty of coal- perhaps even enough to put a submarine rubble berm across the entire Amundsen sea (e.g. Gurses et al. 2019).

Furthermore, the infrastructure to dig coal up, transport it to a port, and load it onto a bulk carrier already exists, and is in use. The only difference is the direction in which the ship sails after leaving port. In fact, Pine Island Bay is several hundred km closer to the port of Newcastle than any of the major East Asian ports are- it is just in the other direction. As a result, everybody in the Australian coal industry gets to keep their job, because they are still doing the same work. In fact, it makes jobs more secure, as the risk of having an asset stranded is reduced.

 Furthermore, the coal, once dumped, isn’t going to be burned. It is effectively sequestered. There should be enough WWI shipwrecks in the North Atlantic to be able to determine the behaviour of coal on the seabed on the 100 year timescale, but the recovery of coal from the Titanic suggests that it holds up reasonably well.

Obviously, there are other potential problems. Although today’s bulk carriers traverse areas of high typhoon activity, these tropical storms are both more localized and more predictable than the huge temperate lows which spin through the Southern Ocean. There could be seaworthiness issues with the current fleet. Coal may not be a dense enough rock to stay in a pile on the bottom of the ocean without getting washed away be currents, so shipping overburden as well, or instead, may be necessary. And operating a floating unloader in the Amundsen Sea could prove to be challenging. But these are things than can be tested today, as opposed to technologies that are decades away. If someone spent the next 6 months integrating a selfunloader into a bulk coal carrier, it could potentially do a test run as soon as the pack ice melts in January. And while a phase-in from Asian exports would be the least disruptive approach, if urgent action was required, based on current export tonnages, a 250m high, 2 km deep, and 50 km long berm could potentially be dumped across the trough west of Burke Island in less than 30 years.

Global warming is happening now. So should our solutions.