9 ms·
Huge Cavity in Antarctic Glacier Signals Rapid Decay
- makerofspoons 8y agoPrevious modeling predicted this glacier would collapse in the next 200-1000 years, producing a 3M rise in sea level: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4655561/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4655561/
- robodale 8y agoHere's what a ~3 meter rise in the ocean would look like for the Miami-area of Florida. https://ss2.climatecentral.org/#8/25.738/-80.398?show=satellite&projections=0-K14_RCP85-SLR&level=10&unit=feet&pois=hide https://ss2.climatecentral.org/#8/25.738/-80.398?show=satell...
- mothsonasloth 8y agoWelp my place in the west coast of Scotland will be gone in 2 metres :(
- mr_luc 8y agoUnless your place is also slowly moving upwards. :) Most of Scotland is still slowly moving upwards due to the post-glacial rebound from the last ice age. It's a centimeter a year at the fastest in Europe, I think, and technically is slowing down over time, but over 200-1000 years it still might be significant. ... I mean, in either case, neither you not your children are likely to see it ...
- theandrewbailey 8y agoMore info: https://en.wikipedia.org/wiki/Post-glacial_rebound https://en.wikipedia.org/wiki/Post-glacial_rebound
- WhompingWindows 8y agoYikes, not to mention the storm surge during a hurricane, which is predicted to be a much larger hurricane and much more frequent in future. People are just not mentally prepared for this. In the late 21st century, we are going to start seeing massive refugee crises all over the world every year. We are in this "golden age" of wealth and prosperity now, even if it isn't equitably distributed, however that whole system may come crashing down if 15% or 25% of the world's vulnerable to massive ocean flooding and storms.
- cbluth 8y agoI have this strange feeling that some cities will continue to "oporate" after a rise in the ocean like this... Or maybe I'm just thinking of Waterworld.
- kaybe 8y agoThe Netherlands have been demonstrating for a long time it can be done.
- roenxi 8y agoMiami was incorporated as a city in 1896 [0]. Over a 200-1000 year timeframe, it probably makes more sense to just move the city. The infrastructure probably only has a shelf life of 50-100 years. [0] https://en.wikipedia.org/wiki/History_of_Miami https://en.wikipedia.org/wiki/History_of_Miami
- toomuchtodo 8y agoIt's important to note that even before rising sea level makes the land uninhabitable, it's already causing the loss of drinking water aquifers and septic systems to become unusable. https://www.bloomberg.com/news/features/2018-08-29/miami-s-other-water-problem https://www.bloomberg.com/news/features/2018-08-29/miami-s-o... (Miami Will Be Underwater Soon. Its Drinking Water Could Go First) https://www.miamiherald.com/news/local/environment/article224132115.html https://www.miamiherald.com/news/local/environment/article22... (A $3 billion problem: Miami-Dade’s septic tanks are already failing due to sea rise) Miami Beach is already spending $500 million dollars to mitigate the impact of climate change today. http://time.com/4932565/hurricane-irma-miami-beach/ http://time.com/4932565/hurricane-irma-miami-beach/
- irrational 8y agoIs there anyone here who has moved to South Florida recently? Did you take the potential ocean rise into consideration when relocating down there?
- Junk_Collector 8y agoIf the Thwaites Glacier melts fully, it would produce a 2ft rise or about 0.6M. If all of the adjacent glaciers it currently prevents the sea from reaching were to then also melt, then you would get an estimated sea level rise of 2.4 additional meters according to NASA. So it's 200-1000 years for the Thwaites Glacier, and probably several thousand more for the rest of them assuming some other warming effect doesn't dramatically result in the speed up of glacial melt. "About the size of Florida, Thwaites Glacier is currently responsible for approximately 4 percent of global sea level rise. It holds enough ice to raise the world ocean a little over 2 feet (65 centimeters) and backstops neighboring glaciers that would raise sea levels an additional 8 feet (2.4 meters) if all the ice were lost"
- anigbrowl 8y agoIt's worth bearing in ind that other things are going to be melting at the same time.
- Junk_Collector 8y agoAgreed, but I think it's worth keeping some perspective when people are calling this things like, "The Doomsday Glacier" and discussing whether or not this will make it safe to move to South Florida presumably in response to the projected 3M rise.
- amanaplanacanal 8y agoI think the idea here is that it doesn't even have to melt. If water gets underneath it so it floats, it will have the same effect.
- Junk_Collector 8y agoSure. I shouldn't have termed it as all of the ice melting. I believe the term the paper uses is actually ice-shelf destabilization which is a combination of wash out, melting, calving, etc. leading to all of the ice winding up in the ocean or floating due to retreat of the ground line by melt underneath the glacier. It's happening much faster than previously thought because we didn't have a good way of measuring or modelling it until recently. One of the major concerns is that we don't have a way of preventing melt of the under ice that is causing this because it is caused by oceanic effects. Warming oceans will exacerbate this. However, Here is the main take away from the abstract. "Antarctica will irrevocably contribute at least 3 m to global sea-level rise during the coming centuries to millennia." That's very fast on a geological timeline but not on a human timeline and it assumes a total loss of the West Antarctica Ice shelf. There are plenty of problems we should be worrying about, many of which are climate related, but there is no use in people here worrying themselves about this specific problem unless they have an interest in glacier science and certainly it shouldn't be impacting their assessment of whether they want to move to Miami in the next 10 years.
- lenticular 8y agoWest Antarctica is something that glaciologists are really worried about in the long term. The West Antarctic Ice Sheet's bed slopes downward as you go inland, especially around Amundsen Sea where Thwaites Glacier is. This reverse slope means that if the grounding line (where the ice begins to float) retreats back, it is in deeper water. This causes the ice flux to increase, making it retreat backwards into deeper water still, etc. This is called the marine ice sheet instability. There's no mechanism known thus far that would countervail it, so it is something that should be taken seriously. Antarctica is too cold to melt much from surface warming anytime soon. Ocean warming and changing currents are a different story, though.
- Simon_says 8y agoI'm sorry, but could you break this down more for stupid people? What exactly are glaciologists afraid will happen and why is it bad?
- lenticular 8y agoIce sheets, of which the West Antartic, East Antarctic, and Greenland ice sheets are the only current examples, are basically like very large domes of ice, on the order of 1000 kilometers wide and 1-3 kilometers high. Unlike mountain glaciers, they completely cover the underlying topography. They flow outwards under their own weight into the ocean. In Antarctica, it is cold enough that melting at the surface is negligible. This means that almost all snow that falls ultimately must flow into the ocean. At some point at the edge, the ice loses contact with the ground and floats. This is the grounding line. For a constant ice flow velocity, the amount of ice that gets spit out into the ocean is proportional to how thick the ice is at the grounding line. Now, suppose that the slope of the bed gets deeper as you go from the grounding line into the interior of the ice sheet. Then, if the grounding line retreats, it's in deeper water. So, the ice flux increases. The increasing ice flux means that the ice sheet thins near the edge. Since it's thinner, it can't stay grounded in as deep of water. Imagine a big chunk of ice in a puddle of water that sits at the bottom of a puddle, versus a little piece that floats. Now, since it can't float in as deep of water, the grounding line retreats because bouyancy is pulling up on the edge. This makes it go into deeper water, ice flux increases more, etc. This could cause a collapse of the ice sheet, resulting in a few meters of rise. The timescale that this could happen is very poorly constrained (decades? centuries? a couple millenia?). It may have already irreversibly begun, or maybe not.
- deleted 8y ago[deleted]
- 75dvtwin 8y agoThis sentence helped me to visualize what might be happening. "Just as a grounded boat can float again when the weight of its cargo is removed, a glacier that loses ice weight can float over land where it used to stick. When this happens, the grounding line retreats inland. That exposes more of a glacier's underside to sea water, increasing the likelihood its melt rate will accelerate. " not clear from the article though, what do they think is causing the retreat? Is it warming of ocean water, or we do not know yet?
- pas 8y agohttps://en.wikipedia.org/wiki/Circumpolar_deep_water https://en.wikipedia.org/wiki/Circumpolar_deep_water typically 1-2°C warm and salty. http://cdn.antarcticglaciers.org/wp-content/uploads/2014/05/PIG.ai_.jpg http://cdn.antarcticglaciers.org/wp-content/uploads/2014/05/... http://www.antarcticglaciers.org/glaciers-and-climate/ice-ocean-interactions/changes-circumpolar-deep-water/ http://www.antarcticglaciers.org/glaciers-and-climate/ice-oc...
- fdggdfsvscvsd 8y ago"Thanks to a new generation of satellites, we can finally see the detail" So at least it is not clear if this compares unfavorably to situations in the past, as there is no data about it.
- kaybe 8y agoThere is a lot of proxy data for the amount of sea water missing though. It only goes missing for so long when it is in ice form. The only question is where exactly all that ice was.
- fdggdfsvscvsd 8y agoWhat do you mean - they measured rising sea levels, and wanted to find the missing ice it came from?
- kaybe 8y agoNo, basically the isotope composition of the sea changes when a lot of water evaporates and doesn't come back over the rivers (because it fell as snow and just stayed on land). The heavier isotopes need a little bit more energy to evaporate, so the remaining sea water has more and more heavy isotopes left. The most commonly used tracer is oxygen 16 vs oxygen 18 [0]. The isotopes are also used by sea organisms when they grow [1]. When they die and their shells become part of the sea floor (this is optional, there are also old corals that can be used), the signal can remain for a very long time (essentially as long as the sea floor remains, a few 100,000 years). So we know quite well how much water was missing from the ocean at these points in time. The method can also be used to deduce temperatures from back then. [0] https://en.wikipedia.org/wiki/%CE%9418O https://en.wikipedia.org/wiki/%CE%9418O [1] https://en.wikipedia.org/wiki/Foraminifera https://en.wikipedia.org/wiki/Foraminifera
- fdggdfsvscvsd 8y agoThanks for the explanation.
- kaybe 8y agoIf you need some good news today, check page 34 on the new Ozone report: http://ozone.unep.org/sites/default/files/Assessment_Panel/SAP-2018-Assessment-report.pdf http://ozone.unep.org/sites/default/files/Assessment_Panel/S... The finding that the ozone layer is behaving as predicted - probably healing - is not unexpected. It was depleting due to the gases now controlled under the Montreal protocol, the emission of which is decreasing very rapidly. This plot however shows the contribution of these gases to global warming. As you can see there, it is going down over time! Of course the contribution pales in comparison to CO2, Methane and N2O, but it is still significant. And, if nobody messes up, it will go down. It can be done! It's the easiest part, but it is a start. edit: It also says that the main reason for 20th century climate changes in the southern hemisphere summer is actually the ozone hole over Antarctica. When it closes (projected to 2060) the changes will be undone. (p. 38) (pending too much influence from other greenhouse gases) I haven't seen the details, but maybe there's hope for Australia.
- madengr 8y agoDid a little work on these ice penetrating radars when I was at KU.
- infradig 8y agoWhy no mention that this is a known area of undersea volcanoes? They are already causing considerable melting of glaciers from below. See: https://www.livescience.com/46194-volcanoes-melt-antarctic-glaciers.html https://www.livescience.com/46194-volcanoes-melt-antarctic-g... Literally the first paragraph at that link I supplied addresses this situation at Thwaites Glacier.