What Will Be Left Once the Sea Levels Rise?

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Take a walk with me through  an ancient, verdant land:   so vivid are the colours and  aroma of the entangled fauna,   that it takes you an age to notice something  isn’t as it should be. It’s all quiet. The near absence of birds and mammals is  the only indication that this land is dying,   its fate sealed by the ending of an  ice age — waters are rising. The lush   landscape below your feet will soon be  30 m below the surface of the Pacific. Any species able to migrate have escaped to  continue their fight for survival in a warming,   shrinking world. Those given life  by their roots, are held to perish   by them. What is happening here? What we can  learn from the history recorded deep in the   melting polar ice is of vital importance,  because right now, it is happening again. What is causing the ice caps to melt in  the present? How will it affect the most   powerful climate systems on earth? And,  what hidden dangers does the ice contain? I’m Alex McColgan and you are watching  Astrum. Join me today as we look at   what makes ice such an interesting  and crucial feature of our planet,   and imagine a future, wetter Earth, one  whose existence may have already been forged. On Astrum, we love to explore gigantic  objects in our universe whose scale through   time and space stretch almost beyond  our grasp. Look up towards Cassiopeia,   and there is our closest Galaxy,  Andromeda. 2.5 million light years away,   200,000 light years from edge to edge. Yet,  despite its magnitude, we can connect to it. So it’s curious to me that looking only 80 years  to our future feels too distant to connect with;   to understand that things we do today affect  tomorrow’s world. So, let me take you there. At the beginning of our journey is the  Ice. Ice is a remarkable substance,   one that can store vast amounts of energy. As a  comparison, energy stored in modern electric cars,   capable of accelerating tons of metal  to over 160 km per hour and carry both   it and you hundreds of kms, could scarcely  melt ice that would fit on its back seats. The energy storage capacity of ice is a large part  of the reason that the climate has been so stable   for the past 12,000 years [holocene]. The ice is  acting as a buffer against extreme temperature   rises and falls. The holocene has been a unique  period in Earth’s history for another reason   too — the rise of human civilisations. (Made  possible through the development of agriculture) The Antarctic ice cap first formed around 37  million years ago, the Arctic 2.7 million,   as old as the light reaching us from  Andromeda, and both caps are important   for our stable climate to this day. Their  historical size has largely been defined by   Earth’s position and tilt in the solar system,  movements that affect the amount of energy that   our planet receives. These movements are known  as Milankovich cycles, which I have covered in   a previous video. According to these cycles the  ice at the poles should be increasing, we should   be heading into an ice age, and sea levels  should be falling as the ice caps get deeper. But, instead, the polar ice is melting, massive  amounts of energy are being absorbed by the caps,   and not only are we going in the opposite  direction that the Milankovich cycles   predict — the ice loss is accelerating!  Should all the ice melt, we are facing a   70 m sea level rise, which will flood all  coastal cities on the planet. Fortunately,   that degree of ice loss is exceptionally  unlikely. But we do need to know how much   sea level rise to expect so that we  can plan ahead and protect Earth’s   ecosystems. To predict just how much, we need  to understand why and how the ice is melting. We know the release of greenhouse gasses  is a driver of today’s global warming,   overpowering the Milankovich cycles, causing the  ice caps to melt and the sea level to rise. But I   was astonished to find out this hasn’t always  been the case! Detailed records kept in the   Antarctic ice core reveal that in the past, it was  increasing temperatures that caused increasing CO2   levels. Cause and effect were flipped. But,  isn’t that a blatant contradiction?! Well,   actually, no! Each positively influences the  other. It’s just a case of which happens first. We see this play out as the increased  temperatures of today’s climate thaw   the permafrost around the Arctic circle,  releasing long-stored carbon reserves,   which in turn accelerate further global warming. The mechanism by which increased  CO2 and temperature affect the   polar regions reveals a complicated  and fascinating climate system. Greenhouse gases trap infrared (heat)  radiation emitted by the surface of   the earth. This heat is retained by the  atmosphere (5.5 quadrillion tons) and the   ocean (1.34 quintillion tons); around 90%  of the energy increase is absorbed by the   ocean which is no surprise given it has  almost 250 times the atmosphere’s mass! So where does this extra energy go?  Well, as anyone who’s touched a hot   stove or licked a ski lift chair knows,  heat moves from hot things to cold things,   so it makes sense that it is at the cold  poles where we see many times the average   global temperature increase - because that’s  where the temperature gradient demands that   the energy flows. And it’s flowing there  primarily through the ocean currents. Because of its density and heat capacity,  water is very effective at transferring energy;   that’s why water is used both as a coolant in  cars and a heating medium in homes. And why air,   with a low density and low heat capacity, is  often used as an insulator. That difference   allows you to sit comfortably in  a 90 ºC sauna for many minutes,   while you’d reflexively be unable to insert past  your fingertip into water of the same temperature! Other factors play a role in melting the ice  too, like the albedo, or whiteness of the ice.   Soot darkens the surface of the ice, causing  it to absorb more energy from the sun. Air   quality measures are reducing particulates in  the atmosphere and on the ice, meaning we will   see less melt from ice directly absorbing the  sun’s energy. But, the lowering of particulates   in the atmosphere also blocks less sunlight  overall, so more energy reaches the surface,   accelerating the greenhouse effect.  I told you it is complicated! Let’s explore the ways that the oceans are  melting the polar ice, as is happening right now   on the West Antarctic Ice Shelf, a particularly  vulnerable area. It contains ice in several forms. Sea Ice is very seasonal, and is responsible  for the doubling of Antarctica’s area through   winter. This ice melts through contact with the  ocean as ice cubes do in a cocktail. The direct   impact of all the sea ice melting would only  contribute a few centimetres to sea level rise,   but its importance lies in its role as a barrier  to the otherwise exposed ice shelf. The sea ice   insulates the oceans from atmospheric warming,  and keeps the humidity and temperature of the air   above it low. Being fresh and white, like the  most fairytale of glistening winter flurries,   it also reflects a large proportion of sunlight  back into space. When this sea ice is low   it exposes the Ice shelf which protrudes  almost all the way around the Antarctic. These floating ice shelves can be gigantic, some  - like the Ross and Ronne-Filchner shelves - are   greater in area than my home country -  the United Kingdom. The warm sea water   eats at the underside of the shelves; huge  icebergs the size of our biggest cities can   break away as it weakens and drift as far as  Africa. Since these ice shelves are floating,   they also contribute minimally to rising  sea levels. But it’s what the ice-shelves   hold back that has the most potential for  sea level rise. As the shelves shrink,   the main body of sheet ice that sits atop land  is more exposed allowing faster flow rates from Glaciers and ice streams. But don’t be  fooled, these ice streams are far bigger   than their name would suggest! Incredibly,  some are as wide as the mouth of the Amazon,   hundreds of kilometres long and kilometres deep  – all flowing towards the sea. Feeding these   streams is the colossal ice sheet itself.  Since the ice sheet is supported on land,   the mass of ice melt leads to  a direct increase in sea level. These ice-melting processes are natural  phenomena, and would still occur without   global warming. The poles take fresh  snowfall and ice formation every year,   which adds to the mass of the ice. And just  for them to remain at their current size,   we would witness sea ice melting,  ice shelf calving and glacial flow. Though at this very moment, Earth’s polar ice  sheets are far from equilibrium: the rate at   which they are losing ice is quicker than fresh  snow can fall, meaning that they are shrinking.   Because of the extra energy in our oceans and  in the atmosphere captured by greenhouse gases,   we are already committed to  significant ice sheet loss. Can we say how much sea levels will rise  from the melting alone? If you thought it   would be a simple case of calculating the  volume of ice lost and adding it to the   volume of water in the seas, well,  you can join me in being wrong! To   arrive at an accurate estimate we need  to understand a few other interactions. We tend to think of Earth’s crust as solid,   but given enough force the earth will  change shape too. As the ice melts,   the continental plate that supports it bears less  weight and rises up above sea level, while at the   equator the coastal land sinks into the sea,  creating localised sea level falls and rises. But the single biggest addition to sea level  rise to date required no additional water, and   was simply due to the thermal expansion of what  was already there! Around half of the sea level   rise we have already seen since the industrial  revolution has been due to this expansion. This   process is easy to calculate, and we know how it  will contribute to sea level rise in the future. However, the deluge of cold, fresh water being  dumped into the salty sea has other, less   predictable consequences. Remember, Earth’s  systems are dynamically intertwined. A feature   of these dynamic systems is that they are  vulnerable to dramatic changes in behaviour,   known as tipping points. As with playing  jenga, the tower becomes less and less   stable as we mine the lower levels for  material to build ever higher. Eventually,   merely touching the next brick brings it crashing  down. This would cause a very rapid phase change! One tipping point that could occur within our  lifetime is the slowing of the Atlantic meridional   overturning circulation (AMOC). This is an oceanic  flow, a powerful energy transfer system. Should it   weaken or collapse completely, sea levels on the  eastern seaboard of America could rise by up to   1 m, but in Europe, coastal waters would  recede. However, Europe would face other   more extreme consequences. Around the world,  rainfall patterns would change drastically,   pushing some ecosystems to become rainforests  while pushing others toward desertification. To understand how all of that is possible let's  look at how the AMOC functions now. The AMOC   is part of the thermohaline circulation  system. It is driven by changes in heat   (thermo) and salt concentration (haline).The  AMOC brings warm tropical waters up past the   United States and across to Europe, helping  to make northern Europe warmer than it ought   to be considering its proximity to the polar  circle! As these waters continue north to the   Arctic it is partially frozen into sea ice,  which leaves cooler, saltier water to sink   to the bottom of the ocean where it then  flows back south to complete the cycle. However, the melting of the Greenland ice  sheet is inundating the northern part of   the AMOC with fresh water, diluting the  sea water making it less salty and less   dense. This makes the gradient directing  the water to sink to become shallower,   slowing down this part of the cycle and reducing  flow; just as a slow middle-lane driver on the   motorway can cause a tailback stretching  frustratingly far back across all lanes. The slowing down of the AMOC backs up water  on the American east coast and reduces the   flow to Europe meaning that sea levels would rise  further in America while Europe would be spared,   though that’s little consolation to a  continent that will lose much of its   way of life and food production capacity  through cooler temperatures. The UK alone   is facing an average temperature drop of 10  ºC, which would make it colder than Iceland! The melting Greenland ice sheet also contains  organisms that we haven’t seen on Earth in   hundreds of thousands of years. When a new  predator travels to a ecosystem not evolved   to live with it, it can upset its delicate  balance. This is also true of a pathogen   travelling through time. Most of the species  will be harmless, but as we saw in 2020, it   only takes one ‘black swan’ to change everything.  With more cells being released from ice melt each   year than there are grains of sand on earth,  the risk one is a black swan is significant. A risk that increases with the  depth of the permafrost thaw. The   further back in time a potential pathogen is from,   the bigger the jump in its genome and the  lower our ecosystem’s readiness for it. So, the world is changing. As we have seen, ice is an incredible  recorder of Earth’s history.   Through studying its secrets, we can see  Earth’s past. Just as the ice cores detail   Earth’s ecosystem as the Bering Strait flooded,  it contains our history too. As the Ice melts   it replays many of humanity’s environmental  missteps by re-releasing trapped chemicals   we have produced. CFCs stored in the ice can again  deplete the ozone, and accelerate arctic ice loss.   Chlorinated pesticides, many long-banned from use,  can find their way back into Earth’s ecosystem;   some of which will have been made even more potent  by their time stored in ice. Vaporised lead from   the use of leaded petrol will also be re-released  as the ice layers that contain it melt away. This chemical cocktail adds yet more stress  to a global ecosystem moving ever closer to   an invisible edge. When we add all these factors  together, 2100 could look very different. Exactly   how different is under our control. The current  predicted average sea-level rise is 0.5 m. That   doesn’t sound like much, does it. A map of the  world’s coastlines would look almost unchanged. Though, it’s not the averages but  the black swan events – the storms,   the floods, the heatwaves – that drive  human behaviour. By 2100 a population the   size of the US will be exposed to regular  coastal floods. Faced with increased risk,   where will Earth's coastal populations move  to? How much will our way of life change? The rich diversity we see in cultures and  species on Earth is born out of adapting to   the environment. Both humanity and life itself  have demonstrated time and time again that they   are irrepressibly adaptive. Humanity can and has  to learn from its past and look to the future. So, there is hope. While the melting ice reminds us of the  environmental damage that we have been   responsible for since the industrial revolution,  it also reminds us of how often we came together   to make a change for the better when we understood  how we were affecting our planet and ourselves. I believe we can and need to do it again. It may well be that some engineering might be in  order in Earth’s future, to design and then build   the technology that eases the pressures on our  planet’s ecosystems. Creating something that helps   the planet might seem a tall order, something  only a brilliant inventor might accomplish,   but have you considered that brilliant inventor  may just be you? “But Alex,” I hear some of you   say, “I don’t have the technical skills  to accomplish something like that!”   Well, maybe that’s true… but would you like them?  Thanks to Brilliant, the sponsor of today’s video,   it’s possible for anyone to get a grasp  on engineering or other STEM subjects,   at beginner, intermediate or advanced levels.  Brilliant’s online interactive courses have   been proven to be one of the most effective  ways to learn STEM skills, with bite-sized   lessons that are 6 times better for learning than  simply listening to lectures. Brilliant can help   you develop skills and knowledge that can enhance  your career options or better your understanding   of the world. Click my link brilliant.org/astrum  or scan my QR code to get everything brilliant   has to offer for free, for the first 30 days,  and 20% off the premium annual subscription. Thanks for watching and thanks to our crew  of Astrumnauts over at Patreon who help us   make science knowledge freely available  to everyone. Chasing the algorithm can   be hit or miss sometimes, so your contributions  help us keep making the content we love. And if   you haven't already but you want to join the  Patreon, there's never been a better time to   get in on the party. Just sign up with the link  in the description. when you join you'll be able   to watch the whole video ad free, see you  name in the credits and submit questions to   our team. Once again, a huge thank you from  myself and the whole Astrum team. Meanwhile,   click the link to this playlist for more  Astrum content. I'll see you next time.
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Channel: Astrum
Views: 274,410
Rating: undefined out of 5
Keywords: astrum, astronomy, earth, space, earth weather, environment, climate, climate change, polar ice, polar ice caps, arctic, Antarctic, north pole, south pole, melting polar ice, climate systems, greenhouse gas, global warming, sea level, rising sea levels, co2, arctic circle, permafrost, Milankovitch, west Antarctic ice self, oceans, sea ice, ice shelves, ice berg, glaciers, AMOC, Europe, Atlantic, Pacific, Atlantic meridional overturning circulation, ecosystems, ice sheet, ozone, ice core
Id: WMFL_Ve9e2M
Channel Id: undefined
Length: 20min 37sec (1237 seconds)
Published: Thu May 30 2024
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