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Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:13.12,Default,,0000,0000,0000,,{\i1}preroll music{\i0}
Dialogue: 0,0:00:13.12,0:00:19.53,Default,,0000,0000,0000,,Herald: It's simple when ice gets above\N0°, it melts. But is it really that simple
Dialogue: 0,0:00:19.53,0:00:23.27,Default,,0000,0000,0000,,if we are not talking about a small ice\Ncube, but a big sheet of ice covering an
Dialogue: 0,0:00:23.27,0:00:28.91,Default,,0000,0000,0000,,entire continent? Is that really the only\Nfactor? And, am I right with my
Dialogue: 0,0:00:28.91,0:00:34.09,Default,,0000,0000,0000,,assessment? I'm looking forward to be\Nenlightened by Professor Doctor Ricarda
Dialogue: 0,0:00:34.09,0:00:38.16,Default,,0000,0000,0000,,Winkelmann. Ricarda Winkelmann is a\Nprofessor of climate science at the
Dialogue: 0,0:00:38.16,0:00:44.19,Default,,0000,0000,0000,,University of Potsdam, and she's also a\Nresearcher for climate impact. She leads
Dialogue: 0,0:00:44.19,0:00:48.54,Default,,0000,0000,0000,,the Ice Dynamics Working Group and Co-\Nleads PIK Future Lab on Earth Resilience
Dialogue: 0,0:00:48.54,0:00:52.65,Default,,0000,0000,0000,,in the Anthropocene. Her research focuses\Non tipping elements from the Earth system.
Dialogue: 0,0:00:52.65,0:00:57.18,Default,,0000,0000,0000,,And today she'll be talking about the\NGreenland and Antarctic ice dynamics and
Dialogue: 0,0:00:57.18,0:01:03.13,Default,,0000,0000,0000,,the future sea level rise that are\Nimpacted by them. It appears like she's
Dialogue: 0,0:01:03.13,0:01:07.11,Default,,0000,0000,0000,,surely an expert on all things related to\Nice. So please give a warm hand of
Dialogue: 0,0:01:07.11,0:01:11.67,Default,,0000,0000,0000,,applause for Professor Doctor Ricarda\NWinkelman with her talk: "The Big Melt:
Dialogue: 0,0:01:11.67,0:01:17.71,Default,,0000,0000,0000,,Tipping Points in Greenland and\NAntarctica" Have fun!
Dialogue: 0,0:01:17.71,0:02:35.65,Default,,0000,0000,0000,,[no audio]\N{\i1}in between music{\i0}
Dialogue: 0,0:02:35.65,0:02:39.71,Default,,0000,0000,0000,,Ricarda Winkelmann: {\i1}audio not working{\i0}\NThanks and welcome. Today, we're going to
Dialogue: 0,0:02:39.71,0:02:45.18,Default,,0000,0000,0000,,take a little excursion to the far north\Nand the far south, to our polar ice sheets
Dialogue: 0,0:02:45.18,0:02:51.61,Default,,0000,0000,0000,,on Greenland and Antarctica. As this year\Nis coming to a close, I thought we'd take
Dialogue: 0,0:02:51.61,0:02:58.54,Default,,0000,0000,0000,,a brief moment to reflect back. 2020 has\Ncertainly been an exceptional year for all
Dialogue: 0,0:02:58.54,0:03:05.08,Default,,0000,0000,0000,,of us. It was supposed to be a super year\Nfor nature and the environment, as world
Dialogue: 0,0:03:05.08,0:03:09.29,Default,,0000,0000,0000,,leaders put it at the beginning of the\Nyear. It's five years after the Paris
Dialogue: 0,0:03:09.29,0:03:13.86,Default,,0000,0000,0000,,climate accord. It's five years after the\NSustainable Development Goals have been
Dialogue: 0,0:03:13.86,0:03:19.79,Default,,0000,0000,0000,,announced. However, 2020 turned out to be\Nthe year when we've had to face several
Dialogue: 0,0:03:19.79,0:03:26.39,Default,,0000,0000,0000,,global crises, including the ongoing\Ncovid-19 pandemic and also the ongoing
Dialogue: 0,0:03:26.39,0:03:33.10,Default,,0000,0000,0000,,climate crisis. What almost got lost in\Nthe turmoil is that this year also saw
Dialogue: 0,0:03:33.10,0:03:37.94,Default,,0000,0000,0000,,several weather and climate extremes,\Nwhich spaned the globe from pole to pole,
Dialogue: 0,0:03:37.94,0:03:47.33,Default,,0000,0000,0000,,with temperatures reaching record highs in\Nthe Arctic and Antarctica with +38°C in
Dialogue: 0,0:03:47.33,0:03:51.37,Default,,0000,0000,0000,,the Arctic and in Siberia. That's the\Nhighest temperature that was ever recorded
Dialogue: 0,0:03:51.37,0:03:55.57,Default,,0000,0000,0000,,north of the Arctic Circle and it's\Nroughly 18° warmer than the average
Dialogue: 0,0:03:55.57,0:04:02.72,Default,,0000,0000,0000,,maximum daily temperature in June, when\Nthis was recorded. And we also saw +18° at
Dialogue: 0,0:04:02.72,0:04:07.52,Default,,0000,0000,0000,,the Antarctic Peninsula, which is, again,\Nthe highest temperature ever recorded in
Dialogue: 0,0:04:07.52,0:04:15.22,Default,,0000,0000,0000,,Antarctica. And this was followed by\Nwidespread melting on nearby glaciers.
Dialogue: 0,0:04:15.22,0:04:21.09,Default,,0000,0000,0000,,Now, if we're kind of zooming out and\Ntaking a look at the bigger picture, we're
Dialogue: 0,0:04:21.09,0:04:25.67,Default,,0000,0000,0000,,also at a very significant point in\NEarth's history. Here you see the global
Dialogue: 0,0:04:25.67,0:04:31.59,Default,,0000,0000,0000,,mean temperature evolution since the last glacial\Nmaximum. So the last ice age until today.
Dialogue: 0,0:04:31.59,0:04:35.95,Default,,0000,0000,0000,,And whenever I look at this graph, I see\Ntwo things that still strike me to this
Dialogue: 0,0:04:35.95,0:04:40.94,Default,,0000,0000,0000,,day. One is that the Holocene, the\Ninterglacial or the warm age, in which
Dialogue: 0,0:04:40.94,0:04:45.50,Default,,0000,0000,0000,,human civilizations have developed and\Nthrived, has been characterized by very
Dialogue: 0,0:04:45.50,0:04:50.65,Default,,0000,0000,0000,,stable climate conditions, by a very\Nstable global mean temperature. And the
Dialogue: 0,0:04:50.65,0:04:54.59,Default,,0000,0000,0000,,other thing is that the difference between\Nan ice age, here, 20 000 years ago
Dialogue: 0,0:04:54.59,0:05:00.54,Default,,0000,0000,0000,,roughly, and a warm age, that's roughly\Nthree to four degrees of global average
Dialogue: 0,0:05:00.54,0:05:05.69,Default,,0000,0000,0000,,temperature change. And right now we're on\Nthe verge of achieving the same
Dialogue: 0,0:05:05.69,0:05:12.70,Default,,0000,0000,0000,,temperature difference, but at much, much\Nfaster rates. So here you see several
Dialogue: 0,0:05:12.70,0:05:17.73,Default,,0000,0000,0000,,future temperature projections from the\NIPCC. And what you can see is, that in all
Dialogue: 0,0:05:17.73,0:05:22.29,Default,,0000,0000,0000,,of them, the temperature increase, even\Nthe lowest one, the temperature increase
Dialogue: 0,0:05:22.29,0:05:27.97,Default,,0000,0000,0000,,is much faster than it was ever recorded\Nbefore. So I think it's safe to say that
Dialogue: 0,0:05:27.97,0:05:32.80,Default,,0000,0000,0000,,we have truly entered the Anthropocene and\Nthat humans have become a geological
Dialogue: 0,0:05:32.80,0:05:39.52,Default,,0000,0000,0000,,force. So in the Anthropocene, humans have\Nbecome the single most important driver of
Dialogue: 0,0:05:39.52,0:05:45.27,Default,,0000,0000,0000,,global change affecting the entire Earth\Nsystem, including our ice sheets. But it
Dialogue: 0,0:05:45.27,0:05:50.69,Default,,0000,0000,0000,,was kind of the opposite in the past. Like\Nno other forces on the planet, ice ages
Dialogue: 0,0:05:50.69,0:05:55.77,Default,,0000,0000,0000,,have actually shaped our surroundings and\Nthereby determined our development as
Dialogue: 0,0:05:55.77,0:06:01.04,Default,,0000,0000,0000,,human civilizations. For instance, we owe\Nour fertile soils, to the last ice age,
Dialogue: 0,0:06:01.04,0:06:06.06,Default,,0000,0000,0000,,that also carved our current landscapes\Nthat we see all around us, leaving
Dialogue: 0,0:06:06.06,0:06:12.90,Default,,0000,0000,0000,,glaciers behind, rivers and lakes. So even\Nthough the ice sheets on Greenland and
Dialogue: 0,0:06:12.90,0:06:18.98,Default,,0000,0000,0000,,Antarctica might seem far away sometimes,\Nthey're actually crucial also for us here
Dialogue: 0,0:06:18.98,0:06:25.01,Default,,0000,0000,0000,,today. And today, I want to leave you with\Nan impression why they are so important.
Dialogue: 0,0:06:25.01,0:06:28.30,Default,,0000,0000,0000,,And one reason why they are so important\Nis because they're an amazing climate
Dialogue: 0,0:06:28.30,0:06:35.26,Default,,0000,0000,0000,,archive. Here you see an ice core taken\Nfrom one of the deepest parts of an ice
Dialogue: 0,0:06:35.26,0:06:40.61,Default,,0000,0000,0000,,sheet. And this is basically like counting\Ntree rings. You can go back to the past
Dialogue: 0,0:06:40.61,0:06:47.48,Default,,0000,0000,0000,,and you can see what the climate was like\Nin the deep past, ranging several hundreds
Dialogue: 0,0:06:47.48,0:06:52.50,Default,,0000,0000,0000,,of thousands of years back. And you can\Nsee the conditions, for instance, in the
Dialogue: 0,0:06:52.50,0:06:58.73,Default,,0000,0000,0000,,CO2 change, the temperature change over\Nthis really long timescales. So that's one
Dialogue: 0,0:06:58.73,0:07:04.35,Default,,0000,0000,0000,,of the reasons why the ice sheets are so\Nimportant. Another one is their so-called
Dialogue: 0,0:07:04.35,0:07:09.94,Default,,0000,0000,0000,,sea level potential. Greenland and\NAntarctica are truly sleeping giants. And
Dialogue: 0,0:07:09.94,0:07:14.68,Default,,0000,0000,0000,,to give you an idea of the sheer size of\Nthese two ice sheets, one way of doing
Dialogue: 0,0:07:14.68,0:07:20.05,Default,,0000,0000,0000,,that is to compute their ice volume in the\Nso-called sea level equivalent. What this
Dialogue: 0,0:07:20.05,0:07:24.51,Default,,0000,0000,0000,,means is, if we were to melt down the\NGreenland ice sheet and distribute that
Dialogue: 0,0:07:24.51,0:07:29.38,Default,,0000,0000,0000,,meltwater around the entire globe, then\Nthis would lead to a global sea level rise
Dialogue: 0,0:07:29.38,0:07:35.09,Default,,0000,0000,0000,,of roughly seven meters. For the West\NAntarctic ice sheet, it's about five
Dialogue: 0,0:07:35.09,0:07:41.36,Default,,0000,0000,0000,,meters, and for East Antarctica, the\Ntenfold. So more than sixty five meters in
Dialogue: 0,0:07:41.36,0:07:47.74,Default,,0000,0000,0000,,total of sea level potential that are\Nstored in these two ice sheets. Now, over
Dialogue: 0,0:07:47.74,0:07:51.96,Default,,0000,0000,0000,,the past decades, the ice sheets have both\Nbeen losing mass and they've been losing
Dialogue: 0,0:07:51.96,0:07:57.65,Default,,0000,0000,0000,,mass at an accelerating pace. In fact,\Nwe're currently on track with the worst
Dialogue: 0,0:07:57.65,0:08:03.45,Default,,0000,0000,0000,,case climate change scenario. Here you see\Nthe observations in gray and you also see
Dialogue: 0,0:08:03.45,0:08:08.06,Default,,0000,0000,0000,,several of the projections from the past\Nfor the ice sheets. And as you can see,
Dialogue: 0,0:08:08.06,0:08:12.17,Default,,0000,0000,0000,,we're tracking this upper branch here. So\Nwe're really on track with the worst case
Dialogue: 0,0:08:12.17,0:08:17.45,Default,,0000,0000,0000,,climate change scenario for the ice\Nsheets. And what this means is even if we
Dialogue: 0,0:08:17.45,0:08:22.21,Default,,0000,0000,0000,,were to stop global warming today, the ice\Nsheets would still keep losing mass
Dialogue: 0,0:08:22.21,0:08:26.59,Default,,0000,0000,0000,,because of the inertia in the system. So\Nsea levels would keep rising for decades
Dialogue: 0,0:08:26.59,0:08:33.46,Default,,0000,0000,0000,,or even centuries to come. Why is that?\NWell, there are several processes that we
Dialogue: 0,0:08:33.46,0:08:39.95,Default,,0000,0000,0000,,need to understand in order to keep track\Nof sea level change and also to understand
Dialogue: 0,0:08:39.95,0:08:43.91,Default,,0000,0000,0000,,the ice sheet's evolution in the past and\Nin the future. Here, you see sort of an
Dialogue: 0,0:08:43.91,0:08:50.09,Default,,0000,0000,0000,,exemplary cut through an ice shelf system,\Nwhere the ice sheet is in contact with the
Dialogue: 0,0:08:50.09,0:08:55.54,Default,,0000,0000,0000,,atmosphere. You have a grounded part and\Nthen in many places, you also have these
Dialogue: 0,0:08:55.54,0:09:00.70,Default,,0000,0000,0000,,extensions, these floating extensions, the\Nso-called ice shelves that surround
Dialogue: 0,0:09:00.70,0:09:06.47,Default,,0000,0000,0000,,particularly Antarctica. The separation\Nbetween the two is the so-called grounding
Dialogue: 0,0:09:06.47,0:09:15.46,Default,,0000,0000,0000,,line. Now, generally ice sheets gain mass\Nthrough snowfall just on top of the ice
Dialogue: 0,0:09:15.46,0:09:21.93,Default,,0000,0000,0000,,sheet, which then is compressed into ice\Nand over time, due to the sheer gravity
Dialogue: 0,0:09:21.93,0:09:27.13,Default,,0000,0000,0000,,and the sheer size of the ice sheets, it's\Nbasically pushing its own mass towards the
Dialogue: 0,0:09:27.13,0:09:32.03,Default,,0000,0000,0000,,ocean. And that's one of the reasons why\Nthere's a constant flow of ice. So ice is
Dialogue: 0,0:09:32.03,0:09:37.16,Default,,0000,0000,0000,,really not only a solid, it's also a\Nfluid. The ice sheets can also lose mass
Dialogue: 0,0:09:37.16,0:09:42.47,Default,,0000,0000,0000,,through surface melting, but also through\Nmelting at the underside of the floating
Dialogue: 0,0:09:42.47,0:09:48.39,Default,,0000,0000,0000,,ice shelves, where they're in contact with\Nwarmer ocean waters. And then there can,
Dialogue: 0,0:09:48.39,0:09:53.88,Default,,0000,0000,0000,,of course, also be ice shelf calving, so\Nicebergs that break off at the margins of
Dialogue: 0,0:09:53.88,0:10:00.48,Default,,0000,0000,0000,,the ice sheet. Now, what we see here, this\Nleft hand side, that's a typical situation
Dialogue: 0,0:10:00.48,0:10:06.54,Default,,0000,0000,0000,,for the Greenland ice sheet. The Greenland\Nice sheet is generally grounded above sea
Dialogue: 0,0:10:06.54,0:10:12.04,Default,,0000,0000,0000,,level in most parts and it's not only much\Nsmaller than Antarctica, but it's also
Dialogue: 0,0:10:12.04,0:10:16.51,Default,,0000,0000,0000,,located further south, so further away\Nfrom the pole. And that means it's
Dialogue: 0,0:10:16.51,0:10:21.94,Default,,0000,0000,0000,,generally warmer in Greenland, leading to\Nmore surface melt for the Greenland ice
Dialogue: 0,0:10:21.94,0:10:30.52,Default,,0000,0000,0000,,sheet. Whereas in Antarctica, it's not\Nonly much colder there, but also the ice
Dialogue: 0,0:10:30.52,0:10:36.58,Default,,0000,0000,0000,,sheet is covered and surrounded by\Nfloating ice shelves almost all around the
Dialogue: 0,0:10:36.58,0:10:40.98,Default,,0000,0000,0000,,coastline. And that means that one of the\Nmost important driving processes for mass
Dialogue: 0,0:10:40.98,0:10:45.64,Default,,0000,0000,0000,,loss in Antarctica is this melting\Nunderneath the ice shelves, so the
Dialogue: 0,0:10:45.64,0:10:51.86,Default,,0000,0000,0000,,subshelf melting in contact with the\Nwarmer ocean waters. Just to give you an
Dialogue: 0,0:10:51.86,0:10:57.82,Default,,0000,0000,0000,,impression of the sheer ice thickness, I\Nbrought this picture here. This is my very
Dialogue: 0,0:10:57.82,0:11:03.56,Default,,0000,0000,0000,,first impression of the Antarctic\Ncoastline, the ice shelf margin. This is
Dialogue: 0,0:11:03.56,0:11:08.03,Default,,0000,0000,0000,,close to the German research station\NNeumayer III. And I will never forget the
Dialogue: 0,0:11:08.03,0:11:12.80,Default,,0000,0000,0000,,moment that I first saw the ice shelf\Nedge. It was in the middle of the night,
Dialogue: 0,0:11:12.80,0:11:17.22,Default,,0000,0000,0000,,but we were there in summer, so we had\Ntwenty four hours of daylight. And I woke
Dialogue: 0,0:11:17.22,0:11:22.37,Default,,0000,0000,0000,,up because it suddenly got dark in our\Ncabin. So I went up to the bridge to see
Dialogue: 0,0:11:22.37,0:11:27.93,Default,,0000,0000,0000,,what was going on and I saw myself in\Nfront of a wall, like really a cliff of
Dialogue: 0,0:11:27.93,0:11:34.18,Default,,0000,0000,0000,,ice. And knowing that these ice shelves\Nbehave like the ice cubes in the water
Dialogue: 0,0:11:34.18,0:11:41.21,Default,,0000,0000,0000,,glass, so only roughly 10 percent are\Nvisible above the sea level, this means
Dialogue: 0,0:11:41.21,0:11:47.71,Default,,0000,0000,0000,,that in this case, we had an ice shelf\Nedge that was more than 100 meters thick.
Dialogue: 0,0:11:47.71,0:11:51.44,Default,,0000,0000,0000,,And that really impressed me. I\Nimmediately had to think of this German
Dialogue: 0,0:11:51.44,0:11:57.21,Default,,0000,0000,0000,,expression, "das ewige Eis", the eternal\Nice. And I really wondered if this is
Dialogue: 0,0:11:57.21,0:12:02.24,Default,,0000,0000,0000,,maybe the right expression because it\Nseemed like it was so static and nothing
Dialogue: 0,0:12:02.24,0:12:07.87,Default,,0000,0000,0000,,was moving. However, that's not true\Nbecause even in equilibrium, the ice is
Dialogue: 0,0:12:07.87,0:12:13.35,Default,,0000,0000,0000,,constantly moving. It's here just\Nvisualized by these little snowflakes and
Dialogue: 0,0:12:13.35,0:12:19.10,Default,,0000,0000,0000,,you can see how the ice is moving from the\Ninterior towards the coastlines. And we
Dialogue: 0,0:12:19.10,0:12:24.09,Default,,0000,0000,0000,,have a wide range of velocities at the\Nsurface, ranging from almost zero in the
Dialogue: 0,0:12:24.09,0:12:29.35,Default,,0000,0000,0000,,interior of the ice sheet to several\Nkilometers per year in the larger ice
Dialogue: 0,0:12:29.35,0:12:34.86,Default,,0000,0000,0000,,shelves and also the so-called ice\Nstreams, the faster flowing ice. If I were
Dialogue: 0,0:12:34.86,0:12:42.03,Default,,0000,0000,0000,,able to take a dive underneath the ice\Nshelves and I could actually take a look
Dialogue: 0,0:12:42.03,0:12:47.31,Default,,0000,0000,0000,,at the grounding line, this would probably\Nbe what what I could see. This is the
Dialogue: 0,0:12:47.31,0:12:52.48,Default,,0000,0000,0000,,triple point basically where solid earth,\Nthe ice and water all come together. And
Dialogue: 0,0:12:52.48,0:12:56.38,Default,,0000,0000,0000,,this grounding line is a very important\Nrole for Antarctic ice dynamics and also
Dialogue: 0,0:12:56.38,0:13:04.06,Default,,0000,0000,0000,,for the future fate of Antarctica. So what\Nmakes the dynamics of the ice sheets and
Dialogue: 0,0:13:04.06,0:13:10.38,Default,,0000,0000,0000,,shelves so particularly difficult to\Nunderstand and also to project the future
Dialogue: 0,0:13:10.38,0:13:15.57,Default,,0000,0000,0000,,evolution is that both ice sheets are\Nsubject to several so-called positive, so
Dialogue: 0,0:13:15.57,0:13:22.49,Default,,0000,0000,0000,,self-reinforcing feedback mechanisms. Here\Nare just some examples with some of the
Dialogue: 0,0:13:22.49,0:13:28.09,Default,,0000,0000,0000,,major ones we know very well. One is the\Nice-albedo-feedback and another one is the
Dialogue: 0,0:13:28.09,0:13:33.49,Default,,0000,0000,0000,,so-called melt-elevation-feedback. As I\Nsaid, in Greenland we observe a lot of
Dialogue: 0,0:13:33.49,0:13:38.33,Default,,0000,0000,0000,,surface melting. If you've ever flown\Nacross the Greenland ice sheet in summer,
Dialogue: 0,0:13:38.33,0:13:43.39,Default,,0000,0000,0000,,you can really see these rivers forming\Nand then even lakes forming at the ice
Dialogue: 0,0:13:43.39,0:13:49.89,Default,,0000,0000,0000,,sheet surface. And over the recent decade,\NGreenland has been subject to several
Dialogue: 0,0:13:49.89,0:13:56.68,Default,,0000,0000,0000,,extreme melt events, including\Nparticularly the year 2010, 2012 and also
Dialogue: 0,0:13:56.68,0:14:01.83,Default,,0000,0000,0000,,last year. And the reason there's this\Nextreme melting at the surface is due to a
Dialogue: 0,0:14:01.83,0:14:06.77,Default,,0000,0000,0000,,combination of factors, it has to do with\Nthe duration of the summer, but also even
Dialogue: 0,0:14:06.77,0:14:13.26,Default,,0000,0000,0000,,here in Europe, we observed very warm and\Ndry summers. And that's also something
Dialogue: 0,0:14:13.26,0:14:18.64,Default,,0000,0000,0000,,that was observed for Greenland. So that,\Nfor instance, in the year 2019 in August,
Dialogue: 0,0:14:18.64,0:14:24.54,Default,,0000,0000,0000,,almost the entire ice sheet surface was\Ncovered with meltwater. Now, why is this
Dialogue: 0,0:14:24.54,0:14:29.68,Default,,0000,0000,0000,,surface melting so important? The reason\Nis that there is also a self-reinforcing
Dialogue: 0,0:14:29.68,0:14:33.97,Default,,0000,0000,0000,,feedback that could be driven by surface\Nmelting. And we all know this mechanism
Dialogue: 0,0:14:33.97,0:14:38.64,Default,,0000,0000,0000,,from mountain climbing. If you climb down\Nfrom the peak of a mountain towards the
Dialogue: 0,0:14:38.64,0:14:43.66,Default,,0000,0000,0000,,valley, it gets warmer around you. And the\Nsame is true also for the ice sheets. So
Dialogue: 0,0:14:43.66,0:14:48.85,Default,,0000,0000,0000,,if there's enough melting, it could\Nactually lower the surface to a region
Dialogue: 0,0:14:48.85,0:14:53.31,Default,,0000,0000,0000,,where the temperatures are higher, the\Nsurface temperatures are higher, leading
Dialogue: 0,0:14:53.31,0:14:57.67,Default,,0000,0000,0000,,to more melting, which again lowers the\Nsurface elevation, leading to higher
Dialogue: 0,0:14:57.67,0:15:03.14,Default,,0000,0000,0000,,temperatures, leading to more melting and\Nso on and so on, so that this can trigger
Dialogue: 0,0:15:03.14,0:15:09.81,Default,,0000,0000,0000,,these self-reinforcing dynamics. And\Nwhenever we have such a positive or self-
Dialogue: 0,0:15:09.81,0:15:15.45,Default,,0000,0000,0000,,reinforcing feedback mechanism, we can\Nalso have a tipping point. And here is the
Dialogue: 0,0:15:15.45,0:15:20.48,Default,,0000,0000,0000,,depiction of a very simple way of\Ncomputing, where this tipping point might
Dialogue: 0,0:15:20.48,0:15:25.24,Default,,0000,0000,0000,,be for the Greenland ice sheet, where\Nwe've really done this with just
Dialogue: 0,0:15:25.24,0:15:31.49,Default,,0000,0000,0000,,analytical work. So pen and paper, trying\Nto understand where we go from a stable
Dialogue: 0,0:15:31.49,0:15:37.45,Default,,0000,0000,0000,,Greenland ice sheet into unstable regime,\Nwhich would then lead to a meltdown of the
Dialogue: 0,0:15:37.45,0:15:43.25,Default,,0000,0000,0000,,entire ice sheet until basically no ice is\Nleft at the surface. So this is something
Dialogue: 0,0:15:43.25,0:15:49.43,Default,,0000,0000,0000,,that we can understand in theory, but also\Nsomething that we find in more complex
Dialogue: 0,0:15:49.43,0:15:57.34,Default,,0000,0000,0000,,numerical ice sheet models. And they find\Nthat this warming threshold that leads to
Dialogue: 0,0:15:57.34,0:16:02.91,Default,,0000,0000,0000,,basically a decay of the entire ice sheet\Nlies somewhere between 0.8°C and 3.2°C of
Dialogue: 0,0:16:02.91,0:16:07.62,Default,,0000,0000,0000,,warming above pre-industrial levels. And\Nyou can see that between these
Dialogue: 0,0:16:07.62,0:16:12.62,Default,,0000,0000,0000,,temperatures, somewhere there's almost a\Nstep change. This is now the computed sea
Dialogue: 0,0:16:12.62,0:16:17.80,Default,,0000,0000,0000,,level rise. So up here, this means that\NGreenland is ice free. So we're going from
Dialogue: 0,0:16:17.80,0:16:23.35,Default,,0000,0000,0000,,an intact Greenland ice sheet to an ice\Nfree Greenland somewhere between these
Dialogue: 0,0:16:23.35,0:16:29.25,Default,,0000,0000,0000,,temperatures. What this looks like can be\Nvisualized with numerical ice sheet
Dialogue: 0,0:16:29.25,0:16:33.83,Default,,0000,0000,0000,,models. And here you see that once this\Nthreshold is exceeded, basically the
Dialogue: 0,0:16:33.83,0:16:39.51,Default,,0000,0000,0000,,eigendynamics lead to a complete meltdown\Noff the ice sheet, until there's almost no
Dialogue: 0,0:16:39.51,0:16:44.16,Default,,0000,0000,0000,,ice left except for in the highest regions\Nhere in the east where there are some
Dialogue: 0,0:16:44.16,0:16:51.90,Default,,0000,0000,0000,,small ice caps remaining. Now, something\Nsimilar, but also different is going on in
Dialogue: 0,0:16:51.90,0:16:58.44,Default,,0000,0000,0000,,Antarctica because, as I said earlier, in\NAntarctica it's much colder. So we have
Dialogue: 0,0:16:58.44,0:17:02.62,Default,,0000,0000,0000,,very little surface melt at the moment.\NBut at the same time, it's surrounded by
Dialogue: 0,0:17:02.62,0:17:07.69,Default,,0000,0000,0000,,the floating ice shelves and they play the\Nmajor role in driving sea changes in
Dialogue: 0,0:17:07.69,0:17:15.36,Default,,0000,0000,0000,,Antarctica. Antarctic mass loss has\Ntripled over the recent years, especially
Dialogue: 0,0:17:15.36,0:17:19.15,Default,,0000,0000,0000,,in the so-called Amundson and\NBellingshausen Sea regions. So these are
Dialogue: 0,0:17:19.15,0:17:24.31,Default,,0000,0000,0000,,these regions here where you see all these\Nred parts. So this is all ice loss that's
Dialogue: 0,0:17:24.31,0:17:32.14,Default,,0000,0000,0000,,been detected here. And the reason for\Nthis is due to the ice shelf ocean
Dialogue: 0,0:17:32.14,0:17:37.12,Default,,0000,0000,0000,,interactions. So here you now see the\Nocean temperatures surrounding Antarctic
Dialogue: 0,0:17:37.12,0:17:42.06,Default,,0000,0000,0000,,ice shelves. And you can see a stark\Ndifference between the temperatures here
Dialogue: 0,0:17:42.06,0:17:46.24,Default,,0000,0000,0000,,around the Amundson and Bellingshausen\Nregions and the temperatures, for
Dialogue: 0,0:17:46.24,0:17:50.03,Default,,0000,0000,0000,,instance, here in the Weddell Sea or in\Nthe Ross Sea, the temperature difference
Dialogue: 0,0:17:50.03,0:17:55.50,Default,,0000,0000,0000,,being roughly two degrees. So there's\Nreally been a switch from a colder to a
Dialogue: 0,0:17:55.50,0:18:01.74,Default,,0000,0000,0000,,warmer cavity, for instance, here in the\NAmundson Sea region. And that drives more
Dialogue: 0,0:18:01.74,0:18:06.78,Default,,0000,0000,0000,,sub shelf melting, which in turn leads to\Na decrease of the so-called buttressing
Dialogue: 0,0:18:06.78,0:18:14.36,Default,,0000,0000,0000,,effect. What this means is, well, first of\Nall, the ice shelves do not contribute to
Dialogue: 0,0:18:14.36,0:18:19.20,Default,,0000,0000,0000,,sea level rise directly, at least not\Nsignificantly. The reason being that they
Dialogue: 0,0:18:19.20,0:18:24.29,Default,,0000,0000,0000,,are like ice cubes in a water glass. And\Nif that melts down, it also doesn't raise
Dialogue: 0,0:18:24.29,0:18:28.78,Default,,0000,0000,0000,,the water level in the glass. So it's\Nsimilar with the ice shelves, but at the
Dialogue: 0,0:18:28.78,0:18:33.08,Default,,0000,0000,0000,,same time they are still attached to the\Ngrounded part of the sheet. So if the ice
Dialogue: 0,0:18:33.08,0:18:39.48,Default,,0000,0000,0000,,shelves melt or there are larger calving\Nevents in the ice shelves, that means that
Dialogue: 0,0:18:39.48,0:18:44.76,Default,,0000,0000,0000,,the flow behind them from the interior of\Nthe ice sheet into the ocean accelerates.
Dialogue: 0,0:18:44.76,0:18:50.91,Default,,0000,0000,0000,,It's almost like pulling a plug. And this\Nis what is the so-called buttressing
Dialogue: 0,0:18:50.91,0:18:54.61,Default,,0000,0000,0000,,effects, so the backstress at the\Ngrounding line. So if we have enhanced ice
Dialogue: 0,0:18:54.61,0:18:59.07,Default,,0000,0000,0000,,shelf melting, that means that this\Nbuttressing effect, this buffering effect
Dialogue: 0,0:18:59.07,0:19:04.04,Default,,0000,0000,0000,,is reduced and therefore we have\Naccelerated outflow into the ocean. Now,
Dialogue: 0,0:19:04.04,0:19:09.11,Default,,0000,0000,0000,,the question is, how does this impact the\Nice sheet dynamics overall, in particular,
Dialogue: 0,0:19:09.11,0:19:15.56,Default,,0000,0000,0000,,the stability of the West and East\NAntarctic ice sheets. You may have come
Dialogue: 0,0:19:15.56,0:19:21.18,Default,,0000,0000,0000,,across some of these headlines in recent\Nyears. My favorite one is still this one
Dialogue: 0,0:19:21.18,0:19:28.15,Default,,0000,0000,0000,,up here from 2014 where the "Holy Shit\NMoment of Global Warming" was declared.
Dialogue: 0,0:19:28.15,0:19:33.30,Default,,0000,0000,0000,,And the reason for this were these\Nobservations from the Amundson region in
Dialogue: 0,0:19:33.30,0:19:38.78,Default,,0000,0000,0000,,West Antarctica. So we're now taking sort\Nof a flight into the Amundson Sea region.
Dialogue: 0,0:19:38.78,0:19:42.86,Default,,0000,0000,0000,,And what was observed over the recent\Ndecades is not only that the glaciers here
Dialogue: 0,0:19:42.86,0:19:48.42,Default,,0000,0000,0000,,have accelerated, so everything that's\Nshown in red is accelerated ice flow, but
Dialogue: 0,0:19:48.42,0:19:54.11,Default,,0000,0000,0000,,at the same time, the glaciers have also\Nretreated into the deeper valleys behind.
Dialogue: 0,0:19:54.11,0:19:59.53,Default,,0000,0000,0000,,So you see this browning at the surface\Nnow. So all of these changes where the
Dialogue: 0,0:19:59.53,0:20:05.05,Default,,0000,0000,0000,,glaciers have basically retreated and with\Nthis comes another self reinforcing
Dialogue: 0,0:20:05.05,0:20:10.14,Default,,0000,0000,0000,,feedback, the so-called marine ice-sheet\Ninstability. For the marine ice sheet
Dialogue: 0,0:20:10.14,0:20:16.36,Default,,0000,0000,0000,,instability to occur, we need two\Nconditions to hold. One, as depicted here,
Dialogue: 0,0:20:16.36,0:20:21.17,Default,,0000,0000,0000,,is that the ice sheet is grounded below\Nsea level, which is true for many parts of
Dialogue: 0,0:20:21.17,0:20:26.41,Default,,0000,0000,0000,,West Antarctica, but also some parts of\NEast Antarctica. And also we need to
Dialogue: 0,0:20:26.41,0:20:32.70,Default,,0000,0000,0000,,generally have a retrograde sloping bed.\NSo that means that the bedrock elevation
Dialogue: 0,0:20:32.70,0:20:38.12,Default,,0000,0000,0000,,decreases towards the interior of the ice\Nsheet. And when these two conditions hold,
Dialogue: 0,0:20:38.12,0:20:42.98,Default,,0000,0000,0000,,then we can show in two dimensions,\Nmathematically, we can prove
Dialogue: 0,0:20:42.98,0:20:49.96,Default,,0000,0000,0000,,mathematically that an instability occurs\Nin this case. The reason is that we have
Dialogue: 0,0:20:49.96,0:20:54.98,Default,,0000,0000,0000,,an feedback between the grounding line\Nretreat and the ice locks across the
Dialogue: 0,0:20:54.98,0:20:59.00,Default,,0000,0000,0000,,grounding line. If the grounding line\Nretreats in a case where we have a
Dialogue: 0,0:20:59.00,0:21:03.39,Default,,0000,0000,0000,,retrograde sloping bed and the ice is\Nground below sea level, that means that
Dialogue: 0,0:21:03.39,0:21:09.75,Default,,0000,0000,0000,,the ice thickness towards the interior is\Nlarger. And this generally also means that
Dialogue: 0,0:21:09.75,0:21:14.45,Default,,0000,0000,0000,,the ice flux across the grounding line is\Nlarger, leading to further retreat off the
Dialogue: 0,0:21:14.45,0:21:18.67,Default,,0000,0000,0000,,grounding line and so on and so on. So\Nagain, we have a positive feedback
Dialogue: 0,0:21:18.67,0:21:23.95,Default,,0000,0000,0000,,mechanism that could drive self-sustained\Nice loss from parts of the West and East
Dialogue: 0,0:21:23.95,0:21:29.20,Default,,0000,0000,0000,,Antarctic ice sheet. And the concern is\Nnow that this marine ice sheet instability
Dialogue: 0,0:21:29.20,0:21:35.86,Default,,0000,0000,0000,,is potentially underway in the Amundson\Nbasin here in West Antarctica. Now, what's
Dialogue: 0,0:21:35.86,0:21:42.08,Default,,0000,0000,0000,,unclear is, how fast this change would\Nactually occur. So if we have actually
Dialogue: 0,0:21:42.08,0:21:46.11,Default,,0000,0000,0000,,triggered the marine ice sheet instability\Nin this region, and that means we have a
Dialogue: 0,0:21:46.11,0:21:52.83,Default,,0000,0000,0000,,committed ice loss of roughly one meter\Nsea level equivalent, then the question is
Dialogue: 0,0:21:52.83,0:21:58.08,Default,,0000,0000,0000,,still, how fast does this occur? And for\Nthis, it really matters how much further
Dialogue: 0,0:21:58.08,0:22:02.87,Default,,0000,0000,0000,,global warming continues. So and at which\Nrate the temperature will change in the
Dialogue: 0,0:22:02.87,0:22:09.92,Default,,0000,0000,0000,,future. So this is what's happening in\Npart of the West Antarctic ice sheet. We
Dialogue: 0,0:22:09.92,0:22:13.55,Default,,0000,0000,0000,,were also asking ourselves, weather could\Nsomething like this also happen for East
Dialogue: 0,0:22:13.55,0:22:19.44,Default,,0000,0000,0000,,Antarctica and how stable are each of the\Ndifferent ice basins in Antarctica? So we
Dialogue: 0,0:22:19.44,0:22:24.39,Default,,0000,0000,0000,,did something of a stability check on the\NAntarctic ice sheet to assess the risk of
Dialogue: 0,0:22:24.39,0:22:28.88,Default,,0000,0000,0000,,long term sea level rise from these\Ndifferent regions. What you will see next
Dialogue: 0,0:22:28.88,0:22:34.22,Default,,0000,0000,0000,,is an animation where we're increasing the\Nglobal mean temperature, but we're
Dialogue: 0,0:22:34.22,0:22:39.57,Default,,0000,0000,0000,,increasing it very, very slowly, at a much\Nslower rate than the typical rate of
Dialogue: 0,0:22:39.57,0:22:45.33,Default,,0000,0000,0000,,change in the ice sheet to test for the\Nstability of these different parts. And
Dialogue: 0,0:22:45.33,0:22:52.36,Default,,0000,0000,0000,,what we see is that at roughly 2°C, we are\Nlosing a large part of the West Antarctic
Dialogue: 0,0:22:52.36,0:22:57.05,Default,,0000,0000,0000,,ice sheet. So there's a first tipping\Npoint around 2°C. And then as the
Dialogue: 0,0:22:57.05,0:23:04.43,Default,,0000,0000,0000,,temperature increases, also the surface\Nelevation is lowered. And that leads to,
Dialogue: 0,0:23:04.43,0:23:10.58,Default,,0000,0000,0000,,potentially then also triggering these\Nsurface elevation and melt elevation
Dialogue: 0,0:23:10.58,0:23:16.87,Default,,0000,0000,0000,,feedbacks in East Antarctica. So around\N6°C to 9°C, there's another major
Dialogue: 0,0:23:16.87,0:23:22.23,Default,,0000,0000,0000,,threshold. And after this, large parts of\Nthe East Antarctic ice sheet could also be
Dialogue: 0,0:23:22.23,0:23:30.97,Default,,0000,0000,0000,,committed to long term sea level rise. At\Nabout 10°C, the Antarctic ice sheet could
Dialogue: 0,0:23:30.97,0:23:36.07,Default,,0000,0000,0000,,potentially become ice free on the long\Nterm. And, this is really important. What
Dialogue: 0,0:23:36.07,0:23:40.61,Default,,0000,0000,0000,,we're seeing here are not projections, but\Nwhat we're seeing here is a stability
Dialogue: 0,0:23:40.61,0:23:44.21,Default,,0000,0000,0000,,check. So we're not looking at something\Nthat's happening within the next century
Dialogue: 0,0:23:44.21,0:23:48.85,Default,,0000,0000,0000,,or so, but rather we're interested in\Nunderstanding, at which temperatures the
Dialogue: 0,0:23:48.85,0:23:55.22,Default,,0000,0000,0000,,Antarctic ice sheet could still survive on\Nthe long term. We also wanted to see if
Dialogue: 0,0:23:55.22,0:24:01.81,Default,,0000,0000,0000,,some of these changes are reversible. And\Nwhat we find is a so-called hysteresis
Dialogue: 0,0:24:01.81,0:24:07.39,Default,,0000,0000,0000,,behavior of the Antarctic ice sheet. That\Nmeans, as we're losing the ice and we'll
Dialogue: 0,0:24:07.39,0:24:13.48,Default,,0000,0000,0000,,then cool the temperatures back down, the\Nice sheet does not regrow back to its
Dialogue: 0,0:24:13.48,0:24:18.99,Default,,0000,0000,0000,,initial state, but it takes much, much\Ncolder temperatures to regrow the same ice
Dialogue: 0,0:24:18.99,0:24:25.27,Default,,0000,0000,0000,,sheet volume that we are currently having\Nat present day temperature levels. So
Dialogue: 0,0:24:25.27,0:24:31.27,Default,,0000,0000,0000,,there's a significant difference between\Nthis retreat and the regrowth path. And
Dialogue: 0,0:24:31.27,0:24:37.45,Default,,0000,0000,0000,,this can be up to 20 meters of sea level\Nequivalent in the difference between these
Dialogue: 0,0:24:37.45,0:24:44.65,Default,,0000,0000,0000,,two paths. What this looks like\Nregionally, you can see here. So again, we
Dialogue: 0,0:24:44.65,0:24:50.13,Default,,0000,0000,0000,,have the retreat and the regrowth path at\N2°C of global warming, and 4°C of global
Dialogue: 0,0:24:50.13,0:24:54.20,Default,,0000,0000,0000,,warming. So these are the long term\Neffects at these temperature levels. And
Dialogue: 0,0:24:54.20,0:25:00.12,Default,,0000,0000,0000,,you can see that, for instance, for 4°C\Nlarge parts of East Antarctic and also of
Dialogue: 0,0:25:00.12,0:25:04.71,Default,,0000,0000,0000,,the West Antarctic ice sheet do not regrow\Nat the same temperature level. So we
Dialogue: 0,0:25:04.71,0:25:10.14,Default,,0000,0000,0000,,clearly observe this hysteresis behavior.\NThat's another sign that the Antarctic ice
Dialogue: 0,0:25:10.14,0:25:16.25,Default,,0000,0000,0000,,sheet is the tipping element in the\Nclimate system. So both Greenland and
Dialogue: 0,0:25:16.25,0:25:21.78,Default,,0000,0000,0000,,Antarctica are tipping elements in the\Nclimate system. There are a number more
Dialogue: 0,0:25:21.78,0:25:27.23,Default,,0000,0000,0000,,candidates for tipping elements, including\Nsome of the larger biosphere components,
Dialogue: 0,0:25:27.23,0:25:31.75,Default,,0000,0000,0000,,for instance, the Amazon rainforest, the\Ntropical coral reefs, and also the boreal
Dialogue: 0,0:25:31.75,0:25:36.40,Default,,0000,0000,0000,,forests, as well as some of the large\Nscale circulations. So, for instance, the
Dialogue: 0,0:25:36.40,0:25:41.45,Default,,0000,0000,0000,,Atlantic thermohaline circulation, what we\Noften term the Gulf Stream, and the Indian
Dialogue: 0,0:25:41.45,0:25:48.65,Default,,0000,0000,0000,,summer monsoon are tipping candidates in\Nthe climate system. Now, if we go back to
Dialogue: 0,0:25:48.65,0:25:54.34,Default,,0000,0000,0000,,our temperature evolution since last\Nglacial maximum, and we now insert what we
Dialogue: 0,0:25:54.34,0:25:59.51,Default,,0000,0000,0000,,know about the tipping thresholds of these\Ndifferent components in the Earth system,
Dialogue: 0,0:25:59.51,0:26:04.61,Default,,0000,0000,0000,,then this is what we get. And we see, that\Nthere are basically three clusters of
Dialogue: 0,0:26:04.61,0:26:09.75,Default,,0000,0000,0000,,tipping elements in comparison to the\Nglobal mean temperature here. And you see
Dialogue: 0,0:26:09.75,0:26:14.60,Default,,0000,0000,0000,,in these burning ember diagrams that some\Nof these tipping elements are at risk of
Dialogue: 0,0:26:14.60,0:26:21.03,Default,,0000,0000,0000,,switching into a different state, even\Nwithin the Paris range of 1.5 - 2°C of
Dialogue: 0,0:26:21.03,0:26:26.05,Default,,0000,0000,0000,,warming. And among these most vulnerable\Ntipping elements are the West Antarctic
Dialogue: 0,0:26:26.05,0:26:32.27,Default,,0000,0000,0000,,ice sheet and the Greenland ice sheet and\Nin general, the cryosphere elements which
Dialogue: 0,0:26:32.27,0:26:38.04,Default,,0000,0000,0000,,seem to react to global warming and\Nclimate change much faster and therefore
Dialogue: 0,0:26:38.04,0:26:44.45,Default,,0000,0000,0000,,belong to the most vulnerable parts of the\NEarth system. So, if there's one thing
Dialogue: 0,0:26:44.45,0:26:51.68,Default,,0000,0000,0000,,that I would like you to take away from\Nthis talk, it is that ice matters. I've
Dialogue: 0,0:26:51.68,0:26:57.21,Default,,0000,0000,0000,,presented you with three reasons why.\NFirst of all, polar ice acts as a climate
Dialogue: 0,0:26:57.21,0:27:05.16,Default,,0000,0000,0000,,archive. It also acts as an early warning\Nsystem. Secondly, glaciers and ice sheets
Dialogue: 0,0:27:05.16,0:27:09.46,Default,,0000,0000,0000,,are important contributors already to\Ncurrent sea level rise, but they will
Dialogue: 0,0:27:09.46,0:27:14.66,Default,,0000,0000,0000,,become even more important in the future\Nas the global mean temperature keeps
Dialogue: 0,0:27:14.66,0:27:20.48,Default,,0000,0000,0000,,rising. And thirdly, both Greenland and\NAntarctica are tipping elements in the
Dialogue: 0,0:27:20.48,0:27:24.77,Default,,0000,0000,0000,,Earth system. And one of the next things\Nwe need to understand is how these tipping
Dialogue: 0,0:27:24.77,0:27:28.35,Default,,0000,0000,0000,,elements interact with one another.\NBecause we have a very good understanding
Dialogue: 0,0:27:28.35,0:27:32.89,Default,,0000,0000,0000,,by now of the different mechanisms behind\Nthese tipping elements and of the
Dialogue: 0,0:27:32.89,0:27:37.47,Default,,0000,0000,0000,,individual temperature thresholds. But one\Nof the, I think, most important questions
Dialogue: 0,0:27:37.47,0:27:42.14,Default,,0000,0000,0000,,we need to ask ourselves, is how the\Ninteraction of the tipping elements
Dialogue: 0,0:27:42.14,0:27:46.12,Default,,0000,0000,0000,,changes the stability of the Earth system\Nas a whole and if there could be something
Dialogue: 0,0:27:46.12,0:27:51.28,Default,,0000,0000,0000,,like domino effects in the Earth system.\NAnd with this, thank you so much for your
Dialogue: 0,0:27:51.28,0:27:56.26,Default,,0000,0000,0000,,attention. And I'm very much looking\Nforward to questions.
Dialogue: 0,0:28:07.23,0:28:28.06,Default,,0000,0000,0000,,Herald: Yeah, OK, fine, good, läuft, könnt\Nihr mich also hör'n, und ihr müsst mir
Dialogue: 0,0:28:28.06,0:28:30.86,Default,,0000,0000,0000,,also sagen, wann ich wieder drauf bin.\NOff: Du bist live.
Dialogue: 0,0:28:30.86,0:28:35.97,Default,,0000,0000,0000,,H: Hallo, wilkommen zurück! Thanks for\Nthis awesome talk, Ricarda, and we are now
Dialogue: 0,0:28:35.97,0:28:40.67,Default,,0000,0000,0000,,going to have a Q&A. And if you have any\Nquestions regarding this awesome talk,
Dialogue: 0,0:28:40.67,0:28:46.49,Default,,0000,0000,0000,,then please post them to the signal\Nangels. They are following on Twitter and
Dialogue: 0,0:28:46.49,0:28:54.14,Default,,0000,0000,0000,,the Fediverse here, using the hashtag\N#rc3one, because this is rc1. And you can
Dialogue: 0,0:28:54.14,0:28:58.69,Default,,0000,0000,0000,,also post your questions to the IRC. You\Nknow, I already have a first question. I
Dialogue: 0,0:28:58.69,0:29:03.82,Default,,0000,0000,0000,,don't know, Ricarda, if you can hear me,\Nbut is there anything that this specific the CCC
Dialogue: 0,0:29:03.82,0:29:09.79,Default,,0000,0000,0000,,community of nerds and hackers can do more\Nthan anyone else to help with this issue?
Dialogue: 0,0:29:09.79,0:29:13.57,Default,,0000,0000,0000,,What do you think that\Nwe can do to help this?
Dialogue: 0,0:29:13.57,0:29:17.22,Default,,0000,0000,0000,,R: Yeah, thank you so much. Great\Nquestion. Let me start by saying I'm a
Dialogue: 0,0:29:17.22,0:29:23.52,Default,,0000,0000,0000,,nerd and hacker myself. I'm a developer,\Nor code developer, of the parallel ice
Dialogue: 0,0:29:23.52,0:29:28.24,Default,,0000,0000,0000,,sheet model. That's one of the ice sheet\Nmodels for Greenland and Antarctica that's
Dialogue: 0,0:29:28.24,0:29:34.13,Default,,0000,0000,0000,,being used around the globe with many\Ndifferent applications. So, yeah, as a
Dialogue: 0,0:29:34.13,0:29:39.67,Default,,0000,0000,0000,,fellow nerd and hacker, I can say there's\Nlots we can do, in particular towards
Dialogue: 0,0:29:39.67,0:29:44.51,Default,,0000,0000,0000,,understanding even better the different\Ndynamics of the Greenland and the
Dialogue: 0,0:29:44.51,0:29:50.30,Default,,0000,0000,0000,,Antarctic ice sheet, but also beyond that,\Nfor the Earth system as a whole. I think
Dialogue: 0,0:29:50.30,0:29:54.49,Default,,0000,0000,0000,,we're now at a point where we understand\Nthe individual components of the Earth
Dialogue: 0,0:29:54.49,0:29:58.83,Default,,0000,0000,0000,,system better and better. We also have\Nbetter and better observations, satellite
Dialogue: 0,0:29:58.83,0:30:05.78,Default,,0000,0000,0000,,observations, but also observations at the\Nground to further understand the different
Dialogue: 0,0:30:05.78,0:30:11.07,Default,,0000,0000,0000,,processes. But what we need now is to\Ncombine this with our knowledge in the
Dialogue: 0,0:30:11.07,0:30:16.97,Default,,0000,0000,0000,,modeling community and also with some of\Nthe approaches from big data, machine
Dialogue: 0,0:30:16.97,0:30:21.73,Default,,0000,0000,0000,,learning and so on, to really put this\Ntogether, all the different puzzle pieces
Dialogue: 0,0:30:21.73,0:30:26.46,Default,,0000,0000,0000,,to understand what this means for the\NEarth system as a whole. And what I mean
Dialogue: 0,0:30:26.46,0:30:30.81,Default,,0000,0000,0000,,by that is, we now understand that there\Nare several individual tipping points in
Dialogue: 0,0:30:30.81,0:30:35.75,Default,,0000,0000,0000,,the Earth system. And we also know that as\Nglobal warming continues, we're at higher
Dialogue: 0,0:30:35.75,0:30:40.58,Default,,0000,0000,0000,,risks of transgressing individual tipping\Npoints. But what we still need to
Dialogue: 0,0:30:40.58,0:30:49.48,Default,,0000,0000,0000,,understand is what does this mean for the\Noverall stability of our planet Earth?
Dialogue: 0,0:30:49.48,0:30:56.07,Default,,0000,0000,0000,,H: Thank you for this extended answer to\Nthis question. I have another one. I would
Dialogue: 0,0:30:56.07,0:31:01.02,Default,,0000,0000,0000,,like to know, I mean, you showed a slide\Nwhere you showed the browning of the ice
Dialogue: 0,0:31:01.02,0:31:07.92,Default,,0000,0000,0000,,surface and then explained that this\Nspeeds up the process of melting as well.
Dialogue: 0,0:31:07.92,0:31:13.21,Default,,0000,0000,0000,,But, can we just paint it white or with a\Nreflective paint on it? Has this been
Dialogue: 0,0:31:13.21,0:31:16.50,Default,,0000,0000,0000,,simulated? Is this of interest to you\Nscientists?
Dialogue: 0,0:31:16.50,0:31:20.11,Default,,0000,0000,0000,,R: Yeah, very good question. So basically\Nwhat you're addressing here is the
Dialogue: 0,0:31:20.11,0:31:25.92,Default,,0000,0000,0000,,question of the so-called ice albedo\Nfeedback. We all know this. As we're
Dialogue: 0,0:31:25.92,0:31:29.30,Default,,0000,0000,0000,,wearing black clothes in summer, it's\Nwarmer than when we're wearing white
Dialogue: 0,0:31:29.30,0:31:35.37,Default,,0000,0000,0000,,clothes. And the same is basically true\Nfor our planet as well. So the ice sheets
Dialogue: 0,0:31:35.37,0:31:40.92,Default,,0000,0000,0000,,and also the sea ice in the Arctic and\NAntarctica, they contribute considerably
Dialogue: 0,0:31:40.92,0:31:48.73,Default,,0000,0000,0000,,to a net cooling still of the planet. So\Nif we didn't have these ice landscapes,
Dialogue: 0,0:31:48.73,0:31:52.94,Default,,0000,0000,0000,,that would mean that the planet would warm\Neven faster and even further than it
Dialogue: 0,0:31:52.94,0:31:59.14,Default,,0000,0000,0000,,already is today. So currently, the ice\Nalbedo feedback is still helping us with
Dialogue: 0,0:31:59.14,0:32:04.83,Default,,0000,0000,0000,,keeping the temperatures at lower levels\Nthan they would be without the ice
Dialogue: 0,0:32:04.83,0:32:09.90,Default,,0000,0000,0000,,landscapes. And, yeah, therefore, it is\Ndefinitely of interest to further
Dialogue: 0,0:32:09.90,0:32:14.87,Default,,0000,0000,0000,,understand what would this mean for, for\Ninstance, the global mean temperature, but
Dialogue: 0,0:32:14.87,0:32:21.09,Default,,0000,0000,0000,,also regional changes, if we were to lose\Nour ice cover completely? And also the
Dialogue: 0,0:32:21.09,0:32:25.32,Default,,0000,0000,0000,,reverse question, of course, if we were to\Nwhiten parts of the planet, then how would
Dialogue: 0,0:32:25.32,0:32:33.52,Default,,0000,0000,0000,,this affect temperature? One thing that we\Nfound out is that if we were to lose the
Dialogue: 0,0:32:33.52,0:32:40.65,Default,,0000,0000,0000,,ice sheets and the sea ice in terms of the\Nice albedo feedback alone entirely, then
Dialogue: 0,0:32:40.65,0:32:48.42,Default,,0000,0000,0000,,this could already lead to an additional\Nglobal warming of roughly 0.2°C. Now, that
Dialogue: 0,0:32:48.42,0:32:53.35,Default,,0000,0000,0000,,may not seem very much, but it certainly\Nis important in the grand scheme of
Dialogue: 0,0:32:53.35,0:32:58.56,Default,,0000,0000,0000,,things. As we're thinking of, for\Ninstance, the Paris range of 1.5°C to 2°C
Dialogue: 0,0:32:58.56,0:33:03.33,Default,,0000,0000,0000,,of warming, every tenth of a degree\Nmatters. So, yeah, very interesting
Dialogue: 0,0:33:03.33,0:33:08.35,Default,,0000,0000,0000,,question. And this is something that has\Nbeen done with numerical models, just to
Dialogue: 0,0:33:08.35,0:33:15.16,Default,,0000,0000,0000,,understand what kind of an effect these\Nkind of what-if-scenarios would have also
Dialogue: 0,0:33:15.16,0:33:21.65,Default,,0000,0000,0000,,in terms of the albedo.\NH: Very interesting. So should we now
Dialogue: 0,0:33:21.65,0:33:24.16,Default,,0000,0000,0000,,start to develop drones\Nwho can spray paint?
Dialogue: 0,0:33:24.16,0:33:28.83,Default,,0000,0000,0000,,R: {\i1}laughs{\i0} That's a good question. I\Ndon't think that's the solution. I think
Dialogue: 0,0:33:28.83,0:33:33.59,Default,,0000,0000,0000,,we have a much better solution. And that\Nis we know that we need to to mitigate
Dialogue: 0,0:33:33.59,0:33:39.20,Default,,0000,0000,0000,,climate change and reduce greenhouse gas\Nemissions. And that is one that would work
Dialogue: 0,0:33:39.20,0:33:44.09,Default,,0000,0000,0000,,for sure. Whereas these questions of,\Nwell, should we spray paint all of our
Dialogue: 0,0:33:44.09,0:33:50.11,Default,,0000,0000,0000,,buildings at the at the top white? That is\Nsomething that cannot be done at such a
Dialogue: 0,0:33:50.11,0:33:56.30,Default,,0000,0000,0000,,large scale as we would need it in order\Nto reverse global warming. And another
Dialogue: 0,0:33:56.30,0:34:03.51,Default,,0000,0000,0000,,thing to keep in mind is that even if we\Nwere able to reduce the global signal,
Dialogue: 0,0:34:03.51,0:34:09.99,Default,,0000,0000,0000,,this still doesn't mean that we could also\Nreverse the regional scale changes. We're
Dialogue: 0,0:34:09.99,0:34:16.49,Default,,0000,0000,0000,,already experiencing a large increase in\Nextreme weather and climate events. And
Dialogue: 0,0:34:16.49,0:34:20.71,Default,,0000,0000,0000,,that is certainly something that I haven't\Nseen so far, that this could also be
Dialogue: 0,0:34:20.71,0:34:26.03,Default,,0000,0000,0000,,reversed just by reversing the global mean\Ntemperature change as a whole.
Dialogue: 0,0:34:26.03,0:34:30.86,Default,,0000,0000,0000,,H: I have another question. I think that's\Nquite interesting. How old is the oldest
Dialogue: 0,0:34:30.86,0:34:35.47,Default,,0000,0000,0000,,ice in Antarctica? Are you aware of that?\NAnd how long would it take a minimum to
Dialogue: 0,0:34:35.47,0:34:40.45,Default,,0000,0000,0000,,lose that entirely?\NR: Yeah, very good question. So the oldest
Dialogue: 0,0:34:40.45,0:34:45.11,Default,,0000,0000,0000,,ice, there's actually an ongoing search\Nfor the oldest ice in Antarctica. So to
Dialogue: 0,0:34:45.11,0:34:51.31,Default,,0000,0000,0000,,say, we know that Antarctica was ice free\Nfor the last time, roughly 34 million
Dialogue: 0,0:34:51.31,0:34:56.92,Default,,0000,0000,0000,,years ago. So when we're talking about\Nthese scenarios that eventually Antarctica
Dialogue: 0,0:34:56.92,0:35:02.41,Default,,0000,0000,0000,,could become ice free with, of course,\Nvery strong global warming scenarios of
Dialogue: 0,0:35:02.41,0:35:08.53,Default,,0000,0000,0000,,about 10°C of global warming, then we need\Nto keep in mind that this was the case for
Dialogue: 0,0:35:08.53,0:35:14.01,Default,,0000,0000,0000,,the last time, about 34 million\Nyears ago. Now, as we're speaking, there
Dialogue: 0,0:35:14.01,0:35:20.84,Default,,0000,0000,0000,,is an ongoing project, an international\Ncollaboration to find and and also drill
Dialogue: 0,0:35:20.84,0:35:25.96,Default,,0000,0000,0000,,for the oldest ice so that we can really\Nunderstand our Earth's history better and
Dialogue: 0,0:35:25.96,0:35:31.62,Default,,0000,0000,0000,,better. And so this is a very exciting\Nproject because, as I said, the ice cores
Dialogue: 0,0:35:31.62,0:35:35.82,Default,,0000,0000,0000,,are kind of like tree rings and we can\Ncount back in time and really understand
Dialogue: 0,0:35:35.82,0:35:42.25,Default,,0000,0000,0000,,what our global climate was like several,\Nhundreds of thousands of years ago. So,
Dialogue: 0,0:35:42.25,0:35:47.54,Default,,0000,0000,0000,,yeah, with that being said, I think it's\Nimportant to keep in mind that this is
Dialogue: 0,0:35:47.54,0:35:52.01,Default,,0000,0000,0000,,something that humans certainly have never\Nexperienced and that's therefore
Dialogue: 0,0:35:52.01,0:35:58.07,Default,,0000,0000,0000,,unprecedented in our world.\NH: ...for this very elaborate answer to
Dialogue: 0,0:35:58.07,0:36:04.73,Default,,0000,0000,0000,,this question, I know it is not the core\Nof your research, but someone from the
Dialogue: 0,0:36:04.73,0:36:10.36,Default,,0000,0000,0000,,internet asked, if it's possible for old\Nviruses and all the bacteria from back
Dialogue: 0,0:36:10.36,0:36:16.21,Default,,0000,0000,0000,,when Antarctica was like beginning to\Nfreeze over or from like
Dialogue: 0,0:36:16.21,0:36:19.99,Default,,0000,0000,0000,,millions of years ago, is it possible for\Nthem to thaw out again? Is that a danger
Dialogue: 0,0:36:19.99,0:36:22.52,Default,,0000,0000,0000,,for us?\NR: Oh, that's also a very interesting
Dialogue: 0,0:36:22.52,0:36:27.43,Default,,0000,0000,0000,,question. So I'm no expert on this, but I\Ncould imagine that at the temperatures
Dialogue: 0,0:36:27.43,0:36:34.07,Default,,0000,0000,0000,,that we have, Antarctica, especially the\Ncore ice body, there we have temperatures
Dialogue: 0,0:36:34.07,0:36:39.67,Default,,0000,0000,0000,,that go down to, well, I think the coldest\Ntemperature was something like -90°C that
Dialogue: 0,0:36:39.67,0:36:45.54,Default,,0000,0000,0000,,was recorded there. But in any case, it's\Nvery cold there. So there might be some
Dialogue: 0,0:36:45.54,0:36:50.84,Default,,0000,0000,0000,,bacteria that can survive these\Nconditions. And I've read about bacteria
Dialogue: 0,0:36:50.84,0:36:57.29,Default,,0000,0000,0000,,like that, but I wouldn't know that there\Nare many bacterial species or specimen
Dialogue: 0,0:36:57.29,0:37:02.64,Default,,0000,0000,0000,,that could survive these kinds of\Nconditions. So to be honest, I would have
Dialogue: 0,0:37:02.64,0:37:05.92,Default,,0000,0000,0000,,to read up on that. That's a very\Ninteresting question.
Dialogue: 0,0:37:05.92,0:37:11.39,Default,,0000,0000,0000,,H: Yeah. Thank you for this answer. I\Nremember that you watched, that you showed
Dialogue: 0,0:37:11.39,0:37:17.44,Default,,0000,0000,0000,,an animation and a graph for a simulated\Nice decline to find the tipping points in
Dialogue: 0,0:37:17.44,0:37:24.16,Default,,0000,0000,0000,,Antarctica. And on the x axis of that, I\Ncouldn't see a time scale. And now someone
Dialogue: 0,0:37:24.16,0:37:28.01,Default,,0000,0000,0000,,asked on the internet, what are the\Ntimescales between reaching a tipping
Dialogue: 0,0:37:28.01,0:37:32.36,Default,,0000,0000,0000,,point? And most of the ice being melted?\NIs that years, decades, centuries,
Dialogue: 0,0:37:32.36,0:37:38.24,Default,,0000,0000,0000,,millennia? What's kind of the scale there?\NR: Yes, very important point. So it's
Dialogue: 0,0:37:38.24,0:37:43.13,Default,,0000,0000,0000,,important to note that we're here showing\Nthis over the global mean temperature
Dialogue: 0,0:37:43.13,0:37:47.81,Default,,0000,0000,0000,,change. And the reason for this is that\Nthe way these kind of hysteresis
Dialogue: 0,0:37:47.81,0:37:53.45,Default,,0000,0000,0000,,experiments are run is that you have a\Nvery slow temperature increase. So slow,
Dialogue: 0,0:37:53.45,0:37:59.34,Default,,0000,0000,0000,,in fact, that it's much slower than the\Nsort of internal time scales of the ice
Dialogue: 0,0:37:59.34,0:38:05.12,Default,,0000,0000,0000,,itself. And in this case, for instance, we\Nhad a temperature increase of
Dialogue: 0,0:38:05.12,0:38:12.91,Default,,0000,0000,0000,,10^-4°C/year. And the reason for this is\Nbecause this is the way you're approaching
Dialogue: 0,0:38:12.91,0:38:17.39,Default,,0000,0000,0000,,the actual hysteresis curve that we were\Ninterested in. So this should not be
Dialogue: 0,0:38:17.39,0:38:24.58,Default,,0000,0000,0000,,mistaken for sea level projections of any\Nsort. So what we find here are the actual,
Dialogue: 0,0:38:24.58,0:38:29.46,Default,,0000,0000,0000,,so to say, tipping points, the actual\Ncritical thresholds, that parts of the
Dialogue: 0,0:38:29.46,0:38:35.55,Default,,0000,0000,0000,,Antarctic ice sheet cannot survive.\NNonetheless, of course, we're also working
Dialogue: 0,0:38:35.55,0:38:39.73,Default,,0000,0000,0000,,towards sea level projections and trying\Nto understand what kind of sea level
Dialogue: 0,0:38:39.73,0:38:44.70,Default,,0000,0000,0000,,change we can expect from the ice sheets\Nover the next decades to centuries to
Dialogue: 0,0:38:44.70,0:38:53.36,Default,,0000,0000,0000,,millennia. And one important thing there\Nis that most of the ice loss that could be
Dialogue: 0,0:38:53.36,0:38:58.35,Default,,0000,0000,0000,,triggered now, would actually happen after\Nthe end of this century. So very often,
Dialogue: 0,0:38:58.35,0:39:03.10,Default,,0000,0000,0000,,when we see these sea level curves, we're\Nlooking until the year 2100. So for the
Dialogue: 0,0:39:03.10,0:39:10.06,Default,,0000,0000,0000,,next decades, how does the sea level\Nrespond to changes in temperature? But
Dialogue: 0,0:39:10.06,0:39:18.45,Default,,0000,0000,0000,,because we have so much inertia in the\Nsystem, that means that even if the global
Dialogue: 0,0:39:18.45,0:39:24.14,Default,,0000,0000,0000,,warming signal was stopped right now, we\Nwould still see continued sea level rise
Dialogue: 0,0:39:24.14,0:39:29.95,Default,,0000,0000,0000,,for several decades to centuries. And that\Nis something important to keep in mind. So
Dialogue: 0,0:39:29.95,0:39:34.69,Default,,0000,0000,0000,,I think we really need to start thinking\Nof sea level rise in terms of commitment
Dialogue: 0,0:39:34.69,0:39:41.17,Default,,0000,0000,0000,,rather than these short term predictions.\NThat being said, another important
Dialogue: 0,0:39:41.17,0:39:45.13,Default,,0000,0000,0000,,question and factor is the rate of sea\Nlevel change, because this is actually
Dialogue: 0,0:39:45.13,0:39:50.71,Default,,0000,0000,0000,,what we need to adapt to as civilizations.\NWhen we think of building dams, there are
Dialogue: 0,0:39:50.71,0:39:57.35,Default,,0000,0000,0000,,two questions we need to answer. One is\Nthe magnitude of sea level rise and and
Dialogue: 0,0:39:57.35,0:40:03.74,Default,,0000,0000,0000,,also in its upper scale and upper limit to\Nthat. And the other question is the rate
Dialogue: 0,0:40:03.74,0:40:10.36,Default,,0000,0000,0000,,at which this changes. And what we find is\Nthat on the long term, there is something
Dialogue: 0,0:40:10.36,0:40:17.69,Default,,0000,0000,0000,,like 2.3m/°C of sea level change. So this\Nis sort of a number to keep in mind when
Dialogue: 0,0:40:17.69,0:40:23.08,Default,,0000,0000,0000,,we think of sea level projections. And\Nyeah, I think it's really important to
Dialogue: 0,0:40:23.08,0:40:29.43,Default,,0000,0000,0000,,consider longer timescales than the one to\Nthe year 2100 when we talk about sea level
Dialogue: 0,0:40:29.43,0:40:35.01,Default,,0000,0000,0000,,rise.\NH: Thank you for this answer, very
Dialogue: 0,0:40:35.01,0:40:41.06,Default,,0000,0000,0000,,interesting and we are out of time now, so\Nthanks for all the questions and thank
Dialogue: 0,0:40:41.06,0:40:45.74,Default,,0000,0000,0000,,you, Ricarda, for this amazing talk. The\Nnext talk on this stage will be about a
Dialogue: 0,0:40:45.74,0:40:51.73,Default,,0000,0000,0000,,related topic, measuring CO2 indoors, but\Nalso in the atmosphere in general. But
Dialogue: 0,0:40:51.73,0:40:55.90,Default,,0000,0000,0000,,before that, we have a Herald News Show\Nfor your prepared. So enjoy!
Dialogue: 0,0:40:55.90,0:41:01.05,Default,,0000,0000,0000,,{\i1}Outro music{\i0}
Dialogue: 0,0:41:01.05,0:41:36.00,Default,,0000,0000,0000,,Subtitles created by c3subtitles.de\Nin the year 2021. Join, and help us!