Zeittakt von Eiszeiten: Was steht uns bevor?Jan 28, 2022
i would like to introduce mr thiede, today's speaker was born in berlin and later studied geology and paleontology in kiel with further trips to vienna and buenos aires he was scientifically active in various other institutions at aarhus university in bergen at oregon state university in the usa and in oslo and since 1982 he has held a chair of historical geology at the university of kiel this role then changed a bit, so to speak, since 1987 he became professor of pathology at the university of kiel and at the al At the same time, founding director of the center for marine geosciences, a large institution now known by the abbreviation geomar, which is currently supported by the helmholtz society and was director there for ten years, after which he directed the alfred-Wegener-institut in bremerhaven for ten years another helmholtz institute and he was actually there so at the age most of us don't retire it didn't stop him from assuming r a visiting professorship in copenhagen and also works as a professor at st petersburg state university and is therefore constantly going back and forth between kiel st petersburg and other stations the list of honors and i will just name three of the awards he has received , namely the Gottfried Wilhelm Leibniz Award from the German Research Foundation, the Federal Cross of Merit and perhaps interesting to know.
He belongs to five different scientific academies, including the Royal Norwegian Scientific Academy of Sciences and the Russian Academy of Sciences, as you can see, you have great international connections and that's why we are particularly happy today, you came from Kiel, it's almost around the corner and the journey is not just an adventure on the federal railway. , but this time it went well and I am very happy that you came to us and we look forward to your introduction and then as always there will be discussions about it please thank you very much for the friendly introduction Herrsching I think everyone has understood that I have much fun in my life so far and I hope there will be more.
I will continue to experiment something. I want to talk to you today about ice age phenomena, and I really just want to get four or five points across clearly. Can you say that the ice ages lasted? Much longer in the first half than you thought. I would show you that ice age animals that are pretty good these days can alternate between warm periods and cold periods in a relatively regular pattern. Finally, I hope I have time. say a few words about how i could go on but that's the big question if i can make a truthful statement now that ice ages are not an exception on earth but are actually regular in earth history and if you look at this diagram look at this complicated diagram and see a bar across the top consisting of white and blue fields and in the last 500 million years there have been four of the five major ice ages so it's not a state of emergency in the that is our land wood too expensive and we are here in ice age mode it can work more or less in the current situation he german this is different than before the game pelle geography and tectonics of plates meant that the land masses were brought together into one large continent and large The continents are usually higher than the small continents we have today and while the opposite side of the globe was then covered by a large ocean today we have a situation that has led to the formation of bipolar ice and the fact that a small continent in the southern hemisphere is surrounded by a large ring-shaped deep ocean which is also the largest coalition on earth houses and leads to the fact that Antarctica is climatically completely isolated in the northern hemisphere we have the opposite situation we have a small ocean above the north pole and this small ocean is actually only connected to the world further by a lower path, viz , the area between greenland and svalbard, the so-called agricultural road that is about three kilometers deep, while the other roads that connect the arctic sea with the world are quite flat and every time we will have an ice age, the sea level It will be between 120 and 140 meters. lower than it is today these posts are punishing dry so that's it l this strait of frame between spitsbergen or the open air pool as seen in norway and greenland is of crucial importance to arctic ocean properties now about this area the areas will publish a lot of nonsense in the newspapers i will give you some photos some illustrations in the following photos but when i was able to travel to the north pole with the polar stern for the first time in 2000 in 2001 the bild newspaper published last year that the entire north pole had already disappeared, eleven kilos of ice had disappeared, although we all know that the north polar sea was only a thin layer, thin as a wafer of sea ice covered and this because it got into the situation that some scientists The Americans published the times and the image shows that he made the choice.
He had taken a Russian nuclear icebreaker to the North Pole and wanted to have a picnic on an ice floe. and suddenly there was a big poland So a channel opened up and they couldn't hold their picnic and we will see the North Star exactly one year later the ice was completely intact again only the situation in the Arctic sea is complicated and this this this this wafer -thin layer mostly this so powerful from two to four meters, it moves very fast under the influence of the wind and on the western side I know that here on the western side, that is, through the area between Siberia and North America a big vortex moves this supposed ship and on the east side it pulls this strip this transport hits the ice through Frauenstrasse towards the Norwegian sea i want to open it up again and let it be if you can see it clearly again this is a movie made up of a bunch of satellite images and so in fast motion time you summarize the movements of the ice for a year and that's what most people do It's not clear that all this layer of ice and ice is so thin and so sensitive and that is why it reacts very strongly to modern climate change and climate change and in relation to the year to the first years of this millennium there are still about electric blankets of this arctic sea two thirds as much in thickness as well as extent because there is no doubt that the climate is changing these days and we have actually been observing for the last 70 to 80 or maybe 100 to 100 years that this climate has been raising global average temperatures for relatively cool periods the average value has gone from 1901 to 2000 and currently the climate is in a significant warming phase and many interpret the summer of this year in this sense, but this is only a meteorological event and the average temperatures have increased throughout the world and the g I think this diagram is pretty good again if you compare it to the historical variability that there was even in hall 10, so in the international moment to current or at the present time there were also phases that were even warmer so not a very dramatic situation now in germany in 1979. the 1979 federal republic joined the antarctic treaty and thus founded the alfred institute Wegener and built a very complex and good infrastructure for polar research and now we have carried out the 160 180th anniversary of the first German expedition to the north pole this year and if today you can see that at the location of the alfred wegener institute is the polarstern which is the german research icebreaker with which the georg von neumayer station is supplied and also allows us to go to the north pole there you can also find the grasslands in the same ford area a small nordic cargo sailor owned by captain c Oldewey was used in 1868 for the first expedition to Greenland and to Spitzbergen and is still maintained by an amateur club in seaworthy condition and can be see together as the most modern German polar research ship and the green one that is from the founder not very comfortable working conditions I think you can imagine that there were 14 people and there was no heating the machine on board in the police there were all the comforts that you can dream of including a swimming pool and sauna etc. polar star sometimes also very very unreal inhospitable against the visit that you can see here in its crossing through the trawl pass on 3 the drake passage between south america and antarctica and that is the noisy sea area that we know all over the world world and therefore in this image it lifts the wake of the boat from the water and it can move a lot, but it offers an excellent enough work platform even for people who go there and the force of the wind 10 does not absorb water but still allows to discover a good scientific work only one that illustrated the history of the north pole I have already shown you the following image had similar news but much more recent dated at the south pole some time ago a large slab of iceberg broke off which is a completely natural process the layer antarctic ice caps or the ice sheets both in green we flip them due to the physical properties of their it takes time and it's cold for me over and over again big big icebergs and due to the geography that the dax breaks a big slab of iceberg from time to time this warning is particularly big and the bild newspaper made the story that the iceberg that the south pole breaks this slab of icebergs that are already swimming and have no effect on sea level and sea level increased because the bild newspaper has t because the seabed can rise strongly and so on because please do not believe anything that is written in the newspapers about these phenomena in the polar regions in against these extremes that either the scientists express themselves so confusedly that the journalists do not understand it or that the journalists want to make this news headlines that are read to halter was that this does not correspond to the facts now the situation on the southern line is completely different for us there is also a more than belt around antarctica the species is yes, almost completely covered by interior ice and later You will see some maps of some ice core data, but since each year a belt has been building up around the facility, actually disappearing entirely again over the course of the summer, i.e. in contrast in the northern hemisphere at the arctic sea have more than that you live up to 67 years may disappear in the southern hemisphere this colorful belt of the region illustrated the fear around so the sea ice belt packed with the seasonal changes of paradise and the content of bern taxis densely populated by great swimmers and one of all the very diverse fauna in germany has a permanent station installed at night and the normal station spends the winter there and you will see in 23 minutes how this station was installed it was installed for the third time in February of 2009 because the previous station was completely built on the ice and there approximately one meter of precipitation falls per year in the area, the ice disappeared. or slowly and finally these tubular stations were crushed by ice the new station they both installed in 2009 during my time as director of the alfred wegner institute stands on stilts and can be lifted hydraulically So you are in this pressure to resist or dodge is and its permanent base for ongoing weather measurements throughout the year gives new people a chance to overwinter the station cannot be reached in winter, neither by plane nor by boat, so people are really alone and doing their i work there in total isolation so now i come to the topic well it was some impressions of the situation in the northern hemisphere and i will start in the northern hemisphere with the history which was almost completely unknown until the late 1970s because one really I had no data at all from the actual arctic sea i.e. in the area north of svalbard greenland and one couldn't do anything e Except making statements about ice age worth of arctic sea history, I actually knew quite well about the surrounding land areas because, namely, in North in the northeastern part of Eurasia and in North America, huge layers of ice have built up. ice and a modest small remnant of this glacial ice sheet still remains in greenland, but they were much larger overall and caused about 120 meters of global ocean water to evaporate and that precipitation has been transferred mostly to the northern hemisphere, these sheets Some of the ice also accumulates in Antarctica, so we are in the northern hemisphere in response to these cold climatic phases changing and the ice sheets in response to cold climatic phases. of the most recent part of the cenozoic period of the quarter have had extraordinarily different counts this is an example of a shield that existed 140 1000 years ago and was perhaps the largest in recent history the three most recent examples I can show you are much smaller and can't spread that far but every time its cold weather phase came it would form an ice sheet and it can also be reconstructed pretty well by doing research on the ground until very recently it wasn't actually known why this shield spread extended to the east. although now we have solved this very well in cooperationwith many Russian research institutions and people really thought that this whole ice age phenomenon is a young phenomenon and that it has only developed in the last hundreds of thousands of years of our earth's history and then in 2004 the The he first succeeded in the first expedition with a ship in the central arctic ocean and since this story has changed significantly, the polar stern had invaded a ridge in the central axis of the arctic ocean, the north polar sea during his first expedition to the pole north and therefore found the With the help of geophysical measurements, the summit floor, this so-called lomonosov ridge that runs almost along the north pole under the entire Arctic sea, made a very clear story and I think you can see that pretty well in the diagram on the right hand side on the map where you draw a red dot where the drilling starts they have sunk and that was an extraordinarily complex expedition that was completed. carried out by 31 common vehicles, that is, by a ship that can be seen below left that went further than a swedish icebreaker diodes and a russian nuclear icebreaker oman this should start now and the drilling has us our vision of the world of the longest duration of the glaciation completely changed and then it turned out and that left the diagram shows that such numbers have been home to the tracks of icebergs for 45 million years and that means icebergs and what is on the left is once freshly thawed traced from zero to 50 million years so about 48 million years ago first iceberg fault or iceberg transported material transported in action ocean bottom of this strategy was entered something seen on talks that the entry of this ice-carried material begins very modestly around 48 million years ago and then increases very sharply at 45 million years ago, actually it reached values such as those we have been observing in recent times now, unfortunately this drilling has turned out that the drilling is not quite complete, but there are large gaps in the hole that have been discovered in the meantime about 45 million years ago and 18 million years and then about ten million years ago and that now a new expedition base to this area is planned for this year or next year Unfortunately it was not possible to carry this out for political reasons and it is expected that these drilling are done in 2021, but after these drilling it is completely clear to plummet that the iceberg of the ice age history of our earth is much longer than has been believed until now that, therefore, i went back to the middle of tc about 48 million years ago k that's enough that's an understanding that has completely revolutionized our understanding of the local sphere of climate then suddenly and strange to us until now the app was supposed to be the first continent and the first big ice sheet had developed there now we will know that the Arctic froze about ten million years before Antarctica so one by one all textbooks have to be rewritten that report this now that, first of all, it answers the question of the age of the ice age mode we are now observing. earth if we look at that internal teamwork then you are presented with a journal of earth history and that is a core that was taken on pole star we have a facility to take calls without box that is why you might win a very large volume I would like to win and had to see its stripes the gray stripes the corresponding ice ages the brown stripes the corresponding waiting times and the result can then, depending on how finely this core is affected as a reader of the history of the earth, one can read the properties of these sediments and that was done a few years ago with the help of a deep-water core of the then north atlantic has been interpreted and that actually reflects a very interesting story of our climate a story of our earth's climate once by its oceanic core which means that the oceans have the properties and really reflect the global properties then these data were derived from the isotope ratios identically twisted organisms are on vacation at the bottom of the sea where the temperature has probably changed a lot and you can see that this curve varies a lot between large red intervals where it was relatively warm and towards the blue interval where It was relatively cold this acid outside of the isotopes, ultimately reflecting the global volume of ice because the oxygen isotope fraction has been wrong in the process of fca evaporation discounts and precipitation on the ice sheets and, so ultimately they reflect the intensity of the ice ages and that shows up quite nicely, in these diagrams breaking through time three times, I don't want to go on about the technology, how do you determine the age of this item that , if you now have my life significantly exceeded my reading time, you can see the age from one million years to five million years ago, so from average tcs to toilet 10 the time scale breaks down between 0.2 and a million yes and then the last 200 thousand years are not there yet and this is this weird pattern that results from these reconstructions it has a number of properties that are hard to understand once it's not for example you understand why the timeouts and these are the red spikes are all relatively short events and then again in kirn for a cold weather conclusion that they don't exceed the maximum was the same with what the ice age climate scenarios reach the decimal point also a maximum value and then the whole system tilts and warms again, to this day we don't know what process actually determines these threshold values or kim's death but we can see that the weather was stable but always changing has very strongly and that it actually has stable weather as politicians often demand nowadays never existed at all mourning was always very variable that the climate on earth was sometimes warmer there now we return to the cinema 10 are the values of the choice of warm intervals a little higher, but still it is something very strange and you have thought about it a lot I thought on how the climate changes so regularly and there's a lot we can say about that today because and now I've switched to ice cores because we know ice core data from both the Antarctic and the Arctic and it's very interesting because it tells us to give a signal of temperature once and that is a nucleus of the so-called sun concordia which is then a peak or peaks is in the action of the ice sheet and in the upper courtyard is first of all a temperature curve that is shown with the peaks of the warm period in the villa after pointing up and cold time intervals pointing down and are actually quite regular do they oscillate between hot and cold or does it look like we had to believe today that we know how this p is generated tron now the red curve represents the content of dust of this hot type measured by himself in the same samples and we know that in the ice age the gradient between the Onen plan and the tropical climate was much stronger, much steeper than today and that the atmosphere during the ice ages was much more dynamic and absorbed much more dust and that's why you'll find a maximum for each ice age so if the blue curve points downwards then you'll find a peak on the red curve where the concentration of dust in the 1 has increased now this this this diagram reflects some more interesting I said before that we still don't know why the cold values reach such an average value and then again and again around Kidman a warmer climate even with a warm climate at least for the last five or six 100,000 years such a peak is reached only in the oldest part of the ice cores then there are resistances that are somewhat lower and now you know We show that these weather changes are controlled by the geometry of the earth's orbit around the sun which creates a changing setup there are three geome tric elements in these cutters namely once the eccentricity of the ellipse that the earth revolves around the sun then the second is the depth of the earth's axis in these strawberries the public call becomes objectivity and finally the precision of the earth's rotation around its own axis and here before about 5,500 thousand years, instead of the eccentricity that it changes every 100 every 400,000 years a different frequency suddenly plays a role with the depth of the earth's axis and in the older part of the diagram the ice ages and those in between about a 40,000 change yeah you still don't know why this change happened and i'm still trying to understand it with more time than kernel to investigate what actually happened at that time and that doesn't just affect temperatures as or the dust content but that also affects greenhouse gases and can be seen in the parallel progression These two customers and at the bottom methane are shown above carbon dioxide and finally the temperature that was measured from oxygen in this ice house that there is parallelism to some degree in development and these ice houses actually have the same parameters that the parameters can be measured in the same core in the same ice cores they have a very important function that comprises something about the mechanics of these climate changes we now know that this climate change has spread throughout the recent part of the modern era this is an idea that von koeppen eventually pursued and vladimir köppen and alfred weger and milutin milankovic who had not said that isolation of the installation, which is the radiation that is in the lower part of the lower diagram, can be calculated very precisely from this celestial mechanics that it is only through the three geometric elements of this earth's orbit are controlled around the sun and he said before that isolation really controls the weather and that is still being intensively researched today and I have shown it a little better , I think in a German diagram like that where you can three geometric elements in the upper diagram, then it shows the climate curves that I have already shown here in the lower diagram, and finally the irradiation curve that is shown in the same curve in the medium.
I think you can derive a good close connection and we know you can do that today not only can it be documented with these calculations but there are also series of samples from the ice core and all the segments as illustrated here in the bottom curve, which prove that this relationship between the geometry of the earth's orbit around the sun and the climate and the development on earth really does take place and man can prove that, but he can also project it into the future in a way very interesting and that was done on this curve here, which represents the historical state of time before the last 500,000 theaters and then this scobel setup was calculated into the future for the next hundred thousand years and there are about 400,000 350 to 400 thousand years the part of the curve drawn in dark red on the right and what has been calculated for the future are a very good match and therefore we believe that not immediately stumbling upon an age of hi elo, but the climate after the warm peak of the so-called Holocene of the current election time will give way to a colder climate again if, of course, it allows a climatic development and if the human influence is not so strong that this change natural climate is really disturbed now that it had such a small film In the way that this should be industrialized again, these geometric changes are in the upper curves are the eccentricity, the depth of the earth's axis and the precision that shows how long a few hundreds of thousands of years and you can see how complicated this idea that de koeppen and wegner and milankovic has developed is, but there seems to be a real connection between these celestial mechanisms and the development of climate on earth, well if we turn to phenomena somewhat shorter, of course, there is an influence between atmospheric pollution and climate and it has often been postulated that volcanic eruptions t They have a great impact, but given that the volcanic ash, which does prevent the passage of the sun, the penetration of the or the installation is seriously impeded because the manufacturers calculate again, the kuka eruptions that we have experienced in the last centuries or millennia actually play a role not a big role here the volcanic eruptions have been reconstructed from ice cores drawn below you can see the volcanic ash in the core and above is a temperature curve plotted where the red intervals represent slightly warmer temperatures warm blue intervals represent slightly cooler temperatures temperatures you can see So, after each major volcanic eruption, there was a somewhat cooler climatic phase that might last for a short time and has no major lasting impact on the earth.
Now, if we now make our second question. so we have to close the ice cores in the northern hemisphere that have been drilled in greenland and this is data that cannot be obtained in the southern hemisphere simply because the snow is so slow in the boarding that this stratificationannual caused by oxygen Isotopes are falling here in this core to be reflected from Greenland that now cannot be derived in the same detail because it had to be a seasonal rhythm in precipitation from snow and ice formation, but that it's just this technology that uses the use of natural climate rescue, it was actually first developed in the 1950s and 1960s when the yes am das a The US military urgently wanted to obtain physical properties on the structure of the ice and the processes that take place there, they had the idea that they wanted to let their carriage-supported rockets travel under the ice surface in an ice tunnel in Greenland, so they commissioned Danish researchers to take a very close look at the physical and chemical properties of this and that's why the colleagues in Copenhagen are doing walks, then they very quickly got to the point of drilling this ice cellar lo and then came to the conclusion that a very tight stratification represents countless Danish divinity students who have engaged in counting and measuring each layer for the last 80 thousand years and producing this age scale and here two I gave you a part of a core from 1200 10 to about 12 180 or so at 1240 and you can do it great then of course all in egg Using one more second scale it only gets more interesting when you look at the whole ice core and you see from the distance this graph actually has two parts and on the left is a relatively stable curve of the change factor in oxygen isotopes. recorded in the last thousand for the first 1500 meters and almost for the entire forest 1 and then very stable conditions the same parameters are plotted on the right hand side for the entire last ice age and the picture is very different because it is a very variable situation with the cold intervals on the left side and meanwhile it was on the right side and you can see that the weather must have fluctuated strongly continuously that's a very interesting thing when you were able to make a very precise statement for the first time about how quickly, for example, the transition from the last ice age were currently occurring that could be done it didn't exactly do it before but now it has been done and this transition has been dated very precisely which is shown again here in the ice sweep, their own data in the central part of the graph for citizens is the first relatively warm interval together around all red and then comes a new relapse to ultimately the ice age young she the youngest dryas and then the current election time begins and on the left is a core of the gerzensee which is in switzerland to show how far this signal goes climate on the right side. but this went over this ice age transition between the heise of the younger dryas to the holocene in detail in the conversation and there you can see that once the temperature changes, the steep gradient of temperature changes is limited to one period 50 years. the difference that dust ingress is limited to even a ten to 20 year interval is very, very rapid time periods that characterize these changes and that is actually also an understanding that is rarely communicated to the transmission and is it gets even more exciting if you look at these ice time intervals again here on the right hand side then that has been dated very precisely and part of this ice core is showing again from the grasslands the blue cow shows temperature development you can see that within a few years the ice age temperatures have lower values here at the bottom of the diagram to almost warm the values jump over time and that these all these violent jumps in temperature that today we call the train dance beaver countries that are such a characteristic element of the ice age climate the red cross provides the places methane concentrations and it shows and methane it does not form in ice, it is a property of the glob as a privacy atmosphere that measures itself in a few years and therefore represents a low latitude biological signal of climate zones and reacts just as quickly we know that a lot of these jumps have played out over a few years and that's from the cold interval sometimes just over the course of five years it's also jumped into the warm weather situation and there being a very, very wild development in dynamics of the weather is taking place in the city and the great fear that we have today is that the human influence on the natural climate system has such an effect that this ice age system, which fluctuated very strongly, breaks out again.
You can also see that greenhouse gases follow the temperature changes a bit and that is why a big discussion has broken out on the quality issue now it is being written in a newspaper that greenhouse gases the temperature tre Iben, but if you look at natural changes i can or modern weather measurements then you can see greenhouse gases follow changes in temperature and that will have to be considered very carefully what that means well i have my own hypothesis as to what triggered the ice ages could and would like to tie this to the story of the great siberian currents the arctic ocean has a relatively stable majority cover it is covered by a thin layer of brackish water and brackish water freezes much more easily and quickly it is sea water again and this layer of brackish water is fed by the entire system of East Siberian currents all rivers s to the east of the urals that go north towards the arctic ocean and here is the mouth of the lena to see that the longest siberian current that is still completely in nature or almost completely in a natural state that rises near lake baikal and over four and a half thousand kilometers through the central saka republic to the north polar sea freezes and flows and then here also in the fans because this in this great delta about 500 by 500 km and then the sea arctic as a deck north of the arctic sea as the term mentioned now this this river has a very checkered history that is very little known and we are working intensively with our working group in st petersburg to date these terraces which reflect the history of the river and to find out how long the wood actually flowed and how its story on the boards also the tactic had more influence on the story idea and i said it before how we mos I gave the ice-carried material entry on the back of the booking number that I actually suspect that these energy systems have been around for many millions of years and that this system is an ancient system and in fact I think along with tectonics of plates that can be reconstructed because we know the age of the ocean floor very well today we want to construct the age of the cavalry we know the magnetic field of the earth very well and you can do that, then put it into a computer and here you see a little film reflecting the dynamics of plate tectonics in the southern hemisphere and here in the lower left corner of the map now appears india and that is transported north by plate tectonics until it meets the southern edge of the european continent at that time it collided and that happened about 55 million years ago, so the material transported by the inflow of ice in the arctic sea is inserted and I think that e This movement has caused the great mountain ranges in the southern part of Asia to fold and totalize the Siberian plain that tilted somewhat northwards and as a result developed this present system which today drains exclusively into the Arctic sea. about the technology it is because of the projects that have been developed how this age distribution has been shown but all that is red is a very young ocean floor and blue is ancient residents but this is a movement from india to across the indian ocean through the indian subcontinent it's been so far with the southern edge of the ahrens eurasian continent before at the beginning of the tts for about 55 million hand collided so i think liberation was the trigger i developed this regime of flow that carried so much fresh water into the arctic sea and that the cooling of the northern hemisphere and then the southern hemisphere has triggered now I am almost at the end of my In my story, I want to add two more slides once there is a lot of discussion about the fact that the climate is now actually being consumed by greenhouse gases, but the natural variability and that's shown here in two diagrams, one has the changes Natural temperature s of the climate from around 1900 onwards The year 2000 has been drawn as it is and how it has been modeled These temperature changes have been shown in the diagrams below and the influence of greenhouse gases has been calculated in the blue curve So a clear greenhouse effect influence Human-driven gases can be observed and that's where all the scientific discussion is focused on how far this is progressing, how far is this development from natural variability so In the end I am the last image that I show. it is in memory of the alpha expedition because the 1929 1930 in green managed the seasons as mean and there is the first really year-round mythological record of the top the peak of the peaks for one of the ice caps won that was a great performance had told the emergency association for german research at the time that they had to urgently carry out the expedition before their 50th birthday in the first when they turned 19 30 turned 50 at the station as a center and they celebrated with their three companions and that the party old stock an apple because the station was poorly supplied and only then was he born with his founding mission companion the same day on his way to the west coast and was found buried in ice the next spring, other things died in her heart, so that was a little swoon. ug to north grassland, but these historical memories of those who laid the foundation for german polar research should not be forgotten either.
I am at the end of my story and I hope you have understood that the ice ages lasted much longer than before. assuming that they regularly alternate between warm and cold periods and that this change is controlled by the geometry of the earth's orbit around the sun and thirdly that the changes occurred much faster than we previously assumed, that means that I am at the end and i'm finished thank you for your attention i think this last slide should show you the announcement of the next conference show me here thank you very much i hope you understood what i wanted to convey to you
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