MSGID: 1:317/3 646306df   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Out of this world control on Ice Age cycles    
      
     Date:   
         May 15, 2023   
     Source:   
         National Institutes of Natural Sciences   
     Summary:   
         A research team, composed of climatologists and an astronomer, have   
         used an improved computer model to reproduce the cycle of ice ages   
         (glacial periods) 1.6 to 1.2 million years ago. The results show   
         that the glacial cycle was driven primarily by astronomical forces   
         in quite a different way than it works in the modern age. These   
         results will help us to better understand the past, present,   
         and future of ice sheets and the Earth's climate.   
      
      
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   FULL STORY   
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   A research team, composed of climatologists and an astronomer, have   
   used an improved computer model to reproduce the cycle of ice ages   
   (glacial periods) 1.6 to 1.2 million years ago. The results show that   
   the glacial cycle was driven primarily by astronomical forces in quite   
   a different way than it works in the modern age. These results will help   
   us to better understand the past, present, and future of ice sheets and   
   the Earth's climate.   
      
   Earth's orbit around the Sun and its spin axis orientation change   
   slowly over time, due to the pull of gravity from the Sun, the Moon,   
   and other planets.   
      
   These astronomical forces affect the environment on Earth due to changes   
   in the distribution of sunlight and the contrast between the seasons. In   
   particular, ice sheets are sensitive to these external forces resulting   
   in a cycle between glacial and interglacial periods.   
      
   The present-day glacial-interglacial cycle has a period of about 100,000   
   years.   
      
   However, the glacial cycle in the early Pleistocene (about 800,000 years   
   ago) switched more rapidly, with a cycle of about 40,000 years. It has   
   been believed that astronomical external forces are responsible for this   
   change, but the details of the mechanism have not been understood. In   
   recent years, it has become possible to investigate in more detail the   
   role of astronomical forces through the refinement of geological data   
   and the development of theoretical research.   
      
   A team led by Yasuto Watanabe at the University of Tokyo focused on   
   the early Pleistocene Epoch from 1.6 to 1.2 million years ago using an   
   improved climate computer model. Astronomical forces based on modern   
   state-of-the-art theory are considered in these simulations. The large   
   numerical simulations in this study reproduce well the glacial cycle   
   of 40,000-year of the early Pleistocene as indicated by the geological   
   record data.   
      
   From analysis of these simulation results, the team has identified three   
   facts about the mechanisms by which astronomical forces caused changes   
   in climate in those times. (1) The glacial cycle is determined by small   
   differences in the amplitude of variation of the spin axis orientation   
   and the orbit of the Earth.   
      
   (2) The timing of deglaciation is determined mainly by the position of   
   the summer solstice on its orbit, which is at perihelion, not only by   
   the effect of periodical change of the tilt of the Earth's axis. (3)   
   The timing of the change in the spin axis orientation and the position   
   of the summer solstice on its orbit determines the duration of the   
   interglacial period.   
      
   "As geological evidence from older times comes to light, it is   
   becoming clear that the Earth had a different climatic regime than   
   it does today. We must have a different understanding of the role of   
   astronomical forcing in the distant past," says Takashi Ito from the   
   National Astronomical Observatory of Japan, a member of this research team   
   who led the discussion on astronomical external forces. "The numerical   
   simulations performed in this study not only reproduce the Pleistocene   
   glacial-interglacial cycle well, but also successfully explain the   
   complex effects of how astronomical forcing drove the cycle at that time.   
      
   We can regard this work as a starting point for the study of glacial   
   cycles beyond the present day Earth."   
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Earth_Science # Ice_Ages # Climate # Geochemistry   
             o Fossils_&_Ruins   
                   # Early_Climate # Fossils # Origin_of_Life # Evolution   
       * RELATED_TERMS   
             o Ice_age o Ice_sheet o Global_climate_model   
             o Greenland_ice_sheet o Mammoth o   
             Antarctic_ice_sheet o Geologic_temperature_record o   
             Temperature_record_of_the_past_1000_years   
      
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   Story Source: Materials provided by   
   National_Institutes_of_Natural_Sciences. Note: Content may be edited   
   for style and length.   
      
      
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   Journal Reference:   
      1. Yasuto Watanabe, Ayako Abe-Ouchi, Fuyuki Saito, Kanon Kino, Ryouta   
         O'ishi, Takashi Ito, Kenji Kawamura, Wing-Le Chan. Astronomical   
         forcing shaped the timing of early Pleistocene glacial   
         cycles. Communications Earth & Environment, 2023; 4 (1) DOI:   
         10.1038/s43247-023-00765-x   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230515132024.htm   
      
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