Kursus: Issue (Is Deep Circulation Permanent?)

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Issue: Is deep circulation permanent?
- 　The "water flow" we have been describing is the ocean circulation in the present (at least, from after the last glacial period to the present). What about the past? Before and after the glacial period, when the ice sheets spread to the mid-latitudes, and even further back, after 2.75 million years ago.
  　If we want to know the present global environment and the future, it is important to learn from the past.
  
  Is deep circulation permanent?　Please organize information from several references (papers or books) on changes in the marine environment during the Cenozoic Era (mainly the Quaternary, including the present day) and summarize the information on about one A4 sheet of paper. You may include figures and tables.
  
  Theme:　Please feel free to focus on events in the marine environment before and after the beginning of the Quaternary, glacial cycles, including the last glacial period and the last interglacial period, summarizing these events, specific past events, or events that are considered mysterious and controversial in the scientific community. You may wish to focus on changes in the conveyor belt (deep circulation).
  
  ・Available Japanese papers (Click on each volume - each issue to find the article title, respectively)
  　　Back numbers of the Journal of Quaternary Science (Japan Association for Quaternary Research)（Download from J-stage）
  　　Back numbers of Journal of Geochemistry (The Geochemical Society of Japan)（Download from J-stage）
  　　Back numbers of the Journal of Marine Research (The Oceanographic Society of Japan)（Download from J-stage）
  There are others. You can also enter the name of a journal in J-stage and jump to its back number page.
- Link to PDF file of "Marine Environmental Changes during Glacial and Interglacial Periods as Seafloor Sediments Revealed", Quaternary Research, OOKOUCHI & TAIRA (1991) URL
  
  Several hypotheses are presented on the ocean circulation during the glacial period. Methods of paleoenvironmental analysis are also explained.
- Link to PDF file of "Paleoceanographic Reconstruction Study in the North Pacific Ocean - Ocean circulation changes since the last glacial period". Marine Research, OKAZAKI (2012) URL
  
  It indicates that the North Pacific temporarily replaced the North Atlantic during the last deglaciation as the starting point for the subduction of the deep circulation.
- Link to PDF (open) file of "On Glacial Deep Ocean Carbon Reservoirs", Geochemistry, OKAZAKI (2015) URL
  
  The hypothesis that "deep circulation stopped during the glacial period" is rejected (rejecting the existence of isolated deep-water masses during the glacial period).
- Hints for Theme Setting
  The event 2.75 million years ago led to the creation of the "Quaternary" time period - the establishment of the Isthmus of Panama, how did the world's oceans change before and after this event?
  The Quaternary is the most recent period in the Earth's 4.6 billion year-long history, including the present, during which humans have evolved, spread, and been active on the Earth. The period from about 2.6 million years ago to the present is roughly divided into the Pleistocene (from the beginning of the Quaternary to 11.5 thousand years ago) and the Holocene (from then to the present). The Quaternary is a period of rapid changes in the natural environment, with large-scale ice sheets distributed over high-latitude continents, alternating cooling and warming of the global climate, expansion, and contraction of ice sheets and mountain glaciers in the Northern Hemisphere, lowering and rising sea levels worldwide, and shifts in the distribution areas of plants, animals, and other organisms (From the HP of Japan Association for Quaternary Research: http://quaternary.jp/intro/daiyonki.html). The Pleistocene is the period up to the last glacial period, and the Holocene is the last interglacial period (the present).
  
  It is clear that the current deep circulation is not permanent.
  
  The following is a reference.
- Link to PDF file of "Establishment of the Panama Isthmus and Global Cooling", Quaternary Research, SATO (2010) URL
- It is introduced as one of the hypotheses in one line on p. 140 of "The 4.6 Billion Year History of Earth's Environmental Changes (by TAJIKA Eiichi, Chemistry Doujin, 2009). The writing is easy to read.
  It is described in 12 lines on p175 of "Evolution of the Earth's Surface Environment (by KAWAVATA Hotaka, University of Tokyo Press, 2011). The writing is somewhat difficult. The textbook.
  In paleoenvironmental studies, new discoveries often overturn established theories. Keep in mind that interpretations in textbooks and readings can also change.
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Thank you for your hard work.

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Issue: Is deep circulation permanent?

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