MSGID: 1:317/3 6483fc6b   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Eddies: Circular currents and their influence on the world's hottest   
   ocean    
      
     Date:   
         June 9, 2023   
     Source:   
         Tohoku University   
     Summary:   
         Water from the Pacific Ocean flows into the Indian Ocean via the   
         Indonesia Archipelago thanks to a vast network of currents that act   
         as a conveyor belt, transporting warmth and nutrients. Currents can   
         sometimes form circular motions and these are known as eddies. An   
         international group of researchers has modeled the impacts of   
         eddies on the currents that carry water from the Pacific Ocean to   
         the Indian Ocean.   
      
      
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   FULL STORY   
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   Water from the Pacific Ocean flows into the Indian Ocean via the   
   Indonesia Archipelago Seas thanks to a vast network of currents dubbed the   
   Indonesian Throughflow (ITF). The ITF acts as a heat and moisture conveyer   
   belt, transporting warm and nutrient waters. Yet the ITF is neither a   
   steady nor a straight path, but experiences fluctuations and turbulence   
   as it passes through the various sea regions, straits, and passages.   
      
   Currents can sometimes formulate into circular motions, forming a   
   whirlpool- like phenomena. These are known as eddies, and they are   
   prominent in areas where there are strong gradients in temperature,   
   salinity, or velocity. Their rotating motion can cause nutrients from   
   the colder, deeper waters to rise to the surface.   
      
   To investigate the role eddies play in determining the path of the ITF,   
   an international research group has harnessed a high-resolution ocean   
   general circulation model that reproduces eddies. The group featured   
   researchers from Tohoku University, JAMSTEC, Kyushu University, the   
   University of Hawai`i at Manoa, and the National Research and Innovation   
   Agency of Indonesia.   
      
   Details of their research were reported in the Journal of Geophysical   
   Research -- Oceans on May 14, 2023.   
      
   The group's model enabled them to calculate the transport of   
   simulated particles in a daily-averaged flow field with eddies and a   
   monthly-averaged flow field with smoothed eddy currents, respectively,   
   and estimate the flow rate transported by the simulated particles.   
      
   In the Sulawesi Sea, which is situated along the northeastern coast   
   of Borneo and also borders the southern Filipino island of Mindanao,   
   the Sulu archipelago, and Sulawesi Island's western coast, the group   
   found that large flow fluctuations occur, and seawater circulates over a   
   wider area for an extended period. Seawater also rises from the middle   
   to near the surface, which may cause significant changes in the water   
   when flowing through due to turbulent mixing.   
      
   On the eastern side of Sulawesi Island sits the Banda Sea, which surrounds   
   the Maluku Islands and borders the islands of New Guinea and Timor. Here,   
   the current fluctuation is slight, and the model predicted negligible   
   influence from the eddies on the Indonesian Current.   
      
   "Our results indicate that the path and residence time of the ITF, along   
   with the mixing process of seawater, must be appropriately reproduced   
   by an ocean general circulation model to gain further insights into   
   and better predict sea surface temperature fluctuations in each region   
   of the Indonesian Archipelago," points out Toshio Suga, professor of   
   physical oceanography at Tohoku University's Graduate School of Science   
   and co-author of the paper.   
      
   Global warming's progression is expected to change the ITF. Such changes   
   could have profound repercussions for water temperatures in the Indonesia   
   Archipelago and the Indian Ocean, El Nin~o and the Indian Ocean Dipole,   
   and the frequency and scale of marine heatwaves that affect marine   
   ecosystems and local weather.   
      
   Therefore, it is vital to predict accurately such phenomena.   
      
   Looking ahead, the group hopes to improve the accuracy of future   
   predictions by clarifying the degree to which eddies impact the path   
   and residence time of the ITF, something quantitatively linked to the   
   determination of water temperature in these areas.   
      
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Oceanography # Water # Global_Warming # Geography #   
                   Climate # Weather # Ecosystems # Ecology   
       * RELATED_TERMS   
             o Ocean_current o Ocean o El_Nin~o-Southern_Oscillation o   
             Mid-ocean_ridge o 1997_Pacific_typhoon_season o Climate o   
             Ocean_surface_wave o List_of_Category_5_Pacific_hurricanes   
      
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   Story Source: Materials provided by Tohoku_University. Note: Content   
   may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Mochamad Riza Iskandar, Yanli Jia, Hideharu Sasaki, Ryo Furue,   
      Shinichiro   
         Kida, Toshio Suga, Kelvin J. Richards. Effects of   
         High‐Frequency Flow Variability on the Pathways of the   
         Indonesian Throughflow. Journal of Geophysical Research: Oceans,   
         2023; 128 (5) DOI: 10.1029/2022JC019610   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230609125656.htm   
      
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