Effects of atmospheric dynamics and ocean resolution on bi-stability of the thermohaline circulation examined using the Grid ENabled Integrated Earth system modelling (GENIE) framework |
| |
| Authors: | T M Lenton R Marsh A R Price D J Lunt Y Aksenov J D Annan T Cooper-Chadwick S J Cox N R Edwards S Goswami J C Hargreaves P P Harris Z Jiao V N Livina A J Payne I C Rutt J G Shepherd P J Valdes G Williams M S Williamson A Yool |
| |
| Institution: | (1) School of Environmental Sciences, University of East Anglia, Norwich, UK;(2) Tyndall Centre, UK,;(3) National Oceanography Centre, University of Southampton, Southampton, UK;(4) Southampton e-Science Centre, University of Southampton, Southampton, UK;(5) School of Geographical Sciences, University of Bristol, Bristol, UK;(6) Frontier Research Centre for Global Change, Yokohama, Japan;(7) Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR), Earth Sciences, Open University, Milton Keynes, UK;(8) Centre for Ecology and Hydrology, Wallingford, UK;(9) School of Physics and Astronomy, University of Leeds, Leeds, UK |
| |
| Abstract: | We have used the Grid ENabled Integrated Earth system modelling (GENIE) framework to undertake a systematic search for bi-stability
of the ocean thermohaline circulation (THC) for different surface grids and resolutions of 3-D ocean (GOLDSTEIN) under a 3-D
dynamical atmosphere model (IGCM). A total of 407,000 years were simulated over a three month period using Grid computing.
We find bi-stability of the THC despite significant, quasi-periodic variability in its strength driven by variability in the
dynamical atmosphere. The position and width of the hysteresis loop depends on the choice of surface grid (longitude-latitude
or equal area), but is less sensitive to changes in ocean resolution. For the same ocean resolution, the region of bi-stability
is broader with the IGCM than with a simple energy-moisture balance atmosphere model (EMBM). Feedbacks involving both ocean
and atmospheric dynamics are found to promote THC bi-stability. THC switch-off leads to increased import of freshwater at
the southern boundary of the Atlantic associated with meridional overturning circulation. This is counteracted by decreased
freshwater import associated with gyre and diffusive transports. However, these are localised such that the density gradient
between North and South is reduced tending to maintain the THC off state. THC switch-off can also generate net atmospheric
freshwater input to the Atlantic that tends to maintain the off state. The ocean feedbacks are present in all resolutions,
across most of the bi-stable region, whereas the atmosphere feedback is strongest in the longitude–latitude grid and around
the transition where the THC off state is disappearing. Here the net oceanic freshwater import due to the overturning mode
weakens, promoting THC switch-on, but the atmosphere counteracts this by increasing net freshwater input. This increases the
extent of THC bi-stability in this version of the model.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
