story by Helen Hill 
Motivated by satellite data, researchers at the State Key Laboratory of Tropical Oceanography at the Chinese Academy of Science’s South China Sea Institute of Oceanology, Guangzhou, China, have been using MITgcm to investigate the interaction of internal solitary waves with mesoscale eddies in the context of the northeastern South China Sea.
Based on an analysis of synthetic aperture radar and satellite altimeter data, co-authors Jieshuo Xie, Yingui He, Zhiwu Chen, and Shuqun Cai, observed peculiar distortion of the front associated with an internal solitary wave (ISW) and postulated it to be the result of an interaction with an oceanic mesoscale eddy.
Motivated by this, the team carried out numerical experiments using a fully nonhydrostatic and nonlinear implementation of MITgcm to probe how ISWs might be affected by the transit of an isolated cyclonic or anti-cyclonic eddy.
Model results demonstrated that retardation and acceleration effects to each side of an eddy can indeed act to produce distortions to the ISW front in good qualitative agreement with satellite observations.
Subsequent analysis revealed that the ISW energy along the front is focused onto (scattered from) the wave fragment where a concave (convex) pattern is formed, with the previously accumulated energy in the focusing region gradually released after the ISW propagates away from an eddy.
The team also found that the ISW amplitude is modulated greatly by a passing eddy due to the energy redistribution along the front. Sensitivity results indicate that the magnitude of the modulated ISW amplitude in the focusing region can reach twice the incident ISW amplitude, while in the scattering region it can be reduced by more than a half reinforcing the need to use eddy resolving models to further improve amplitude predictions in the region.
In addition the authors find that for an anti-cyclonic eddy, the internal gravity wave formed behind the energy focusing region can steepen and break with the consequent formation of a secondary trailing ISW packet, again showing good qualitative agreement with features observed in the satellite data.
To find out more about this work contact Shuqun Cai 
Two small movies showing the internal solitary wave front passing through a cyclonic/an anticyclonic eddy
Cyclonic Eddy – video credit: Jieshuo Xie
Anti-Cyclonic Eddy – video credit: Jieshuo Xie
About the Researchers
This Month’s Featured Publication
- Jieshuo Xie, Yinghui He, Zhiwu Chen, Jiexin Xu, and Shuqun Cai (2015), Simulations of internal solitary wave interactions with mesoscale eddies in the northeastern South China Sea, Journal of Physical Oceanography 2015 ; e-View, doi: 10.1175/JPO-D-15-0029.1 
Other Related Papers Using MITgcm
Xu Jiexin, Chen Zhiwu, Xie Jieshuo, Cai Shuqun (2016), On generation and evolution of seaward propagating internal solitary waves in the northwestern South China Sea, Communications in Nonlinear Science and Numerical Simulation, 2016, 32: 122-136. doi: 10.1016/j.cnsns.2015.08.013 
He Yinghui, Cai Shuqun, Dongxiao Wang, He Jianling (2015), A model study of Luzon Cold Eddies in the northern South China Sea, Deep-Sea Research Part I, 2015, 97: 107-123, doi:10.1016/j.dsr.2014.12.007 
Other New Publications this Month
E. Akoglu, S. Libralato, B. Salihoglu, T. Oguz, and C. Solidoro (2015), EwE-F 1.0: an implementation of Ecopath with Ecosim in Fortran 95/2003 for coupling and integration with other models, Geosci. Model Dev., 8, 2687–2699, 2015 www.geosci-model-dev.net/8/2687/2015/ 
Ian Fenty, Dimitris Menemenlis, Hong Zhang (2015), Global coupled sea ice-ocean state estimation, online at Climate Dynamics, 10.1007/s00382-015-2796-6 
Daniel C. Jones, Takamitsu Ito, Thomas Birner, Andreas Klocker, David Munday (2015), Planetary-geometric constraints on isopycnal slope in the Southern Ocean, Journal of Physical Oceanography 2015 ; e-View doi: 10.1175/JPO-D-15-0034.1 
A. R. Karspeck , D. Stammer, A. Köhl, G. Danabasoglu, M. Balmaseda, D. M. Smith, Y. Fujii, S. Zhang, B. Giese and 2 more (2015), Comparison of the Atlantic meridional overturning circulation between 1960 and 2007 in six ocean reanalysis products, online at Climate Dynamics, doi: 10.1007/s00382-015-2787-7 
I. Kriest and A. Oschlies (2015), MOPS-1.0: towards a model for the regulation of the global oceanic nitrogen budget by marine biogeochemical processes, Geosci. Model Dev., 8, 2929–2957, 2015 www.geosci-model-dev.net/8/2929/2015/ doi: 10.5194/gmd-8-2929-2015 
Marina Lévy, Oliver Jahn, Stephanie Dutkiewicz, Michael J. Follows, Francesco d’Ovidio (2015), The dynamical landscape of marine phytoplankton diversity, Interface, Journal of the Royal Society, Published 23 September 2015, doi: 10.1098/rsif.2015.0481 
Katsumi Matsumoto, Kathy S. Tokos, Chad Gregory (2015), Ventilation and dissolved oxygen cycle in Lake Superior: Insights from a numerical model, online at Geochemistry, Geophysics, Geosystems, doi: 10.1002/2015GC005916 
D.R. Munday, X. Zhai (2015), Sensitivity of Southern Ocean circulation to wind stress changes: Role of relative wind stress, Ocean Modelling, Volume 95, November 2015, Pages 15–24, doi: 10.1016/j.ocemod.2015.08.004 
Océane Richet, Jean-Marc Chomaz, Caroline Muller (2015), Impact of a mean current on internal tide energy dissipation at the critical latitude, 68th Annual Meeting of the APS Division of Fluid Dynamics, Volume 60, Number 21, Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts, online abstract 
M. D. Palmer, C. D. Roberts, M. Balmaseda, Y.-S. Chang, G. Chepurin, N. Ferry, Y. Fujii, S. A. Good, S. Guinehut and 14 more (2015), Ocean heat content variability and change in an ensemble of ocean reanalyses, online in Climate Dynamics, 10.1007/s00382-015-2801-0 
Maria N. Pisareva, Robert S. Pickart, M.A. Spall, C. Nobre, D.J. Torres, G.W.K. Moore, Terry E. Whitledge (2015), Flow of pacific water in the western Chukchi Sea: Results from the 2009 RUSALCA expedition, Deep Sea Research Part I: Oceanographic Research Papers, Volume 105, November 2015, Pages 53–73, doi: 10.1016/j.dsr.2015.08.011 
Siva Prasad, Igor Zakharov, Pradeep Bobby, Peter McGuire (2015), The implementation of sea ice model on a regional high-resolution scale, Ocean Dynamics, September 2015, Volume 65, Issue 9, pp 1353-1366, do: 10.1007/s10236-015-0877-z 
Michael A. Spall (2015), Thermally forced transients in the thermohaline circulation, Journal of Physical Oceanography 2015 ; e-View, doi: 10.1175/JPO-D-15-0101.1 
Hongbao Qian, Xiaodong Huang , Jiwei Tian, Wei Zhao (2015), Shoaling of the internal solitary waves over the continental shelf of the northern South China Sea, Acta Oceanologica Sinica, September 2015, Volume 34, Issue 9, pp 35-42, doi: 10.1007/s13131-015-0734-4 
Denis L. Volkov, Arseny A. Kubryakov, Rick Lumpkin (2015), Formation and variability of the Lofoten basin vortex in a high-resolution ocean model, Deep Sea Research Part I: Oceanographic Research Papers, Volume 105, November 2015, Pages 142–157, doi: doi:10.1016/j.dsr.2015.09.001 
Catherine A. Vreugdenhil, Andrew McC. Hogg, Ross W. Griffiths, and Graham O. Hughes (2015), Adjustment of the meridional overturning circulation and its dependence on depth of mixing, Journal of Physical Oceanography 2015 ; e-View, doi: 10.1175/JPO-D-15-0050.1 
Xiaohui Yan, Abdolmajid Mohammadian, Hazim Qiblawey (2015), Numerical simulation of the long-term balance of salinity in the Gulf, 1st Worksop on Mixing in Coastal Waters, Rivers & Atmosphere, PDF 
Jieshuo Xie, Yinghui He, Zhiwu Chen, Jiexin Xu, and Shuqun Cai (2015), Simulations of internal solitary wave interactions with mesoscale eddies in the northeastern South China Sea, Journal of Physical Oceanography 2015 ; e-View, doi: 10.1175/JPO-D-15-0029.1 
Ping Zhai, Amy S. Bower, William M. Smethie Jr., Larry J. Pratt (2015), Formation and spreading of Red Sea Outflow Water in the Red Sea, Journal of Geophysical Research – Oceans, doi: 10.1002/2015JC010751 
Do you have news about research using MITgcm? We are looking for contributions to these pages. If you have an interesting MITgcm project (ocean, atmosphere, sea-ice, physics, biology or otherwise) that you want to tell people about, get in touch. To make a post, contact Helen