story by Helen Hill  for MITGCM
A group from National Taiwan University has been using MITgcm to study submesoscale island wakes in the Kuroshio Current off Taiwan.
Like a sailboat on a calm sea, a canoe on a lake, or indeed a vessel on any body of water, islands too can produce wakes.
To study submesoscale island wake formation, researchers Ming-Huei Chang and Chih-Lun Liu from the Institute of Oceanography, National Taiwan University, have been using MITgcm to carry out three-dimensional numerical simulations of the circulation around a neighboring island to enable them, given sparse observational data, to carry out a detailed fluid dynamical analysis of the system.
The Kuroshio, a strong western boundary current in the northwestern Pacific Ocean, flows northward along Taiwan’s east coast with a width of 100–150 km and a maximum speed of 1–1.5 m s–1. Around 50km offshore to the southeast lies Green Island, a ~7 km diameter conical feature, the first in a series of features that form a submarine ridge which extends north to Taiwan. With average current speeds at a depth of ~ 200 m reaching > 0.5 ms-1, the waters in the lee of Green Island provide a natural laboratory for studying submesoscale dynamics of island wakes.
Using a hydrostatic implementation of MITgcm, Liu and Chang set up a domain 80km square by just under 300m deep, prescribing (constant) inflow on the southern and western walls, with outflow at the northern and eastern walls, and a representative topography based on Ocean Data Bank data for the region (See the paper for full details).
Liu and Chang’s experiments successfully reproduce an island wake formed of sequentially detached recirculations, each containing a region of upwelling cold water, which propagate downstream via advection to form an along stream wake reminiscent of a von Kármán vortex street (VKVS).
Analysis of the circulation shows the shedding frequency (which is a function of the horizontal eddy viscosity) exhibits a trend analogous with classical wakes, that wake behavior exhibits the appropriate dependence on Reynolds number, and that the wake aspect ratio is similar to that predicted for classical VKVS.
Unlike classical VKVS, however, Liu and Chang report finding their wake features being adapted by inertial and barotropic instabilities. In particular they found that the inertial instability had a large growth rate that tended to slightly destabilize anticyclonic recirculation, leading them to propose that barotropic instability may act as a secondary process generating eddy kinetic energy downstream.
To find out more about this work contact Ming-Huei 
Story image: https://commons.wikimedia.org/wiki/File:Vortex-street-1-90deg.jpg
This Month’s Featured Publication
- C. ‐L. Liu M. ‐H. Chang (2018), Numerical Studies of Submesoscale Island Wakes in the Kuroshio , Journal of Geophysical Research Oceans, doi: 10.1029/2017JC013501
Other New Publications this Month
Olivier Arzel, Thierry Huck, and Alain Colin de Verdière (2018), The Internal Generation of the Atlantic Ocean Interdecadal Variability , Journal of Climate, doi: 10.1175/JCLI-D-17-0884.1
Edward W. Blockley and K. Andrew Peterson (2018), Improving Met Office seasonal forecasts of Arctic sea ice using assimilation of CryoSat-2 thickness , The Cryosphere Discuss., doi: 10.5194/tc-2018-62
M. Cameron Rencurrel and Brian E. J. Rose (2018), Exploring the Climatic Response to Wide Variations in Ocean Heat Transport on an Aquaplanet , Journal of Climate, doi: 10.1175/JCLI-D-17-0856.1
Ahmed Eladawy, Mohamed Shaltout, Magda Catarina Sousa, João Miguel Dias, Kazuo Nadaoka (2018), Estimating the Mean Circulation and Water Exchange of the Gulf of Suez-Red Sea via a Validated One-Way Atmospheric-Hydrodynamic Coupled Model , Earth Systems and Environment, doi: 10.1007/s41748-018-0049-7
Sindre M. Fritzner, Rune G. Graversen, Keguang Wang, Kai H. Christensen (2018), Comparison between a multi-variate nudging method and the ensemble Kalman filter for sea-ice data assimilation , Journal of Glaciology, doi: 10.1017/jog.2018.33
D. Giglio, V. Lyubchich, M.R. Mazloff (2018), Estimating Oxygen in the Southern Ocean Using Argo Temperature and Salinity , Journal of Geophysical Research Oceans, doi: 10.1029/2017JC013404
Subhajit Kar and Anirban Guha (2018), Accurate reconstruction of ocean bathymetry from surface data , arXiv:1805.00297 [physics.flu-dyn],
Laura KreidBerg, Michael R. Line, Vivien Parmentier, Kevin B. Stevenson, Tom Louden, Mickael Bonnefoy, Jacqueline K. Faherty, Gregory W. Henry, Michael H. Williamson, Keivan Stassun, Thomas G. Beatty, Jacob L. Bean, Jonathan J. Fortney, Adam P. Showman, Jean-Michel Desert and Jacob Arcangeli (2018), Global Climate and Atmospheric Composition of the Ultra-Hot Jupiter WASP-103b from HST and Spitzer Phase Curve Observations , arXiv:1805.00029 [astro-ph.EP],
Anurag Kumar, Suneet Dwivedi, D. Ram Rajak, A.C.Pandey (2018), Impact of air-sea forcings on the southern ocean sea ice variability around the Indian Antarctic stations , Polar Science, doi: 10.1016/j.polar.2018.05.005
Yu-Chiao Liang, Matthew R. Mazloff, Isabella Rosso, Shih-Wei Fang and Jin-Yi Yu (2018), A Multivariate Empirical Orthogonal Function Method to Construct Nitrate Maps in the Southern Ocean , Journal of Atmospheric and Oceanic Technology, doi: 10.1175/JTECH-D-18-0018.1
S.N. Losa, M.A. Soppa, V. Perfanis, M. Losch, B. Heim, J. Oelker, S. Sutkiewicz, T. Dinter, V.V. Rozanov, A. Bracher (2018), Modeling the Arctic coloured dissolved organic matter (CDOM) and phytoplankton diversity in/with support to satellite retrievals, POSTER  http://epic.awi.de/47235/1/REKLIM_2018.pdf
Megan Mansfield, Jacob L. Bean, Michael R. Line, Vivien Parmentier, Laura Kreidberg, Jean-Michael Desert. Jonathan J. Fourtney, Kevin B. Stevenson, Jacob Arcangeli, and Diana Dragomir (2018), A HST/WFC3 Thermal Emission Spectrum of the Hot Jupiter HAT-P-7B , arXiv:1805.00424 [astro-ph.EP]
Vivien Parmentier, Mike R. Line, Jacob L. Bean, Megan Mansfield, Laura Kreidberg, Roxana Lupu, Channon Visscher, Jean-Michel Desert, Jonathan J. Fortney, Magalie Deleuil, Jacob Arcangeli, Adam P. Showman, and Mark S. Marley (2018), From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context , arXiv:1805.00096 [astron-ph.EP]
Diana Powell, Xi Zhang, Peter GAo, and Vivien Parmentier (2018), Formation of Silicate and Titanium Clouds on Hot Jupiters , arXiv:1805.01468
O. Richet, J.‐M. Chomaz, C. Muller (2018), Internal Tide Dissipation at Topography: Triadic Resonant Instability Equatorward and Evanescent Waves Poleward of the Critical Latitude,  Journal of Geophysical Research Oceans, doi: 10.1029/2017JC013591
E.L. Shroyer and Robert S. Pickart (2018), Pathways, timing, and evolution of Pacific Winter Water through Barrow Canyon , Deep Sea Research Part II: Topical Studies in Oceanography, doi: 10.1016/j.dsr2.2018.05.004
Adil Siripatana, Talea Mayo, Omar Knio, Clint Dawson, Olivier Le Maître, Ibrahim Hoteit (2018), Ensemble Kalman filter inference of spatially-varying Manning’s n coefficients in the coastal ocean , Journal of Hydrology, doi: 10.1016/j.jhydrol.2018.05.021
Habib Toye, Samuel Kortas, Peng Zhan, Ibrahim Hoteit (2018), A fault-tolerant HPC scheduler extension for large and operational ensemble data assimilation: Application to the Red Sea , Journal of Computational Science, doi: 10.1016/j.jocs.2018.04.018
Giuliana A. Viglione, Andrew F. Thompson, and Mar M. Flexas (2018), Abrupt transitions in submesoscale structure in Southern Drake Passage: Glider observations and model results , Journl of Physical Oceanography, doi: 10.1175/JPO-D-17-0192.1
Yixin Wang (2018), Simulating Coral Reef Connectivity in the Southern Red sea, Masters Dissertation, KAUST, Saudi Arabia, https://repository.kaust.edu.sa/bitstream/handle/10754/627890/Updated_MS_Thesis_Yixin_Wang.pdf 
Collin P. Ward, Cassia J. Armstrong, Robyn N. Conmy, Deborah P. French-McCay, and Christopher M. Reddy (2018), Photochemical Oxidation of Oil Reduced the Effectiveness of Aerial Dispersants Applied in Response to the Deepwater Horizon Spill , Environmental Science and Technology Letters, doi: 10.1021/acs.estlett.8b00084
Jianfen Wei, Xiangdong Zhang, Zhaomin Wang (2018), Impacts of extratropical storm tracks on Arctic sea ice export through Fram Strait , Climate Dynamics, doi: 10.1007/s00382-018-4254-8
Shengmu Yang, Jiuxing Xing, Shengli Chen, Tian Jiwei, and Daoyi Chen (2018), The impact of the planetary β-effect on the tilting vertical structure of a mesoscale eddy , Ocean Sci. Discuss., doi: 10.5194/os-2018-39
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