An assessment of the Indian Ocean mean state and seasonal cycle in a suite of interannual CORE-II simulations

H. Rahaman*, U. Srinivasu, S. Panickal, J. V. Durgadoo, S. M. Griffies, M. Ravichandran, A. Bozec, A. Cherchi, A. Voldoire, D. Sidorenko, E. P. Chassignet, G. Danabasoglu, H. Tsujino, K. Getzlaff, M. Ilicak, M. Bentsen, M. C. Long, P. G. Fogli, R. Farneti, S. DanilovS. J. Marsland, S. Valcke, S. G. Yeager, Q. Wang

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Özet

We present an analysis of annual and seasonal mean characteristics of the Indian Ocean circulation and water masses from 16 global ocean–sea-ice model simulations that follow the Coordinated Ocean-ice Reference Experiments (CORE) interannual protocol (CORE-II). All simulations show a similar large-scale tropical current system, but with differences in the Equatorial Undercurrent. Most CORE-II models simulate the structure of the Cross Equatorial Cell (CEC) in the Indian Ocean. We uncover a previously unidentified secondary pathway of northward cross-equatorial transport along 75 °E, thus complementing the pathway near the Somali Coast. This secondary pathway is most prominent in the models which represent topography realistically, thus suggesting a need for realistic bathymetry in climate models. When probing the water mass structure in the upper ocean, we find that the salinity profiles are closer to observations in geopotential (level) models than in isopycnal models. More generally, we find that biases are model dependent, thus suggesting a grouping into model lineage, formulation of the surface boundary, vertical coordinate and surface salinity restoring. Refinement in model horizontal resolution (one degree versus [Formula presented] degree) does not significantly improve simulations, though there are some marginal improvements in the salinity and barrier layer results. The results in turn suggest that a focus on improving physical parameterizations (e.g. boundary layer processes) may offer more near-term advances in Indian Ocean simulations than refined grid resolution.

Orijinal dilİngilizce
Makale numarası101503
DergiOcean Modelling
Hacim145
DOI'lar
Yayın durumuYayınlandı - Oca 2020

Bibliyografik not

Publisher Copyright:
© 2019 The Authors

Finansman

The encouragement and facilities provided by Dr. S S C Shenoi, Director, Indian National Centre for Ocean Information Services (INCOIS), are gratefully acknowledged. Graphics were generated using the NOAA product Ferret. We thank Prof. Raghu Murthugude for useful suggestions that greatly improved the manuscript. We thank N Kiran Kumar for his help to generate the schematic diagram in Fig. 1. The fourth author (J.V.D) acknowledges funding from the Helmholtz-Gemeinschaft and the GEOMAR Helmholtz Centre for Ocean Research Kiel (grant IV014/GH018). NCAR is a major facility sponsored by the U.S. National Science Foundation under Cooperative Agreement 1852977. Q. Wang and D. Sidorenko are supported by the German Helmholtz Climate Initiative REKLIM (Regional Climate Change). We thank Matthew Harrison and P S Swathi for their comments and discussions that have helped this paper. This is INCOIS contribution no. 358 and NCPOR contribution no. J-38/2019-20. We thank all five anonymous reviewers for their constructive comments by which we have improved the manuscript immensely. The encouragement and facilities provided by Dr. S S C Shenoi, Director, Indian National Centre for Ocean Information Services (INCOIS), are gratefully acknowledged. Graphics were generated using the NOAA product Ferret. We thank Prof. Raghu Murthugude for useful suggestions that greatly improved the manuscript. We thank N Kiran Kumar for his help to generate the schematic diagram in Fig. 1 . The fourth author (J.V.D) acknowledges funding from the Helmholtz-Gemeinschaft and the GEOMAR Helmholtz Centre for Ocean Research Kiel (grant IV014/GH018 ). NCAR is a major facility sponsored by the U.S. National Science Foundation under Cooperative Agreement 1852977. Q. Wang and D. Sidorenko are supported by the German Helmholtz Climate Initiative REKLIM (Regional Climate Change). We thank Matthew Harrison and P S Swathi for their comments and discussions that have helped this paper. This is INCOIS contribution no. 358 and NCPOR contribution no. J-38/2019-20. We thank all five anonymous reviewers for their constructive comments by which we have improved the manuscript immensely.

FinansörlerFinansör numarası
GEOMAR Helmholtz Centre for Ocean Research Kiel
German Helmholtz Climate Initiative REKLIMJ-38/2019-20, 358
NOAA product Ferret
National Science Foundation1852977
Helmholtz-Gemeinschaft
GEOMAR Helmholtz-Zentrum für Ozeanforschung KielIV014/GH018
Indian National Centre for Ocean Information Services

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