The seasonal variability of the circulation in the South Indian Ocean: Model and observations

2008 ◽  
Vol 74 (1-2) ◽  
pp. 315-328 ◽  
Author(s):  
R.P. Matano ◽  
E.J. Beier ◽  
P.T. Strub
Keyword(s):  
Indian Ocean ◽  
Seasonal Variability ◽  
Ocean Model ◽  
The South ◽  
South Indian Ocean ◽  
South Indian

scholarly journals The sensitivity of the Seychelles–Chagos thermocline ridge to large-scale wind anomalies

2009 ◽  
Vol 66 (7) ◽  
pp. 1455-1466 ◽  
Author(s):  
Juliet C. Hermes ◽  
Chris J. C. Reason
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Regional Climate ◽  
Austral Summer ◽  
Tropical Indian Ocean ◽  
Ocean Model ◽  
The South ◽  
South Indian Ocean ◽  
Southwest Indian Ocean ◽  
South Indian

Abstract Hermes, J. C., and Reason, C. J. C. 2009. The sensitivity of the Seychelles–Chagos thermocline ridge to large-scale wind anomalies. – ICES Journal of Marine Science, 66: 1455–1466. The Seychelles–Chagos thermocline ridge (SCTR) in the southwest tropical Indian Ocean is important for regional climate, the Madden–Julian Oscillation, as well as upper-ocean nutrients and related phytoplankton and zooplankton densities. Subsurface variability in this region has been proved to influence the overlying sea surface temperatures, which in turn can influence eastern African rainfall. There is evidence that austral summers with a deeper (shallower) SCTR tend to have more (less) tropical cyclone (TC) days in the Southwest Indian Ocean. The importance of this relationship was underlined during the 2006/2007 austral summer, when areas of Madagascar and central Mozambique experienced devastating floods, because of ten named tropical storms, including several intense TCs, effecting on these areas. At the same time, the SCTR during this season was anomalously deep, partly because of a downwelling Rossby wave that propagated across the South Indian Ocean during the previous austral winter/spring. In this paper, a regional ocean model is used to investigate the effect of remote forcing on this region and to study the sensitivity of the SCTR to changes in the large-scale winds over the South Indian Ocean, with a particular focus on the events of the 2006/2007 austral summer.

Impacts of ocean currents on the South Indian Ocean extratropical storm track through the relative wind effect

2021 ◽  
pp. 1-61
Author(s):  
Hyodae Seo ◽  
Hajoon Song ◽  
Larry W. O’Neill ◽  
Matthew R. Mazloff ◽  
Bruce D. Cornuelle
Keyword(s):  
Indian Ocean ◽  
Ocean Circulation ◽  
Storm Track ◽  
Ocean Current ◽  
Wind Effect ◽  
Turbulent Heat ◽  
The South ◽  
South Indian Ocean ◽  
South Indian ◽  
Relative Wind

AbstractThis study examines the role of the relative wind (RW) effect (wind relative to ocean current) in the regional ocean circulation and extratropical storm track in the South Indian Ocean. Comparison of two high-resolution regional coupled model simulations with/without the RW effect reveals that the most conspicuous ocean circulation response is the significant weakening of the overly energetic anticyclonic standing eddy off Port Elizabeth, South Africa, a biased feature ascribed to upstream retroflection of the Agulhas Current (AC). This opens a pathway through which the AC transports the warm and salty water mass from the subtropics, yielding marked increases in sea surface temperature (SST), upward turbulent heat flux (THF), and meridional SST gradient in the Agulhas retroflection region. These thermodynamic and dynamic changes are accompanied by the robust strengthening of the local low-tropospheric baroclinicity and the baroclinic wave activity in the atmosphere. Examination of the composite lifecycle of synoptic-scale storms subjected to the high THF events indicates a robust strengthening of the extratropical storms far downstream. Energetics calculations for the atmosphere suggest that the baroclinic energy conversion from the basic flow is the chief source of increased eddy available potential energy, which is subsequently converted to eddy kinetic energy, providing for the growth of transient baroclinic waves. Overall, the results suggest that the mechanical and thermal air-sea interactions are inherently and inextricably linked together to substantially influence the extratropical storm tracks in the South Indian Ocean.

Eastward Shift of Interannual Climate Variability in the South Indian Ocean since 1950

2021 ◽  
pp. 1-46
Author(s):  
Lei Zhang ◽  
Weiqing Han ◽  
Kristopher B. Karnauskas ◽  
Yuanlong Li ◽  
Tomoki Tozuka
Keyword(s):  
Indian Ocean ◽  
Climate Variability ◽  
Decadal Variability ◽  
Dominant Role ◽  
Tropical Pacific ◽  
The South ◽  
South Indian Ocean ◽  
Climate Modes ◽  
South Indian ◽  
Interannual Climate Variability

AbstractThe subtropical Indian Ocean Dipole (SIOD) and Ningaloo Niño are the two dominant modes of interannual climate variability in the subtropical South Indian Ocean. Observations show that the SIOD has been weakening in the recent decades, while Ningaloo Niño has been strengthening. In this study, we investigate the causes for such changes by analyzing climate model experiments using the NCAR Community Earth System Model version 1 (CESM1). Ensemble-mean results from CESM1 large-ensemble (CESM1-LE) suggest that the external forcing causes negligible changes in the amplitudes of the SIOD and Ningaloo Niño, suggesting a dominant role of internal climate variability. Meanwhile, results from CESM1 pacemaker experiments reveal that the observed changes in the two climate modes cannot be attributed to the effect of sea surface temperature anomalies (SSTA) in either the tropical Pacific or tropical Indian Oceans. By further comparing different ensemble members from the CESM1-LE, we find that a Warm Pool Dipole mode of decadal variability, with opposite SSTA in the southeast Indian Ocean and the western-central tropical Pacific Ocean plays an important role in driving the observed changes in the SIOD and Ningaloo Niño. These changes in the two climate modes have considerable impacts on precipitation and sea level variabilities in the South Indian Ocean region.

Sign in / Sign up

Export Citation Format

Share Document