scholarly journals Decadal Sea Level Variations in the Indian Ocean Investigated with HYCOM: Roles of Climate Modes, Ocean Internal Variability, and Stochastic Wind Forcing*

2015 ◽  
Vol 28 (23) ◽  
pp. 9143-9165 ◽  
Author(s):  
Yuanlong Li ◽  
Weiqing Han
Keyword(s):  
Heat Flux ◽  
Indian Ocean ◽  
Sea Level ◽  
Surface Heat Flux ◽  
Internal Variability ◽  
Surface Heat ◽  
Wind Forcing ◽  
Sea Level Variability ◽  
The Indian Ocean ◽  
Sea Level Variations

Abstract In this study decadal (≥10 yr) sea level variations in the Indian Ocean (IO) during 1950–2012 are investigated using the Hybrid Coordinate Ocean Model (HYCOM). The solution of the main run agrees well with observations in the western-to-central IO. Results of HYCOM experiments reveal large spatial variations in the mechanisms of decadal sea level variability. Within the tropical IO (north of 20°S), decadal sea level variations achieve maximum amplitude in the south IO thermocline ridge region. They are predominantly forced by decadal fluctuations of surface wind stress associated with climate variability modes, while the impact of other processes is much smaller. The Somali coast and the western Bay of Bengal are two exceptional regions, where ocean internal (unforced) variability has large contribution. Between 28° and 20°S in the subtropical south IO, surface heat flux and ocean internal variability are the major drivers of decadal sea level variability. Heat budget analysis for the upper 300 m of this region suggests that surface heat flux affects regional thermosteric sea level through both local surface heating and heat transport by ocean circulation. In the southwestern IO south of 30°S, where stochastic winds are strong, stochastic wind forcing and its interaction with ocean internal variability generate pronounced decadal variations in sea level. The comprehensive investigation of decadal sea level variability over the IO from an oceanic perspective will contribute to decadal sea level prediction research, which has a high societal demand.

Variability of surface heat flux over the Indian Ocean

2004 ◽  
Vol 42 (3) ◽  
pp. 183-199 ◽  
Author(s):  
Hiroyuki Tomita ◽  
Masahisa Kubota
Keyword(s):  
Heat Flux ◽  
Indian Ocean ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
The Indian Ocean

scholarly journals Asymmetry of the Indian Ocean Basinwide SST Anomalies: Roles of ENSO and IOD

2010 ◽  
Vol 23 (13) ◽  
pp. 3563-3576 ◽  
Author(s):  
Chi-Cherng Hong ◽  
Tim Li ◽  
LinHo ◽  
Yin-Chen Chen
Keyword(s):  
Heat Flux ◽  
Indian Ocean ◽  
Mixed Layer ◽  
Surface Heat Flux ◽  
Surface Heat ◽  
Ocean Temperature ◽  
Positive Skewness ◽  
Cold Events ◽  
The Indian Ocean ◽  
The Asymmetry

A basinwide warming (cooling) in the Indian Ocean is observed following the El Niño (La Niña) mature phase, with the amplitude of the warming being significantly larger than the cooling. A composite analysis reveals that the amplitude asymmetry (positive skewness) between the warm and cold Indian Ocean basinwide sea surface temperature anomaly pattern (IOB) appears only when ENSO is concurrent with the Indian Ocean dipole (IOD). The amplitude asymmetry becomes insignificant during the ENSO-only and the IOD-only events. The physical mechanism for the amplitude asymmetry is investigated by analyzing the mixed layer heat budget based on the Simple Ocean Data Assimilation (SODA) 2.0.2 data. It is found that the positive skewness in the IOD west pole (IODW) is mainly caused by the asymmetry of ocean temperature advection, whereas the positive skewness in the IOD east pole (IODE) is caused by the asymmetry of the surface heat flux anomaly (primarily shortwave radiation) in response to the ENSO remote forcing. The asymmetry of the mixed layer depth (MLD) between warm and cold events is another factor contributing to the IOB positive skewness. The MLD in IODE during the warm events (27 m) is shallower than that of the cold events (45 m), resulting a larger (smaller) temperature tendency during the warm (cold) events. In contrast, the MLD in IODW during the warm events (44 m) is deeper than that of the cold events (37 m). Because the positive skewness in IODW is caused by the ocean temperature advection and the surface heat flux plays a damping role, a larger (smaller) MLD leads to a weaker (stronger) thermodynamic damping. Thus the asymmetry of MLD in both IODE and IODW favors a greater basinwide warming than cooling.

Natural decadal sea-level variability in the Indian Ocean: lessons from CMIP models

2019 ◽  
Vol 53 (9-10) ◽  
pp. 5653-5673
Author(s):  
A. G. Nidheesh ◽  
Matthieu Lengaigne ◽  
Jérôme Vialard ◽  
Takeshi Izumo ◽  
A. S. Unnikrishnan ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Sea Level Variability ◽  
The Indian Ocean

scholarly journals Evolution of Turbulence in the Diurnal Warm Layer

2018 ◽  
Vol 48 (2) ◽  
pp. 383-396 ◽  
Author(s):  
Aurélie J. Moulin ◽  
James N. Moum ◽  
Emily L. Shroyer
Keyword(s):  
Heat Flux ◽  
Time Series ◽  
Steady State ◽  
Indian Ocean ◽  
Surface Heat Flux ◽  
Equatorial Indian Ocean ◽  
Surface Heat ◽  
Temperature Ramps ◽  
Decaying Turbulence ◽  
Shear Production

AbstractThe daily evolution of temperature, stratification, and turbulence in the diurnal warm layer is described from time series measurements at low to moderate winds and strong insolation in the equatorial Indian Ocean. At 2.0-m depth, turbulence dissipation rates (ε) decreased by two orders of magnitude over 1–2 h immediately after sunrise, initiated by stratification caused by penetrating solar radiation prior to the change in sign of net surface heat flux from cooling to warming. Decaying turbulence preceded a period of rapid growth, in which ε increased by two orders of magnitude over a few hours, and following which ε approached a daytime period of near-steady state. Decay and growth rates predicted by a simplified turbulence model are consistent with those observed. During the daytime period of near-steady state, asymmetric temperature ramps were associated with enhanced ε, supporting the interpretation that this period represents a balance between buoyancy and shear production associated with a shear-driven response to trapping of momentum within the diurnal warm layer.

scholarly journals Indian Ocean Dynamic Sea Level, Variability And Projections In CMIP6 Models

2022 ◽  
Author(s):  
Abhisek Chatterjee ◽  
Sajidh C K
Keyword(s):  
High Resolution ◽  
Indian Ocean ◽  
Sea Level Rise ◽  
Sea Level ◽  
Sea Level Variability ◽  
Regional Sea Level ◽  
The Indian Ocean ◽  
High Resolution Models ◽  
Mean State ◽  
Dynamic Sea Level

Abstract The regional sea level variability and its projection amidst the global sea level rise is one of the major concerns for coastal communities. The dynamic sea level plays a major role in the observed spatial deviations in regional sea level rise from the global mean. The present study evaluates 27 climate model simulations from the sixth phase of the coupled model intercomparison project (CMIP6) for their representation of the historical mean states, variability and future projections for the Indian Ocean. Most models reproduce the observed mean state of the dynamic sea level realistically, however consistent positive bias is evident across the latitudinal range of the Indian Ocean. The strongest sea level bias is seen along the Antarctic Circumpolar Current (ACC) regime owing to the stronger than observed south Indian Ocean westerlies and its equatorward bias. Further, this equatorward shift of the wind field resulted in stronger positive windstress curl across the southeasterly trade winds in the southern tropical basin and easterly wind bias along the equatorial waveguide. These anomalous easterly equatorial winds cause upwelling in the eastern part of the basin and keeps the thermocline shallower in the model than observed, resulted in enhanced variability for the dipole zonal mode or Indian Ocean dipole in the tropics. In the north Indian Ocean, the summer monsoon winds are weak in the model causing weaker upwelling and positive sea level bias along the western Arabian Sea. The high-resolution models compare better in simulating the sea level variability, particularly in the eddy dominated regions like the ACC regime in interannual timescale. However, these improved variabilities do not necessarily produce a better mean state likely due to the enhanced mixing driven by parametrizations set in these high-resolution models. Finally, the overall pattern of the projected dynamic sea level rise is found to be similar for the mid (SSP2-4.5) and high-end (SSP5-8.5) scenarios, except that the magnitude is higher under the high emission situation. Notably, the projected dynamic sea level change is found to be milder when only the best performing models are used compared to the full ensemble.

A CORAL BASED QUATERNARY SEA LEVEL VARIABILITY RECORD IN THE PALK STRAIT OF THE INDIAN OCEAN

2017 ◽  
Author(s):  
P.N. Ranasinghe ◽  
◽  
L.H.M.T.M.B. Ambillapitiya ◽  
C.H.E.R. Siriwardena ◽  
Y.N. Jayaratne ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Sea Level Variability ◽  
The Indian Ocean
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