scholarly journals Mixed layer temperature balance in the eastern Indian Ocean during the 2006 Indian Ocean dipole

2009 ◽  
Vol 114 (C7) ◽  
Author(s):  
Takanori Horii ◽  
Yukio Masumoto ◽  
Iwao Ueki ◽  
Hideaki Hase ◽  
Keisuke Mizuno
Keyword(s):  
Indian Ocean ◽  
Mixed Layer ◽  
Indian Ocean Dipole ◽  
Eastern Indian Ocean ◽  
Mixed Layer Temperature

scholarly journals Impact of the Strong Downwelling (Upwelling) on Small Pelagic Fish Production during the 2016 (2019) Negative (Positive) Indian Ocean Dipole Events in the Eastern Indian Ocean off Java

Climate ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 29
Author(s):  
Jonson Lumban-Gaol ◽  
Eko Siswanto ◽  
Kedarnath Mahapatra ◽  
Nyoman Metta Nyanakumara Natih ◽  
I Wayan Nurjaya ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Pelagic Fish ◽  
Eastern Indian Ocean ◽  
Fish Production ◽  
Small Pelagic Fish ◽  
Field Surveys ◽  
Chl A ◽  
Positive Indian Ocean Dipole ◽  
The Impact

Although researchers have investigated the impact of Indian Ocean Dipole (IOD) phases on human lives, only a few have examined such impacts on fisheries. In this study, we analyzed the influence of negative (positive) IOD phases on chlorophyll a (Chl-a) concentrations as an indicator of phytoplankton biomass and small pelagic fish production in the eastern Indian Ocean (EIO) off Java. We also conducted field surveys in the EIO off Palabuhanratu Bay at the peak (October) and the end (December) of the 2019 positive IOD phase. Our findings show that the Chl-a concentration had a strong and robust association with the 2016 (2019) negative (positive) IOD phases. The negative (positive) anomalous Chl-a concentration in the EIO off Java associated with the negative (positive) IOD phase induced strong downwelling (upwelling), leading to the preponderant decrease (increase) in small pelagic fish production in the EIO off Java.

scholarly journals Asymmetry of the Indian Ocean Dipole. Part I: Observational Analysis

2008 ◽  
Vol 21 (18) ◽  
pp. 4834-4848 ◽  
Author(s):  
Chi-Cherng Hong ◽  
Tim Li ◽  
LinHo ◽  
Jong-Seong Kug
Keyword(s):  
Indian Ocean ◽  
Mixed Layer ◽  
Indian Ocean Dipole ◽  
Heat Budget ◽  
Mature Phase ◽  
Budget Analysis ◽  
Nonlinear Advection ◽  
Negative Skewness ◽  
The Indian Ocean ◽  
The Asymmetry

The physical mechanism for the amplitude asymmetry of SST anomalies (SSTA) between the positive and negative phases of the Indian Ocean dipole (IOD) is investigated, using Simple Ocean Data Assimilation (SODA) and NCAR–NCEP data. It is found that a strong negative skewness appears in the IOD east pole (IODE) in the mature phase [September–November (SON)], while the skewness in the IOD west pole is insignificant. Thus, the IOD asymmetry is primarily caused by the negative skewness in IODE. A mixed-layer heat budget analysis indicates that the following two air–sea feedback processes are responsible for the negative skewness. The first is attributed to the asymmetry of the wind stress–ocean advection–SST feedback. During the IOD developing stage [June–September (JJAS)], the ocean linear advection tends to enhance the mixed-layer temperature tendency, while nonlinear advection tends to cool the ocean in both the positive and negative events, thus contributing to the negative skewness in IODE. The second process is attributed to the asymmetry of the SST–cloud–radiation (SCR) feedback. For a positive IODE, the negative SCR feedback continues with the increase of warm SSTA. For a negative IODE, the same negative SCR feedback works when the amplitude of SSTA is small. After reaching a critical value, the cold SSTA may completely suppress the mean convection and lead to cloud free conditions; a further drop of the cold SSTA does not lead to additional thermal damping so that the cold SSTA may grow faster. A wind–evaporation–SST feedback may further amplify the asymmetry induced by the aforementioned nonlinear advection and SCR feedback processes.

CHARACTERISTIC OF PHYSICAL OCEANOGRAPHY IN EAST INDIAN OCEAN DURING POSITIVE PHASE OF INDIAN OCEAN DIPOLE (IOD) OF 1994/1995, 1997/1998, AND 2006/2007

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Pramudyo Dipo ◽  
I Wayan Nurjaya ◽  
Fadli Syamsudin
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Eastern Indian Ocean ◽  
Comparative Characteristic ◽  
Physical Oceanography ◽  
The South ◽  
Bipolar Structure ◽  
Maturation Phase ◽  
The Difference ◽  
Formation Phase

There is an inter-annual phenomenon in the Indian Ocean that occurs because of the interaction between atmosphere and ocean are known Indian Ocean Dipole (IOD). IOD is a bipolar structure that characterized by the difference of sea surface temperature to normal. The objectives of this study is to know the characteristic of physical oceanography in the eastern part of Indian Ocean during the formation phase, maturation phase and decay phases of positive IOD. The second objective was to determine the comparative characteristic of physical oceanography in the eastern Indian Ocean between the positive IOD in different years. The strengthening of the South Equatorial Current in transitional seasons I (March-May) followed by early cooling of the SST which is indicated by the formation phase of IOD. At the Southeast monsoon (June to August) and the beginning of the season transition II, there is a visible presence of upwelling in the south of Java, which is then further extends to the peak in September (maturation phase) and begin to disappear in October followed by warming of the SST on the East of Indian Ocean in November (decay phase).Keywords: Indian Ocean Dipole, upwelling, Empirical Orthogonal Function (EOF) analysis, Eastern Indian Ocean

Genesis of Indian Ocean Mixed Layer Temperature Anomalies: A Heat Budget Analysis

2010 ◽  
Vol 23 (20) ◽  
pp. 5375-5403 ◽  
Author(s):  
Agus Santoso ◽  
Alexander Sen Gupta ◽  
Matthew H. England
Keyword(s):  
Indian Ocean ◽  
Time Scales ◽  
Mixed Layer ◽  
Heat Budget ◽  
Heat Fluxes ◽  
Temperature Anomalies ◽  
Mixed Layer Temperature ◽  
The Indian Ocean ◽  
The Tropics

Abstract The genesis of mixed layer temperature anomalies across the Indian Ocean are analyzed in terms of the underlying heat budget components. Observational data, for which a seasonal budget can be computed, and a climate model output, which provides improved spatial and temporal coverage for longer time scales, are examined. The seasonal climatology of the model heat budget is broadly consistent with the observational reconstruction, thus providing certain confidence in extending the model analysis to interannual time scales. To identify the dominant heat budget components, covariance analysis is applied based on the heat budget equation. In addition, the role of the heat budget terms on the generation and decay of temperature anomalies is revealed via a novel temperature variance budget approach. The seasonal evolution of the mixed layer temperature is found to be largely controlled by air–sea heat fluxes, except in the tropics where advection and entrainment are important. A distinct shift in the importance and role of certain heat budget components is shown to be apparent in moving from seasonal to interannual time scales. On these longer time scales, advection gains importance in generating and sustaining anomalies over extensive regions, including the trade wind and midlatitude wind regimes. On the other hand, air–sea heat fluxes tend to drive the evolution of thermal anomalies over subtropical regions including off northwestern Australia. In the tropics, however, they limit the growth of anomalies. Entrainment plays a role in the generation and maintenance of interannual anomalies over localized regions, particularly off Sumatra and over the Seychelles–Chagos Thermocline Ridge. It is further shown that the spatial distribution of the role and importance of these terms is related to oceanographic features of the Indian Ocean. Mixed layer depth effects and the influence of model biases are discussed.

scholarly journals The Horizontal Distribution of Siliceous Planktonic Radiolarian Community in the Eastern Indian Ocean

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3502
Author(s):  
Sonia Munir ◽  
John Rogers ◽  
Xiaodong Zhang ◽  
Changling Ding ◽  
Jun Sun
Keyword(s):  
Indian Ocean ◽  
Chlorophyll A ◽  
Mixed Layer ◽  
Diversity Index ◽  
Horizontal Distribution ◽  
Eastern Indian Ocean ◽  
Entire Area ◽  
Factors Affecting ◽  
Major Factors ◽  
First Time

The plankton radiolarian community was investigated in the spring season during the two-month cruise ‘Shiyan1’ (10 April–13 May 2014) in the Eastern Indian Ocean. This is the first comprehensive plankton tow study to be carried out from 44 sampling stations across the entire area (80.00°–96.10° E, 10.08° N–6.00° S) of the Eastern Indian Ocean. The plankton tow samples were collected from a vertical haul from a depth 200 m to the surface. During the cruise, conductivity–temperature–depth (CTD) measurements were taken of temperature, salinity and chlorophyll a from the surface to 200 m depth. Shannon–Wiener’s diversity index (H’) and the dominance index (Y) were used to analyze community structure. There was a total of 168 plankton species, composed of Acantharia, Phaeodaria, Polycystina, Collodaria and Taxopodida (monospecific—Sticholonche zanclea, Hertwig is the only recognized species). Hence, it included both celestine-based and siliceous organisms, which are also described here for the first time from this region. Total radiolarians ranged from 5 to 5500 ind/m−3, dominated by co-occurrences of Sphaerozoum punctatum and Stichonche zanclea species at the south-equator zone (SEQ)-transect 80° E and equator zone (EQ)-transect Lati-0. The possible environmental variables were tested through RDA analysis; although no result was obtained for the full species dataset, the samples from the equatorial transect related strongly to mixed-layer chlorophyll a concentration and those of a north–south transect to surface silicate concentrations or mixed-layer nitrate were significantly correlated (p < 0.01) to the radiolarian community. Our results indicate that the silicate and chlorophyll-a concentrations are the two major factors affecting the radiolarian distribution along two of the investigated transects (southern equator and equator) in the study area.

In Situ Observations of Madden–Julian Oscillation Mixed Layer Dynamics in the Indian and Western Pacific Oceans

2012 ◽  
Vol 25 (7) ◽  
pp. 2306-2328 ◽  
Author(s):  
Kyla Drushka ◽  
Janet Sprintall ◽  
Sarah T. Gille ◽  
Susan Wijffels
Keyword(s):  
Heat Flux ◽  
Indian Ocean ◽  
Mixed Layer ◽  
Heat Budget ◽  
Mixed Layer Depth ◽  
Layer Depth ◽  
Temperature Variations ◽  
Central Indian Ocean ◽  
Mixed Layer Temperature

Abstract The boreal winter response of the ocean mixed layer to the Madden–Julian oscillation (MJO) in the Indo-Pacific region is determined using in situ observations from the Argo profiling float dataset. Composite averages over numerous events reveal that the MJO forces systematic variations in mixed layer depth and temperature throughout the domain. Strong MJO mixed layer depth anomalies (&gt;15 m peak to peak) are observed in the central Indian Ocean and in the far western Pacific Ocean. The strongest mixed layer temperature variations (&gt;0.6°C peak to peak) are found in the central Indian Ocean and in the region between northwest Australia and Java. A heat budget analysis is used to evaluate which processes are responsible for mixed layer temperature variations at MJO time scales. Though uncertainties in the heat budget are on the same order as the temperature trend, the analysis nonetheless demonstrates that mixed layer temperature variations associated with the canonical MJO are driven largely by anomalous net surface heat flux. Net heat flux is dominated by anomalies in shortwave and latent heat fluxes, the relative importance of which varies between active and suppressed MJO conditions. Additionally, rapid deepening of the mixed layer in the central Indian Ocean during the onset of active MJO conditions induces significant basin-wide entrainment cooling. In the central equatorial Indian Ocean, MJO-induced variations in mixed layer depth can modulate net surface heat flux, and therefore mixed layer temperature variations, by up to ~40%. This highlights the importance of correctly representing intraseasonal mixed layer depth variations in climate models in order to accurately simulate mixed layer temperature, and thus air–sea interaction, associated with the MJO.

scholarly journals Subsurface oceanic structure associated with atmospheric convectively coupled equatorial Kelvin waves in the eastern Indian Ocean

2021 ◽  
Author(s):  
Marina Azaneu ◽  
Adrian Matthews ◽  
Dariusz Baranowski
Keyword(s):  
Indian Ocean ◽  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Phase Speed ◽  
Heat Content ◽  
Life Cycles ◽  
Kelvin Waves ◽  
Eastern Indian Ocean ◽  
Dynamical Response ◽  
Ocean Atmosphere

&lt;p&gt;Atmospheric convectively coupled equatorial Kelvin waves (CCKWs) are a major tropical weather feature strongly influenced by ocean--atmosphere interactions. However, prediction of the development and propagation of CCKWs remains a challenge for models. The physical processes involved in these interactions are assessed by investigating the oceanic response to the passage of CCKWs across the eastern Indian Ocean and MC using the NEMO ocean model analysis with data assimilation. Three-dimensional life cycles are constructed for &quot;solitary&quot; CCKW events. As a CCKW propagates over the eastern Indian Ocean, the immediate thermodynamic ocean response includes cooling of the ocean surface and subsurface, deepening of the mixed layer depth, and an increase in the mixed layer heat content. Additionally, a dynamical downwelling signal is observed two days after the peak in the CCKW westerly wind burst, which propagates eastward along the Equator and then follows the Sumatra and Java coasts, consistent with a downwelling oceanic Kelvin wave with an average phase speed of 2.3 m s&lt;sup&gt;-1&lt;/sup&gt;. Meridional and vertical structures of zonal velocity anomalies are consistent with this framework. This dynamical feature is consistent across distinct CCKW populations, indicating the importance of CCKWs as a source of oceanic Kelvin waves in the eastern Indian Ocean. The subsurface dynamical response to the CCKWs is identifiable up to 11 days after the forcing. These ocean feedbacks on time scales longer than the CCKW life cycle help elucidate how locally driven processes can rectify onto longer time-scale processes in the coupled ocean--atmosphere system.&lt;/p&gt;

scholarly journals CHARACTERISTIC OF PHYSICAL OCEANOGRAPHY IN EAST INDIAN OCEAN DURING POSITIVE PHASE OF INDIAN OCEAN DIPOLE (IOD) OF 1994/1995, 1997/1998, AND 2006/2007

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Pramudyo Dipo ◽  
I Wayan Nurjaya ◽  
Fadli Syamsudin
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Eastern Indian Ocean ◽  
Comparative Characteristic ◽  
Physical Oceanography ◽  
The South ◽  
Bipolar Structure ◽  
Maturation Phase ◽  
The Difference ◽  
Formation Phase

<p>There is an inter-annual phenomenon in the Indian Ocean that occurs because of the interaction between atmosphere and ocean are known Indian Ocean Dipole (IOD). IOD is a bipolar structure that characterized by the difference of sea surface temperature to normal. The objectives of this study is to know the characteristic of physical oceanography in the eastern part of Indian Ocean during the formation phase, maturation phase and decay phases of positive IOD. The second objective was to determine the comparative characteristic of physical oceanography in the eastern Indian Ocean between the positive IOD in different years. The strengthening of the South Equatorial Current in transitional seasons I (March-May) followed by early cooling of the SST which is indicated by the formation phase of IOD. At the Southeast monsoon (June to August) and the beginning of the season transition II, there is a visible presence of upwelling in the south of Java, which is then further extends to the peak in September (maturation phase) and begin to disappear in October followed by warming of the SST on the East of Indian Ocean in November (decay phase).</p><p>Keywords: Indian Ocean Dipole, upwelling, Empirical Orthogonal Function (EOF) analysis, Eastern Indian Ocean</p>

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