scholarly journals Coherent intraseasonal oceanic variations in the eastern equatorial Indian Ocean and in the Lombok and Ombai Straits from observations and a high-resolution OGCM

2014 ◽  
Vol 119 (2) ◽  
pp. 615-630 ◽  
Author(s):  
Iskhaq Iskandar ◽  
Yukio Masumoto ◽  
Keisuke Mizuno ◽  
Hideharu Sasaki ◽  
Azhar K. Affandi ◽  
...  
Keyword(s):  
High Resolution ◽  
Indian Ocean ◽  
Equatorial Indian Ocean ◽  
Eastern Equatorial Indian Ocean

Photosynthetic physiologies of phytoplankton in the eastern equatorial Indian Ocean during the spring inter-monsoon

2019 ◽  
Vol 38 (6) ◽  
pp. 83-91 ◽  
Author(s):  
Chao Yuan ◽  
Zongjun Xu ◽  
Xuelei Zhang ◽  
Qinsheng Wei ◽  
Huiwu Wang ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Equatorial Indian Ocean ◽  
Eastern Equatorial Indian Ocean

scholarly journals Intraseasonal meridional current variability in the eastern equatorial Indian Ocean

2008 ◽  
Vol 113 (C7) ◽  
Author(s):  
Tomomichi Ogata ◽  
Hideharu Sasaki ◽  
V. S. N. Murty ◽  
M. S. S. Sarma ◽  
Yukio Masumoto
Keyword(s):  
Indian Ocean ◽  
Equatorial Indian Ocean ◽  
Eastern Equatorial Indian Ocean

scholarly journals Response of the South Asian Summer Monsoon to Global Warming: Mean and Synoptic Systems*

2009 ◽  
Vol 22 (4) ◽  
pp. 1014-1036 ◽  
Author(s):  
Markus Stowasser ◽  
H. Annamalai ◽  
Jan Hafner
Keyword(s):  
Indian Ocean ◽  
Arabian Sea ◽  
Climate Model ◽  
Asian Summer Monsoon ◽  
Equatorial Indian Ocean ◽  
South Asian Summer Monsoon ◽  
Eastern Equatorial Indian Ocean ◽  
Asian Summer ◽  
The Mean ◽  
Gfdl Model

Abstract Recent diagnostics with the Geophysical Fluid Dynamics Laboratory Climate Model, version 2.1 (GFDL CM2.1), coupled model’s twentieth-century simulations reveal that this particular model demonstrates skill in capturing the mean and variability associated with the South Asian summer monsoon precipitation. Motivated by this, the authors examine the future projections of the mean monsoon and synoptic systems in this model’s simulations in which quadrupling of CO2 concentrations are imposed. In a warmer climate, despite a weakened cross-equatorial flow, the time-mean precipitation over peninsular parts of India increases by about 10%–15%. This paradox is interpreted as follows: the increased precipitation over the equatorial western Pacific forces an anomalous descending circulation over the eastern equatorial Indian Ocean, the two regions being connected by an overturning mass circulation. The spatially well-organized anomalous precipitation over the eastern equatorial Indian Ocean forces twin anticyclones as a Rossby wave response in the lower troposphere. The southern component of the anticyclone opposes and weakens the climatological cross-equatorial monsoon flow. The patch of easterly anomalies centered in the southern Arabian Sea is expected to deepen the thermocline north of the equator. Both these factors limit the coastal upwelling along Somalia, resulting in local sea surface warming and eventually leading to a local maximum in evaporation over the southern Arabian Sea. It is shown that changes in SST are predominantly responsible for the increase in evaporation over the southern Arabian Sea. The diagnostics suggest that in addition to the increased CO2-induced rise in temperature, evaporation, and atmospheric moisture, local circulation changes in the monsoon region further increase SST, evaporation, and atmospheric moisture, leading to increased rainfall over peninsular parts of India. This result implies that accurate observation of SST and surface fluxes over the Indian Ocean is of urgent need to understand and monitor the response of the monsoon in a warming climate. To understand the regional features of the rainfall changes, the International Pacific Research Center (IPRC) Regional Climate Model (RegCM), with three different resolution settings (0.5° × 0.5°, 0.75° × 0.75°, and 1.0° × 1.0°), was integrated for 20 yr, with lateral and lower boundary conditions taken from the GFDL model. The RegCM solutions confirm the major results obtained from the GFDL model but also capture the orographic nature of monsoon precipitation and regional circulation changes more realistically. The hypothesis that in a warmer climate, an increase in troposphere moisture content favors more intense monsoon depressions is tested. The GFDL model does not reveal any changes, but solutions from the RegCM suggest a statistically significant increase in the number of storms that have wind speeds of 15–20 m s−1 or greater, depending on the resolution employed. Based on these regional model solutions a possible implication is that in a CO2-richer climate an increase in the number of flood days over central India can be expected. The model results obtained here, though plausible, need to be taken with caution since even in this “best” model systematic errors still exist in simulating some aspects of the tropical and monsoon climates.

Nutrient characteristics of the water masses and their seasonal variability in the eastern equatorial Indian Ocean

2010 ◽  
Vol 70 (3-4) ◽  
pp. 272-282 ◽  
Author(s):  
S. Sardessai ◽  
Suhas Shetye ◽  
M.V. Maya ◽  
K.R. Mangala ◽  
S. Prasanna Kumar
Keyword(s):  
Indian Ocean ◽  
Seasonal Variability ◽  
Equatorial Indian Ocean ◽  
Water Masses ◽  
Eastern Equatorial Indian Ocean

Importance of wind variations and intersecting waveguides near Sri Lanka for the intraseasonal sea level variability along the west coast of India

2020 ◽  
Author(s):  
Iyyappan Suresh ◽  
Jerome Vialard ◽  
Matthieu Lengaigne ◽  
Takeshi Izumo ◽  
Muraleedharan Pillathu Moolayil
Keyword(s):  
Sri Lanka ◽  
Indian Ocean ◽  
Sea Level ◽  
Bay Of Bengal ◽  
West Coast ◽  
Equatorial Indian Ocean ◽  
Direct Connection ◽  
Local Wind ◽  
The West ◽  
Eastern Equatorial Indian Ocean

<p>Remote wind forcing plays a strong role in the Northern Indian Ocean, where oceanic anomalies can travel long distances within the coastal waveguide. Previous studies for instance emphasized that remote equatorial forcing is the main driver of the sea level and currents intraseasonal variability along the west coast of India (WCI). Until now, the main pathway for this connection between the equatorial and coastal waveguides was thought to occur in the eastern equatorial Indian Ocean, through coastal Kelvin waves that propagate around the Bay of Bengal rim and then around Sri Lanka to the WCI. Using a linear, continuously stratified ocean model, the present study demonstrates that two other mechanisms in fact dominate. First, the equatorial waveguide also intersects the coastal waveguide at the southern tip of India and Sri Lanka, creating a direct connection between the equator and WCI. Rossby waves reflected from the eastern equatorial Indian Ocean boundary indeed have a sufficiently wide meridional scale to induce a pressure signal at the Sri Lankan coast, which eventually propagates to the WCI as a coastal Kelvin wave. Second, local wind variations in the vicinity of Sri Lanka generate strong intraseasonal signals, which also propagate to the WCI along the same path. Sensitivity experiments indicate that these two new mechanisms (direct equatorial connection and local wind variations near Sri Lanka) dominate the WCI intraseasonal sea level variability, with the “classical” pathway around the Bay of Bengal only coming next. Other contributions (Bay of Bengal forcing, local WCI forcing) are much weaker.</p><p>We further show that the direct connection between the equatorial waveguide and WCI is negligible at seasonal timescale, but not at interannual timescales where it contributes to the occurrence of anoxic events. By providing an improved understanding of the mechanisms that control the WCI thermocline and oxycline variability, our results could have socio-economic implications for regional fisheries and ecosystems.</p>

scholarly journals Temporal changes in surface partial pressure of carbon dioxide and carbonate saturation state in the eastern equatorial Indian Ocean during the 1962–2012 period

2014 ◽  
Vol 11 (22) ◽  
pp. 6293-6305 ◽  
Author(s):  
L. Xue ◽  
W. Yu ◽  
H. Wang ◽  
L.-Q. Jiang ◽  
L. Feng ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Indian Ocean ◽  
Partial Pressure ◽  
Ocean Acidification ◽  
Inorganic Carbon ◽  
Equatorial Indian Ocean ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Saturation State ◽  
Eastern Equatorial Indian Ocean

Abstract. Information on changes in the oceanic carbon dioxide (CO2) concentration and air–sea CO2 flux as well as on ocean acidification in the Indian Ocean is very limited. In this study, temporal changes of the inorganic carbon system in the eastern equatorial Indian Ocean (EIO, 5° N–5° S, 90–95° E) are examined using partial pressure of carbon dioxide (pCO2) data collected in May 2012, historical pCO2 data since 1962, and total alkalinity (TA) data calculated from salinity. Results show that sea surface pCO2 in the equatorial belt (2° N–2° S, 90–95° E) increased from ∼307 μatm in April 1963 to ∼373 μatm in May 1999, ∼381 μatm in April 2007, and ∼385 μatm in May 2012. The mean rate of pCO2 increase in this area (∼1.56 μatm yr−1) was close to that in the atmosphere (∼1.46 μatm yr−1). Despite the steady pCO2 increase in this region, no significant change in air–sea CO2 fluxes was detected during this period. Ocean acidification as indicated by pH and saturation states for carbonate minerals has indeed taken place in this region. Surface water pH (total hydrogen scale) and saturation state for aragonite (Ωarag), calculated from pCO2 and TA, decreased significantly at rates of −0.0016 ± 0.0001 and −0.0095 ± 0.0005 yr−1, respectively. The respective contributions of temperature, salinity, TA, and dissolved inorganic carbon (DIC) to the increase in surface pCO2 and the decreases in pH and Ωarag are quantified. We find that the increase in DIC dominated these changes, while contributions from temperature, salinity, and TA were insignificant. The increase in DIC was most likely associated with the increasing atmospheric CO2 concentration, and the transport of accumulated anthropogenic CO2 from a CO2 sink region via basin-scale ocean circulations. These two processes may combine to drive oceanic DIC to follow atmospheric CO2 increase.

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