scholarly journals Indian Ocean Dipole modulated wave climate of eastern Arabian Sea

Ocean Science ◽  
2016 ◽  
Vol 12 (2) ◽  
pp. 369-378 ◽  
Author(s):  
T. R. Anoop ◽  
V. Sanil Kumar ◽  
P. R. Shanas ◽  
J. Glejin ◽  
M. M. Amrutha
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Arabian Sea ◽  
Wave Climate ◽  
Study Region ◽  
Climatic Oscillations ◽  
Modes Of Variability ◽  
Short Period ◽  
Eastern Arabian Sea ◽  
Induced Changes

Abstract. Intrinsic modes of variability have a significant role in driving the climatic oscillations in the oceanic processes. In this paper, we investigate the influence of an inter-annual mode of variability, the Indian Ocean Dipole (IOD), on the wave climate of the eastern Arabian Sea (AS). Using measured, modeled and reanalysis wave data and reanalysis wind data, we show that the IOD plays a major role in the variability of wave climate of the study region. Due to the IOD-induced changes in equatorial sea surface temperature and sea level pressure, the winds from the northern AS gets modified and cause inter-annual variability in the wave climate over the eastern AS. The changes in wind field over the AS due to the IOD influence the generation or dissipation of the wave field and hence cause a decrease in northwest short-period waves during positive IOD and an increase during negative IOD.

scholarly journals Indian Ocean Dipole modulated wave climate of eastern Arabian Sea

2015 ◽  
Vol 12 (5) ◽  
pp. 2473-2496
Author(s):  
T. R. Anoop ◽  
V. Sanil Kumar ◽  
P. R. Shanas ◽  
G. Johnson ◽  
M. M. Amrutha
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Arabian Sea ◽  
Wave Climate ◽  
Study Region ◽  
Climatic Oscillations ◽  
Modes Of Variability ◽  
Annual Variability ◽  
Short Period ◽  
Eastern Arabian Sea

Abstract. Intrinsic modes of variability have a significant role in driving climatic oscillations in the ocean. In this paper, we investigate the influence of inter-annual variability, the Indian Ocean Dipole (IOD), on the wave climate of the eastern Arabian Sea (AS). Using measured, modeled and reanalysis wave data and reanalysis wind data, we show that the IOD plays a major role in the variability of wave climate of the study region due to the IOD induced changes in equatorial sea surface temperature and sea level pressure. Inter-annual variability in the wave climate over the eastern AS during the IOD is due to the modification of winds from the northern AS. The change in wind field over the AS due to IOD influences the generation or dissipation of wave field and hence causes the decrease in northwest short period waves during positive IOD and increase during negative IOD.

scholarly journals The influence of tropical Indian Ocean warming and Indian Ocean Dipole on the surface chlorophyll concentration in the eastern Arabian Sea

2019 ◽  
Author(s):  
Syam Sankar ◽  
Anoop Thondithala Ramachandran ◽  
Kemgang Ghomsi Franck Eitel ◽  
Dmitry Kondrik ◽  
Radharani Sen ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Indian Ocean Dipole ◽  
Arabian Sea ◽  
Coastal Upwelling ◽  
Chlorophyll Concentration ◽  
Ocean Warming ◽  
Oceanic Circulation ◽  
Western Basin ◽  
Indian Ocean Warming ◽  
Eastern Arabian Sea

Abstract. This study examines the role of increased Indian Ocean warming and positive Indian Ocean Dipole (IOD) events on the surface chlorophyll concentration in the Eastern Arabian Sea (EAS) during the period 1998 to 2014. Remotely sensed surface chlorophyll concentration – during the month of October when IOD strength is maximum – at three selected areas in the EAS, viz., the central eastern Arabian Sea (CEAS, 73° E–76° E, 13° N–18° N), south eastern Arabian Sea (SEAS, 74° E–77° E, 8° N–13° N) and the southern tip of India (TIP, 74° E–78° E, 5° N–8° N) shows a steady decreasing trend, though not statistically significant. The EAS also has a higher warming trend when compared to the western basin during the study period. Our analysis has shown that in the EAS, local surface winds, remote forcing by equatorial winds and the surface and sub-surface oceanic circulation features are less (respectively more) favorable for inducing coastal upwelling during positive (respectively negative) IOD years. The Dipole Mode Index (DMI) and surface chlorophyll concentration in the EAS is significantly and negatively correlated, pointing to the fact that in the event of occurrence of frequent positive IOD years under a global warming regime, the surface chlorophyll concentration is likely to decrease during fall.

scholarly journals Seasonal and interannual variations in the nitrogen cycle in the Arabian Sea

2014 ◽  
Vol 11 (20) ◽  
pp. 5733-5747 ◽  
Author(s):  
T. Rixen ◽  
A. Baum ◽  
B. Gaye ◽  
B. Nagel
Keyword(s):  
Indian Ocean ◽  
Nitrogen Cycle ◽  
Arabian Sea ◽  
Equatorial Indian Ocean ◽  
Global Ocean ◽  
Interannual Variations ◽  
Minimum Zone ◽  
Induced Changes ◽  
Seasonal And Interannual Variations ◽  
Sw Monsoon

Abstract. The Arabian Sea plays an important role in the marine nitrogen cycle because of its pronounced mid-water oxygen minimum zone (OMZ) in which bio-available nitrate (NO3−) is reduced to dinitrogen gas (N2). As the nitrogen cycle can respond fast to climate-induced changes in productivity and circulation, the Arabian Sea sediments are an important palaeoclimatic archive. In order to understand seasonal and interannual variations in the nitrogen cycle, nutrient data were obtained from the literature published prior to 1993, evaluated, and compared with data measured during five expeditions carried out in the framework of the Joint Global Ocean Flux Study (JGOFS) in the Arabian Sea in 1995 and during a research cruise of RV Meteor in 2007. The data comparison showed that the area characterized by a pronounced secondary nitrite maximum (SNM) was by 63% larger in 1995 than a similarly determined estimate based on pre-JGOFS data. This area, referred to as the core of the denitrifying zone, showed strong seasonal and interannual variations driven by the monsoon. During the SW monsoon, the SNM retreated eastward due to the inflow of oxygen-enriched Indian Ocean Central Water (ICW). During the NE monsoon, the SNM expanded westward because of the reversal of the current regime. On an interannual timescale, a weaker SW monsoon decreased the inflow of ICW from the equatorial Indian Ocean and increased the accumulation of denitrification tracers by extending the residence time of water in the SNM. This is supported by palaeoclimatic studies showing an enhanced preservation of accumulative denitrification tracers in marine sediments in conjunction with a weakening of the SW monsoon during the late Holocene.

scholarly journals Worsening Drought of Nile Basin under shift in Atmospheric Circulation, Stronger ENSO and Indian Ocean Dipole

2021 ◽  
Author(s):  
Shereif Mahmoud ◽  
Thian Yew Gan ◽  
Richard Allan ◽  
Jianfeng Li ◽  
Chris Funk
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
Indian Ocean Dipole ◽  
Arabian Sea ◽  
El Nino ◽  
Drought Severity ◽  
Zonal Winds ◽  
Driving Mechanisms ◽  
Stream Functions ◽  
Combined Impact

Abstract Until now, driving mechanisms behind recurring droughts and hydroclimate variations that controls the Nile River Basin (NRB) remain not well understood. In this study, we demonstrate that recent increasing aridity of NRB is attributed to the growing influence of stronger ENSO and Indian Ocean dipole (IOD), and SST gradient over the Arabian Sea (WTIO) in NRB after 1980s, which have significantly contributed to NRB’s drought severity at inter-annual to inter-decadal timescales. Further, the southward (westward) shift in stream functions and meridional (zonal) winds caused an enhancement in the blocking pattern, with strong anticyclonic waves of dry air that keeps moving into NRB, has resulted in drier NRB, where its streamflow at gauging stations have decreased from 137 to 114.1 m3/s/decade. Contrary to past findings, we show that IOD and WTIO are better predictors of the Nile streamflow than El Niño. Under the combined impact of warming and stronger WTIO and El Niño, future droughts of the NRB will worsen.

Monsoon-induced changes in surface hydrography of the eastern Arabian Sea during the early Pleistocene

2019 ◽  
Vol 157 (6) ◽  
pp. 1001-1011 ◽  
Author(s):  
Rajeev Kumar Satpathy ◽  
Stephan Steinke ◽  
Arun Deo Singh
Keyword(s):  
Water Column ◽  
Asian Indian ◽  
South Asian ◽  
Mixed Layer ◽  
Arabian Sea ◽  
Early Pleistocene ◽  
The South ◽  
Eastern Arabian Sea ◽  
Induced Changes ◽  
South Asian Indian

AbstractUpper water column dynamics in the eastern Arabian Sea were reconstructed in order to investigate changes in the activity of the South Asian / Indian monsoon during the early Pleistocene (c. 1.5–2.7 Ma). We used planktic foraminiferal assemblage records combined with isotopic (δ18O and δ13C) data, Mg/Ca-based sea surface temperatures and seawater δ18O records to estimate changes in surface water conditions at International Ocean Discovery Program (IODP) Site U1457. Our records indicate two distinct regimes of monsoon-induced changes in upper water structure during the periods c. 1.55–1.65 Ma and c. 1.85–2.7 Ma. We infer that a more stratified upper water column and oligotrophic mixed layer conditions prevailed during the period 1.85–2.7 Ma, which may be due to overall weaker South Asian / Indian winter (NE) and summer (SW) monsoon circulations. The period 1.55–1.65 Ma was characterized by enhanced eutrophication of the mixed layer, which was probably triggered by intensified winter (NE) monsoonal winds. The long-term trend in hydrographic changes during 1.55–1.65 Ma appears to be superimposed by short-term variations, probably reflecting glacial/interglacial changes. We suggest that an intensification of the South Asian / Indian winter monsoon circulation occurred between ∼1.65 Ma and 1.85 Ma, which is most likely due to the development of strong meridional and zonal atmospheric circulations (i.e. Walker Circulation and Hadley Circulation) because of strong equatorial East–West Pacific temperature gradients.

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