Hydrography and water masses in the southeastern Arabian Sea during March–June 2003

Shenoi, S. S. C.; Shankar, D.; Michael, G. S.; Kurian, Jaison; Varma, K. K.; Kumar, M. R. Ramesh; Almeida, A.M.; Unnikrishnan, A.S.; Fernandes, William; Barreto, Naurinete; Gnanaseelan, C.; Mathew, R.; Praju, K. V.; Mahale, V.

doi:10.1007/bf02702024

Cited by 45 publications

(25 citation statements)

References 26 publications

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“…The coastal waters off Mumbai-Goa region experiences high the SSS lowers up to 33.5 psu over the coastal waters of Mangalore-Kochi region. The presence of low-salinity plumes in this southern part of the coast is a result of freshwater runoff from heavy precipitation over the Western Ghats of the region (Shankar et al 2005). With the arrival of NE monsoon in November, the wind changes its direction from SW to NE and at the same time the strength of the wind reduces significantly (∼2-5 m s −1 ) and continues during this season.…”

Section: Numerical Experimentsmentioning

confidence: 98%

Oceanic upwelling and downwelling processes in waters off the west coast of India

2008

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A three-dimensional model based on the Princeton Ocean Model (POM) has been implemented to study the circulation of the west coast of India. The model uses a curvilinear orthogonal horizontal grid with higher resolution near the coast (3-9 km) and a terrain following sigma coordinate in the vertical. The model is able to simulate Lakshadweep High and Lakshadweep Low (LL) during the winter and summer monsoons, respectively. During winter, the downwelling processes noticed along the coast help in the formation of temperature inversions. The inversions can be seen even up to the depths of ∼50 m, which agrees with the available ARGO data in the region. Model simulations show that coastal upwelling off Kerala is at its peak in July. The intensity of upwelling reduces along the coast towards north. During the existence of LL, there is a cyclonic eddy in the sub-surface waters over the South-Eastern Arabian Sea, with vertical extent up to the depths of 100-150 m and it is strengthened due to the presence of northward counter current in the shelf region. The southerly coastal jet formed along the southern coast as a result of upwelling is noticed a westward shift along with LL. The location of the eddy off Kerala is tilted towards the open ocean with depth and our experiments suggest that this flow can be understood as a first baroclinic mode.

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Section: Numerical Experimentsmentioning

confidence: 98%

Oceanic upwelling and downwelling processes in waters off the west coast of India

2008

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“…In particular, it is hard to distinguish between the measurement error of altimetric sea level and possible subsurface halosteric contribution in the absence of systematic subsurface salinity measurements. Indeed, the LS is known for vigorous haline variability in the thermocline and below (Shankar et al, 2005;Shenoi et al, 2005b).…”

Section: Role Of Salinity On the Sea-level Variationsmentioning

confidence: 99%

Observed intra-seasonal to interannual variability of the upper ocean thermal structure in the southeastern Arabian Sea during 2002–2008

Gopalakrishna

Durand

Nisha

et al. 2010

Deep Sea Research Part I: Oceanographic Research Papers

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The southeastern Arabian Sea (SEAS), located in the Indian Ocean warm pool, is a key-region of the regional climate system. It is suspected to play an important role in the dynamics of the Asian summer monsoon system. The present study reports the salient features derived from a newly harvested observational dataset consisting of repeated fortnightly XBT transects in the SEAS over the period [2002][2003][2004][2005][2006][2007][2008]. The fortnightly resolution of such a multi-year record duration is unprecedented in this part of the world ocean and provides a unique opportunity to examine the observed variability of the near-surface thermal structure over a wide spectrum, from intra-seasonal to interannual time scales. We find that most of the variability is trapped in the thermocline, taking the form of upwelling and downwelling motions of the thermal stratification. The seasonal variations are consistent with past studies and confirm the role of the monsoonal wind forcing through linear baroclinic waves (coastally-trapped Kelvin and planetary Rossby waves). Subseasonal variability takes the form of anomalous events lasting a few weeks to a few months and occurs at two preferred time-scales: in the 30-110 day band, within the frequency domain of the Madden-Julian Oscillation and in the 120-180 day band. While this subseasonal variability appears fairly barotropic in the offshore region, the sign of the anomaly in the upper thermocline is opposite to that in its lower part on many occasions along the coast. Our dataset also reveals relatively large interannual temperature variations of about 1°C from 50 m to 200 m depth that reflect a considerable year-to-year variability of the magnitude of both upwelling and downwelling events. This study clearly demonstrates the necessity for sustained long-term temperature measurements in the SEAS.Keywords: XBT data, Arabian Sea, Lakshadweep Sea, Inter-annual variability, Intra-seasonal variability, WICC. IntroductionThe Lakshadweep Sea (henceforth LS), in the southeastern Arabian Sea (SEAS), is of prime climatic importance, being situated in the Indian Ocean warm pool (Fig. 1). It is also an area of marked oceanic dynamical activity. Several hydrographic cruises carried out during different seasons revealed striking contrasts between summer monsoon and winter monsoon seasons (Shetye et al., 1990(Shetye et al., , 1991. The advent of altimetry in the early 1990s allowed documentation of a clear seasonal cycle in the SEAS, with positive sea level anomaly (SLA) during winter and negative SLA during summer (Shankar and Shetye, 1997;Bruce et al., 1998). This feature was termed the Lakshadweep High and Low (henceforth LH/LL), after the name of the island chain (see Fig. 1 Arabian Sea) takes place over timescales of a few weeks to a few months for the lowest-order baroclinic modes (McCreary et al., 1993). Over the last 15 years, a hierarchy of numerical studies (McCreary et al., 1993;Shankar and Shetye 1997; led to the conclusion that the seasonal variability of LS hy...

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“…During May (spring intermonsoon), surface salinity was high compared to November, whereas in the bottom salinity was high during November. The high salinity of water during May (spring intermonsoon period) is the normal nature of the Arabian Sea (Shenoi ., 2005) and the salinity of the coastal waters may go down due to riverine inputs from the adjacent areas and littoral inputs from small canals. denotes copepods density >0.1 to 10; ++ denotes 10.1 to 50; +++ denotes 50.1 to 100; ++++ denotes 100.1 to 200; * denotes 200.1 to 300; **denotes 300.1 and 400; *** denotes 400.1 to 500; 0 denotes absence…”

Section: Methodsmentioning

confidence: 99%

Seasonal variation of copepod community structure in Chavara coast along the Southern Kerala, India

N.¹,

Hatha²

2018

JEB

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Aim : Methodology :Results : Interpretation :To analyze whether the seasonally differing hydrographical parameters can alter chlorophyll a and zooplankton community distribution in Chavara coast during two different seasons.The samples were collected from 10 m and 30 m locations from Chavara during November 2013 (Northeast Monsoon), May 2014 (Spring Intermonsoon). The collected zooplankton samples were analyzed in a stereo zoom microscope and copepods were identified to the species level. The relation between environmental parameters and zooplankton abundance was examined using statistical tools.Water column was cool, nutrient rich and less oxygenated (subsurface) during November. Water column was characterized as warm, high saline and with less nutrients during May. These variations were closely linked with the increased cooling and continuation of weakened upwelling during November. Chlorophyll a was found two to five folds higher during northeast monsoon compared to the spring intermonsoon. Overall, 14 zooplankton groups were recorded in the present study of which copepods contributed more than 70% to the total zooplankton density. Zooplankton (3619.5 No.m-3) and copepod abundance (3212.8 No.m-3) was high in November. Non-metric Multidimensional Scaling (NMDS), Agglomerative Hierarchical Cluster Analysis (AHCA) on Bray-Curtis similarity clearly separated the samples of two clusters (30 m and 10 m) in two different seasons.The copepods showed more similarity within season and more heterogeneity between two seasons. Some copepod species showed positive relationship with the environmental variables.

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Hydrography and water masses in the southeastern Arabian Sea during March–June 2003

Cited by 45 publications

References 26 publications

Oceanic upwelling and downwelling processes in waters off the west coast of India

Oceanic upwelling and downwelling processes in waters off the west coast of India

Observed intra-seasonal to interannual variability of the upper ocean thermal structure in the southeastern Arabian Sea during 2002–2008

Seasonal variation of copepod community structure in Chavara coast along the Southern Kerala, India

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