Arabian Sea Mini Warm Pool and its Influenceon Acoustic Propagation

A systematic experiment was conducted in the eastern Arabian Sea for the first time exclusivelyto study the characteristics of the Arabian Sea mini warm pool1. The analysis revealed complexnature of the thermohaline and sonic layer distributions across the Arabian Sea mini warm pool.This mini warm pool was identified between 67.5 oE and 75 oE, where the sea surface temperaturewas in excess of 30.25 oC. At the core of this mini warm pool, warmer (>31.2 oC) and low saline(<34.6 PSU) waters were noticed. Further, very thin sonic layer (< 5 m) was noticed at the miniwarm pool core, which increased eastward and westward. In this study, the acoustic propagationcharacteristics across and outside of the core, i.e., (i) within the mini warm pool core, (ii) easternside of the mini warm pool core, and (iii) western side of the mini warm pool core, were assessedbased on the output of a range-dependant acoustic model. In general, the occurrence of this miniwarm pool was found to alter the propagation characteristics. Better propagation was obtainedwhen the simulation was carried out on the eastern side of this mini warm pool, with source nearthe coast (i.e., downslope condition

Spatial and temporal variability of chlorophyll-a concentration in the South Eastern Arabian Sea (SEAS)

Satellite remote sensing is being effectively used in monitoring the ocean surface. Among the ocean observing satellite sensors, ocean colour sensors make use of visible band of electromagnetic spectrum (shorter wavelength). The use of shorter wavelength ensures fine spatial resolution of these parameters to depict oceanographic characteristics of any region having significant spatio-temporal variability. The Southeastern Arabian Sea (SEAS; encompassing between 70.5-77.5oE longitude and 8-15oN latitude) is such an area showing very significant spatio-temporal oceanographic and atmospheric variability due to the seasonally reversing surface winds and currents (Shankar et al., 2002; Shetye et al., 1990

Formulation of an Empirical Relation between Chlorophyll and Sea Surface Temperature in the Southeastern Arabian Sea

Present study formulates an empirical relation between sea surface temperature (SST) and chlorophyll (Chl) in the Southeastern Arabian Sea using data collected during 2017. SST was found to decrease due to upwelling of cold nutrient rich waters, thus causing enhancement of Chl in the coastal and nearshore waters. Based on this, an empirical relationship exists which is inversely correlated during peak upwelling and intense biological production. The linear regression generated a significant correlation coefficient (0.52 ≤ R2 ≥ 0.64) in the month of July, August and October. Although other factors influence Chl, SST can be considered as a significant indicator of biological production with respect to seasonal upwelling. Among the empirical relations, a definite single equation requires the assessment of subsurface Chl to reveal the underlying relationship

Understanding our seas: National Institute of Oceanography, Goa

The present article summarizes the research done at the CSIR–National Institute of Oceanography in 2014 in ocean science, resources and technology. Significant research has been conducted on air–sea interactions and coastal circulation, biogeochemistry, biology, marine geophysics, palaeoceanography, marine fishery, gas hydrates and wave energy. Technological advances covered topics like oceanographic tools. Major strides have been made in marine resources research and evaluation

Understanding our seas: National Institute of Oceanography, Goa

The present article summarizes the research done at the CSIR–National Institute of Oceanography in 2014 in ocean science, resources and technology. Significant research has been conducted on air–sea interactions and coastal circulation, biogeochemistry, biology, marine geophysics, palaeoceanography, marine fishery, gas hydrates and wave energy. Technological advances covered topics like oceanographic tools. Major strides have been made in marine resources research and evaluation

Long period waves in the coastal regions of north Indian Ocean

150-154The sea surface height (SSH) anomaly derived from TOPEX/POSEIDON altimeter was used to study the characteristics of long period waves in the coastal belt of north Indian Ocean. Wavelet analysis at typical locations revealed that the most dominant signals were in the bands of intra-seasonal oscillation (ISO), i.e. 30-60 days, 3-4 months, semi-annual and annual. Among them, the annual signal contained maximum energy at all the locations. But, inside the Andaman Sea, and off the Gulf of Aden, the ISO component is of nearly equal magnitude as that of annual. In the regions of large SSH variability, low frequency components (more than 3 months) dominated, whereas they contained less energy in the region of minimum SSH variability. Hovmullor diagrams revealed large inter- and intra-annual variability in the SSH fields. In general, along the eastern boundary of the ocean, high sea level was observed during April-June and October-December in association with equatorial Kelvin waves. Another notable observation was the formation of high SSH in the western Indian Ocean during February-May and August-October. Among them, the former one propagated northward while latter one was found stationary. The Markan coast was found as the region of meeting place of two waves, one from the western Indian Ocean and the other from the eastern Bay. The results can be utilized to enhance the understanding of various coastal processes controlled by long period waves, viz. upwelling, sinking, circulation and meso-scale features

Shallow Water Internal Waves and Associated Acoustic Intensity Fluctuations

Physical oceanographic and acoustic data were simultaneously collected from the coastal waters of the Arabian Sea. Acoustic transmissions were carried out from an anchored vessel using 620 Hz transducer and received by an array of hydrophones moored at ~5 km away from the anchorage. Thermal structure in this region was characterised by a tri-layer structure, ie, a strong thermocline (> 0.4 oC/m) sandwiched between an upper (< 10 m) and bottom (> 25 m) homogeneous layer. High-resolution (sampled at 10 s interval) temperature data from moored sensors revealed intense internal wave activity. The maximum value of Brunt-Vaisala frequency, which is the maximum frequency limit of internal waves in the thermocline, suggests that the upper frequency limit of the internal wave, which can be generated during this period, is 23 cph (2.6 min). High and low frequency waves caused variations of ~3 oC and ~5 oC respectively in the temperature field. But the low frequency internal waves were found to contain maximum energy compared to the high frequency waves. Fluctuations of 8-12 dB were noticed in the measured acoustic intensity values in the presence of low frequency internal waves. Simulation studies carried out using parabolic equation model using 620 Hz source indicated well-defined ducted propagation with minimum transmission loss, when the source was kept within the homogeneous layer. The presence of tri-layer thermal structure, ie, a strong gradient layer sandwiched between an upper and bottom homogeneous layer, caused surface and bottom channel propagation in this region

Land use/Land cover changes around Rameshwaram Island, east coast of India

1183-1186Land-use/land cover changes are studied using the Indian Remote Sensing satellite (IRS-1C, IRS-P6) Linear Image Self-scan Sensor (LISS) III data of 1998 and 2010. Coastal land use categories such as sand, vegetation, coral reef and water have been identified using interpretation keys. Results of land-use/land cover assessment based on visual interpretation are presented. The study indicates water body of 178 and 177 km2, sand features of 32 and 32 km2, vegetation of 28 and 35 km2 and coral reef of 5 and 6 km2 respectively.</span

A NEW SPECIES OF GARNOTIA (POACEAE) FROM KERALA, INDIA

Volume: 8Start Page: 517End Page: 52

Microalgae in the Southwest Coast of India

Department of Marine Biology, Microbiology and Biochemistry, Cochin University of Science and Technolog