National Institute of Oceanography, India

About: National Institute of Oceanography, India is a facility organization based out in Panjim, Goa, India. It is known for research contribution in the topics: Monsoon & Population. The organization has 4713 authors who have published 6927 publications receiving 174272 citations.

Propagation of tides in the Mandovi-Zuari estuarine network

Abstract: Located in Goa on the west coast of India and joining the Arabian Sea, the Mandovi and the Zuari are two estuaries, each about 50 km long, connected by a narrow canal. A number of small rivers join the two estuaries, forming a network of channels, whose cross-sectional area decreases rapidly in the upstream direction. They receive large freshwater influx during the southwest monsoon and little during the rest of the year. During April (dry season) and August (wet season) 1993, the water level and salinity at 15 locations in the network were monitored for 3 days to determine characteristics of tidal propagation in the network. Analysis of the data shows that the speed of propagation of both the diurnal and the semi-diurnal tide through the main channels of the network is approximately 6 m/s. Amplitudes of these tides in the channels remain unchanged over a distance of about 40 km from the mouth and then decay rapidly upstream over the next 10 km. The undamped propagation is a consequence of the balance between geometric amplification, due to decrease in the cross-sectional area in the upstream direction, and frictional dissipation. The rapid decay near the upstream end of the channels appears to result primarily from freshwater influx.

Active mud volcanoes on- and offshore eastern Makran, Pakistan

Abstract: To study the activity, source and driving force of the venting of fluidized mud in the coastal Makran, we carried out reconnaissance surveys of two active onshore mud volcano fields (Chandragup and Jebel-u-Ghurab) and of a newly born (March 1999) offshore mud volcano (Malan Island). All studied on- and offshore mud volcanoes line up along one southwest/northeast-trending structural lineament, the axis of the Dhak Anticline. Isotopic data point to a bacterial origin of the gas (mainly methane). Mixed benthic foraminiferal faunas and calcareous nannofloras suggest that the source level of the extruded mud is at a sub-surface depth of 2–3 km. Observed mud discharge varied between 0 and 1.4 m3 h–1 and gas discharge rates between negligible amounts to 1 m3 s–1. Mud temperatures in the crater lake of Chandragup I are near-ambient temperatures. They rise slightly (≤1.5°C) during episodes of modest mud outflow. An area of 160,000 m3 of soft mud was vigorously extruded from the sea floor at a water depth of 10 m within days after 15 March 1999, forming Malan Island. The island was destroyed within a few months after its birth by deep-reaching wave action during the SW monsoon. This was possibly aided by local subsidence of the mud volcano structure due to the volume loss following rapid degassing and mud extrusion.