Estimation of Air-Sea CO 2 Flux in the Coastal Waters of Visakhapatnam
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SHORT NOTE
Estimation of Air-Sea CO2 Flux in the Coastal Waters of Visakhapatnam T. Preethi Latha & K. H. Rao & V. V. S. S. Sarma & P. Seetaram & S. B. Choudhury & P. V. Nagamani & C. B. S. Dutt & V. K. Dhadwal & Sudip Manna
Received: 9 July 2014 / Accepted: 18 December 2014 # Indian Society of Remote Sensing 2015
Abstract Observations were conducted in a time series mode off Visakhapatnam in Bay of Bengal, for a period of 10 days from 8 to 19th February 2013 to examine the short-term atmospheric events on chemical processes in the upper 100 m water column. Water column temperature, salinity at 2 h interval from surface to 100 m were collected using CTD whereas water samples were collected for nutrients (phosphate and silicate), dissolved inorganic carbon (DIC), pH, total alkalinity (TA) at 4 h interval in the upper 25 m water column. Atmospheric properties such as air temperature, humidity, and wind speed were measured in 1 min interval. The winds were normally northeast direction with speed ranged between 0.1 and 8 m/s from 8 to 13th February and decreased to 0.1–4 m/s between 14 and 19th February 2013. The atmospheric pCO2 ranged from 380 to 420 μatm whereas surface water pCO2 ranges from ~370 to 470 μatm during study period. The low pCO2 levels were associated with low saline water indicating the rich nutrient T. P. Latha : K. H. Rao : S. B. Choudhury : P. V. Nagamani (*) : C. B. S. Dutt : V. K. Dhadwal National Remote Sensing Centre, ISRO, Hyderabad, India e-mail: [email protected] V. V. S. S. Sarma National Institute of Oceanography, RC-Visakhapatnam, India P. Seetaram Department of Inorganic and Analytical Chemistry, Andhra University, Visakhapatnam, India S. Manna School of Oceanographic Studies, Jadavpur University, Kolkata, India
coastal waters were under saturated with reference to atmosphere. The CO2 flux estimations for this region showed a significant source to the atmospheric CO2. This study provides information on changes in the physical and chemical processes in relation to the CO2 flux at the air-water interface in the coastal Bay of Bengal. Keywords pCO2 . pH . TA . CO2 Flux
Introduction The Bay of Bengal is a unique semi enclosed tropical basin, forced locally by the semi-annually reversing monsoon winds and remotely by zonal winds in the equatorial Indian Ocean (EIO) (McCreary et al. 1993). In addition, the Bay of Bengal also receives large quantity of freshwater by excess precipitation and river runoff over evaporation (Varkey et al. 1996). Studies have been conducted (Rao et al. 1994) in order to understand the nutrients and inorganic carbon system in the Bay of Bengal during pre-monsoon periods during both the south west and north east monsoon periods and noticed that surface waters are completely devoid of nutrients due to strong vertical stratification, whereas surface pCO2 levels were mostly less than atmospheric values. Thus, low pCO2 levels in the North West coastal region of Bay of Bengal were influenced by both physical and biological processes. Coastal Bay of Bengal shows low
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