Estimation of air-sea CO₂ flux in the coastal waters of Visakhapatnam

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 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.