Characterizing air-sea CO2 exchange dynamics during winter in the coastal water off the Hugli-Matla estuarine system in the northern Bay of Bengal, India

Anirban Akhand*, Abhra Chanda, Sachinandan Dutta, Sudip Manna, Sugata Hazra, Debasis Mitra, K. H. Rao, V. K. Dadhwal

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


The distribution of the fugacity of CO2 (fco2) and air-sea CO2 exchange were comprehensively investigated in the outer estuary to offshore shallow water region (lying adjacent to the Sundarban mangrove forest) covering an area of ~2,000 km2 in the northern Bay of Bengal during the winter. A total of ten sampling surveys were conducted between 1 December, 2011 and 21 February, 2012. Physico-chemical variables like sea surface temperature (SST), salinity, pH, total alkalinity (TAlk), dissolved inorganic carbon (DIC) and in vivo chlorophyll-a along with atmospheric variables were measured in order to study their role in controlling the CO2 flux. Surface water fco2 ranged between 111 and 459 μatm which correlated significantly with the SST (r = 0.71, p < 0.001, n = 62). Neither DIC nor TAlk showed any linear relationship with varying salinity in the estuarine mixing zone, demonstrating the significant presence of non-carbonate alkalinity. An overall net biological control on the surface fco2 distribution was established during the study, although no significant correlation was found between chlorophyll-a and fco2 (water). The shallow water region studied was mostly under-saturated with CO2 and acted as a sink for atmospheric CO2. The difference between surface water and atmospheric Fco2) (Δfco2) ranged from -274 to 69 μatm, with an average seaward flux of -10.5 ± 12.6 μmol m-2 h-1. The Δfco2 and hence the air-sea CO2 exchange was primarily regulated by the variation in sea surface fco2, since atmospheric fco2 varied over a comparatively narrow range of 361.23-399.05 μatm.

Original languageEnglish
Pages (from-to)687-697
Number of pages11
JournalJournal of Oceanography
Issue number6
Publication statusPublished - Dec 2013


  • Air-sea CO exchange
  • Bay of Bengal
  • Biological effect
  • Fugacity of CO
  • Outer estuary
  • Sea surface temperature

ASJC Scopus subject areas

  • Oceanography

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