@article{fdi:010089487,
  title = {{M}ixing of rain and river water in the {B}ay of {B}engal {F}rom basin-scale freshwater balance},
  author = {{J}arugula, {S}. and {S}engupta, {D}. and {S}hroyer, {E}. and {P}apa, {F}abrice},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e construct freshwater balance in the {B}ay of {B}engal ({B}o{B}) within a control volume ({CV}) bounded by 1,018 kg/m(3) isopycnal surface using observations and ocean reanalysis during 2011-2015. {F}reshwater in {CV} is maximum in {O}ctober-{N}ovember due to monsoonal rain and river inflows, and minimum in {A}pril-{M}ay. {W}ater lighter than 1,018 kg/m(3) is not transported out of {B}o{B}, implying that freshwater lost from {CV} is mixed away entirely within the basin. {F}rom freshwater budget, we infer moderate diapycnal mixing rates (similar to 0.8 x 10-5 m(2)/s) in boreal spring and summer; in winter ({D}ecember-{J}anuary), the rate of freshwater loss to subsurface ocean is 0.015 m/day, corresponding to a median turbulent diffusivity of 4.2 x 10(-5) m(2)/s, with standard error of 25%. {W}e show that enhanced winter mixing across the shallow pycnocline is due to reduced shortwave radiation and subseasonal episodes of surface buoyancy loss when cool, dry northeast monsoon winds blow over {B}o{B}. {P}lain {L}anguage {S}ummary {T}he freshwater from monsoonal rivers and rain discharged into the {B}ay of {B}engal ({B}o{B}) forms a shallow (<10 m deep) salinity-stratified layer which has implications for the regional air-sea interaction. {T}here is very limited understanding of the mixing of the freshwater owing to the absence of near-surface turbulence measurements in {B}o{B}. {I}t is important to understand the disappearance of the shallow fresh layer in the {B}ay due to it's linkages to the regional hydrological cycle and the near-surface stratification. {I}n this study, we infer the seasonality of basin-scale mixing beneath the surface layer of {B}o{B} from a freshwater volume balance using a combination of observations and ocean analysis. {W}e find that the highest rates of freshwater mixing (mean and median values of about 5.5 x 10(-5) m(2)/s and 4.2 x 10(-5) m(2)/s) occur during winter ({D}ecember-{J}anuary), mainly driven by enhanced surface buoyancy loss thereby reducing the freshwater content at a mean rate of 0.015 m/day. {T}his study has implications for improvement of ocean and climate models, which generally have too-high mixing rates and poor representation of the salinity-stratified near-surface layer in {B}o{B}.},
  keywords = {mixing ; near-surface salinity ; freshwater balance ; stratification ; {B}ay of {B}engal ; river water ; {OCEAN} {INDIEN} ; {GOLFE} {DU} {BENGALE}},
  booktitle = {},
  journal = {{G}eophysical {R}esearch {L}etters},
  volume = {51},
  numero = {3},
  pages = {e2023{GL}106451 [11 ]},
  ISSN = {0094-8276},
  year = {2024},
  DOI = {10.1029/2023gl106451},
  URL = {https://www.documentation.ird.fr/hor/fdi:010089487},
}