Mixing of Rain and River Water in the Bay of Bengal From Basin‐Scale Freshwater Balance

We construct freshwater balance in the Bay of Bengal (BoB) within a control volume (CV) bounded by 1,018 kg/m3 isopycnal surface using observations and ocean reanalysis during 2011–2015. Freshwater in CV is maximum in October–November due to monsoonal rain and river inflows, and minimum in April–May...

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Bibliographic Details
Published in:Geophysical research letters 2024-02, Vol.51 (3), p.n/a
Main Authors: Jarugula, Sreelekha, Sengupta, Debasis, Shroyer, Emily, Papa, Fabrice
Format: Article
Language:English
Subjects:
Atmospheric precipitations
Bay of Bengal
Buoyancy
Climate models
Diapycnal mixing
Earth Sciences
Fresh water
Freshwater
freshwater balance
Freshwater budget
Hydrologic cycle
Hydrological cycle
Inland water environment
Jupiter
mixing
Monsoon winds
near‐surface salinity
Ocean models
Oceans
Pycnocline
Pycnoclines
Rain
River discharge
River flow
River water
Rivers
Salinity
Salinity effects
Sciences of the Universe
Seasonal variations
Seasonality
Short wave radiation
Standard error
Strata
Stratification
Surface boundary layer
Surface layers
Turbulence
Turbulence measurement
Winds
Winter
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Summary:We construct freshwater balance in the Bay of Bengal (BoB) within a control volume (CV) bounded by 1,018 kg/m3 isopycnal surface using observations and ocean reanalysis during 2011–2015. Freshwater in CV is maximum in October–November due to monsoonal rain and river inflows, and minimum in April–May. Water lighter than 1,018 kg/m3 is not transported out of BoB, implying that freshwater lost from CV is mixed away entirely within the basin. From freshwater budget, we infer moderate diapycnal mixing rates (∼0.8 × 10−5 m2/s) in boreal spring and summer; in winter (December–January), the rate of freshwater loss to subsurface ocean is 0.015 m/day, corresponding to a median turbulent diffusivity of 4.2 × 10−5 m2/s, with standard error of 25%. We 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 BoB. Plain Language Summary The freshwater from monsoonal rivers and rain discharged into the Bay of Bengal (BoB) forms a shallow (
ISSN:0094-8276
1944-8007
DOI:10.1029/2023GL106451