# Rama Satish Aslekar: Biological Control on Upper Ocean CaCO3 Dissolution and Its Role in Ocean Alkalinity Cycling and Carbon Dioxide Removal

**URL:** <https://forum.access-hive.org.au/t/rama-satish-aslekar-biological-control-on-upper-ocean-caco3-dissolution-and-its-role-in-ocean-alkalinity-cycling-and-carbon-dioxide-removal/7235>\
**Category:** COSIMA/Cryosphere Workshop 2026 Lightning Talks\
**Created:** [5 November 2026 22:10 UTC](https://forum.access-hive.org.au/t/rama-satish-aslekar-biological-control-on-upper-ocean-caco3-dissolution-and-its-role-in-ocean-alkalinity-cycling-and-carbon-dioxide-removal/7235 "2026-11-05T22:10:38Z")\
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**Author:** ![lachlanswhyborn](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.access-hive.org.au/lachlanswhyborn/32/1837_2.png) [@lachlanswhyborn](https://forum.access-hive.org.au/u/lachlanswhyborn)\
**Post date:** [5 November 2026 22:10 UTC](https://forum.access-hive.org.au/t/rama-satish-aslekar-biological-control-on-upper-ocean-caco3-dissolution-and-its-role-in-ocean-alkalinity-cycling-and-carbon-dioxide-removal/7235/1 "2026-11-05T22:10:38Z")

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Rama Satish Aslekar: Biological Control on Upper Ocean CaCO3 Dissolution and Its Role in Ocean Alkalinity Cycling and Carbon Dioxide Removal

The ocean’s capacity to absorb anthropogenic CO₂ depends on the vertical distribution of alkalinity, set by the production of biogenic calcium carbonate near the surface and its dissolution as particles sink. Thermodynamics confines dissolution below the saturation horizon, but growing observational evidence indicates that a substantial fraction dissolves in supersaturated waters, driven by corrosive microenvironments within zooplankton guts and sinking aggregates. Estimates of this shallow fraction span a wide range, and most ocean biogeochemical models do not resolve these processes well. They tend to place too little dissolution in the upper ocean and too much at depth, and can be tuned to reproduce observed alkalinity while misrepresenting the underlying mechanisms, undermining confidence in their use for verifying ocean alkalinity enhancement.  
We introduce a mechanistically grounded carbonate cycle into WOMBAT-lite within the ACCESS-OM2 1° ocean–sea ice model. Production is constrained against a global compilation of calcification measurements, open-water dissolution adopts a two-regime kinetic formulation, and mineral phases are tracked as particles sink, attributing dissolution to the solubility and saturation state of each mineral. Dissolution in zooplankton guts and due to detrital remineralisation is represented explicitly, explored through a set of sensitivity runs and evaluated against observations of surface alkalinity and sinking fluxes. The role of carbonate ballasting in setting particle sinking rates and organic carbon transfer efficiency is also examined.  
These experiments quantify how much calcium carbonate dissolves in supersaturated waters, revealing the consequences for the vertical alkalinity gradient and simulated CO₂ uptake. By establishing a mechanistically defensible baseline for natural carbonate cycling, this work will interest ocean biogeochemical modelling, marine carbon cycle research, and the verification of marine carbon dioxide removal