Question

how does carbon transfer between the atmosphere and ocean?

Explanation:

Carbon transfer between atmosphere and ocean: 1) Diffusion: Atmospheric $\ce{CO2}$ diffuses into ocean water—higher atmospheric $\ce{CO2}$ pressure drives diffusion. Ocean water can also release $\ce{CO2}$ to atmosphere if ocean $\ce{CO2}$ partial pressure > atmospheric. 2) Biological processes: Marine plants (phytoplankton) use $\ce{CO2}$ for photosynthesis (removing from atmosphere/ocean surface), and when organisms respire/decompose, $\ce{CO2}$ is released. 3) Chemical reactions: $\ce{CO2}$ reacts with ocean water to form carbonic acid ($\ce{H2CO3}$), which dissociates into bicarbonate ($\ce{HCO^-_{3}}$) and carbonate ($\ce{CO^{2-}_{3}}$), storing carbon in ocean.

Answer:

Carbon transfers between the atmosphere and ocean through: 1) Diffusion: $\ce{CO2}$ moves from areas of higher partial pressure (e.g., atmosphere with high $\ce{CO2}$) to lower (ocean, initially), and vice versa if ocean $\ce{CO2}$ levels rise. 2) Biology: Phytoplankton photosynthesize, taking $\ce{CO2}$ from ocean/atmosphere; respiration/decomposition releases $\ce{CO2}$. 3) Chemistry: $\ce{CO2}$ reacts with $\ce{H2O}$ to form $\ce{H2CO3}$, then $\ce{HCO^-_{3}}$/$\ce{CO^{2-}_{3}}$, storing carbon in the ocean.