Abstract Atlantic Water (AW) is the main oceanic heat source in the Arctic and a key driver of sea ice retreat. Based on Multidisciplinary drifting Observatory for the Study of Arctic Climate microstructure data from the Eurasian Basin, we examined the spatial heterogeneity of AW upward heat flux. We found that diffusive convection (∼76% occurrence; heat flux 2.14 W m−2) dominates upward heat transport in the AW interface layer (∼130–180 m) in the inner Eurasian Basin, whereas turbulent mixing (∼80% occurrence; heat flux 5.01 W m−2) prevails in the outer region. Intrusion‐induced negative temperature gradients (∼81% occurrence in the entire Eurasian Basin) trap heat below the AW interface layer (∼180–240 m), suppressing upward heat transfer. Our results indicate that AW upward heat release mainly originates from the interface layer in the Eurasian Basin, whereas most AW heat remains trapped beneath this layer and is largely isolated from upper‐ocean processes, thereby influencing Arctic sea ice variability.