Mixed layer heat budget in the Iceland Basin from Argo

The mixed layer processes that govern the mode water properties in the Iceland Basin are quantified through a mixed layer heat budget from Argo data collected over 2001-2007. This budget includes the mixed layer heat content variation, the surface heat fluxes, and the Ekman contribution to advection. The geostrophic advection cannot be directly estimated from Argo data but, following previous works, an ad hoc procedure is implemented to take it into account. The resulting annual budget is closed within the error bar but this closure hides some compensation between the summer and the winter residuals (-16 +/- 9 W m(-2) and 21 +/- 26 W m(-2), respectively). A similar heat budget built by using colocated Argo floats in the 1/4 degrees DRAKKAR ORCA025-G70fo simulation over 2001-2007 shows seasonal patterns similar to the Argo-based budget. An Eulerian model-based heat budget in the Iceland Basin shows that the mixed layer heat content variation is driven by the air-sea fluxes, the advection, and the vertical diffusion. The indirect estimate of the latter in a new Argo-based budget leads to a summer residual of 2 +/- 11 W m(-2) and to an unchanged winter residual. The summer and winter standard errors of the Argo-based budget (11 and 26 W m(-2), respectively) reflect the limited sampling of the Iceland Basin by Argo floats. Sensitivity experiments show that such errors would be reduced by a denser Argo sampling.