Mixed-layer Interannual variability in the Southern Ocean (MISO)
The ML heat budget will be analyzed for the period 1992-present based on simulations from a simple, insightful, model with advection prescribed from altimetry which ensures a correct positioning of the currents. This model will explicitly consider ML depth and entrainment anomalies, which can either be modeled or mapped from in situ observations. Although the Southern Ocean is a data depleted region, expectations for mapping ML parameters for recent years are much better with the advent of the Argo program. An important prerequisite, however, is to assess whether this improved data coverage is sufficient to map interannual changes with a reasonable accuracy and acceptable spatial resolution. Here mapping procedure will be tested on synthetic hydrographic profiles with realistic space-time distribution, and mapped fields compared with relevant satellite datasets. Analyses will particularly focus on wintertime budgets, relevant for mode water formation, and investigate the relation of the dominant term of the budget with the main climate modes of the Southern Hemisphere.
In a complementary fashion, we will also examine to what extent nonseasonal SSH anomalies reflect changes in the upper ocean heat content, and investigate factors driving its variability. This first requires to sort out the ocean's barotropic response at interannual time scales, which will be done with a finite element barotropic model, assessed against gravimetric observations from Grace. A joint analysis of the ML temperature and steric SSH has the potential to shed light on the interplay between the ML and the subsurface, and buoyancy anomalies stored below the ML.
Finally, we will attempt a similar diagnostic analysis for Sea Surface Salinity (SSS) anomalies based on the same model architecture. Investigating anomalies of SSS, which is a critical ML parameter in the Southern Ocean, is both important and timely and should be possible for recent years owing both to improved hydrographic data coverage (Argo) and dedicated satellite mission (SMOS).