Reconstruction of the 3-D Dynamics From Surface Variables in a High-Resolution Simulation of North Atlantic

Several methods that reconstruct the three-dimensional ocean dynamics from sea level are presented and evaluated in the Gulf Stream region with a 1/60° realistic numerical simulation. The use of sea level is motivated by its better correlation with interior pressure or quasigeostrophic potential vorticity (PV) compared to sea surface temperature and sea surface salinity, and, by its observability via satellite altimetry. The simplest method of reconstruction relies on a linear estimation of pressure at depth from sea level. Another method consists in linearly estimating PV from sea level first and then performing a PV inversion. The last method considered, labeled SQG for surface quasigeostrophy, relies on a PV inversion but assumes no PV anomalies. The first two methods show comparable skill at levels above -800∼m. They moderately outperform SQG which emphasizes the difficulty of estimating interior PV from surface variables. Over the 250-1000∼m depth range, the three methods skillfully reconstruct pressure at wavelengths between 500 and 200 km whereas they exhibit a rapid loss of skill between 200 and 100 km wavelengths. Applicability to a real case scenario and leads for improvements are discussed.