The Impact of Near-Surface Salinity Structure on SMOS Retrievals

The European Space Agency recently launched their Soil Moisture and Ocean Salinity (SMOS) mission, providing measurements of sea surface salinity on a global scale for the first time. However, SMOS is only able to sense the upper 1 cm of the ocean, and there are questions as to how representative this point measurement is of the upper several metres of the water column. Here we present results from investigations into near-surface salinity structure. These observations were made using a novel, upwardly rising, microstructure profiler and the data came from the tropical North Atlantic Ocean. Analysis is presented whereby the in situ data was used to quantify the strength of near-surface salinity gradients in this region. A comparison was also conducted between the in situ observations and the co-located SMOS Level 3 data. This showed that the difference between these two datasets was normally larger than the salinity gradients seen in the upper 5 m of the ocean. Effectively, this implies that near-surface salinity gradients cannot explain the discrepancy between the two datasets. Future research is required to repeat this analysis using higher temporal resolution Level 2 data.