Monitoring Sea Surface Salinity at the Arctic Ocean and high latitude oceans using SMOS data

Abstract

In recent years, the Arctic Ocean has been under significant transformation as shown by numerous in‐situ and remote sensing measurements. The temperature of the upper layer of the Arctic Ocean has been increasing and more solar heat has been absorbed by the increasing ice‐free areas [1,2]. The launch of the Soil Moisture and Ocean Salinity (SMOS) mission, in 2009, marked the dawn of a new type of space‐based microwave observations. Although the mission was originally conceived for hydrological and oceanographic studies [3,4], SMOS is also making inroads in the cryospheric sciences. SMOS carries an L‐band (1.4 GHz, or 21‐cm wavelength), passive interferometric radiometer (the so‐called MIRAS) that measures the electromagnetic radiation emitted by the Earth's surface, at about 50 km spatial resolution, full polarization, continuous multi‐angle viewing, large wide swath (1200‐km), and with a 3‐day revisit time at the equator, but more frequently at the poles. With the introduction of a new retrieval methodology, it is now possible to retrieve salinity information in ice‐free areas of the Arctic Ocean, a key region for monitoring the extent and rate of climate change. The quality of the sea surface salinity (SSS) retrievals in the Arctic region, will be presented, for which a rather exhaustive validation with in situ data (ARGO, EN4 and vessel measurements) has been performed as well as a comparison with the TOPAZ model output. It is shown that, with the current accuracy, it is possible to monitor the spatial and temporal variability of the salinity close to the mouth of the main Arctic river. [1] Comiso, J. C. (2012), Large decadal decline of the arctic multiyear ice cover, doi:10.1175/jcli‐d‐11‐00113.1., J. Clim, 25 (3), 11761193. [2] Haas, C., A. Pfa_ing, S. Hendricks, L. Rabenstein, J.‐L. Etienne, and I. Rigor (2008), Reduced ice thickness in arctic transpolar drift favors rapid ice retreat, doi:10.1029/2008gl034457., Geophys. Res. Lett., 35. [3]Font, J.; Camps, A.; Borges, A.; Martin‐Neira, M.; Boutin, J.; Reul, N.; Kerr, Y.; Hahne, A. & Mecklenburg, S. SMOS: The Challenging Sea Surface Salinity Measurement From Space Proceedings of the IEEE, no. 5, 2010, 98, 649 ‐665 [4] Kerr, Y.; Waldteufel, P.; Wigneron, J. P..; Delwart, S.; Cabot, F.; Boutin, J.; Escorihuela, M.J..; Font, J.; Reul, N.; Gruhier, C.; Juglea, S.; Drinkwater, M.; Hahne, A.; Martin‐Neira, M. & Mecklenburg, S. The SMOS mission: New tool for monitoring key elements of the global water cycle Proc. IGARSS 2010, no. 5, 2010, 98, 666‐687