Evolution of SST and XCO₂ in the summer ice free Arctic Ocean: is IASI able to contribute to climate change studies?

Abstract : The Arctic Ocean is a very important region of the globe in which the effect of climate change can be detected over short time periods. We have used the possibility provided by the two infrared sounders IASI-A and IASI-B on the MetOp platforms to retrieve the sea surface temperature (Tsurf) and the column averaged mixing ratio of several trace gases including CO2. A strict filtering based on the AVHRR cloud fraction and the radiance analysis within the IASI footprints lead to a large number of spectra for which a 1D-var inversion (Tsurf and XCO2 as the main parameters in the state vector, plus scaling factors for the profiles of H2O and O3) has been performed. For this purpose, we used during retrieval the atmospheric window between 940 and 980 cm-1 (CO2 laser band) for which the sensitivity to the surface is maximum. The statistics of the comparison between IASI-A and IASI-B retrievals will be presented and compared to the corresponding Eumetsat L2 products. The months of July, August and September for the years 2013 to 2015 have been considered since in these Arctic summer conditions the ice pack coverage is reduced. The monthly climatology for the consecutive years from 2010 (for which only IASI-A was in orbit) to 2015 is confirming that IASI can indeed be used for climate change studies.