| Abstract: |
Because of the sparse coverage of the in situ measurements in Antarctica and due to the limited possibility of operating in such harsh environment, remote sensing data are of paramount importance for the climate study in this continent. Up to recent years, passive microwave sensors were extensively used for the monitoring of ice sheet surface parameters (i.e. snow melting, grains size an density in the first meters) because of the limited penetration depth of the frequency bands available on the satellite sensors. With the launch of L-band microwave radiometers (ESA’s SMOS in 2009, and NASA’s Aquarius and SMAP in 2011 and 2015 respectively), having a longer wavelength (i.e. 21 cm), the capability to explore deeper portions of the ice sheet increased and opened up new research scenarios. In particular, recent research activities, demonstrate the L- band sensitivities to the temperature gradient of the ice profile (i.e. from the surface to the bottom). It should be mentioned that the internal temperature is a key parameter for the understanding of the ice sheet dynamics which, at present, is available only from glaciological models or in the few boreholes where temperature has been measured. Results demonstrate that, by using an appropriate glaciological and microwave emission model, it is possible to retrieve the ice sheet temperature profile starting from SMOS data. By using this approach temperature maps , at the different depth form the surface on the bottom, have been realized for a large portion of Antarctica. Areas where the retrieval was not applicable (i.e. near to the coast or where the ice sheet velocity is higher than 10m/yr) were masked out and a quality flag with the confidence of the estimation was also provided. Secondary products are the geothermal heat flux and snow accumulation maps at the same spatial resolution of SMOS. By using a similar approach, it has been demonstrated that it is possible to exploit SMOS data to retrieve the ice thickness. The methodology was tested in region of Antarctica where the ice thickness is well known (i.e. uncertainty lower than 100 m measured by means of radio echo soundings) and provides a maximum difference from the reference of 200m. This result seems to be very promising for those areas of Antarctica where the current estimate have an uncertainty of about 1000m. Preliminary model sensitivity analysis also suggests the capability of L- band to detect the presence of subglacial lakes if the ice thickness is lower than 1000m and the possibility to monitor the water volume variations (charge or discharge). |
