Project description
The aim of the SMOSIce study is to develop, improve and validate algorithms for sea ice thickness retrieval from the 1.4 GHz (L-band, wavelength=20cm) data of the European Space Agency's (ESA) Soil Moisture and Ocean Salinity (SMOS) mission. SMOS payload is the Microwave Imaging Radiometer Using Aperture Synthesis (MIRAS) measuring the brightness temperature at a range of incidence angles and at different polarizations.
Electromagnetic radiation with wavelengths of 20 cm can emerge from deep inside the sea ice layer. The attenuation mainly depends on the relative brine volume which is a function of ice bulk salinity and temperature. The penetration depth is up to 1.5m for cold low-salinity ice and reduces to a few centimeters for saline sea ice at high temperatures. The potential to derive the ice thickness from L-band radiometry thus depends on sea ice temperature and salinity.
A sea ice emissivity model is an integral part for the retrieval of ice thickness from SMOS measurements. The most simple setup consists of a three layer (ocean-ice-atmosphere) dielectric slab with plane-parallel specular surfaces (Kaleschke et al.,2010). The dielectric properties are parameterized as a function of the bulk ice salinity and temperature. One main objective of the SMOSIce study is to define the Algorithm Theoretical Basis Documents (ATBD) for SMOS sea ice retrieval, as well as to generate a SMOS sea ice product. This product is assessed using independent ice thickness measurements mainly from thermal infrared satellite imagery (MODIS) as well as from electromagnetic induction (EM) measurements.
First results
SMOS provides daily coverage of the polar regions with a resolution of about 35 km and can be used to measure sea ice thickness up to half a meter. The ice thickness derived from SMOS agrees with the ice thickness from thermal infrared MODIS images with 10cm standard deviation. SMOS thickness retrieval is well feasible and practical under ideal cold conditions such as typically encountered during the Arctic freeze-up period. Changes in ice concentration and ice temperature, as well as the snow thickness are the largest uncertainties which are neglected for the first operational prototype of a retrieval algorithm.
Sea ice thickness during the Arctic freeze-up as seen by SMOS
SMOSIce User Workshop
A workshop to present the SMOS ice thickness product, as well as the scientific and technical outcome of the study will take place at the KlimaCampus of the University of Hamburg. Potential participants are modelers, sea ice remote sensing and assimilation experts, as well as representatives from operational ice services and international projects (e.g. CliC, CCI) and potential data users. Contributions, conclusions and recommendations from the participants will be compiled in a workshop report.
Workshop details
- Date: 17 Feb 2012
- Time: 9:00-17:00
Place: Institute of Oceanography at the KlimaCampus, University of Hamburg
Registration: until 15 Jan, 2012 by email to Dr. Xiangshan Tian-Kunze: <xiangshan DOT tian-kunze AT SPAMFREE zmaw DOT de>
Technical programme
The SMOS Mission: Introduction (Yann Kerr)
Validation: Sea ice thickness measurements in the Baltic Sea and in the Arctic (Stefan Hendricks, Marko Mäkynen)
Algorithms: SMOS sea ice thickness retrieval algorithms (Lars Kaleschke, Georg Heygster)
Uncertainties: SMOS sea ice thickness product validation, sensitivities and uncertainties (Xiangshan Tian-Kunze, Nina Maaß, Rasmus Tonboe)
Assimilation : Assimilation system for sea ice thickness (Frank Kauker)
ESA Climate Change Initiative (CCI): User requirements for the Essential Climate Variable (ECV) Sea Ice (Stefan Kern)