Using current and future L-band (1.4GHz)missions for sea ice thickness retrieval.Maciej Miernecki(email:maciej.miernecki@uv.es)

INRA - Institute de la Recherche Agronomique, Bordeaux

In the past three decades average sea ice thickness in the Arctic has dropped dramatically.Furthermore the loss of summer ice is more rapid than any model predictions. This new con-ditions enable the usage of new sea routes such as the Northwest Passage, and exploitationof natural resources. Satellite sea ice products based on passive microwave are well estab-lished navigation aid. Those techniques are useful in estimating ice concentration however, thethickness measurements pose more difficulties. L-band missions: ESA SMOS, NASA Aquarius,NASA SMAP could supplement this data with direct measurements of the sea ice thickness upto 0.5 m. This thin sea ice is important from the scientific point of view, since it controls the gasand heat exchange in Ocean - atmosphere system. Knowing the thickness of the ice togetherwith its concentration will also allow to extend the short navigation season for vesselswith strengthened hull. Promising results presented by Kaleschke et.al 2012 [1,2], encouragedme to make a general study of possible advantages and disadvantages of each mission withrespect to sea ice measurements. Although none of those missions was originally designed forthis particular purpose such usage of the data could be an interesting scientific and commercialproject.

The AlgorithmBrightness temperature observed by the satellite (Tbobserved) could be ex-pressed as a function of the ice contrition C, Ice and water physical tem-perature (T ) and their emissivities (e). Following formula expresses thatrelationship together with galactic noise and atmosphere radiation in theremainder term R.

Tbobserved = C ∗ eiceTice + (1 − C) ∗ ewaterTwater + R

Emissivity of sea water as described by Klein & Swift (1977) is a func-tion of temperature and salinity. As shown by Kaleschke el al.(2012) theemissivity of ice is mainly a function of its thickness.

The RetrievalIn this study atmospheric and galactic noise are neglected and sea iceconcentration C is assumed to be 1 or 0. Those assumptions led to thesimplified retrieval model (Kaleschke et al. 2010):

Tobserved = Tbice − (Tbice − Tbwater)exp(−γd)

First beam from NASA Aquarius, with incidence angle 28.7 degree wasused to obtain 1st Stokes parameter: (TbH + TbV)/2. The simplified re-trieval model was then applied to weekly composites of the orbits.In order to calibrate the constant γ and tie points Tbice, Tbwater, point inthe middle of The Boufort Gyre was selected: 79.6N, 157.1W.

Figure: TB, ice concetration and T at calibration point.

Results2011-08-26

2011-10-23

2011-10-30

2011-10-14

2011-10-28

Overview

ESA SMOS NASA SMAP NASA Aquarius

Figure: Sizes of the pixels for SMOS(dark blue), SMAP(pink)and Aquarius (green).

Satellite Coverage > 50N Resolution IncidanceangleSMOS 1 day 45 km 0-70°

Aquarius 4-5 days 74 km x 94 km (1st b.) 28.7°SMAP 2 days 39 km X 47 km 40°

Conclusions

NASA Aqarius too low resolution and special coverage foroperational serviceESA SMOS venerable to RFI and land/sea contamination(corrupted data close to shore)NASA SMAP combines the time and special resolution

of SMOS and radiometric properties of Aquarius, (to belaunch in 2015)

References[1] F. Bayle, F. Bayle, J.-P. Wigneron, Y. Kerr, P. Waldteufel, E. Anterrieu, J.-C. Orlhac, A. Chanzy, O.Marloie, M. Bernardini, S. Sobjaerg, S. A10 Sobjaerg, J.-C. Calvet, J.-C. A11 Calvet, J.-M. Goutoule,J.-M. A12 Goutoule, and N. Skou, N. A13 Skou, Two-dimensional synthetic aperture images over a landsurface scene, IEEE J GRS, vol. 40, no. 3, pp. 710714, 2002.Kaleschke, L., X. Tian-Kunze, N. Maa, M. Mkynen, and M. Drusch (2012), Sea ice thickness retrievalfrom SMOS brightness temperatures during the Arctic freeze-up period, Geophys. Res. Lett.,doi:10.1029/2012GL050916[3] Kaleschke, L., Maa, N., Haas, C., Hendricks, S., Heygster, G., and Tonboe, R. T.: A sea-icethickness retrieval model for 1.4 GHz radiometry and application to airborne measurements over lowsalinity sea-ice, The Cryosphere, 4, 583-592, doi:10.5194/tc-4-583-2010, 2010.[4] Kalnay et al.,The NCEP/NCAR 40-year reanalysis project, Bull. Amer. Meteor. Soc., 77, 437-470,1996.

maciej.miernecki@uv.es