16:00 Radar Interferometric and Polarimetric Possibilities for Determining Sea Ice Thickness
Hensley, Scott (1); Holt, Ben (1); Jaruwatanadilok, Sermsak (1); Steward, Jeff (1); Oveisgharan, Shadi (1); Moller, Delwyn (2); Reis, Jim (3); Mahoney, Andy (4); Soofi, Khalid A. (5) 1: Jet Propulsion Laboratory,; 2: Remote Sensing Solutions; 3: Fugro Earthdata International; 4: University of Alaska at Fairbanks; 5: Conoco Phillips
Show abstract
Sea ice thickness is a primary indicator of climate change in the polar oceans, as the thickness is a time-integrated result of both thermodynamic and dynamic processes. The large-scale ocean and atmospheric forcing acts on the fine-scale (a few to 10s of meters) opening and closing of the sea ice cover along fractures. The mean thickness and variance of sea thickness at km scales (50 cm uncertainty) are derived from recent spaceborne observations from the ICESat lidar and in the Arctic from sporadic upward looking sonar measurements. However, accurate measurements of sea ice thickness at the fine-scales at which the forcing is occurring are virtually non-existent. In this paper we explore two potential radar interferometric means of obtaining sea ice thickness. One method uses high frequency Ka-band (8.5 mm wavelength) to infer sea ice thickness by measuring elevations to the surface of the ice and to the ocean surface in nearby open leads. Data from the NASA Glistin radar is used to illustrate this methodology. Alternatively, we consider the use of dual frequency X-band and P-band (3 cm and 85 cm wavelengths) to exploit the differential penetration of longer versus shorter wavelength to estimate sea ice thickness. This technique is illustrated with data collected by the Furgo Earthdata GeoSAR system. Portions of this research were conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
15:40 Extraction of late summer sea ice properties from polarimetric SAR features in C- and X- band
Fors, Ane (1); Brekke, Camilla (1); Eltoft, Torbjørn (1); Gerland, Sebastian (2); Doulgeris, Anthony Paul (1) 1: University of Tromsø, Norway; 2: Norwegian Polar Institute, Norway
Show abstract
With the decline in sea ice extent and a lengthening of the summer melt season observed in the Arctic, a need of more detailed monitoring of the summer sea ice cover is required both for shipping, oil- and gas industries, and for climate science. Synthetic aperture radar (SAR) offers all weather high-resolution imagery of the Arctic region. SAR polarimetry is known to provide information about scattering mechanisms, which may help interpreting microwave signatures of sea ice. Polarimetric parameters may also add knowledge about important geophysical quantities like sea ice thickness and degree of deformation. Interpreting SAR scenes in the melt season is however difficult. Temperatures varying around freezing point leads to large changes in the dielectrical properties of the sea ice, and high moisture contents in the top layers of the ice mask ice type differences. To the authors knowledge, few studies have previously focused on the interpretation of active microwave polarimetric signatures of late summer sea ice (Gogineni et al. (1992), Isleifson et al. (2009), Warner et al. (2013), Scharien et al. (2014)). In this study we examine the potential use of six features, 1 statistical and 5 polarimetric, for interpretation and labeling of late summer sea ice types, based on five high-resolution C- and X- band scenes from Radarsat-2 and TerraSAR-X. These scenes were acquired during a week in the melt-freeze transition in the Fram Strait in 2011. The six features are previously described in Moen et al. (2013) for an application over spring sea ice, and they include relative kurtosis, geometric brightness, co-polarisation ratio, cross-polarisation ratio, co-polarisation correlation magnitude and co-polarisation correlation angle. The study investigates the relationships between the individual features and in situ measured sea ice thickness, melt pond fraction and surface roughness under changing temperature conditions in a multi-temporal dataset. The in situ measurements are retrieved from a helicopter flight in the observation area during the period of the satellite campaign, and include measurements of sea ice thickness, surface roughness and systematic, automatised photography images. Relationships between some of the polarimetric features and the measured sea ice properties were found. In particular, it was found that the relative kurtosis associated with the polarimetric scattering vector seems to carry information useful for separating areas with low and high melt pond fraction. This preliminary study also demonstrates the complexity of sea ice type discrimination in late summer conditions, which may put limitations on the use of individual polarimetric features for sea ice interpretation and ice type discrimination. References: Gogineni, S.P. et al., 1992. The effects of freeze-up and melt processes on microwave signatures. In F. D. Carsey, ed. Microwave Remote Sensing of Sea Ice. Washington, D. C.: American Geophysical Union, pp. 329–341. Isleifson, D. et al., 2009. C-Band Scatterometer Measurements of Multiyear Sea Ice Before Fall Freeze-Up in the Canadian Arctic. IEEE Transactions on geoscience and remote sensing, 47(6), pp.1651–1661. Moen, M.-A. et al., 2013. Comparison of feature based segmentation of full polarimetric SAR satellite sea ice images with manually drawn ice charts. The Cryosphere, 7(6), pp.1693–1705. Scharien, R.K., Landy, J. & Barber, D.G., 2014. Sea ice melt pond fraction estimation from dual-polarisation C-band SAR – Part 1: In situ observations. The Cryosphere Discussions, 8(1), pp.805–844. Warner, K. et al., 2013. On the classification of melt season first-year and multi-year sea ice in the Beaufort Sea using Radarsat-2 data. International Journal of Remote Sensing, 34(11), pp.3760–3774.
In May 2013, the Biomass mission concept was selected to become the next in the series of satellites developed to further our understanding of Earth.
REPLAY EARTH EXPLORER 7 USER CONSULTATION MEETING (PART 1)
POLinSAR 2013 Workshop