The rapid decline of sea ice in the Arctic has resulted in a variable sea ice roughness that necessitates improved methods for efficient observation using high-resolution spaceborne radar. The utility of C-band polarimetric backscatter, coherences, and ratios as a discriminator of ice surface roughness is evaluated. An existing one-dimensional backscatter model has been modified to two-dimensions (2D) by considering deviation in the orientation (i.e., the slopes) in azimuth and range direction of surface roughness simultaneously as an improvement in the model. It is shown theoretically that the circular coherence ( ) decreases exponentially with increasing surface roughness. The crosspolarized coherence ( ) is found to be less sensitive to surface roughness, whereas the copolarized coherence ( ) decreases at far-range incidence angles for all ice types. A complete validation of the adapted 2D model using direct measurements of surface roughness is suggested as an avenue for further research. 1. Introduction Arctic sea ice is going through a rapid decline [1, 2]. Thinner first-year ice (FYI) is replacing multiyear ice, leaving an ice cover, which is more sensitive to deformation and changes in atmospheric and ocean forcing. Increased open water and marginal ice zones (MIZs), due to the enhanced mobility of a relatively thinned pack ice, are further susceptible to increases in surface roughness and greater surface roughness variability [3]. Greater surface roughness in the MIZ is of importance due to higher rates of heat flux [4] and momentum [5] exchanges occurring across the ocean-sea ice-atmosphere interface, greater biological productivity [6], and potential limitations imposed on ship navigation. Although the literature contains information on how the MIZ responds to wind and wave forces, it is necessary to investigate the electromagnetic (EM) response of the MIZ to facilitate satellite-based observations. Satellite-based observation is necessary due to the scarcity of surface observations in a MIZ, as well as the difficulties in collecting physical measurements due to the instability and roughness of the ice floes. The use of polarimetric synthetic aperture radar (pol-SAR) represents a promising approach for satellite-based monitoring of surface roughness and, concurrently, discriminating sea ice types within a MIZ. A pol-SAR records the amplitude and phase information of backscattered energy for four transmit-receive polarizations (HH, HV, VH, and VV), thereby facilitating the derivation of the full polarimetric response of the target. It is
References
[1]
R. Kwok and G. F. Cunningham, “Contribution of melt in the Beaufort Sea to the decline in Arctic multiyear sea ice coverage: 1993–2009,” Geophysical Research Letters, vol. 37, Article ID L20501, 2010.
[2]
R. Kwok and D. A. Rothrock, “Decline in Arctic sea ice thickness from submarine and ICESat records: 1958–2008,” Geophysical Research Letters, vol. 36, Article ID L15501, 2009.
[3]
S. V. Nghiem, I. G. Rigor, D. K. Perovich, P. Clemente-Colon, J. W. Weatherly, and G. Neumann, “Rapid reduction of Arctic perennial sea ice,” Geophysical Research Letters, vol. 34, Article ID L19504, 2007.
[4]
M. G. McPhee, J. H. Morison, and F. Nilsen, “Revisiting heat and salt exchange at the ice-ocean interface: ocean flux and modelling considerations,” Journal of Geophysical Research, vol. 113, Article ID C06014, 2008.
[5]
E. L. Andreas, T. W. Horst, A. A. Grachev et al., “Parameterizing turbulent exchange over summer sea ice and the marginal ice zone,” Quarterly Journal of the Royal Meteorological Society, vol. 136, pp. 927–943, 2010.
[6]
D. Lavoie, R. W. Macdonald, and K. L. Denman, “Primary productivity and export fluxes on the Canadian shelf of the Beaufort Sea: a modelling study,” Journal of Marine Systems, vol. 75, no. 1-2, pp. 17–32, 2009.
[7]
R. Kwok, E. Rignot, B. Holt, and R. Onstott, “Identification of sea ice types in spaceborne synthetic aperture radar data,” Journal of Geophysical Research, vol. 97, no. 2, pp. 2391–2402, 1992.
[8]
H. Melling, “Detection of features in first-year pack ice by synthetic aperture radar (SAR),” International Journal of Remote Sensing, vol. 19, no. 6, pp. 1223–1249, 1998.
[9]
G. M. Wohl, “Operational sea ice classification from synthetic aperture radar imagery,” Photogrammetric Engineering & Remote Sensing, vol. 61, no. 12, pp. 1455–1462, 1995.
[10]
D. G. Barber and E. F. LeDrew, “SAR sea ice discrimination using texture statistics: a multivariate approach,” Photogrammetric Engineering & Remote Sensing, vol. 57, no. 4, pp. 385–395, 1991.
[11]
Q. A. Holmes, D. R. Nüesch, and R. A. Shuchman, “Textural analysis and real-time classification of sea-ice types using digital SAR data,” IEEE Transactions on Geoscience and Remote Sensing, vol. 22, no. 2, pp. 113–120, 1984.
[12]
S. V. Nghiem and C. Bertoia, “Study of multi-polarization C-band backscatter signatures for arctic sea ice mapping with future satellite SAR,” Canadian Journal of Remote Sensing, vol. 27, no. 5, pp. 387–402, 2001.
[13]
D. L. Schuler, J. S. Lee, D. Kasilingam, and G. Nesti, “Surface roughness and slope measurements using polarimetric SAR data,” IEEE Transactions on Geoscience and Remote Sensing, vol. 40, no. 3, pp. 687–698, 2002.
[14]
D. G. Barber and J. M. Hanesiak, “Meteorological forcing of sea ice concentrations in the southern Beaufort Sea over the period 1979 to 2000,” Journal of Geophysical Research C, vol. 109, no. 6, pp. C06014–16, 2004.
[15]
D. G. Barber, M. G. Asplin, Y. Gratton et al., “The International Polar Year (IPY) Circumpolar Flaw Lead (CFL) system study: overview and the physical system,” Atmosphere, vol. 48, no. 4, pp. 225–243, 2010.
[16]
J. S. Lee, D. L. Schuler, and T. L. Ainsworth, “Polarimetric SAR data compensation for terrain azimuth slope variation,” IEEE Transactions on Geoscience and Remote Sensing, vol. 38, no. 5 I, pp. 2153–2163, 2000.
[17]
R. Rignot and M. R. Drinkwater, “Winter sea-ice mapping from multi-parameter synthetic-aperture radar data,” Journal of Glaciology, vol. 40, no. 134, pp. 31–45, 1994.
[18]
T. Geldsetzer and J. J. Yackel, “Sea ice type and open water discrimination using dual co-polarized C-band SAR,” Canadian Journal of Remote Sensing, vol. 35, no. 1, pp. 73–84, 2009.
[19]
D. P. Winebrenner, L. D. Farmer, and I. R. Joughin, “On the response of polarimetric synthetic aperture radar signatures at 24-cm wavelength to sea ice thickness in Arctic leads,” Radio Science, vol. 30, no. 2, pp. 373–402, 1995.
[20]
H. Wakabayashi, T. Matsuoka, K. Nakamura, and F. Nishio, “Polarimetric characteristics of sea ice in the sea of okhotsk observed by airborne L-band SAR,” IEEE Transactions on Geoscience and Remote Sensing, vol. 42, no. 11, pp. 2412–2425, 2004.
[21]
K. Nakamura, H. Wakabayashi, K. Naoki, F. Nishio, T. Moriyama, and S. Uratsuka, “Observation of sea-ice thickness in the sea of okhotsk by using dual-frequency and fully polarimetric airborne SAR (Pi-SAR) data,” IEEE Transactions on Geoscience and Remote Sensing, vol. 43, no. 11, pp. 2460–2468, 2005.
[22]
T. Geldsetzer, J. B. Mead, J. J. Yackel, R. K. Scharien, and S. E. L. Howell, “Surface-based polarimetric C-band scatterometer for field measurements of sea ice,” IEEE Transactions on Geoscience and Remote Sensing, vol. 45, no. 11, pp. 3405–3416, 2007.
[23]
D. Isleifson, B. Hwang, D. G. Barber, R. K. Scharien, and L. Shafai, “C-band polarimetric backscattering signatures of newly formed sea ice during fall freeze-up,” IEEE Transactions on Geoscience and Remote Sensing, vol. 48, no. 8, pp. 3256–3267, 2010.
[24]
S. V. Nghiem, R. Kwok, S. H. Yueh, and M. R. Drinkwater, “Polarimetric signatures of sea ice 2. Experimental observations,” Journal of Geophysical Research, vol. 100, no. C7, pp. 13681–13698, 1995.
[25]
S. V. Nghiem, S. H. Yueh, R. Kwok, and F. K. Li, “Symmetry properties in polarimetric remote sensing,” Radio Science, vol. 27, no. 5, pp. 693–711, 1992.
[26]
S. H. Yueh, R. Kwok, and S. V. Nghiem, “Polarimetric backscattering and emission properties of targets with reflection symmetry,” Radio Science, vol. 29, no. 6, pp. 1409–1420, 1994.
[27]
F. D. Carsey, Ed., Microwave Remote Sensing of Sea Ice, American Geophysical Union, Washington, DC, USA, 1992.
[28]
S. R. Cloude and E. Pottier, “A review of target decomposition theorems in radar polarimetry,” IEEE Transactions on Geoscience and Remote Sensing, vol. 34, no. 2, pp. 498–518, 1996.
[29]
J. S. Lee, D. L. Schuler, T. L. Ainsworth, E. Krogager, D. Kasilingam, and W. M. Boerner, “On the estimation of radar polarization orientation shifts induced by terrain slopes,” IEEE Transactions on Geoscience and Remote Sensing, vol. 40, no. 1, pp. 30–41, 2002.
[30]
I. Hajnsek, E. Pottier, and S. R. Cloude, “Inversion of surface parameters from polarimetric SAR,” IEEE Transactions on Geoscience and Remote Sensing, vol. 41, no. 4, pp. 727–744, 2003.
