Multifrequency Microwave Backscatter From a Highly Saline Snow Cover on Smooth First-Year Sea Ice: First-Order Theoretical Modeling

Ku- and C-band spaceborne scatterometer sigma nought (σ°) backscatter data of snow covered landfast first-year sea ice from the Canadian Arctic Archipelago are acquired during the winter season with coincident in situ snow-thickness observations. Our objective is to describe a methodological framework for estimating relative snow thickness on first-year sea ice based on the variance in σ° from daily time series ASCAT and QuikSCAT scatterometer measurements during the late winter season prior to melt onset. We first describe our theoretical basis for this approach, including assumptions and conditions under which the method is ideally suited and then present observational evidence from four independent case studies to support our hypothesis. Results suggest that the approach can provide a relative measure of snow thickness prior to σ° detected melt onset at both Ku- and C-band frequencies. We observe that, during the late winter season, a thinner snow cover displays a larger variance in daily σ° compared to a thicker snow cover on first-year sea ice. This is because for a given increase in air temperature, a thinner snow cover manifests a larger increase in basal snow layer brine volume owing to its higher thermal conductivity, a larger increase in the dielectric constant and a larger increase in σ° at both Ku- and C bands. The approach does not apply when snow thickness distributions on first-year sea ice being compared are statistically similar, indicating that similar late winter σ° variances likely indicate regions of similar snow thickness.

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Multi-frequency polarimetric microwave observations of snow cover on first-year Arctic sea ice

2015 IEEE International Geoscience and Remote Sensing Symposium (IGARSS) ◽

10.1109/igarss.2015.7327015 ◽

2015 ◽

Author(s):

Vishnu Nandan ◽

John J. Yackel ◽

Jagvijay P. S. Gill ◽

Torsten Geldsetzer ◽

Mark C. Fuller

Keyword(s):

Sea Ice ◽

Snow Cover ◽

Arctic Sea Ice ◽

First Year ◽

Arctic Sea

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Multi-frequency microwave backscatter indices from saline snow covers on smooth first-year sea ice

2017 IEEE International Geoscience and Remote Sensing Symposium (IGARSS) ◽

10.1109/igarss.2017.8126967 ◽

2017 ◽

Author(s):

Vishnu Nandan ◽

Torsten Geldsetzer ◽

Mallik Mahmud ◽

John Yackel ◽

Mark C. Fuller ◽

...

Keyword(s):

Sea Ice ◽

First Year ◽

Microwave Backscatter

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C-band backscatter from a complexly-layered snow cover on first-year sea ice

Hydrological Processes ◽

10.1002/hyp.10255 ◽

2014 ◽

Vol 28 (16) ◽

pp. 4614-4625 ◽

Cited By ~ 15

Author(s):

M. Christopher Fuller ◽

Torsten Geldsetzer ◽

Jagvijay P. S. Gill ◽

John J. Yackel ◽

Chris Derksen

Keyword(s):

Sea Ice ◽

Snow Cover ◽

First Year

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Analyses of c-band microwave backscatter to wind-roughened first-year sea ice melt ponds

IEEE International IEEE International IEEE International Geoscience and Remote Sensing Symposium, 2004. IGARSS '04. Proceedings. 2004 ◽

10.1109/igarss.2004.1370334 ◽

2004 ◽

Author(s):

R.K. Scharien ◽

J.J. Yackel

Keyword(s):

Sea Ice ◽

First Year ◽

Ice Melt ◽

Melt Ponds ◽

Microwave Backscatter

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Ku-, X- and C-Band Microwave Backscatter Indices from Saline Snow Covers on Arctic First-Year Sea Ice

Remote Sensing ◽

10.3390/rs9070757 ◽

2017 ◽

Vol 9 (7) ◽

pp. 757 ◽

Cited By ~ 7

Author(s):

◽

Keyword(s):

Sea Ice ◽

First Year ◽

Microwave Backscatter

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Comparison of a coupled snow thermodynamic and radiative transfer model with in situ active microwave signatures of snow-covered smooth first-year sea ice

The Cryosphere ◽

10.5194/tc-9-2149-2015 ◽

2015 ◽

Vol 9 (6) ◽

pp. 2149-2161 ◽

Cited By ~ 7

Author(s):

M. C. Fuller ◽

T. Geldsetzer ◽

J. Yackel ◽

J. P. S. Gill

Keyword(s):

Sea Ice ◽

Reanalysis Data ◽

Physical Models ◽

Radiative Transfer Model ◽

Wave Radiation ◽

First Year ◽

Transfer Model ◽

Long Wave ◽

Microwave Backscatter

Abstract. Within the context of developing data inversion and assimilation techniques for C-band backscatter over sea ice, snow physical models may be used to drive backscatter models for comparison and optimization with satellite observations. Such modeling has the potential to enhance understanding of snow on sea-ice properties required for unambiguous interpretation of active microwave imagery. An end-to-end modeling suite is introduced, incorporating regional reanalysis data (NARR), a snow model (SNTHERM89.rev4), and a multilayer snow and ice active microwave backscatter model (MSIB). This modeling suite is assessed against measured snow on sea-ice geophysical properties and against measured active microwave backscatter. NARR data were input to the SNTHERM snow thermodynamic model in order to drive the MSIB model for comparison to detailed geophysical measurements and surface-based observations of C-band backscatter of snow on first-year sea ice. The NARR variables were correlated to available in situ measurements with the exception of long-wave incoming radiation and relative humidity, which impacted SNTHERM simulations of snow temperature. SNTHERM snow grain size and density were comparable to observations. The first assessment of the forward assimilation technique developed in this work required the application of in situ salinity profiles to one SNTHERM snow profile, which resulted in simulated backscatter close to that driven by in situ snow properties. In other test cases, the simulated backscatter remained 4–6 dB below observed for higher incidence angles and when compared to an average simulated backscatter of in situ end-member snow covers. Development of C-band inversion and assimilation schemes employing SNTHERM89.rev4 should consider sensitivity of the model to bias in incoming long-wave radiation, the effects of brine, and the inability of SNTHERM89.Rev4 to simulate water accumulation and refreezing at the bottom and mid-layers of the snowpack. These impact thermodynamic response, brine wicking and volume processes, snow dielectrics, and thus microwave backscatter from snow on first-year sea ice.

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Upwelling Irradiance below Sea Ice—PAR Intensities and Spectral Distributions

Journal of Marine Science and Engineering ◽

10.3390/jmse9080830 ◽

2021 ◽

Vol 9 (8) ◽

pp. 830

Author(s):

Lars Chresten Lund-Hansen ◽

Michael Bjerg-Nielsen ◽

Tanja Stratmann ◽

Ian Hawes ◽

Brian K. Sorrell

Keyword(s):

Sea Ice ◽

Snow Cover ◽

Daily Maximum ◽

First Year ◽

Ice Algae ◽

Sea Ice Algae ◽

Spectral Distributions ◽

And Performance ◽

Light Saturation Point ◽

Upwelling And Downwelling

Upwelling and downwelling spectral (320–920 nm) distributions and photosynthetic active radiation (PAR) intensities were measured below a first-year land-fast sea ice in a western Greenland fjord with and without a snow cover. Time-series of surface upwelling PAR, downwelling PAR, and under-ice PAR were also obtained. Spectral distributions of upwelling and downwelling irradiances were similar except for reduced intensities in the UV, the red, and NIR parts of the spectrum when the ice was snow-covered. Upwelling PAR amounted to about 10% of downwelling intensities, giving 5.1 µmol photons m−2 s−1 at the bottom of the ice with a snow cover and 8.2 µmol photons m−2 s−1 without. PAR partitioning analyses showed that the upwelling was related to scattering by suspended particles in the water column. A snow melt increased under-ice daily maximum downwelling PAR from 50 to 180 µmol photons m−2 s−1 and overall under-ice PAR of 55 and 198 µmol photons m−2 s−1 with 10% upwelling. It is concluded that upwelling PAR below sea ice might be an important factor regarding sea ice algae photophysiology and performance with a 10% higher PAR; specifically when PAR > Ek the light saturation point of the sea ice algae.

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Comparison of a coupled snow thermodynamic and radiative transfer model with in-situ active microwave signatures of snow-covered smooth first-year sea ice

The Cryosphere Discussions ◽

10.5194/tcd-9-3293-2015 ◽

2015 ◽

Vol 9 (3) ◽

pp. 3293-3329

Author(s):

M. C. Fuller ◽

T. Geldsetzer ◽

J. Yackel ◽

J. P. S. Gill

Keyword(s):

Sea Ice ◽

Longwave Radiation ◽

Reanalysis Data ◽

Physical Models ◽

Radiative Transfer Model ◽

First Year ◽

Transfer Model ◽

Data Inversion ◽

Microwave Backscatter

Abstract. Within the context of developing data inversion and assimilation techniques for C-band backscatter over sea ice, snow physical models may be used to drive backscatter models for comparison and optimization with satellite observations. Such modeling has potential to enhance understanding of snow on sea ice properties required for unambiguous interpretation of active microwave imagery. An end-to-end modeling suite is introduced, incorporating regional reanalysis data (NARR), a snow model (SNTHERM), and a multi-layer snow and ice active microwave backscatter model (MSIB). This modeling suite is assessed against measured snow on sea ice geophysical properties, and against measured active microwave backscatter. NARR data was input to the SNTHERM snow thermodynamic model, in order to drive the MISB model for comparison to detailed geophysical measurements and surface-based observations of C-band backscatter of snow on first-year sea ice. The NARR data was well correlated to available in-situ measurements, with the exception of long wave incoming radiation and relative humidity, which impacted SNTHERM simulations of snow temperature. SNTHERM reasonably represented snow grain size and density when compared to observations. The application of in-situ salinity profiles to one SNTHERM snow profile resulted in simulated backscatter close to that driven by in-situ snow properties. In other test cases, the simulated backscatter remained 4 to 6 dB below observed for higher incidence angles, and when compared to an average simulated backscatter of in-situ end-member snowcovers. Development of C-band inversion and assimilation schemes employing SNTHERM89.rev4 should consider sensitivity of the model to bias in incoming longwave radiation, the effects of brine, and the inability of SNTHERM89.Rev4 to simulate water accumulation and refreezing at the bottom and mid-layers of the snowpack with regard to thermodynamic response, brine wicking and volume processes, snow dielectrics, and microwave backscatter from snow on first-year sea-ice.

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