Characterization of snow on floating ice and case studies of brightness temperature changes during the onset of melt

Garrity, C.

doi:10.1029/gm068p0313

Cited by 48 publications

(46 citation statements)

References 23 publications

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“…Based on the same laboratory experiments, Beaven et al (1995) showed that the radar return originates at the snow/ice interface, and snow influence -as long as the snow is dry and cold -can be neglected. Dielectric properties of water have been found to dominate over those of dry snow for volumetric water contents of 1 % (Howell et al, 2005), which can occur at temperatures above −5 • C (Garrity, 1992). Based on forward modeling of the reflected radar signal, Makynen and Hallikainen (2009) found that this wet snow cannot be neglected because it alters the waveform shape substantially by adding more volume scattering to the power echo.…”

Section: Discussionmentioning

confidence: 99%

Waveform classification of airborne synthetic aperture radar altimeter over Arctic sea ice

Zygmuntowska¹,

Khvorostovsky²,

Helm

et al. 2013

The Cryosphere

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Abstract. Sea ice thickness is one of the most sensitive variables in the Arctic climate system. In order to quantify changes in sea ice thickness, CryoSat-2 was launched in 2010 carrying a Ku-band radar altimeter (SIRAL) designed to measure sea ice freeboard with a few centimeters accuracy. The instrument uses the synthetic aperture radar technique providing signals with a resolution of about 300 m along track. In this study, airborne Ku-band radar altimeter data over different sea ice types have been analyzed. A set of parameters has been defined to characterize the differences in strength and width of the returned power waveforms. With a Bayesian-based method, it is possible to classify about 80 % of the waveforms from three parameters: maximum of the returned power waveform, the trailing edge width and pulse peakiness. Furthermore, the maximum of the power waveform can be used to reduce the number of false detections of leads, compared to the widely used pulse peakiness parameter. For the pulse peakiness the false classification rate is 12.6 % while for the power maximum it is reduced to 6.5 %. The ability to distinguish between different ice types and leads allows us to improve the freeboard retrieval and the conversion from freeboard into sea ice thickness, where surface type dependent values for the sea ice density and snow load can be used.

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Section: Discussionmentioning

confidence: 99%

Waveform classification of airborne synthetic aperture radar altimeter over Arctic sea ice

Zygmuntowska¹,

Khvorostovsky²,

Helm

et al. 2013

The Cryosphere

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“…In the Arctic, the stage of advanced melt (Livingstone et al, 1997) characterized by persistent melt water saturated snow is dominant during summer (Comiso and Kwok, 1996;Garrity, 1992). However, diurnal freeze-thaw cycles prevail on Antarctic sea ice .…”

Section: S Willmes Et Al: Microwave Emissivity Variability Of Snow-mentioning

confidence: 99%

The microwave emissivity variability of snow covered first-year sea ice from late winter to early summer: a model study

2014

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Abstract. Satellite observations of microwave brightness temperatures between 19 GHz and 85 GHz are the main data sources for operational sea-ice monitoring and retrieval of ice concentrations. However, microwave brightness temperatures depend on the emissivity of snow and ice, which is subject to pronounced seasonal variations and shows significant hemispheric contrasts. These mainly arise from differences in the rate and strength of snow metamorphism and melt. We here use the thermodynamic snow model SNTHERM forced by European Re-Analysis (ERA) interim data and the Microwave Emission Model of Layered Snowpacks (MEMLS), to calculate the sea-ice surface emissivity and to identify

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“…Numerous studies in Antarctica (Eicken et al, 1994;Massom et al, 2002) have shown that salinities up to 5 psu could often be found in snow at a height of 20 cm above the sea ice. More limited studies in the Arctic have also shown that a slush layer was present at the surface of Arctic ice (Garrity, 1992) from which the capillary motion of a brine can be inferred. Direct salinity measurements (Eicken et al, 2002) have also shown that high salinities could be found in snow on sea ice.…”

Section: Introductionmentioning

confidence: 99%

The origin of sea salt in snow on Arctic sea ice and in coastal regions

et al. 2004

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Abstract. Snow, through its trace constituents, can have a major impact on lower tropospheric chemistry, as evidenced by ozone depletion events (ODEs) in oceanic polar areas. These ODEs are caused by the chemistry of bromine compounds that originate from sea salt bromide. Bromide may be supplied to the snow surface by upward migration from sea ice, by frost flowers being wind-blown to the snow surface, or by wind-transported aerosol generated by sea spray. We investigate here the relative importance of these processes by analyzing ions in snow near Alert and Ny-Ålesund (Canadian and European high Arctic) in winter and spring. Vertical ionic profiles in the snowpack on sea ice are measured to test upward migration of sea salt ions and to seek evidence for ion fractionation processes. Time series of the ionic composition of surface snow layers are investigated to quantify wind-transported ions. Upward migration of unfractionated sea salt to heights of at least 17 cm was observed in winter snow, leading to Cl − concentration of several hundred µM. Upward migration thus has the potential to supply ions to surface snow layers. Time series show that wind can deposit aerosols to the top few cm of the snow, leading also to Cl − concentrations of several hundred µM, so that both diffusion from sea ice and wind transport can significantly contribute ions to snow. At Ny-Ålesund, sea salt transported by wind was unfractionated, implying that it comes from sea spray rather than frost flowers. Estimations based on our results suggest that the marine snowpack contains about 10 times more Na + than the frost flowers, so that both the marine snowpack and frost flowers need to be considered as sea salt sources. Our data suggest that ozone depletion chemistry can significantly enhance the Br − content of snow. We speculate that this can also take place in coastal regions and contribute to propagate ODEs inland. Finally, we stress the need to measure snow physical parameters such as permeability and specific surface area to understand quantitatively changes in snow chemistry.

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Characterization of snow on floating ice and case studies of brightness temperature changes during the onset of melt

Cited by 48 publications

References 23 publications

Waveform classification of airborne synthetic aperture radar altimeter over Arctic sea ice

Waveform classification of airborne synthetic aperture radar altimeter over Arctic sea ice

The microwave emissivity variability of snow covered first-year sea ice from late winter to early summer: a model study

The origin of sea salt in snow on Arctic sea ice and in coastal regions

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