Evaluation of AMSR-E snow depth product over East Antarctic sea ice using in situ measurements and aerial photography

Abstract. Knowledge of the snow depth distribution on Antarctic sea ice is poor but is critical to obtaining sea ice thickness from satellite altimetry measurements of freeboard. We examine the usefulness of various snow products to provide snow depth information over Antarctic fast ice with a focus on a novel approach using a high-resolution numerical snow accumulation model (SnowModel). We compare this model to results from ECMWF ERA-Interim precipitation, EOS Aqua AMSR-E passive microwave snow depths and in situ measurements at the end of the sea ice growth season. The fast ice was segmented into three areas by fastening date and the onset of snow accumulation was calibrated to these dates. SnowModel falls within 0.02 m snow water equivalent (swe) of in situ measurements across the entire study area, but exhibits deviations of 0.05 m swe from these measurements in the east where large topographic features appear to have caused a positive bias in snow depth. AMSR-E provides swe values half that of SnowModel for the majority of the sea ice growth season. The coarser resolution ERA-Interim, not segmented for sea ice freeze up area reveals a mean swe value 0.01 m higher than in situ measurements. These various snow datasets and in situ information are used to infer sea ice thickness in combination with CryoSat-2 (CS-2) freeboard data. CS-2 is capable of capturing the seasonal trend of sea ice freeboard growth but thickness results are highly dependent on the assumptions involved in separating snow and ice freeboard. With various assumptions about the radar penetration into the snow cover, the sea ice thickness estimates vary by up to 2 m. However, we find the best agreement between CS-2 derived and in situ thickness when a radar penetration of 0.05-0.10 m into the snow cover is assumed.

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Snow-driven uncertainty in CryoSat-2-derived Antarctic sea ice thickness – insights from McMurdo Sound

The Cryosphere ◽

10.5194/tc-13-1409-2019 ◽

2019 ◽

Vol 13 (4) ◽

pp. 1409-1422

Author(s):

Daniel Price ◽

Iman Soltanzadeh ◽

Wolfgang Rack ◽

Ethan Dale

Keyword(s):

Sea Ice ◽

Snow Depth ◽

Snow Accumulation ◽

In Situ Measurements ◽

Ice Thickness ◽

Growth Season ◽

Mcmurdo Sound ◽

Sea Ice Thickness ◽

Antarctic Sea Ice

Abstract. Knowledge of the snow depth distribution on Antarctic sea ice is poor but is critical to obtaining sea ice thickness from satellite altimetry measurements of the freeboard. We examine the usefulness of various snow products to provide snow depth information over Antarctic fast ice in McMurdo Sound with a focus on a novel approach using a high-resolution numerical snow accumulation model (SnowModel). We compare this model to results from ECMWF ERA-Interim precipitation, EOS Aqua AMSR-E passive microwave snow depths and in situ measurements at the end of the sea ice growth season in 2011. The fast ice was segmented into three areas by fastening date and the onset of snow accumulation was calibrated to these dates. SnowModel captures the spatial snow distribution gradient in McMurdo Sound and falls within 2 cm snow water equivalent (s.w.e) of in situ measurements across the entire study area. However, it exhibits deviations of 5 cm s.w.e. from these measurements in the east where the effect of local topographic features has caused an overestimate of snow depth in the model. AMSR-E provides s.w.e. values half that of SnowModel for the majority of the sea ice growth season. The coarser-resolution ERA-Interim produces a very high mean s.w.e. value 20 cm higher than the in situ measurements. These various snow datasets and in situ information are used to infer sea ice thickness in combination with CryoSat-2 (CS-2) freeboard data. CS-2 is capable of capturing the seasonal trend of sea ice freeboard growth but thickness results are highly dependent on what interface the retracked CS-2 height is assumed to represent. Because of this ambiguity we vary the proportion of ice and snow that represents the freeboard – a mathematical alteration of the radar penetration into the snow cover – and assess this uncertainty in McMurdo Sound. The ranges in sea ice thickness uncertainty within these bounds, as means of the entire growth season, are 1.08, 4.94 and 1.03 m for SnowModel, ERA-Interim and AMSR-E respectively. Using an interpolated in situ snow dataset we find the best agreement between CS-2-derived and in situ thickness when this interface is assumed to be 0.07 m below the snow surface.

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In situ measurements of the direct-current conductivity of Antarctic Sea ice: implications for airborne electromagnetic Sounding of Sea-ice thickness

Annals of Glaciology ◽

10.3189/172756406781811772 ◽

2006 ◽

Vol 44 ◽

pp. 217-223 ◽

Cited By ~ 15

Author(s):

J.E. Reid ◽

A. Pfaffling ◽

A.P. Worby ◽

J.R. Bishop

Keyword(s):

Sea Ice ◽

Direct Current ◽

Sea Water ◽

Vertical Direction ◽

In Situ Measurements ◽

Ice Thickness ◽

Sea Ice Thickness ◽

Antarctic Sea Ice ◽

Direct Current Conductivity

AbstractAirborne, Ship-borne and Surface low-frequency electromagnetic (EM) methods have become widely applied to measure Sea-ice thickness. EM responses measured over Sea ice depend mainly on the Sea-water conductivity and on the height of the Sensor above the Sea-ice–sea-water interface, but may be Sensitive to the Sea-ice conductivity at high excitation frequencies. We have conducted in Situ measurements of direct-current conductivity of Sea ice using Standard geophysical geoelectrical methods. Sea-ice thickness estimated from the geoelectrical Sounding data was found to be consistently underestimated due to the pronounced vertical-to-horizontal conductivity anisotropy present in level Sea ice. At five Sites, it was possible to determine the approximate horizontal and vertical conductivities from the Sounding data. The average horizontal conductivity was found to be 0.017 Sm–1, and that in the vertical direction to be 9–12 times higher. EM measurements over level Sea ice are Sensitive only to the horizontal conductivity. Numerical modelling has Shown that the assumption of zero Sea-ice conductivity in interpretation of airborne EM data results in a negligible error in interpreted thickness for typical level Antarctic Sea ice.

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In situ measurements of the resistivity of Antarctic sea ice

Cold Regions Science and Technology ◽

10.1016/0165-232x(86)90041-8 ◽

1986 ◽

Vol 12 (3) ◽

pp. 285-290 ◽

Cited By ~ 16

Author(s):

R.G. Buckley ◽

M.P. Staines ◽

W.H. Robinson

Keyword(s):

Sea Ice ◽

In Situ Measurements ◽

Antarctic Sea Ice

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In-situ measurements of the low frequency dielectric permittivity of first-year Antarctic sea ice

Cold Regions Science and Technology ◽

10.1016/j.coldregions.2012.07.008 ◽

2012 ◽

Vol 83-84 ◽

pp. 139-146 ◽

Cited By ~ 5

Author(s):

M. Ingham ◽

G. Gouws ◽

S. Buchanan ◽

R. Brown ◽

T. Haskell

Keyword(s):

Dielectric Permittivity ◽

Sea Ice ◽

Low Frequency ◽

In Situ Measurements ◽

First Year ◽

Antarctic Sea Ice

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Accuracy assessment of sea-ice concentrations from MODIS using in-situ measurements

Remote Sensing of Environment ◽

10.1016/j.rse.2004.12.004 ◽

2005 ◽

Vol 95 (2) ◽

pp. 139-149 ◽

Cited By ~ 18

Author(s):

C. Drüe ◽

G. Heinemann

Keyword(s):

Sea Ice ◽

Accuracy Assessment ◽

In Situ Measurements

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Validation of modeled snow properties in Afghanistan, Pakistan, and Tajikistan

10.5194/tc-2019-150 ◽

2019 ◽

Author(s):

Edward H. Bair ◽

Karl Rittger ◽

Jawairia A. Ahmad ◽

Doug Chabot

Keyword(s):

Snow Depth ◽

Snow Water Equivalent ◽

Median Number ◽

In Situ Measurements ◽

Snow Properties ◽

Wide Range ◽

Spatial Estimates ◽

Snow Water ◽

Critical Layers

Abstract. Ice and snowmelt feed the Indus and Amu Darya rivers, yet there are limited in situ measurements of these resources. Previous work in the region has shown promise using snow water equivalent (SWE) reconstruction, which requires no in situ measurements, but validation has been a problem until recently when we were provided with daily manual snow depth measurements from Afghanistan, Tajikistan, and Pakistan by the Aga Khan Agency for Habitat (AKAH). For each station, accumulated precipitation and SWE were derived from snow depth using the SNOWPACK model. High-resolution (500 m) reconstructed SWE estimates from the ParBal model were then compared to the modeled SWE at the stations. The Alpine3D model was then used to create spatial estimates at 25 km to compare with estimates from other snow models. Additionally, the coupled SNOWPACK and Alpine3D system has the advantage of simulating snow profiles, which provide stability information. Following previous work, the median number of critical layers and percentage of facets across all of the pixels containing the AKAH stations was computed. For SWE at the point scale, the reconstructed estimates showed a bias of −42 mm (−19 %) at the peak. For the coarser spatial SWE estimates, the various models showed a wide range, with reconstruction being on the lower end. For stratigraphy, a heavily faceted snowpack is observed in both years, but 2018, a dry year, according to most of the models, showed more critical layers that persisted for a longer period.

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2 – 8 GHz FMCW radar for estimating snow depth on antarctic sea ice

2008 International Conference on Radar ◽

10.1109/radar.2008.4653931 ◽

2008 ◽

Cited By ~ 4

Author(s):

N. Galin ◽

A. Worby ◽

R. Massom ◽

G. Brooker ◽

C. Leuschen ◽

...

Keyword(s):

Sea Ice ◽

Snow Depth ◽

Fmcw Radar ◽

Antarctic Sea Ice

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Evolution of supercooling under coastal Antarctic sea ice during winter

Antarctic Science ◽

10.1017/s0954102011000265 ◽

2011 ◽

Vol 23 (4) ◽

pp. 399-409 ◽

Cited By ~ 30

Author(s):

Gregory H. Leonard ◽

Patricia J. Langhorne ◽

Michael J.M. Williams ◽

Ross Vennell ◽

Craig R. Purdie ◽

...

Keyword(s):

Sea Ice ◽

Freezing Point ◽

Circulation Pattern ◽

Late Winter ◽

Ice Shelf ◽

Mcmurdo Sound ◽

The North ◽

Antarctic Sea Ice ◽

Ice Production

AbstractHere we describe the evolution through winter of a layer of in situ supercooled water beneath the sea ice at a site close to the McMurdo Ice Shelf. From early winter (May), the temperature of the upper water column was below its surface freezing point, implying contact with an ice shelf at depth. By late winter the supercooled layer was c. 40 m deep with a maximum supercooling of c. 25 mK located 1–2 m below the sea ice-water interface. Transitory in situ supercooling events were also observed, one lasting c. 17 hours and reaching a depth of 70 m. In spite of these very low temperatures the isotopic composition of the water was relatively heavy, suggesting little glacial melt. Further, the water's temperature-salinity signature indicates contributions to water mass properties from High Salinity Shelf Water produced in areas of high sea ice production to the north of McMurdo Sound. Our measurements imply the existence of a heat sink beneath the supercooled layer that extracts heat from the ocean to thicken and cool this layer and contributes to the thickness of the sea ice cover. This sink is linked to the circulation pattern of the McMurdo Sound.

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