Snow Property Controls on Modeled Ku-Band Altimeter Estimates of First-Year Sea Ice Thickness: Case Studies From the Canadian and Norwegian Arctic

Nandan, Vishnu; Scharien, Randall K.; Geldsetzer, Torsten; Kwok, R.; Yackel, John J.; Mahmud, Mallik; Rösel, Anja; Tonboe, Rasmus; Granskog, Mats A.; Willatt, Rosemary; Stroeve, Julienne; Nomura, Daïki; Frey, M. M.

doi:10.1109/jstars.2020.2966432

Cited by 36 publications

(49 citation statements)

References 66 publications

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“…Kroisleitner et al, 2018), but usage of satellite altimetry in this context remains unexplored. Signal interaction with vegetation limits the applicability of Ku-and Ka-bands for soil observations regarding freeze and thaw status (Park et al, 2011) as well as surface height. Wider use of altimetry for snow and permafrost applications requires higher spatial resolution and temporal coverage than what is available to Figure 2.…”

Section: Snow On Land and Permafrostmentioning

confidence: 99%

The Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) high-priority candidate mission

et al. 2020

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Abstract. The Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) mission is one of six high-priority candidate missions (HPCMs) under consideration by the European Commission to enlarge the Copernicus Space Component. Together, the high-priority candidate missions fill gaps in the measurement capability of the existing Copernicus Space Component to address emerging and urgent user requirements in relation to monitoring anthropogenic CO2 emissions, polar environments, and land surfaces. The ambition is to enlarge the Copernicus Space Component with the high-priority candidate missions in the mid-2020s to provide enhanced continuity of services in synergy with the next generation of the existing Copernicus Sentinel missions. CRISTAL will carry a dual-frequency synthetic-aperture radar altimeter as its primary payload for measuring surface height and a passive microwave radiometer to support atmospheric corrections and surface-type classification. The altimeter will have interferometric capabilities at Ku-band for improved ground resolution and a second (non-interferometric) Ka-band frequency to provide information on snow layer properties. This paper outlines the user consultations that have supported expansion of the Copernicus Space Component to include the high-priority candidate missions, describes the primary and secondary objectives of the CRISTAL mission, identifies the key contributions the CRISTAL mission will make, and presents a concept – as far as it is already defined – for the mission payload.

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Section: Snow On Land and Permafrostmentioning

confidence: 99%

The Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) high-priority candidate mission

et al. 2020

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“…due to ice lenses/crusts), radar signals undergo absorption within the snow volume (e.g., Kwok and Maksym, 2014;Ricker et al, 2015). Recent studies suggest reduced signal penetration into the snow pack, with a more diffuse snow/sea ice interface, on both Arctic and Antarctic sea ice (Gerland et al, 2013;Kwok and Kacimi, 2018), especially if the snow pack is saline (Nandan et al, 2020;Nandan et al, 2017) or very deep with ice lenses present (King et al, 2018). In addition, deep snow pushes the ice surface below the water level, leading to negative freeboard and induces flooding and slushy, snow-ice formation in the basal layers of the snow pack, which, when measured with a radar altimeter system, can result in a dominant scattering horizon above the true snow/ice interface (Nandan et al, 2020), and hence an overestimation of ice freeboard and thus sea ice thickness, and an underestimate of total snow thickness.…”

Section: Discussionmentioning

confidence: 99%

“…On FYI, overlying snow also wicks brine upwards from the sea ice surface during freeze-up, producing saline snow layers, predominately observed in the bottom-most 0.06-0.08 m of the snow pack (Drinkwater and Crocker, 1988;Geldsetzer et al, 2009;Nandan et al, 2016Nandan et al, , 2017Nandan et al, , 2020. Sea ice salinity observations from the 1-m thick FYI floe, collected on 5 and 23…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies (Barber et al, 1998;Barber and Nghiem, 1999;Nghiem et al, 1995;Geldsetzer et al, 2009;Nandan et al, 2017;Nandan et al, 2020) have reported the impact of saline snow on FYI, which alters the geophysical, thermodynamic, dielectric and radar scattering properties of the snow cover, thereby impacting radar signal penetration through the snow pack. Nandan et al (2017) and (2020) showed that a saline snow cover on a FYI setting, induced by upward brine wicking from the sea ice surface, shifted the main radar scattering horizon away from the snow/sea ice interface by up to 0.07 m, and weakened the signal arising from the saline scattering horizon.…”

Section: Discussionmentioning

confidence: 99%

“…In recent years, a significant change towards thinner ice with thicker snow cover (Renner et al, 2014;Rösel et al, 2018) has been observed in this region, caused by an increase in intense storm events and associated precipitation in this area (Woods and Caballero, 2016;Graham et al, 2017;Rinke et al, 2017). In addition, previous studies indicate that radar signal penetration through the snow pack might be lower under certain geophysical snow-ice conditions in this area (Gerland et al, 2013;King et al, 2018;Nandan et al, 2020) and also in the Weddell Sea ice in the Antarctic (Kwok and Kacimi, 2018). Snow and ice conditions in this region differ to those in the Canada Basin and central Arctic (e.g., Webster et al, 2014;2018), and they have been found to induce substantial negative freeboards with subsequent flooding of the snow pack, more akin to the conditions in the seasonal ice pack of the Southern Ocean (Massom et al, 2001).…”

Section: Introductionmentioning

confidence: 91%

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Implications of surface flooding on airborne thickness measurements of snow on sea ice

Rösel

Farrell

Nandan

et al. 2020

Preprint

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Abstract. Snow thickness observations from airborne snow radars, such as the NASA’s Operation IceBridge (OIB) mission, have recently been used in altimeter-derived sea ice thickness estimates, as well as for model parameterization. A number of validation studies comparing airborne and in situ snow thickness measurements have been conducted in the western Arctic Ocean, demonstrating the utility of the airborne data. However, there have been no validation studies in the Atlantic sector of the Arctic. Recent observations in this region suggest a significant and predominant shift towards a snow-ice regime, caused by deep snow on thin sea ice. During the Norwegian young sea ICE expedition (N-ICE2015) in the area north of Svalbard, a validation study was conducted on March 19, 2015, during which ground truth data were collected during an OIB overflight. Snow and ice thickness measurements were obtained across a two dimensional (2-D) 400 m × 60 m grid. Additional snow and ice thickness measurements collected in situ from adjacent ice floes helped to place the measurements obtained at the gridded survey field site into a more regional context. Widespread negative freeboards and flooding of the snow pack were observed during the N-ICE2015 expedition, due to the general situation of thick snow on relatively thin sea ice. These conditions caused brine wicking and saturation into the basal snow layers, causing more diffuse scattering and influenced the airborne radar signal to detect the radar main scattering horizon well above the snow/sea ice interface, resulting in a subsequent underestimation of total snow thickness, if only radar-based information is used. The average airborne snow thickness was 0.16 m thinner than that measured in situ at the 2-D survey field. Regional data within 10 km of the 2-D survey field suggested however a smaller deviation between average airborne and in situ snow thickness, a 0.06 m underestimate in snow thickness by the airborne radar, which is close to the resolution limit of the OIB snow radar system. Our results also show a broad snow thickness distribution, indicating a large spatial variability in snow across the region. Differences between the airborne snow radar and in situ measurements fell within the standard deviation of the in situ data (0.15–0.18 m). Our results suggest that, with frequent flooding of the snow-ice interface in specific regions of the Arctic in the future, it may result in an underestimate of snow thickness or an overestimate of ice freeboard, measured from radar altimetry, thereby affecting the accuracy of sea ice thickness estimates.

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Snow on sea ice

Mallett,

Nandan,

Macfarlane

et al. 2024

Reference Module in Earth Systems and Environmental Sciences

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Snow Property Controls on Modeled Ku-Band Altimeter Estimates of First-Year Sea Ice Thickness: Case Studies From the Canadian and Norwegian Arctic

Abstract: Uncertainty in snow properties impacts the accuracy of Arctic sea ice thickness estimates from radar altimetry. On firstyear sea ice (FYI), spatiotemporal variations in snow properties

Cited by 36 publications

References 66 publications

The Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) high-priority candidate mission

The Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) high-priority candidate mission

Implications of surface flooding on airborne thickness measurements of snow on sea ice

Snow on sea ice

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