Synoptic Variability in Satellite Altimeter‐Derived Radar Freeboard of Arctic Sea Ice

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(2)

Published: Jan. 9, 2023

Abstract Satellite observations of sea ice freeboard are integral to the estimation thickness. It is commonly assumed that radar pulses from satellite‐mounted Ku‐band altimeters penetrate through snow and reflect snow‐ice interface. We would therefore expect a negative correlation between accumulation measurements, as increased loading weighs floe down. In this study we produce daily resolution products CryoSat‐2 Sentinel‐3 via recently developed optimal interpolation scheme. find statistically significant ( p < 0.05) positive correlations anomalies modeled accumulation. This suggests that, in period after snowfall, not scattering interface assumed. Our results offer satellite‐based evidence winter above interface, violating key assumption thickness retrievals.

Language: Английский

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Different mechanisms of Arctic first-year sea-ice ridge consolidation observed during the MOSAiC expedition

Elementa Science of the Anthropocene, Journal Year: 2023, Volume and Issue: 11(1)

Published: Jan. 1, 2023

Sea-ice ridges constitute a large fraction of the ice volume in Arctic Ocean, yet we know little about evolution these masses. Here examine thermal and morphological an first-year sea-ice ridge, from its formation to advanced melt. Initially mean keel depth was 5.6 m sail height 0.7 m. The initial rubble macroporosity (fraction seawater filled voids) estimated at 29% drilling 43%–46% buoy temperature. From January until mid-April, ridge consolidated slowly by heat loss atmosphere total layer growth during this phase mid-April mid-June, there sudden increase consolidation rate despite no conductive flux. We surmise change related decreased due transport snow-slush via adjacent open leads. In period, thickness increased 2.1 At peak melt June–July suggest that refreezing surface snow meltwater (the latter only 15% consolidation). used morphology parameters calculate hydrostatic equilibrium obtained more accurate estimate actual keel, correcting 2.2 2.8 for average consolidation. This approach also allowed us 0.3 m, June–July, accompanied decrease draft 0.9 An mass balance indicated which rapid mode April June. By resulted drastic interior while flanks had or macroporosity. These results are important understanding role keels as sources sinks sanctuary ice-associated organisms pack ice.

Language: Английский

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Impact of measured and simulated tundra snowpack properties on heat transfer

˜The œcryosphere, Journal Year: 2022, Volume and Issue: 16(10), P. 4201 - 4222

Published: Oct. 11, 2022

Abstract. Snowpack microstructure controls the transfer of heat to, as well temperature of, underlying soils. In situ measurements snow and soil properties from four field campaigns during two winters (March November 2018, January March 2019) were compared to an ensemble CLM5.0 (Community Land Model) simulations, at Trail Valley Creek, Northwest Territories, Canada. Snow micropenetrometer profiles allowed for snowpack density thermal conductivity be derived higher vertical resolution (1.25 mm) a larger sample size (n=1050) traditional snowpit observations (3 cm resolution; n=115). Comparing with simulations shows CLM overestimated by factor 3, leading cold bias in wintertime temperatures (RMSE=5.8 ∘C). Two different approaches taken reduce this bias: alternative parameterisations application correction factor. All evaluated improved temperatures, that Sturm et al. (1997) having greatest impact (RMSE=2.5 The required is strongly related depth (R2=0.77,RMSE=0.066) thus differs between seasons, limiting applicability such approach. Improving simulated corresponding flux important, are important control on subnivean respiration hence Arctic winter carbon fluxes budgets.

Language: Английский

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Rain on snow (ROS) understudied in sea ice remote sensing: a multi-sensor analysis of ROS during MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate)

˜The œcryosphere, Journal Year: 2022, Volume and Issue: 16(10), P. 4223 - 4250

Published: Oct. 11, 2022

Abstract. Arctic rain on snow (ROS) deposits liquid water onto existing snowpacks. Upon refreezing, this can form icy crusts at the surface or within snowpack. By altering radar backscatter and microwave emissivity, ROS over sea ice influence accuracy of variables retrieved from satellite altimetry, scatterometers, passive radiometers. During Ocean MOSAiC (Multidisciplinary drifting Observatory for Study Climate) expedition, there was an unprecedented opportunity to observe a event using in situ active instruments similar those deployed platforms. accumulation snowpack increased melt, 4-fold decrease energy returned Ku- Ka-bands. After refroze layers formed, followed by 6-fold increase energy. Besides backscatter, analysis waveforms shows waveform shape changed response refreezing. Microwave emissivity 19 89 GHz with increasing content decreased as refroze, yet subsequent altered polarization difference. Corresponding CryoSat-2 well AMSR2 brightness temperatures further that refreeze were significant enough impact returns. Our provides first detailed impacts refreezing both observations, providing important baseline knowledge detecting assessing their satellite-derived variables.

Language: Английский

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Winter Arctic sea ice thickness from ICESat-2: upgrades to freeboard and snow loading estimates and an assessment of the first three winters of data collection

˜The œcryosphere, Journal Year: 2023, Volume and Issue: 17(1), P. 127 - 156

Published: Jan. 13, 2023

Abstract. NASA's ICESat-2 mission has provided near-continuous, high-resolution estimates of sea ice freeboard across both hemispheres since data collection started in October 2018. This study provides an impact assessment upgrades to the (ATL10) and NASA Eulerian Snow On Sea Ice Model (NESOSIM) snow loading on winter Arctic thickness. Misclassified leads were removed from algorithm third release (rel003) ATL10, which generally results increase freeboards compared rel002 data. The thickness increases due increased ATL10 improved comparisons Inner Ocean with ESA's CryoSat-2. upgrade NESOSIM v1.0 v1.1 only small changes depth density have a less significant rel003 changes. updated monthly gridded are validated against draft measurements obtained by upward-looking sonar moorings deployed Beaufort Sea, showing strong agreement (r2 0.87, differences 11 ± 20 cm). seasonal cycle mean shows good various CryoSat-2 products (and merged ICESat-2–CryoSat-2 product) PIOMAS (Pan-Arctic Ice-Ocean Modeling Assimilation System). Finally, conditions over past three seasons (November 2018–April 2021) presented discussed, including 50 cm decline multiyear negligible interannual first-year ice. Interannual provide notable retrievals regional scales. Our analysis is online Jupyter Book format transparency user engagement our

Language: Английский

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Wind redistribution of snow impacts the Ka- and Ku-band radar signatures of Arctic sea ice

˜The œcryosphere, Journal Year: 2023, Volume and Issue: 17(6), P. 2211 - 2229

Published: June 2, 2023

Abstract. Wind-driven redistribution of snow on sea ice alters its topography and microstructure, yet the impact these processes radar signatures is poorly understood. Here, we examine effects over Arctic waveforms backscatter obtained from a surface-based, fully polarimetric Ka- Ku-band at incidence angles between 0∘ (nadir) 50∘. Two wind events in November 2019 during Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition are evaluated. During both events, changes coefficients nadir observed, coincident with surface measured by terrestrial laser scanner. At frequencies, caused densification uppermost layers, increasing scattering air–snow interface prevalence as dominant surface. The waveform data also detected presence previous interfaces, buried beneath newly deposited snow. additional interfaces could therefore affect range retrieved satellite altimeters. With angles, relative contribution decreases, snow–sea increases. Relative to pre-wind event conditions, azimuthally averaged increases up 8 dB (Ka-band) 5 (Ku-band). Results show substantial variability within scan area all polarizations, response speed direction. Our results that compaction need be accounted interpret airborne measurements snow-covered ice.

Language: Английский

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Linking scales of sea ice surface topography: evaluation of ICESat-2 measurements with coincident helicopter laser scanning during MOSAiC

˜The œcryosphere, Journal Year: 2023, Volume and Issue: 17(3), P. 1411 - 1429

Published: March 31, 2023

Abstract. Information about sea ice surface topography and related deformation is crucial for studies of mass balance, modeling, ship navigation through the pack. The Ice, Cloud, land Elevation Satellite-2 (ICESat-2), part National Aeronautics Space Administration (NASA) Earth Observing System, has been on orbit over 4 years, sensing with six laser beams capable capturing individual features such as pressure ridges. To assess capabilities uncertainties ICESat-2 products, coincident high-resolution measurements are required. During yearlong Multidisciplinary drifting Observatory Study Arctic Climate (MOSAiC) expedition in Ocean, we successfully carried out a underflight helicopter-based airborne scanner (ALS), achieving an overlap more than 100 km. Despite comparably short data set, centimeter-scale ALS can be used to evaluate performance products. Our goal investigate how roughness represented different products well sensitive leads small cracks cover. Here, compare ICESat-2's primary height product, ATL07, high-fidelity elevation product developed by University Maryland (UMD). By applying ridge-detection algorithm, find that 16 % (4 %) number obstacles set found using strong (weak) center beam ATL07. Significantly higher detection rates 42 (30 achieved when UMD product. While only one lead indicated ATL07 underflight, reveals many small, narrow, partly open appear overlooked

Language: Английский

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High-resolution repeat topography of drifting ice floes in the Arctic Ocean from terrestrial laser scanning

Scientific Data, Journal Year: 2024, Volume and Issue: 11(1)

Published: Jan. 13, 2024

Snow and ice topography impact are impacted by fluxes of mass, energy, momentum in Arctic sea ice. We measured the on approximately a 0.5 km

Language: Английский

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Nudging allows direct evaluation of coupled climate models with in situ observations: a case study from the MOSAiC expedition

Geoscientific model development, Journal Year: 2023, Volume and Issue: 16(7), P. 1857 - 1873

Published: April 4, 2023

Abstract. Comparing the output of general circulation models to observations is essential for assessing and improving quality models. While numerical weather prediction are routinely assessed against a large array observations, comparing climate usually requires long time series build robust statistics. Here, we show that by nudging large-scale atmospheric in coupled models, model can be compared local individual days. We illustrate this three during period April 2020 when warm air intrusion reached MOSAiC (Multidisciplinary drifting Observatory Study Arctic Climate) expedition central Arctic. Radiosondes, cloud remote sensing surface flux from serve as reference observations. The AWI-CM1/ECHAM AWI-CM3/IFS miss diurnal cycle temperature spring, likely because both assume snowpack on ice have uniform temperature. CAM6, uses layers represent snow temperature, represents more realistically. During cold dry with pervasive thin mixed-phase clouds, only produces partial cover overestimates downwelling shortwave radiation at surface. closed but misses liquid water. Our results observed state allows meaningful comparison even short-term observational campaigns. suggest simplify accelerate pathway improvements substantially extends range suitable evaluation.

Language: Английский

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Sea ice concentration satellite retrievals influenced by surface changes due to warm air intrusions: A case study from the MOSAiC expedition

Elementa Science of the Anthropocene, Journal Year: 2023, Volume and Issue: 11(1)

Published: Jan. 1, 2023

Warm air intrusions over Arctic sea ice can change the snow and surface conditions rapidly alter concentration (SIC) estimates derived from satellite-based microwave radiometry without altering true SIC. Here we focus on two warm moist during Multidisciplinary drifting Observatory for Study of Climate (MOSAiC) expedition that reached research vessel Polarstern in mid-April 2020. After events, SIC deviations between different satellite products, including climate data records, were observed to increase. Especially, an underestimation algorithms based polarization difference was found. To examine causes this underestimation, used extensive MOSAiC measurements model computationally brightness temperatures a local scale. We further investigated by ground-based radiometers at frequencies 6.9 GHz, 19 89 GHz. show drop retrieved some products be attributed large-scale glazing, is, formation thin crust top snowpack, caused warming events. Another mechanism affecting which are mainly gradient ratios temperatures, is interplay changed temperature with metamorphism. From analyzed record found one less affected The low frequency channels GHz sensitive these changes, could exploited future obtain more accurate retrievals concentration. Strong expected become frequent thus their influence will In order provide consistent datasets, sensitivity needs addressed.

Language: Английский

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