Arctic sea ice albedo: Spectral composition, spatial heterogeneity, and temporal evolution observed during the MOSAiC drift

Elementa Science of the Anthropocene, Journal Year: 2022, Volume and Issue: 10(1)

Published: Jan. 1, 2022

The magnitude, spectral composition, and variability of the Arctic sea ice surface albedo are key to understanding numerically simulating Earth’s shortwave energy budget. Spectral broadband albedos were spatially temporally sampled by on-ice observers along individual survey lines throughout sunlit season (April–September, 2020) during Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition. seasonal evolution MOSAiC year was constructed from averaged values each line. Specific locations identified as representative types, including accumulated dry snow, melting bare ice, refreezing ponded sediment-laden ice. area-averaged progression total recorded showed remarkable similarity that 22 years prior on multiyear Surface Heat Budget Ocean (SHEBA) In accord with these other previous field efforts, relatively thick, snow-free, shows invariance across location, decade, type. particular, indistinguishable second-year suggesting highly scattering layer forms summer is robust stabilizing. contrast, observed be variable at visible wavelengths. Notable temporal changes in documented melt freeze onset, formation deepening ponds, While model simulations show considerable agreement progression, disparities suggest need improve how both thin, simulated.

Language: Английский

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Sea ice and snow characteristics from year-long transects at the MOSAiC Central Observatory

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

Published: Jan. 1, 2023

Repeated transects have become the backbone of spatially distributed ice and snow thickness measurements crucial for understanding mass balance. Here we detail at Multidisciplinary drifting Observatory Study Arctic Climate (MOSAiC) 2019–2020, which represent first such collected across an entire season. Compared with similar historical transects, MOSAiC was thin (mean depths approximately 0.1–0.3 m), while sea relatively thick first-year (FYI) second-year (SYI). SYI two distinct types: level formed from surfaces extensive melt pond cover, deformed ice. On SYI, spatial signatures refrozen ponds remained detectable in January. At beginning winter thinnest also had snow, growth rates (0.33 m month−1 FYI, 0.24 previously ponded SYI) exceeding that (0.2 month−1). By January, FYI already a greater modal (1.1 m) than (0.9 m). February, all became indistinguishable about 1.4 m. The largest thicknesses were measured May 1.7 Transects included ice, where volumes accumulated by April. remaining on exhibited typical heterogeneity form dunes. Spatial correlation length scales ranged 20 to 40 or 60 90 m, depending sampling direction, suggests known anisotropy dunes manifests patterns thickness. diverse data obtained invaluable resource model remote sensing product development.

Language: Английский

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Sea Ice Melt Pond Fraction Derived From Sentinel‐2 Data: Along the MOSAiC Drift and Arctic‐Wide

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(5)

Published: March 4, 2023

Abstract Melt ponds forming on Arctic sea ice in summer significantly reduce the surface albedo and impact heat mass balance of ice. Therefore, their areal coverage, which can undergo rapid change, is crucial to monitor. We present a revised method extract melt pond fraction (MPF) from Sentinel‐2 satellite imagery, evaluated by MPF products higher‐resolution helicopter‐borne imagery. The analysis evolution during MOSAiC campaign 2020, shows split Central Observatory (CO) into level highly deformed part, latter exhibits exceptional early formation compared vicinity. Average CO MPFs are 17% before 23% after major drainage. Arctic‐wide for years 2017–2021 consistent seasonal cycle all regions years.

Language: Английский

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Thin and transient meltwater layers and false bottoms in the Arctic sea ice pack—Recent insights on these historically overlooked features

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

Published: Jan. 1, 2023

The rapid melt of snow and sea ice during the Arctic summer provides a significant source low-salinity meltwater to surface ocean on local scale. accumulation this on, under, around floes can result in relatively thin layers upper ocean. Due small-scale nature these upper-ocean features, typically order 1 m thick or less, they are rarely detected by standard methods, but nevertheless pervasive critically important summer. Observations Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition 2020 focused evolution such made advancements understanding their role coupled system. Here we provide review Arctic, with emphasis new findings from MOSAiC. Both prior recent observational datasets indicate an intermittent yet long-lasting (weeks months) layer 0.1 1.0 thickness, large spatial range. presence impacts physical system reducing bottom allowing formation via false growth. Collectively, bottoms reduce atmosphere-ocean exchanges momentum, energy, material. far-reaching, including acting as barrier nutrient gas exchange impacting ecosystem diversity productivity.

Language: Английский

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Temporal evolution of under-ice meltwater layers and false bottoms and their impact on summer Arctic sea ice mass balance

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

Published: Jan. 1, 2023

Low-salinity meltwater from Arctic sea ice and its snow cover accumulates creates under-ice layers below ice. These can result in the formation of new layers, or false bottoms, at interface this low-salinity colder seawater. As part Multidisciplinary drifting Observatory for Study Climate (MOSAiC), we used a combination coring, temperature profiles thermistor strings underwater multibeam sonar surveys with remotely operated vehicle (ROV) to study areal coverage temporal evolution bottoms during summer melt season mid-June until late July. ROV indicated that MOSAiC Central (350 by 200 m2) was 21%. Presence reduced bottom 7–8% due local decrease ocean heat flux, which be described thermodynamic model. Under-ice layer thickness larger first-year thinner thicker second-year We also found thick ridge keels confined areas accumulated, preventing mixing underlying While model could reproduce growth melt, it not describe observed rates above bottoms. show meltwater-layer salinity is linked brine flushing accumulating bottom. The results aid estimating contribution mass balance salt budget

Language: Английский

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The MOSAiC Distributed Network: Observing the coupled Arctic system with multidisciplinary, coordinated platforms

Elementa Science of the Anthropocene, Journal Year: 2024, Volume and Issue: 12(1)

Published: Jan. 1, 2024

Central Arctic properties and processes are important to the regional global coupled climate system. The Multidisciplinary drifting Observatory for Study of Climate (MOSAiC) Distributed Network (DN) autonomous ice-tethered systems aimed bridge gaps in our understanding temporal spatial scales, particular with respect resolution Earth system models. By characterizing variability around local measurements made at a Observatory, DN covers both interactions involving ocean-ice-atmosphere interfaces as well three-dimensional ocean, sea ice, atmosphere. more than 200 instruments (“buoys”) were varying complexity set up different sites mostly within 50 km Observatory. During an exemplary midwinter month, observations captured atmospheric on sub-monthly time but less so monthly means. They show significant snow depth ice thickness, provide temporally spatially resolved characterization motion deformation, showing coherency scale smaller scales. Ocean data background gradient across dependent due mixed layer sub-mesoscale mesoscale processes, influenced by variable cover. second case (May–June 2020) illustrates utility during absence manually obtained providing continuity physical biological this key transitional period. We examples synergies between extensive MOSAiC remote sensing numerical modeling, such estimating skill drift forecasts evaluating modeling. has been proven enable analysis atmosphere-ice-ocean potential improve model parameterizations important, unresolved future.

Language: Английский

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Isotopic signatures of snow, sea ice, and surface seawater in the central Arctic Ocean during the MOSAiC expedition

Elementa Science of the Anthropocene, Journal Year: 2024, Volume and Issue: 12(1)

Published: Jan. 1, 2024

The Arctic Ocean is an exceptional environment where hydrosphere, cryosphere, and atmosphere are closely interconnected. Changes in sea-ice extent thickness affect ocean currents, as well moisture heat exchange with the atmosphere. Energy water fluxes impact formation melting of sea ice snow cover. Here, we present a comprehensive statistical analysis stable isotopes various hydrological components central obtained during Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition 2019–2020, including understudied winter. Our dataset comprises >2200 water, snow, samples. Snow had most depleted variable isotopic composition, δ18O (–16.3‰) increasing consistently from surface (–22.5‰) to bottom (–9.7‰) snowpack, suggesting that metamorphism wind-induced transport may overprint original precipitation isotope values. In Ocean, also help distinguish between different types, whether there meteoric contribution. composition salinity seawater indicated relative contributions freshwater sources: lower (approximately –3.0‰) salinities were observed near eastern Siberian shelves towards center Transpolar Drift due river discharge. Higher –1.5‰) associated Atlantic source when RV Polarstern crossed Gakkel Ridge into Nansen Basin. These changes driven mainly by shifts within carried across Ocean. highlights importance investigating fractionation effects, example, melting. A systematic full-year sampling strengthens our understanding cycle provides crucial insights interaction atmosphere, ice, their spatio-temporal variations MOSAiC.

Language: Английский

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Formation and fate of freshwater on an ice floe in the Central Arctic

˜The œcryosphere, Journal Year: 2025, Volume and Issue: 19(2), P. 619 - 644

Published: Feb. 7, 2025

Abstract. The melt of snow and sea ice during the Arctic summer is a significant source relatively fresh meltwater. fate this freshwater, whether in surface ponds or thin layers underneath leads, impacts atmosphere–ice–ocean interactions their subsequent coupled evolution. Here, we combine analyses datasets from Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition (June–July 2020) process study on formation freshwater floes Central Arctic. Our budget suggest that high fraction (58 %) derived melt. Additionally, contribution stored precipitation (snowmelt) outweighs by 5 times input situ (rain). magnitude rate local meltwater production are remarkably similar to those observed prior Surface Heat Budget Ocean (SHEBA) campaign, where cumulative totaled around 1 m both. A small (10 remains ponds, which higher more deformed second-year (SYI) compared first-year (FYI) later summer. Most drains laterally vertically, with vertical drainage enabling storage internally freshening brine channels. In upper ocean, can accumulate transient order 0.1 thick leads under ice. presence such substantially system reducing bottom allowing false growth; heat, nutrient, gas exchange; influencing ecosystem productivity. Regardless, majority inferred be ultimately incorporated into ocean (75 (14 %). Terms as annual could used future work diagnostics global climate models. For example, range values CESM2 model roughly encapsulate total production, while underestimated about 50 %, suggesting pond terms key investigation.

Language: Английский

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Impacts of air fraction increase on Arctic sea ice density, freeboard, and thickness estimation during the melt season

˜The œcryosphere, Journal Year: 2025, Volume and Issue: 19(3), P. 1259 - 1278

Published: March 17, 2025

Abstract. Arctic sea ice has undergone significant changes over the past 50 years. Modern large-scale estimates of thickness and volume come from satellite observations. However, these have limited accuracy, especially during melt season, making it difficult to compare state year year. Uncertainties in density lead high uncertainties retrieval its freeboard. During Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition, we observed a first-year (FYI) freeboard increase 0.02 m, while decreased by 0.5 m season June–July 2020. Over same period, FYI 910 880 kg m−3, air fraction increased 1 % 6 %, due void expansion controlled internal melt. This substantially affected Due differences thermodynamic (such as salinity temperature), is less pronounced second-year (SYI) smaller impact on evolution SYI ridges. We validated our discrete measurements coring using co-located topography observations underwater sonar an airborne laser scanner. Despite decreasing thickness, similar counterintuitive increasing was entire 0.9 km2 MOSAiC floe, with stronger than saline SYI. The surrounding area experienced slightly lower 0.01 July 2020, despite comparable rates obtained mass balance buoys. defines rapid decrease density, complicates altimeters underlines importance considering algorithms.

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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