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, Год журнала: 2023, Номер 11(1)

Опубликована: Янв. 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.

Язык: Английский

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Sea ice classification of TerraSAR-X ScanSAR images for the MOSAiC expedition incorporating per-class incidence angle dependency of image texture

˜The œcryosphere, Год журнала: 2023, Номер 17(3), С. 1279 - 1297

Опубликована: Март 16, 2023

Abstract. We provide sea ice classification maps of a sub-weekly time series single (horizontal–horizontal, HH) polarization X-band TerraSAR-X scanning synthetic aperture radar (TSX SC) images from November 2019 to March 2020, covering the Multidisciplinary drifting Observatory for Study Arctic Climate (MOSAiC) expedition. This classified benefits wide spatial coverage and relatively high resolution TSX SC data is useful basic dataset future MOSAiC studies on physical processes ocean climate modeling. Sea into leads, young with different backscatter intensities, first-year (FYI) or multiyear (MYI) degrees deformation. establish per-class incidence angle (IA) dependencies intensities gray-level co-occurrence matrix (GLCM) textures use classifier that corrects class-specific decreasing increasing IAs, both HH as input features. Optimal parameters texture calculation are derived achieve good class separation while maintaining maximum detail minimizing textural collinearity. Class probabilities yielded by adjusted Markov random field contextual smoothing produce results. The texture-based process yields an average overall accuracy 83.70 % correspondence geometric surface roughness in situ thickness measurements (correspondence consistently close higher than 80 %). A positive logarithmic relationship found between intensity, similar previous C- L-band studies. Areal fractions classes representing openings (leads ice) show prominent increases middle late corresponding well ice-opening this study those satellite (SAR) optical other

Язык: 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, Год журнала: 2023, Номер 11(1)

Опубликована: Янв. 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

Язык: Английский

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

Elementa Science of the Anthropocene, Год журнала: 2024, Номер 12(1)

Опубликована: Янв. 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.

Язык: Английский

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

˜The œcryosphere, Год журнала: 2025, Номер 19(2), С. 619 - 644

Опубликована: Фев. 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.

Язык: 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, Год журнала: 2025, Номер 19(3), С. 1259 - 1278

Опубликована: Март 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.

Язык: Английский

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Sea ice heat and mass balance measurements from four autonomous buoys during the MOSAiC drift campaign

Elementa Science of the Anthropocene, Год журнала: 2023, Номер 11(1)

Опубликована: Янв. 1, 2023

As part of the Multidisciplinary drifting Observatory for Study Arctic Climate (MOSAiC), four autonomous seasonal ice mass balance buoys were deployed in first- and second-year ice. These measured position, barometric pressure, snow depth, thickness, growth, surface melt, bottom vertical profiles temperature from air, through ice, into upper ocean. Observed air temperatures similar at all sites; however, snow–ice interface varied by as much 10°C, primarily due to differences depth. winter growth rates (November May) <1 cm day−1, with summer melt (June July) large 5 day−1. Air changed 2°C hour−1 but dampened <0.3°C interface. Initial October thicknesses ranged 0.3 m first-year 1.2 By February, this range was only 1.20–1.46 m, onset basal freezing. In delay brine-filled voids ice; propagating cold front required freezing brine. Mass results those North Pole 2000 2013. Winter average estimates ocean heat flux 0 3 W m−2, a increase June 2020 floe moved warmer water. Estimates thermal conductivity two during periods linear 0.41 0.42 m−1 °C−1, higher than previously published estimates. Results these can contribute efforts close MOSAiC budget.

Язык: 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, Год журнала: 2023, Номер 11(1)

Опубликована: Янв. 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.

Язык: Английский

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Preconditioning of Summer Melt Ponds From Winter Sea Ice Surface Temperature

Geophysical Research Letters, Год журнала: 2023, Номер 50(4)

Опубликована: Фев. 22, 2023

Abstract Comparing helicopter‐borne surface temperature maps in winter and optical orthomosaics summer from the year‐long Multidisciplinary drifting Observatory for Study of Arctic Climate expedition, we find a strong geometric correlation between warm anomalies melt pond location following summer. Warm are associated with thinner snow ice, that is, depression refrozen leads, allow water accumulation during melt. January were 0.3–2.5 K warmer on sea ice later formed ponds. A one‐dimensional steady‐state thermodynamic model shows observed differences line thickness depth. We demonstrate potential seasonal prediction coverage observations. threshold‐based classification achieves correct 41%

Язык: Английский

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Photosynthetic light requirement near the theoretical minimum detected in Arctic microalgae

Nature Communications, Год журнала: 2024, Номер 15(1)

Опубликована: Сен. 4, 2024

Язык: Английский

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