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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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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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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The Eurasian Arctic Ocean along the MOSAiC drift in 2019–2020: An interdisciplinary perspective on physical properties and processes

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

Published: Jan. 1, 2024

The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC, 2019–2020), a year-long drift with sea ice, has provided scientific community an unprecedented, multidisciplinary dataset from Eurasian Ocean, covering high atmosphere to deep ocean across all seasons. However, heterogeneity data and superposition spatial temporal variability, intrinsic campaign, complicate interpretation observations. In this study, we have compiled quality-controlled physical hydrographic best spatio-temporal coverage derived core parameters, including mixed layer depth, heat fluxes over key layers, friction velocity. We provide comprehensive accessible overview conditions encountered along MOSAiC drift, discuss their interdisciplinary implications, compare common climatologies these new data. Our results indicate that, most part, variability was dominated by regional rather than seasonal signals, carrying potentially strong implications biogeochemistry, ecology, even atmospheric conditions. Near-surface properties were strongly influenced relative position sampling, within or outside river-water Transpolar Drift, warming meltwater input. Ventilation down Atlantic Water in Nansen Basin allowed stronger connectivity between subsurface ice surface via elevated upward fluxes. Yermak Plateau Fram Strait regions characterized heterogeneous water mass distributions, energetic currents, lateral gradients frontal regions. Together presented offer context research, fostering improved understanding complex, coupled System.

Language: Английский

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Observations of preferential summer melt of Arctic sea-ice ridge keels from repeated multibeam sonar surveys

˜The œcryosphere, Journal Year: 2023, Volume and Issue: 17(11), P. 4873 - 4887

Published: Nov. 20, 2023

Abstract. Sea-ice ridges constitute a large fraction of the total Arctic sea-ice area (up to 40 %–50 %); nevertheless, they are least studied part ice pack. Here we investigate melt rates using rare, repeated underwater multibeam sonar surveys that cover period 1 month during advanced stage melt. Bottom increases with draft for first- and second-year level first-year ridge, an average 0.46, 0.55, 0.95 m snow in observation period, respectively. On average, ridge had 4.6 keel bottom draft, was 42 wide, 4 % macroporosity. While were 3.8 times higher than ice, surface almost identical but responsible decrease. Average cross-sectional ranged from 0.2 2.6 m, maximum point loss 6 showcasing its spatial variability. We attribute 57 (surface bottom) variability (36 %), slope (32 width (27 larger steeper slope, smaller width. The rate flanks proportional increased within 10 corners between these comparable ice.

Language: Английский

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Sea ice mass balance during the MOSAiC drift experiment: Results from manual ice and snow thickness gauges

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

Published: Jan. 1, 2024

Precise measurements of Arctic sea ice mass balance are necessary to understand the rapidly changing cover and its representation in climate models. During Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition, we made repeat point snow thickness on primarily level first- second-year (FYI, SYI) using ablation stakes gauges. This technique enabled us distinguish surface bottom (basal) melt characterize importance oceanic versus atmospheric forcing. We also evaluated time series growth context other MOSAiC observations historical from Surface Heat Budget (SHEBA) campaign North Pole Environmental (NPEO). Despite similar freezing degree days, average at was greater FYI (1.67 m) SYI (1.23 than SHEBA (1.45 m, 0.53 m), due part initially thinner conditions MOSAiC. Our estimates effective thermal conductivity, which agree with results observations, unlikely explain difference. On MOSAiC, grew more faster SYI, demonstrating a feedback loop that acts increase production after multi-year loss. (mean 0.50 NPEO (0.18 considerable spatial variability correlated albedo variability. Basal relatively small 0.12 higher (0.07 m). Finally, present showing false bottoms reduced basal rates some cases, agreement These detailed will allow further investigation into connections between carefully observed energy budget, ocean heat fluxes, ice, ecosystem during campaigns.

Language: Английский

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Snowmelt contribution to Arctic first-year ice ridge mass balance and rapid consolidation during summer melt

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

Published: Jan. 1, 2023

Sea ice ridges are one of the most under-sampled and poorly understood components Arctic sea system. Yet, play a crucial role in mass balance have been identified as ecological hotspots for ice-associated flora fauna Arctic. To better understand ridges, we drilled sampled two different first-year (FYI) June–July 2020 during Multidisciplinary drifting Observatory Study Climate (MOSAiC). Ice cores were cut into 5 cm sections, melted, then analyzed salinity oxygen (δ18O) isotope composition. Combined with data snow samples, used mixing model to quantify contribution consolidated ridge mass. Our results demonstrate that meltwater is important summer consolidation overall FYI melt season, representing 6%–11% total ridged or an thickness equivalent 0.37–0.53 m. These findings snowmelt contributes mechanism resulting relative increase volume summer. This can also affect mechanical strength survivability but contribute reduction habitable space light levels within ridges. We proposed combination pathways transport incorporation keels: percolation downward through and/or lateral from under-ice layer. Whether only pathway both likely remains unclear based on our observations, warranting further research morphology.

Language: Английский

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The Eurasian Arctic Ocean along the MOSAiC drift in 2019-2020: An interdisciplinary perspective on physical properties and processes

EarthArXiv (California Digital Library), Journal Year: 2023, Volume and Issue: unknown

Published: Sept. 7, 2023

The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC, 2019--2020), a year-long drift with sea ice, has provided scientific community an unprecedented, multidisciplinary dataset from Eurasian Ocean, covering high atmosphere to deep ocean across all seasons. However, heterogeneity data and superposition spatial temporal variability, intrinsic campaign, complicate interpretation observations. In this study, we have compiled quality-controlled physical hydrographic best spatio-temporal coverage derived core parameters, including mixed layer depth, heat fluxes over key layers, friction velocity. We provide comprehensive accessible overview conditions encountered along MOSAiC drift, discuss their interdisciplinary implications, compare common climatologies these new data. Our results indicate that, most part, variability was dominated by regional rather than seasonal signals, carrying potentially strong implications biogeochemistry, ecology, even atmospheric conditions. Near-surface properties were strongly influenced relative position sampling, within or outside river-water Transpolar Drift, warming meltwater input. Ventilation down Atlantic Water in Nansen Basin allowed stronger connectivity between subsurface ice surface via elevated upward fluxes. Yermak Plateau Fram Strait regions characterized heterogeneous water mass distributions, energetic currents, lateral gradients frontal regions. Together presented offer context research, fostering improved understanding complex, coupled System.

Language: Английский

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