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

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

Опубликована: Янв. 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.

Язык: Английский

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Quantifying false bottoms and under-ice meltwater layers beneath Arctic summer sea ice with fine-scale observations

Elementa Science of the Anthropocene, Год журнала: 2022, Номер 10(1)

Опубликована: Янв. 1, 2022

During the Arctic melt season, relatively fresh meltwater layers can accumulate under sea ice as a result of snow and melt, far from terrestrial freshwater inputs. Such under-ice layers, sometimes referred to ponds, have been suggested play role in summer mass balance both by isolating saltier water below, driving formation ‘false bottoms’ below ice. form at interface fresher layer colder, seawater below. Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition Central Arctic, we observed presence false bottoms throughout July 2020 primarily first-year locations. Here, examine distribution, prevalence, drivers ponds resulting during this period. The average thickness equivalent was 0.08 m, with bottom comprised 74–87% FYI 13–26% melt. Additionally, explore these results using 1D model understand dynamic influences on decoupling comparison suggests that ice-ocean friction velocity likely exceptionally low, implications air-ice-ocean momentum transfer. Overall, prevalence similar or higher than noted other observational campaigns, indicating features may fact be common season. These broader system, provide source growth potentially reduce fluxes between ocean, isolate primary producers pelagic nutrient sources, alter light transmission ocean

Язык: 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, Год журнала: 2023, Номер 50(5)

Опубликована: Март 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.

Язык: Английский

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Surface impacts and associated mechanisms of a moisture intrusion into the Arctic observed in mid-April 2020 during MOSAiC

Frontiers in Earth Science, Год журнала: 2023, Номер 11

Опубликована: Апрель 11, 2023

Distinct events of warm and moist air intrusions (WAIs) from mid-latitudes have pronounced impacts on the Arctic climate system. We present a detailed analysis record-breaking WAI observed during MOSAiC expedition in mid-April 2020. By combining Eulerian with Lagrangian frameworks using simulations across different scales, we investigate aspects mass transformations via cloud processes quantify related surface impacts. The is characterized by two distinct pathways, Siberian Atlantic. A static energy transport Circle above climatological 90th percentile found. Observations at research vessel Polarstern show transition radiatively clear to cloudy state significant precipitation positive balance (SEB), i.e., warming. parcels reach first near tropopause, only 1–2 days later lower altitudes. In 5 prior event, latent heat release formation triggers maximum diabatic heating rates excess 20 K d -1 . For some poleward drifting parcels, this facilitates strong ascent up 9 km. Based model experiments, explore role key cloud-determining factors. First, test moisture availability reducing lateral inflow 30%. This does not significantly affect liquid water path, therefore SEB, central Arctic. cause are counteracting mechanisms along trajectory. Second, impact increasing Cloud Condensation Nuclei concentrations 10 1,000 cm -3 (pristine highly polluted), which enhances content. Resulting stronger longwave cooling top makes entrainment more efficient deepens atmospheric boundary layer. Finally, strongly effect SEB. mainly driven turbulent fluxes over ocean, but radiation sea ice. also contributes large fraction Arctic, reaching 30% total 9-day period site. However, measured varies substantially between platforms. Therefore, estimates subject considerable observational uncertainty.

Язык: 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, 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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A full year of aerosol size distribution data from the central Arctic under an extreme positive Arctic Oscillation: insights from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition

Atmospheric chemistry and physics, Год журнала: 2023, Номер 23(1), С. 389 - 415

Опубликована: Янв. 11, 2023

Abstract. The Arctic environment is rapidly changing due to accelerated warming in the region. trend driving a decline sea ice extent, which thereby enhances feedback loops surface energy budget Arctic. aerosols play an important role radiative balance and hence climate response region, yet direct observations of over Ocean are limited. In this study, we investigate annual cycle aerosol particle number size distribution (PNSD), concentration (PNC), black carbon (BC) mass central during Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition. This first continuous, year-long data set PNSD ever collected Ocean. We use k-means cluster analysis, FLEXPART simulations, inverse modeling evaluate seasonal patterns influence different source regions on population. Furthermore, compare land-based sites across Arctic, using both long-term measurements year MOSAiC expedition (2019–2020), interannual variability give context characteristics from within Our analysis identifies that, overall, exhibits typical aerosols, including anthropogenic haze winter secondary processes summer. pattern corresponds global radiation, air temperature, timing melting/freezing, drive changes transport processes. winter, Norilsk region Russia/Siberia was dominant signals BC observations, contributed higher accumulation-mode PNC concentrations than at observatories. also show that wintertime Oscillation (AO) phenomenon, reported achieve record-breaking positive phase January–March 2020, explains unusual magnitude compared longer-term observations. summer, PNCs nucleation Aitken modes enhanced; however, were notably lower pack further south. presented herein provides current snapshot characterized by rapid changes, will be crucial improving model predictions, understanding linkages between environmental processes, investigating impacts change future studies.

Язык: Английский

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Still Arctic?—The changing Barents Sea

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

Опубликована: Янв. 1, 2023

The Barents Sea is one of the Polar regions where current climate and ecosystem change most pronounced. Here we review state knowledge physical, chemical biological systems in Sea. Physical conditions this area are characterized by large seasonal contrasts between partial sea-ice cover winter spring versus predominantly open water summer autumn. Observations over recent decades show that surface air ocean temperatures have increased, extent has decreased, stratification weakened, chemistry components changed, latter a direction often described as “Atlantification” or “borealisation,” with less “Arctic” appearance. Temporal spatial changes wider relevance, both context large-scale climatic (air, mass sea-ice) transport processes comparison to other Arctic regions. These observed also socioeconomic consequences, including for fisheries human activities. While several ongoing monitored quantified, observation gaps remain, especially months when field observations sample collections still sparse. Knowledge interplay physical biogeochemical drivers responses, complex feedback processes, needs further development.

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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