This study aims to assess the connectivity of currents around the Antarctic Peninsula and identify the structure of flows carrying particles from the Eastern to Western Antarctic Peninsula continental shelves. We use circulation data for the Weddell and Bellingshausen Seas from the “Whole Antarctica Ocean Model” to obtain and analyse particle trajectories using the “Probably A Really Computationally Efficient Lagrangian Simulator” (Parcels) model. In addition to the main Parcels kernels and a previously developed kernel that ensures the conservation of the number of particles during flow around irregularities in the bottom relief and the lower edge of ice shelves, we have also developed a kernel to simulate convection in the ocean upper mixed layer. Around 170,000 virtual particles were released at a depth of 10 m during a year with a spatial step of 1° in two shelf and slope sectors in the southern Weddell Sea where depth is less than 1500 m. The first sector covers a shelf area between 71°S and 77°S adjacent to the Filchner-Ronne Ice Shelf. The second sector covers a shelf area between 70°S and 65°S adjacent to the Larsen Ice Shelf.  The pathways of water masses were characterised by the visitation frequency (the percentage of particles P that visit each 10×10 km grid column at least once in a modelling period of 20 years). The proportion of particles crossing 58°W (tip of the Antarctic Peninsula) is 21% of the total amount, while the proportion of particles turning northeast is 70%.  The smaller sector, adjacent to the Larsen Ice Shelf, is the main source of particles transferred to the Bellingshausen Sea (51%). In contrast, particles released in the larger sector were mostly transported to the northeast (75%). Only 3.4% of the released particles were transported to the west of 80°W, while the Amundsen Sea (105°W) is reached only by 0.1% of released particles. This indicates a virtual lack of connectivity between the ocean circulation from the Weddell to the Amundsen Seas.

How to cite: Maderich, V., Bezhenar, R., Brovchenko, I., Boeira, D. F., Äijälä, C., and Uotila, P.: Lagrangian pathways connecting the Weddell and Bellingshausen Seas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7289, https://doi.org/10.5194/egusphere-egu25-7289, 2025.

The Chemistry in the Arctic: Clouds, Halogens, and Aerosols (CHACHA) field project featured a wide collaboration from six universities to enhance the scientific understanding of multiphase halogen chemistry in the Arctic that took place in Utqiaġvik, Alaska during February-April 2022. This project was spurred by the pursuit of strengthening our understanding of how Arctic Sea ice loss and fossil fuel extraction affects atmospheric halogen chemistry.

In this study, cloud flights from the University of Wyoming King Air are evaluated closely to assess the ambient conditions relevant to the Arctic boundary layer during flights targeting clouds emanating from open leads in the Arctic sea ice. During these flights, the Particle into Liquid Sampler (PILS) was utilized using a Roger’s inlet and Counterflow Virtual Impactor (CVI) with low volume (1.5 mL) samples being collected. This study aims to introduce a methodological basis for prioritizing samples and identifying samples that can be safely grouped together to maximize the chemical analysis possible. Instruments are used for this method include Aerosol microphysics data from instruments including Condensation Particle Counters (CPC), Portable Optical Particle Spectrometer (POPS), and Passive Cavity Aerosol Spectrometer Probe (PCASP) and cloud microphysics data from a Cloud Droplet Probe (CDP) and Two-Dimensional Stereo (2D-S). Ultimately, this work is a key step in chemical analysis of cloud flights that will be used to better understand multiphase Arctic halogen chemistry by constraining a Lagrangian chemical box model and cloud parcel modeling.

How to cite: Lombardo, S., Selimovic, V., Lance, S., Woods, S., Jeong, D., Corral, A. F., Garner, N., Peterson, P., Costanza, C., Bigge, K., Starn, T., Stirm, B. H., Sorooshian, A., Fuentes, J. D., Simpson, W. R., Shepson, P. B., and Pratt, K.: Integrated Analysis of Airborne In-situ Cloud and Aerosol Microphysics Data during the 2022 Chemistry in the Arctic: Clouds, Halogens, and Aerosols (CHACHA) Field Campaign, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7504, https://doi.org/10.5194/egusphere-egu25-7504, 2025.

Recent case studies highlight that warm and moist air intrusion events are significant sources of aerosol particles in the Arctic, influencing cloud properties and thus the resulting radiative forcing in the region. However, the contribution of these short-lived events to different aerosol size modes, cloud condensation nuclei (CCN), and droplet number concentrations remains unconstrained. Here, we investigate the multi-annual aspects of intrusion impacts on aerosol properties using data on aerosol number size distributions, CCN, total particle number concentrations, and optical properties from multiple Arctic stations, including Alert, Tiksi, Utqiaġvik, Villum, and Zeppelin, covering the period 2010-2020.

Preliminary results suggest that particle concentrations change significantly during intrusion episodes, with variations across seasons and stations. For instance, contrary to previous studies, number size distribution data indicate a distinct decrease in accumulation mode concentrations during wintertime intrusion episodes relative to non-intrusion periods at several Arctic stations. In summer, this pattern reverses, although not uniformly across stations. Additionally, at Zeppelin, the average of the yearly mean CCN concentrations during intrusions is increased by 13% compared to non-intrusion periods, with some years showing increases exceeding 40%.

We explore the potential drivers of these observed number size distribution patterns and derive potential source contribution function and removal mechanisms along the trajectories, employing the Lagrangian analysis tool LAGRANTO.

How to cite: Dönmez, B., Pernov, J. B., Asmi, E., Chan, T., Krejci, R., Massling, A., Sharma, S., Skov, H., Tunved, P., Wiedensohler, A., Weinhold, K., Nenes, A., and Schmale, J.: Aerosol Number Concentration and Cloud Condensation Nuclei Variability During Warm and Moist Intrusions into the Arctic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10952, https://doi.org/10.5194/egusphere-egu25-10952, 2025.

Surface albedo, sea ice growth and glacier mass balance in the Arctic are all heavily dependent on snow and thus also impacted by blowing snow through redistribution and increased sublimation. The sublimation of blowing snow is significantly higher than that of ground snow due to the larger surface area of the suspended snow crystals and the continuous entrainment of dry air. Thus, sublimation of blowing snow impacts the exchange of energy, moisture and particles between the snow and atmosphere in windy conditions.

Because of the difficulty of modelling such a small-scale process for large areas, parameterizations of sublimation of blowing snow are necessary for snow mass balance and aerosol production studies. The widely used Déry and Yau (2001) parameterization has only been evaluated with model data from the Canadian Prairie, but never for other surface types, where it is applied, or with in-situ observations. Therefore, the goal of this work is to evaluate the parameterization by Déry and Yau (2001) with observations from the MOSAiC expedition in the central Arctic and the Intensive Observation Period for Water (IOP4H20) field measurements in Ny-Ålesund, Svalbard.

Here we show observations of blowing snow events that were detected and characterized by a snow particle counter and the Video In-Situ Snowfall Sensor (VISSS). During these events, measurements of latent heat fluxes from eddy covariance systems are used to evaluate the parameterized sublimation rate. To address challenges with eddy covariance observations in snowy conditions and calculating column-integrated values the observations are complemented with the 1D-column PIEKTUK-D blowing snow model.

In this way, comparing the parameterization with observations brings insights into its uncertainty or possible limitations for two different surface types and thereby improves the estimation of the accuracy of snow mass balance and aerosol production studies that apply this parameterization.

How to cite: Monrad-Krohn, L., Maahn, M., Frey, M., and Déry, S. J.: Evaluating a Parameterization for Sublimation of Blowing Snow with In-situ Observations in the Arctic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-614, https://doi.org/10.5194/egusphere-egu25-614, 2025.

Vertical profile measurements of aerosol properties in the lower atmosphere still constitute a major observational gap. Focusing on the polar regions, where the planetary boundary layer often forms temperature inversions that inhibit vertical mixing of the lowermost atmosphere, surface measure-ments can often not represent aerosol properties further aloft. However, understanding vertical aerosol distribution is critical for several reasons. From a climate perspective, in the Arctic and Antarctic, cloud formation is often sensitive to aerosol availability. Because clouds strongly influence the surface radiation budget and primarily exert warming, it is important to understand aerosols at cloud level.

Overall, understanding the thermodynamic structure of the lower atmosphere and the dynamics of vertical mixing is critical to answer questions on cloud formation. In situ measurements that describe the (thermo)dynamic, aerosol and cloud variables are indispensible to understand relevant process mechanisms and to improve models that typically struggle to simulate polar lower atmospheric aerosols. 

Here we present results obtained with the Modular Multiplatform Compatible Air Measure-ment System (MoMuCAMS). MoMuCAMS can observe particle number size distributions (8-3000 nm) and overall concentrations, aerosol absorption, cloud droplet size distributions, and trace gas mixing ratios (CO₂, CO, O₃). Based on filter measurements, aerosol chemical composition and INP number concentrations can be obtained. Wind speed and direction, as well as temperature and relative humidity and video images are recorded.

We deployed MoMuCAMS up to 800 m with a payload of ~20 kg in Fairbanks, Alaska (Jan-Feb 2022), Pallas, Finland (Sep-Oct 2022), the Arctic Ocean (May-Jun 2023), southern Greenland (Jun-Aug 2023), and at Neumayer, Antarctica (Dec 2024 – Feb 2025). Overall, more than 350 profiles were flown. This contribution synthesizes observations of aerosol properties below, in and above clouds, and vertically resolved contributions of local and long-range transported particles.

How to cite: Schmale, J., Pohorsky, R., Lonardi, M., Temel, Y., Dyson, J., Calmer, R., and Favre, L.: From the Arctic to Antarctica: Observations of vertical aerosol distribution from tethered balloon measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10134, https://doi.org/10.5194/egusphere-egu25-10134, 2025.

Surface Mass Balance (SMB) is a critical forcing of the long term contribution of the Antarctic Ice Sheet (AIS) to sea level. While most GCMs do not produce SMB as an output, several RCMs, including a new ensemble produced in the PolarRES project do and are used to provide forcing for ice sheet models. There are significant spatial variations between regional climate models forced with reanalysis. RCMs also inherit biases from forcing GCMs when run for historical and future climate pathways which may exacerbate or cancel out biases within the RCM. Since the previous intercomparison, there has been significant regional model development and an expansion of datasets that can be used for evaluating these. We assess the SMB estimates of downscaled GCM and reanalysis simulations over Antarctica, compared to a new updated observational database for the historical period. Our ensemble compares 19 SMB products, generated from 4 different GCMs downscaled by 6 RCMs and SMB models, to observations of SMB gathered in the 2024 SUMup dataset. As 8 datasets do not explicitly calculate SMB, we approximate SMB by subtracting evaporation and melt from precipitation with these models. The various simulations are all pan-Antarctic at resolutions from 11 to 27 km, and span periods from 24 to 64 years, between 1950 and 2023. Fidelity of models to observations varies from product to product. As would be expected given they assimilate observational data, reanalyses perform better overall, with minor biases, whereas climatological SMB from GCM-forced runs  are usually too dry (5/9 GCM, 5/19 total). This is a significant bias in GCMs that will have an impact on modelled future evolution of the Antarctic Ice Sheet. One notable exception is the HIRHAM RCM forced by UKESM. In this case opposing biases appear to cancel out, giving the lowest t-statistic and one of the highest correlation coefficients in the intercomparison, while having the most comparison points due to the length of the simulation. The mean yearly accumulation of the models is 2100 Gt/year on the grounded AIS (Zwally’s mask) with most models predicting about 2000 Gt/year and 3 potential outliers predicting over 2500 Gt/year. Our analysis demonstrates that assessing model performance based on reanalysis driven simulations may provide misleading evidence of model performance for future projections. There are still large divergences in the spatial variability of modelled SMB. We also show the need for observational data with a wide spread in time and space.

How to cite: Cherblanc, C. and Mottram, R.: How well do downscaled Global Climate Models represent SMB in Antarctica?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12992, https://doi.org/10.5194/egusphere-egu25-12992, 2025.

The Korea Institute of Atmospheric Prediction Systems (KIAPS) is developing a spatio-temporal integrated coupled modeling system that is capable of forecasting from one week to two months. This system is based on the Korean Integrated Model (KIM) and incorporates the Nucleus for European Modelling of the Ocean (NEMO) framework to simulate ocean and sea ice components. While the coupled model’s mid-term prediction performance is comparable to that of the atmosphere-only model, it exhibits a significant cold bias in the polar regions when evaluated against reanalysis data such as ECMWF reanalysis version 5 (ERA5).
Polar regions, characterized by sea ice, present unique challenges due to the complex interactions between the atmosphere and the ocean. In winter, reduced sea ice formation allows more heat to transfer from the ocean to the atmosphere, further warming the air. Accurate simulation of these regions requires a further understanding of atmosphere-sea ice interaction. In this study, sensitivity tests of the atmosphere-sea ice exchange coefficient were conducted to optimize the momentum and heat transfer in the Arctic and Antarctic. The exchange coefficients were fixed at 0.0014 in the control run, while two parameterization methods, modulating sea ice roughness length, were applied to the experimental run. The results revealed opposing outcomes: one method caused atmospheric warming, while the other resulted in cooling, implying significant uncertainty in calculating the heat exchange coefficient. Further analysis of atmospheric and sea ice dynamics within the coupled KIM will determine the most suitable parameterization approach for accurate polar region simulations.

Acknowledgements. This work was carried out through the R&D project “Development of a NextGeneration Numerical Weather Prediction Model by the Korea Institute of Atmospheric Prediction Systems (KIAPS)”, funded by the Korea Meteorological Administration (KMA2020-02212).

How to cite: Jeong, J.-Y. and Koo, M.-S.: Effects of advanced atmosphere-sea ice exchange coefficient in the Korean Integrated Model (KIM) , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14691, https://doi.org/10.5194/egusphere-egu25-14691, 2025.

The Greenland Ice Sheet (GrIS) discharges ~1000 Gt yr^-1 of freshwater into Arctic coastal oceans in the form of meltwater runoff and glacial discharge, with the majority entering the ocean via fjords. Fjordic ecosystems lie at the nexus of various facets of the environment, the ocean, land, cryosphere, atmosphere and biosphere, all of which are especially sensitive to climate change exacerbated by the rising global temperature. With the increase in length and intensity of the summer melt periods, both marine and land-terminating glaciers are slowly receding leaving altered downstream ecosystems in their wake. As glaciers recede, glacial outwash plains become exposed and the potential of sediment aerosolization increases. Concurrently, triggered by increasing melt-water discharge, marine biological productivity is changing, due to the evolving fjord dynamics, stratification, and composition.  Hence, the composition and sources of atmospheric aerosols responsible for the cloud formation in this region are evolving and we expect this to influence both the Cloud Condensation Nuclei (CCN) and Ice Nucleating Particle (INP) populations. In addition to natural aerosols sources, also local anthropogenic activities can contribute to the CCN and INP populations. Furthermore, distant emissions e.g., from north American boreal forest fires, occasionally reach Greenlandic Fjord systems and can have significant impact on the aerosol properties. 

In this presentation we aim to provide an overview of the processes which influence aerosol populations in Greenlandic fjord systems during Arctic summer. We will show results from a comprehensive and extensive field campaign in the Kujalleq province of Southern Greenland (60.91°N, 46.05°W) in June-August 2023. We will present aerosol size distributions, particle number concentrations, and scattering and absorption measurements from both ground-based and tethered-balloon measurement platforms. We will explore the following questions:

• What are the local and regional sources of aerosols leading to the formation of CCN in Southern Greenland?
• What is the current contribution of anthropogenic activities to the aerosol budget and how does this compare to the contribution from natural sources?
• How do long-range transport, new particle formation and ground-level fog events affect the concentration and vertical distribution of aerosols and subsequent CCN formation?

How to cite: Dyson, J., Bergner, N., Favre, L., Heutte, B., Surdu, M., Weng, J., Augugliaro, M., Winiger, P., Nenes, A., Violaki, K., Henning, S., and Schmale, J.: Exploring local and long-range aerosol source contributions to summertime CCN in Southern Greenlandic fjord systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16059, https://doi.org/10.5194/egusphere-egu25-16059, 2025.

Aerosol-cloud interactions remain one of the most significant challenges in accurately estimating human-induced radiative forcing, as well as projecting the future climate. To address this uncertainty, establishing the baseline levels of natural aerosols in various environments is crucial. The polar regions are ideal locations for studying natural aerosols due to their distances from anthropogenic influences, yet observations in these regions are relatively limited. Specifically, the role of oceans and sea ice in controlling aerosol concentrations, influencing cloud formation, and determining cloud phase remains unclear. A key component is biological aerosol particles that participate in the formation and microphysical modulation of Arctic mixed-phase clouds. Yet, many questions regarding their Arctic sources, emission processes, and ice nucleating properties remain.

We present a detailed study of potential natural sources of aerosols in the high Arctic over the pack ice during the ARTofMELT expedition (May–June 2023). We collected samples of snow, sea ice, seawater, and the sea-surface microlayer (SML) and utilized the comprehensive aerosol instrumentation setup on-board to analyze them immediately after collection for their chemical, microphysical, and fluorescent properties. After the expedition, further analysis of the samples was conducted including measurements of ice-nucleating properties and biological cell quantification.

Our results show that during the late Arctic spring, heightened biological activity in the seawater and the SML increased emissions of fluorescent primary biological aerosol particles (confirmed by increased cell count) and organic-coated sea salt particles. However, concentrations of ice-nucleating particles in liquid samples did not follow the same trend. We will present the clear distinctions found in the biological, chemical, and physical properties of all sample types, and the effect of salinity on the aerosolization process and ice nucleating activity. These results provide valuable information for future studies aimed at improving the source attribution of natural Arctic aerosols, helping to reduce uncertainties in their representation in models, and understanding their influence on Arctic mixed-phase clouds. 

This work is currently in discussion at Freitas et al. (2024).

Freitas GP, Kojoj J, Mavis C, Creamean J, Mattsson F, Nilsson L, Schmidt JS, Adachi K, Šantl-Temkiv T, Ahlberg E, Mohr C. A comprehensive characterisation of natural aerosol sources in the high Arctic during the onset of sea ice melt. Faraday Discussions. 2024. DOI: 10.1039/D4FD00162A 

How to cite: Kojoj, J., Pereira Freitas, G., Mavis, C., Creamean, J., Mattsson, F., Nilsson, L., Spicker Schmidt, J., Adachi, K., Santl-Temkiv, T., Ahlberg, E., Mohr, C., Riipinen, I., and Zieger, P.: Evaluating natural aerosol sources from the Arctic Ocean during the onset of sea ice melt, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17925, https://doi.org/10.5194/egusphere-egu25-17925, 2025.

Field studies in the high and mid latitudes have demonstrated that snowpack emissions of reactive trace gases driven by photolysis alter regional atmospheric composition, the fate of pollutants and the polar ice core archive of past environmental change. Of particular interest are reactive nitrogen and halogen species released by surface snow, which in turn influence atmospheric levels of O₃ and hydroxyl radicals (OH and HO₂). Previous field campaigns at South Pole and Dome C showed that surface-near air on the high East Antarctic Plateau in summer is highly oxidising due to the interplay of photolytic snow emissions, a shallow boundary layer and cold temperatures.  However, open questions remain regarding the atmospheric oxidant budget above polar snow. Here we present recent observations carried out as part of the ISOL-ICE project at Kohnen Station (75ºS 0ºW) in austral summer 2017, located at a similar latitude as Dome C. Concurrent measurements of nitrogen oxides (NO and NO₂), atmospheric particulate nitrate collected on filters, O₃, slant-column bromine oxide (BrO), actinic flux and atmospheric turbulence were carried out for the first time at Kohnen. The bulk ion composition of in surface snow and shallow pits was measured as well.

While diurnal cycles of NO_x and turbulent diffusivity were similar to previous observations at Dome C, a distinct and strong diurnal cycle of surface O₃ with an amplitude of more than 10 nmol mol^-1 was detected. O₃ showed also a negative correlation with BrO in the lower atmosphere. These observations may imply O₃ photochemical source/sink processes, which are stronger than seen previously on the East Antarctic Plateau. We discuss the role of O₃ precursor emissions from the sunlit snowpack and vertical mixing with a view of the implications for our understanding of O₃ above polar snow.

How to cite: Frey, M., Winton, H., Savarino, J., and Juranyi, Z.: Unusually strong diurnal variability of ozone (O3) above summer snow in East Antarctica – a discussion of pre-cursor snow emissions and atmospheric transport, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12209, https://doi.org/10.5194/egusphere-egu25-12209, 2025.

Stable boundary layers (SBL) commonly form during the Arctic polar night, but their correct representation has been posing major challenges for numerical weather prediction (NWP) systems. To enable innovative model verification, we performed measurements of the lower atmospheric boundary layer with airborne fiber-optic distributed sensing (FODS), a tethered sonde, and ground-based eddy-covariance measurements. Here we contrast findings across two representative synoptic forcings leading to structurally different inversion types in a fjord-valley system in Svalbard, namely inflow and outflow conditions during the arctic polar night in early 2024. The strong gradients of the inversions are accompanied by an increased temperature variance, which is related to enhanced buoyancy fluctuations. The observed vertical temperature and wind speed profiles are compared to two configurations of the HARMONIE-AROME system with different horizontal resolutions at 2.5 km and 0.5 km.

The higher-resolution model captures cold pool and low-level jet formation during weak synoptic forcing and valley outflow, resulting in a well-represented vertical temperature profile down to the snow surface, while the coarser model exhibits a warm bias in near-surface temperatures of up to 8 K due to underestimated inversion strength. During changing background flow to valley inflow conditions, the higher-resolution model is more sensitive to misrepresented fjord-scale wind directions and performs less well, while the coarser NWP system has a seemingly better agreement with the observations lending to the underrepresented interaction with the topography.

The results indicate the importance of the ratio between nominal horizontal model resolution and valley width to represent stable boundary layer features in a physically meaningful manner. Our results underline the substantial benefit of the innovative spatially resolving FODS measurements for model verification studies as well as the importance of model and topography resolution for accurate representation of stable boundary layers in complex terrain.

How to cite: Thomas, C., Mack, L., Kähnert, M., Jonassen, M., Batrak, Y., Remes, T., and Pirk, N.: Investigating Stable Boundary-Layer Temperature Profiles Observed from Fiber-Optic Distributed Sensing on a Tethered Balloon and comparing them against NWP Systems at Different Resolutions for an Arctic Fjord-Valley System in Svalbard, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7195, https://doi.org/10.5194/egusphere-egu25-7195, 2025.