We have modelled how gas seeping from the seafloor spreads in the ocean and how much reaches the atmosphere. We estimate how much free gas dissolves in water, atmospheric release and 3-D concentration using data from a hydrodynamic model and gas loss modules. We applied the framework to a methane (CH₄) seep site offshore Norway showing that atmospheric CH₄ release is spread over a large area. However, with our assumptions, most of the CH₄ (>90 %) is converted to CO₂ by microbes.

The EISCAT_3D radar is a new ionospheric radar under construction in the Fennoscandia region. The radar will make measurements of plasma characteristics at altitudes above approximately 60 km. The capability of the system to make these measurements at spatial scales of less than 100 m using multiple digitised signals from each of the radar antenna panels is highlighted. There are many ionospheric small-scale processes that will be further resolved using the techniques discussed here.

This study reports the first simultaneous records of oxygen (Δ¹⁷O) and nitrogen (δ¹⁵N) isotopes in nitrogen dioxide (NO₂) and nitrate (NO₃⁻). These data are combined with atmospheric observations to explore sub-daily N reactive chemistry and quantify N fractionation effects in an Alpine winter city. The results highlight the necessity of using Δ¹⁷O and δ¹⁵N in both NO₂ and NO₃⁻ to avoid biased estimations of NO_x sources and fates from NO₃⁻ isotopic records in urban winter environments.

We present a second-level calibration method for electron density measurements from multi-beam incoherent scatter radars. It is based on the well-known Flat field correction method used in imaging and photography. The methods improve data quality and useability as they account for unaccounted, and unpredictable variations in the radar system. This is valuable for studies where inter-beam calibration is important such as studies of polar cap patches, plasma irregularities and turbulence.

We report on a 3000-year record of carbon monoxide (CO) levels in the Southern Hemisphere's high latitudes by combining ice core and firn air measurements with modern direct atmospheric samples. Antarctica [CO] remained stable (–835 to 1500 CE), decreased during the Little Ice Age, and peaked around 1985 CE. Such evolution reflects stable biomass burning CO emissions before industrialization, followed by growth from CO anthropogenic sources, which decline after 1985 due to improved combustion.

The study of some ionospheric events benefit from the knowledge of how the physics varies over a volume and over time. Examples are studies of aurora or energy deposition. With EISCAT3D, measurements of ion velocity vectors in a volume will be possible for the first time. We present a technique that uses a set of such measurements to estimate electric field and neutral wind. The technique relies on adding restrictions to the estimates. We successfully consider restrictions based on physics.

The high reactivity of the summer Antarctic boundary layer results in part from the emissions of nitrogen oxides produced during photo-denitrification of the snowpack, but its underlying mechanisms are not yet fully understood. The results of this study suggest that more NO₂ is produced from the snowpack early in the photolytic season, possibly due to stronger UV irradiance caused by a smaller solar zenith angle near the solstice.

The Arecibo radar was used to probe free electrons of the ionized atmosphere between 70 and 100 km altitude. This is also the altitude region were meteors evaporate and form secondary particulate matter, the so-called meteor smoke particles (MSPs). Free electrons attach to these MSPs when the sun is below the horizon and cause a drop in the number of free electrons, which are the subject of these measurements. We also identified a different number of free electrons during sunset and sunrise.

We investigate organic matter composition in the Arctic Ocean water column. We collected seawater samples from sea ice to deep waters at six vertical profiles near an active hydrothermal vent and its plume. In comparison to seawater, we found that the organic matter in waters directly affected by the hydrothermal plume had different chemical composition. We suggest that hydrothermal processes may influence the organic matter distribution in the deep ocean.

Natural sources of atmospheric methane need to be better described and quantified. We present time series from ocean observatories monitoring two seabed methane seep sites in the Arctic. Methane concentration varied considerably on short timescales and seasonal scales. Seeps persisted throughout the year, with increased potential for atmospheric release in winter due to water mixing. The results highlight and constrain uncertainties in current methane estimates from seabed methane seepage.

When radio waves from our galaxy enter the Earth's atmosphere, they are absorbed by electrons in the upper atmosphere. It was thought that by measuring the amount of absorption, it would allow the height of these electrons in the atmosphere to be determined. If so, this would have significance for future instrument design. However, this paper demonstrates that it is not possible to do this, but it does explain how multiple-frequency measurements can nevertheless be useful.

We introduce a new way of estimating winds in the upper atmosphere (about 80 to 100 km in altitude) from the observed Doppler shift of meteor trails using a statistical method called Gaussian process regression. Wind estimates and, critically, the uncertainty of those estimates can be evaluated smoothly (i.e., not gridded) in space and time. The effective resolution is set by provided parameters, which are limited in practice by the number density of the observed meteors.

Measurements of the electric field and neutral wind in the ionosphere are important for understanding energy flows or electric currents. With incoherent scatter radars (ISRs), we can measure the velocity of the ions, which depends on both the electrical field and the neutral wind. In this paper, we investigate methods to use ISR data to find reasonable values for both parameters. We find that electric field can be well measured down to 125 km height and neutral wind below this height.

This work explores the role of EISCAT 3D as a tool for planetary mapping. Due to the challenges inherent in detecting the signals reflected from faraway bodies, we have concluded that only the Moon is a viable mapping target. We estimate the impact of the ionosphere on lunar mapping, concluding that its distorting effects should be easily manageable. EISCAT 3D will be useful for mapping the lunar nearside due to its previously unused frequency (233 MHz) and its interferometric capabilities.

This paper explores the dynamics of gravity waves and turbulence present in the mesosphere and lower thermosphere (MLT) region. We utilized two different techniques on meteor radar observations and simulations to obtain power spectra at different horizontal scales. The techniques are applied to a special campaign conducted in northern Germany in November 2018. The study revealed the dominance of large-scale structures with horizontal scales larger than 500 km during the campaign period.