Arctic permafrost ecosystems may release large amounts of carbon under warmer future climates and may therefore accelerate global climate change. Our study investigated how long-term grazing by large animals influenced ecosystem characteristics and carbon budgets at a Siberian permafrost site. Our results demonstrate that such management can contribute to stabilizing ecosystems to keep carbon in the ground, particularly through drying soils and reducing methane emissions.

The layer of air near the surface is poorly understood during conditions with weak winds. Further, it is even difficult to observe. In this experiment we used distributed temperature sensing to observe air temperature and wind speed at thousands of points simultaneously every couple of seconds. This incredibly rich data set can be used to examine and understand what drives the mixing between the atmosphere and surface during these weak-wind periods.

The relaxed eddy accumulation technique is a method used for measuring fluxes of chemical species in the atmosphere. It relies on a proportionality factor, β, which can be determined using different methods. Also, different techniques for sampling can be used by only drawing air into the measurement system when vertical wind velocity exceeds a certain threshold. We compare different ways to obtain β and different threshold techniques to direct flux measurements for three different sites.

The boundary layer (BL) is well understood when convectively mixed, yet we lack this understanding when it becomes stable and no longer follows classic similarity theories. The NYTEFOX campaign collected a unique meteorological data set in the Arctic BL of Svalbard during polar night, where it tends to be highly stable. Using innovative fiber-optic distributed sensing, we are able to provide unique insight into atmospheric motions across large distances resolved continuously in space and time.

We have all seen trees swaying in the wind, but did you know that this motion can teach us about ecology? We summarized tree motion data from many different studies and looked for similarities between trees. We found that the motion of trees in conifer forests is quite similar to each other, whereas open-grown trees and broadleaf forests show more variation. It has been suggested that additional damping or amplification of tree motion occurs at high wind speeds, but we found no evidence of this.

We evaluated the suitability of fiber-optic distributed temperature sensing (DTS) for observing spatial (>25 cm) and temporal (>1 s) details of airflow within and above forests. The DTS measurements could discern up to third-order moments of the flow and observe spatial details of coherent flow motions. Similar measurements are not possible with more conventional measurement techniques. Hence, the DTS measurements will provide key insights into flows close to roughness elements, e.g. trees.

In this work we present experimental results of a novel actively heated fiber-optic (AHFO) observational wind-probing technique. We utilized a controlled wind-tunnel setup to assess both the accuracy and precision of AHFO under a range of operational conditions (wind speed, angles of attack and temperature differences). AHFO has the potential to provide high-resolution distributed observations of wind speeds, allowing for better spatial characterization of fine-scale processes.

Recession analysis uses the receding streamflow following precipitation events to estimate watershed-average properties. Two methods for recession analysis use recession events individually or all events collectively. Using synthetic case studies, this paper shows that analyzing recessions collectively produces flawed interpretations. Moving forward, recession analysis using individual recessions should be used to describe the average and variability of watershed behavior.

Air masses at the Schneefernerhaus mountain site at Zugspitze Mountain, Germany, were classified with respect to the atmospheric layer from which they originated and their degree of pollution. Measurements of several gases, particulate matter, and standard meteorological quantities indicated that polluted air was lifted to the site in 31 % of cases and clean air descended to the site in approximately 14 % cases while most of the remaining cases were ambiguous.

This study presents surface energy fluxes in an Antarctic polar desert in the summer season, comparing wetted soil at a water track with dominating dry soils. Elevated energy uptake, evaporation, and soil heat fluxes at the water track highlight the importance of wetted soils for water and energy cycling in polar deserts. This connection will grow more relevant, as wetted soils are expected to expand due to climate warming, with implications for landscape-scale hydrology and soil ecosystems.

To obtain magnitudes of flux components of H₂O and CO₂ (e.g., transpiration, soil respiration), we applied source partitioning approaches after Scanlon and Kustas (2010) and after Thomas et al. (2008) to high-frequency eddy covariance measurements of 12 study sites covering various ecosystems (croplands, grasslands, and forests) in different climatic regions. We analyzed the interrelations among turbulence, site characteristics, and the performance of both partitioning methods.

Recently reported trends of carbon dioxide uptake pose the question of whether trends may be the result of the limited digitalization of gas analysers and sonic anemometers used in the 1990s. Modifying a 12 bit digitalization and the instrument error reported for the R2 and R3 sonic anemometers found elsewhere, the influence of these deficits in comparison to the now commonly used 16 bit digitalization were quantified. Both issues have an effect only on trace gas fluxes of small magnitude.

Reaction rates of radiatively and chemically active trace species are influenced by the mobility of air contained within the snowpack. By measuring wind speed and the evolution of a tracer gas with in situ sensors over a 1 m horizontal grid, we found that inhomogeneities in a single snow layer enhanced air movement unevenly as wind speed increased. This result suggests small-scale variability in reaction rates that increases with wind speed and variability in snow permeability.

Intrinsic permeability of snow is an important parameter that regulates snow–atmosphere exchange. Current permeability measurements require specialized equipment for acquisition in the field and have increased variability with increasing snow heterogeneity. To facilitate a field-based, volume-averaged measure of permeability, we designed and assembled an acoustic permeameter. When using reticulated foam samples of known permeability, the mean relative error from known values was less than 20 %.

Fibre optic distributed temperature sensing allows one to measure temperature patterns along a fibre optic cable with resolutions down to 25 cm. In geosciences, we sometimes wrap the cable to a coil to measure temperature at even smaller scales. We show that coils with narrow bends affect the measured temperatures. This also holds for the object to which the coil is attached, when heated by solar radiation. We therefore recommend the necessity to carefully design such distributed temperature probes.

The monitoring and measurement of water flow in groundwater wells allows us to understand how aquifers transmit water. In this paper we develop a simple method, which we call T-POT, that allows flows to be estimated by tracking the movement of a small parcel of warmed water. The parcel is tracked using fibre optic temperature sensing - a technology that allows detailed measurements of temperature, and therefore flow using the T-POT method, to be made in the well.

We present a new instrument for measuring surface runoff rates ranging from very low (~0.05L min-1) to high (300L min-1, with much higher rates possible depending on the device configuration). The device is economical, simple, rugged, accurate and requires little maintenance (the system is self-emptying and contains no moving parts). We have successfully used this instrument in long-term monitoring studies and expect that it will appeal to other scientists studying runoff processes.