Ove Hermansen

Arctic methane sources: Isotopic evidence for atmospheric inputs

By comparison of the methane mixing ratio and the carbon isotope ratio (δ13CCH4) in Arctic air with regional background, the incremental input of CH4 in an air parcel and the source δ13CCH4 signature can be determined. Using this technique the bulk Arctic CH4 source signature of air arriving at Spitsbergen in late summer 2008 and 2009 was found to be −68‰, indicative of the dominance of a biogenic CH4 source. This is close to the source signature of CH4 emissions from boreal wetlands. In spring, when wetland was frozen, the CH4 source signature was more enriched in 13C at −53 ± 6‰ with air mass back trajectories indicating a large influence from gas field emissions in the Ob River region. Emissions of CH4 to the water column from the seabed on the Spitsbergen continental slope are occurring but none has yet been detected reaching the atmosphere. The measurements illustrate the significance of wetland emissions. Potentially, these may respond quickly and powerfully to meteorological variations and to sustained climate warming.

Reconciling reported and unreported HFC emissions with atmospheric observations

Significance Hydrofluorocarbons (HFCs) are among the atmosphere’s fastest growing, and most potent, greenhouse gases. Proposals have been made to phase down their use over the coming decades. Such initiatives may largely be informed by existing emissions inventories, which, we show, are the subject of significant uncertainty. In this work, we use atmospheric models and measurements to examine the accuracy of these inventories for five major HFCs. We show that, when aggregated together, reported emissions of these HFCs from developed countries are consistent with the atmospheric measurements, and almost half of global emissions now originate from nonreporting countries. However, the agreement between our results and the inventory breaks down for individual HFC emissions, suggesting inaccuracies in the reporting methods for individual compounds. We infer global and regional emissions of five of the most abundant hydrofluorocarbons (HFCs) using atmospheric measurements from the Advanced Global Atmospheric Gases Experiment and the National Institute for Environmental Studies, Japan, networks. We find that the total CO2-equivalent emissions of the five HFCs from countries that are required to provide detailed, annual reports to the United Nations Framework Convention on Climate Change (UNFCCC) increased from 198 (175–221) Tg-CO2-eq⋅y–1 in 2007 to 275 (246–304) Tg-CO2-eq⋅y–1 in 2012. These global warming potential-weighted aggregated emissions agree well with those reported to the UNFCCC throughout this period and indicate that the gap between reported emissions and global HFC emissions derived from atmospheric trends is almost entirely due to emissions from nonreporting countries. However, our measurement-based estimates of individual HFC species suggest that emissions, from reporting countries, of the most abundant HFC, HFC-134a, were only 79% (63–95%) of the UNFCCC inventory total, while other HFC emissions were significantly greater than the reported values. These results suggest that there are inaccuracies in the reporting methods for individual HFCs, which appear to cancel when aggregated together.

Extensive release of methane from Arctic seabed west of Svalbard during summer 2014 does not influence the atmosphere

We find that summer methane (CH4) release from seabed sediments west of Svalbard substantially increases CH4 concentrations in the ocean but has limited influence on the atmospheric CH4 levels. Our conclusion stems from complementary measurements at the seafloor, in the ocean, and in the atmosphere from land-based, ship and aircraft platforms during a summer campaign in 2014. We detected high concentrations of dissolved CH4 in the ocean above the seafloor with a sharp decrease above the pycnocline. Model approaches taking potential CH4 emissions from both dissolved and bubble-released CH4 from a larger region into account reveal a maximum flux compatible with the observed atmospheric CH4 mixing ratios of 2.4–3.8 nmol m−2 s−1. This is too low to have an impact on the atmospheric summer CH4 budget in the year 2014. Long-term ocean observatories may shed light on the complex variations of Arctic CH4 cycles throughout the year.

Atmospheric histories and global emissions of halons H‐1211 (CBrClF2), H‐1301 (CBrF3), and H‐2402 (CBrF2CBrF2)

We report ground-based atmospheric measurements and emission estimates for the halons H-1211 (CBrClF₂), H-1301 (CBrF₃), and H-2402 (CBrF₂CBrF₂) from the AGAGE (Advanced Global Atmospheric Gases Experiment) and the National Oceanic and Atmospheric Administration global networks. We also include results from archived air samples in canisters and from polar firn in both hemispheres, thereby deriving an atmospheric record of nearly nine decades (1930s to present). All three halons were absent from the atmosphere until ~1970, when their atmospheric burdens started to increase rapidly. In recent years H-1211 and H-2402 mole fractions have been declining, but H-1301 has continued to grow. High-frequency observations show continuing emissions of H-1211 and H-1301 near most AGAGE sites. For H-2402 the only emissions detected were derived from the region surrounding the Sea of Japan/East Sea. Based on our observations, we derive global emissions using two different inversion approaches. Emissions for H-1211 declined from a peak of 11 kt yr⁻¹ (late 1990s) to 3.9 kt yr⁻¹ at the end of our record (mean of 2013–2015), for H-1301 from 5.4 kt yr⁻¹ (late 1980s) to 1.6 kt yr⁻¹, and for H-2402 from 1.8 kt yr⁻¹ (late 1980s) to 0.38 kt yr⁻¹. Yearly summed halon emissions have decreased substantially; nevertheless, since 2000 they have accounted for ~30% of the emissions of all major anthropogenic ozone depletion substances, when weighted by ozone depletion potentials.

HFC‐43‐10mee atmospheric abundances and global emission estimates

We report in situ atmospheric measurements of hydrofluorocarbon HFC-43-10mee (C5H2F10; 1,1,1,2,2,3,4,5,5,5-decafluoropentane) from seven observatories at various latitudes, together with measurements of archived air samples and recent Antarctic flask air samples. The global mean tropospheric abundance was 0.21 ± 0.05 ppt (parts per trillion, dry air mole fraction) in 2012, rising from 0.04 ± 0.03 ppt in 2000. We combine the measurements with a model and an inverse method to estimate rising global emissions—from 0.43 ± 0.34 Gg yr−1 in 2000 to 1.13 ± 0.31 Gg yr−1 in 2012 (~1.9 Tg CO2-eq yr−1 based on a 100 year global warming potential of 1660). HFC-43-10mee—a cleaning solvent used in the electronics industry—is currently a minor contributor to global radiative forcing relative to total HFCs; however, our calculated emissions highlight a significant difference from the available reported figures and projected estimates.

A Tracer Method for Evaluating Recirculation of Pollutant Releases in Buildings

A method is introduced for evaluating recirculation in a building ventilation system from pollutant emissions in or near the building. Tracer was released at a known rate at the point of pollutant emission. Using measured tracer concentrations, the tracer release rate, and an estimate of the pollutant release rate, pollutant concentrations were estimated at the locations in the building where the tracer was measured. The method can be used to test whether a ventilation system is adequate for maintaining an acceptable work environment before work with a hazardous substance begins. In a case study presented to illustrate the technique, initial attempts to correct a problem of recirculation of sulfuric acid from a fume hood in a chemistry laboratory were shown to be inadequate, prompting the ventilation contractor to make further repairs before work with sulfuric acid could be resumed.

INFLUENCE OF LOCAL AND REGIONAL AIR POLLUTION ON ATMOSPHERIC MEASUREMENTS IN NY-ÅLESUND

The Zeppelin observatory is a research station near the village Ny-Ålesund in Svalbard. The facility delivers data to international projects devoted to high data quality monitoring of the background air pollution in the Arctic. An approach for quantifying the influence of local and regional pollution on measurements that may be misinterpreted as long-range transported one, is presented here. The hourly gas and aerosol data measured in Ny-Ålesund and at the Zeppelin station, respectively, have been analysed along with the meteorological data from Ny-Ålesund, Zeppelin station and Longyearbyen (south-east of Ny-Ålesund). Seasonal fluctuation of the average measured values of SO2 and NOx has been observed. Three main wind directions coincided with the peak concentration of SO2 and NOx. The NW-N flow may bring local pollution from ship traffic and diesel power plant as well as biogenic SO2 from the oxidation of DMS. The monthly average number of particles with diameter characteristic for ship plume (50–100 nm), was elevated for the hours when ships have been registered in the local call list. The number concentration of particles with diameter 200 nm, typical for Arctic haze events, and concentration of non-sea salt sulphate rise during springtime. The FLEXTRA-trajectory analysis indicated that most pollution brought by E-SE and SW flows may be of long-range and/or regional origin. Events with these flow directions need to be interpreted with caution.

Effect of seasonal mesoscale and microscale meteorological conditions in Ny-Ålesund on results of monitoring of long-range transported pollution

ABSTRACT Ny-Ålesund is an international research settlement where the thermodynamics and chemical composition of the air are monitored. The present work investigates the effects of micrometeorological conditions, mesoscale dynamics and local air pollution on the data collected at two different locations around the village. Daily filter measurements of sulphur dioxide and non-sea salt sulphate from the temporary Ny-Ålesund station and permanent Zeppelin mountain station have been analysed along with meteorological data. The influence of different factors representing micrometeorological phenomena and local pollution from ships has been statistically investigated. Seasonal variation of the correlation between the data from Ny-Ålesund and Zeppelin stations is revealed, and the seasonal dependence of the relative contribution of different factors has been analysed. The median concentrations of SO42- measured in Ny-Ålesund increased significantly on days with temperature inversions in winter. In spring, concentrations of SO2 and SO42- were higher than normal at both stations on days with temperature inversions, but lower on days with strong humidity inversions. In summer, local ship traffic affects the SO2 data set from Ny-Ålesund, while no statistically significant influence on the Zeppelin data set has been observed. The pollution from ships has an effect on SO42- values at both stations; however, the concentrations in Ny-Ålesund were higher when local pollution accumulated close to the ground in days with strong humidity inversions.

Temporal Variability in Surface Water pCO2 in Adventfjorden (West Spitsbergen) With Emphasis on Physical and Biogeochemical Drivers

Seasonal and interannual variability in surface water partial pressure of CO2 (pCO2) and air-sea CO2 fluxes from a West Spitsbergen fjord (IsA Station, Adventfjorden) are presented, and the associated driving forces are evaluated. Marine CO2 system data together with temperature, salinity, and nutrients, were collected at the IsA Station between March 2015 and June 2017. The surface waters were undersaturated in pCO2 with respect to atmospheric pCO2 all year round. The effects of biological activity (primary production/respiration) followed by thermal forcing on pCO2 were the most important drivers on a seasonal scale. The ocean was a sink for atmospheric CO2 with annual air-sea CO2 fluxes of 36 ± 2 and 31 ± 2 g C·m ·year 1 for 2015–2016 and 2016–2017, respectively, as estimated from the month of April. Waters of an Arctic origin dominated in 2015 and were replaced in 2016 by waters of a transformed Atlantic source. The CO2 uptake rates over the period of Arctic origin waters were significantly higher (2 mmol C·m ·day ) than the rates of the Atlantic origin waters of the following year.

Atmospheric DMS in the Arctic ocean and its relation to phytoplankton biomass

We recorded and analyzed the atmospheric dimethyl sulfide (DMS) mixing ratios at a remote Arctic location (Svalbard; 78.5°N, 11.8°E) during phytoplankton bloom periods in the years 2010, 2014, and 2015 and found varying regional relationships between the atmospheric DMS and the extent of exposure of the air mass to the phytoplankton biomass in the ocean surrounding the observation site. The DMS production capacity of the Greenland Sea was estimated to be a factor of 3 greater than that of the Barents Sea, whereas the phytoplankton biomass in the Barents Sea was more than twofold than that in the Greenland Sea. These apparently contradictory results may be induced by the occurrence of a greater abundance of DMS-producing phytoplankton in the Greenland Sea than in the Barents Sea during the phytoplankton bloom periods.