New validation method for hydrodynamic fjord models applied in the Hardangerfjord, Norway

We introduce a new intuitive evaluation method for comparison of fjord model results and current measurements. The approach is tested using high resolution model simulations and measurements in the Hardangerfjord, a large fjord system in Norway with huge aquaculture production. The method is easy to interpret, clearly distinguishes periods with good and poor model performance, and relate them to physical driving forces. This makes it possible to identify potential shortcomings in the models’ representation of physical processes. The applied model mostly performs well in the Hardangerfjord. Good performance often coincides with strong local fjord forcing (i.e. strong winds in the fjord). In periods with poor model performance, internal waves induced by pressure perturbations on the coastal shelf tend to propagate erroneously into the fjord. Stratification biases in coastal waters, connected to the applied model boundary conditions, seems to be an important cause. Demonstrated flexibility of time frame and performance criteria suggests applicability of the validation method for a wide set of geophysical variables in various physical environments.publishedVersio

Psykososial tilpasning og psykiske problemer blant barn i innvandrerfamilier

Hensikten med denne rapporten er å formidle kunnskap om psykisk helse, sosiokulturell integrasjon og risikofaktorer knyttet til familie, venner og skole blant barn med innvandrerbakgrunn i alderen 8 – 13 år. Det foreligger svært lite forskningsbasert informasjon, både nasjonalt og internasjonalt, om psykologisk tilpasning blant disse yngste medlemmene i innvandrerfamiliene. Rapporten retter seg både mot politiske myndigheter, fagfolk og frivillige som ser det som sitt ansvar å tilrettelegge gode oppvekstforhold for, og fremme mestring og trivsel blant, barn og unge med innvandrerbakgrunn.publishedVersio

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

© 2016. American Geophysical Union. All Rights Reserved. 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.The project MOCA- Methane Emissions from the Arctic OCean to the Atmosphere: Present and Future Climate Effects is funded by the Research Council of Norway, grant no.225814 CAGE – Centre for Arctic Gas Hydrate, Environment and Climate research work was supported by the Research Council of Norway through its Centres of Excellence funding scheme grant no. 223259. Nordic Center of Excellence eSTICC (eScience Tool for Investigating Climate Change in northern high latitudes) funded by Nordforsk, grant no. 57001

Corrigendum to "Pre-industrial to end 21st century projections of tropospheric ozone from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)" published in Atmos. Chem. Phys., 13, 2063–2090, 2013

No abstract available

Impact of future Arctic shipping on high-latitude black carbon deposition

The retreat of Arctic sea ice has led to renewed calls to exploit Arctic shipping routes. The diversion of ship traffic through the Arctic will shorten shipping routes and possibly reduce global shipping emissions. However, deposition of black carbon (BC) aerosol emitted by additional Arctic ships could cause a reduction in the albedo of snow and ice, accelerating snowmelt and sea ice loss. Here we use recently compiled Arctic shipping emission inventories for 2004 and 2050 together with a global aerosol model to quantify the contribution of future Arctic shipping to high-latitude BC deposition. Our results show that Arctic shipping in 2050 will contribute less than 1% to the total BC deposition north of 60°N due to the much greater relative contribution of BC transported from non-shipping sources at lower latitudes. We suggest that regulation of the Arctic shipping industry will be an insufficient control on high-latitude BC deposition

Discrepancy between simulated and observed ethane and propane levels explained by underestimated fossil emissions

Ethane and propane are the most abundant non-methane hydrocarbons in the atmosphere. However, their emissions, atmospheric distribution, and trends in their atmospheric concentrations are insufficiently understood. Atmospheric model simulations using standard community emission inventories do not reproduce available measurements in the Northern Hemisphere. Here, we show that observations of pre-industrial and present-day ethane and propane can be reproduced in simulations with a detailed atmospheric chemistry transport model, provided that natural geologic emissions are taken into account and anthropogenic fossil fuel emissions are assumed to be two to three times higher than is indicated in current inventories. Accounting for these enhanced ethane and propane emissions results in simulated surface ozone concentrations that are 5–13% higher than previously assumed in some polluted regions in Asia. The improved correspondence with observed ethane and propane in model simulations with greater emissions suggests that the level of fossil (geologic + fossil fuel) methane emissions in current inventories may need re-evaluation

Novel facultative Methylocella strains are active methane consumers at terrestrial natural gas seeps

Natural gas seeps contribute to global climate change by releasing substantial amounts of the potent greenhouse gas methane and other climate-active gases including ethane and propane to the atmosphere. However, methanotrophs, bacteria capable of utilising methane as the sole source of carbon and energy, play a significant role in reducing the emissions of methane from many environments. Methylocella-like facultative methanotrophs are a unique group of bacteria that grow on other components of natural gas (i.e. ethane and propane) in addition to methane but a little is known about the distribution and activity of Methylocella in the environment. The purposes of this study were to identify bacteria involved in cycling methane emitted from natural gas seeps and, most importantly, to investigate if Methylocella-like facultative methanotrophs were active utilisers of natural gas at seep sites

Impacts of Low Load Operation of Modern Four-Stroke Diesel Engines in Generator Configuration

Diesel engines in generator configuration are normally optimized for operations at medium to high engine loads. It is suspected that operations at low loads may increase operational problems and thus the damage frequency. It is also suspected that negative effects off low load operations are aggravated by recent exhaust emission regulations issued by IMO. This thesis describes an investigation of the impacts of low load operations on modern four-stroke diesel engines in generator configuration. The problem has been approached by reviewing existing literature, studying damage cases, analysis of existing finding data and by assessing engine manufacturers experiences with low load operations.Low load operations of diesel engines are defined as engine operations below 40% of maximum continuous rating. Low load operations are typical for, but not limited to, offshore vessels with dynamic positioning systems. Low load operations of diesel engines cause lower cylinder pressure and thus lower temperature. Low temperature can lead to ignition problems and poor combustion which causes increased soot formation and aggregation of unburned fuel in the cylinder. Low cylinder pressure, soot and unburned fuel deteriorate the piston ring sealing efficiency allowing hot combustion gases, soot particles and unburned fuel to leak past the piston rings. This results in increased lubricating oil consumption and dilution. Fuel dilution of the lubricating oil reduces the viscosity which can collapse critical oil film thicknesses. This can cause premature wear of pistons, rings, liners and crank case bearings. The mechanisms of low load lead to a cycle of degradation which means that diesel engines that run at low loads for longer periods of time can become irreversibly damaged. This is illustrated in this paper by an engine damage case. The damage case presents an engine crankcase breakage initially caused by piston scuffing from lubrication oil breakdown after excessive low load operations. Most modern diesel engines operate at lower cylinder pressure and thus lower temperatures to comply with stringent IMO NOX emission requirements. The IMO Tier I and II standards are met by primary measures which aim at reducing the amount of NOX formed during combustion by optimizing certain engine parameters. Modern NOX optimized engines are more exposed to low load operations than their predecessors due to initially lower cylinder pressures and temperatures. However, recent developments such as common rail, variable injection timing and variable valve control permit engine operations at lower loads than earlier. Existing finding data from DNV GL s database have been analysed to determine whether one can substantiate the impacts of low load operations quantitatively. The finding data have been analysed by simple frequency measurements. The results show higher finding frequencies for DP-vessels than non-DP vessels, which could indicate that low load operations may have a negative impact on the operational problems and thus the damage frequency. The finding data have also been evaluated with respect to time to determine whether NOX optimization aggravates the negative impacts of low load operations. The result showed generally higher finding frequencies for engines installed after 2000 than the ones installed prior to 2000. This could indicate that the introduction of Tier I compliant engines have increased operational problems. However, it could not be determined whether NOX optimized engines have aggravated the negative impacts of low load operations. Engine manufacturers that have been interviewed agree that low load operations affect the engine operation negatively, but they do not want confirm that low load operation increases the engine damage frequency. It is consensus among the engine manufacturers that the engines must be loaded to at least 50% of rated power regularly during low load operations to prevent operational problems. The time interval and load requirements can vary from one engine to another and depending on the engine design