Foredrag
AerOzClim Module II:
Description of aerosol particles and their physical properties in a atmospheric global climate model (CCM-Oslo).
Trond Iversen, Øyvind Seland, Alf Kirkevåg, Jon Egill Kristjansson
Department of Geosciences, University of Oslo, P.O. Box 1022, Blindern, N-0315 Oslo. ()
The potential influence of anthropogenic aerosol particle on climate is designated by IPCC TAR as an important source of climate model uncertainty. There are several reasons for this. Particles are partly realeased directly into air and partly produced in situ by gas-to-particle physico-chemical reactions. They are subject to quick depletion by precipitation scavenging, and their tropospheric residence times are generally only a few days to a week. Also they can be produced and processed otherwise in cloud droplets. Hence, the space-time distribution of aerosols is strongly influenced by clouds, and clouds and their properties are themselves very uncertain in atmospheric numerical models.
One potential climate effect of aerosols is the particles’ reflection and absorption of solar radiation; the direct effect. To calculate the radiative forcing due to this requires knowledge of particle composition as a function of particle size, in order to estimate the reflectivity and absorptivity for each wavelength of light. Another potential climate effect of aerosols is linked to the particles’ ability to extract water from water vapor and thus act as cloud condensation nuclei (CCN). More CCNs may cause smaller and more reflective cloud droplets (first indirect effect), less efficient precipitation release and thus more cloudiness (second indirect effect).
In AerOzClim we develop new methods that are simplified compared to “first principles”, but still more accurate than in earlier climate models. In this presentation we will demonstrate the principles behind the schemes along with results from designed experiments for the ongoing intercomparison exercise that prepares for the next IPCC report (Aerocom).
CHEMCLIM: Tropospheric chemistry and climate
Ivar S.A. Isaksen
Department of Geosciences, University of Oslo, P.O. Box 1022, Blindern, N-0315 Oslo. ()
In CHEMCLIM the overall focus is on how natural emission and emission of pollutants affect oxidation processes in the atmosphere and the distribution of chemical active greenhouse gases (e.g. ozone, methane), particles from natural (sea salt, mineral dust) and anthropogenic (e.g. sulfate, organics) sources, and how changes in the emission contribute to the global radiative forcing. Global model studies are being performed in three main areas: Studies of the oxidation potential of the troposphere and how it is changing due to changes in the emission of pollutants. The OsloCTM2 model has been updated with the newest and best emission inventories that are available. The purpose is to be able to make sensitivity studies of different emission source categories impact on current, past and future climate and pollution levels. The oxidation studies include particular model studies of ozone and sulfate particle formation due to ship emissions and studies of changes in sulfate burden due to emission changes over the last 10 to 15 years. Studies of sources of mineral dust and temporal changes in the global distribution have been performed in collaboration with University of California, Irvine. Studies of climate-chemistry interactions of water vapour in the upper troposphere and lower stratosphere (UTLS) region are being performed in collaboration with State University of New York (SUNY), Albany, using the NCAR CCM3 climate model. Most of the modeling studies in the CHEMCLIM project are performed by PhD students as part of their thesis work, and include a significant part of basic process studies and model development. The Oslo CTM2 has been developed to include extensive physical and chemical schemes to study chemical active gaseous and aerosol compounds. Comparisons with observations show that the models developed are able to realistically reproduce the distribution of major chemically active compounds in the troposphere. The modeling activities performed in CHEMCLIM are the basis for particle studies and ozone climate–chemistry studies performed in AerOzClim. Results from the modeling activities in the different areas will be presented.
CHEMCLIM: Studier av kjemisk active klimagasser (ozon, methan) og partikler (sulfat, organiske partikler, sjøsalt, mineralstøv) i atmosfæren og deres innvirkning på strålingen.
Combined Observational and Modeling Based Studies of the Aerosol Indirect Effect (COMBINE)
Jón Egill Kristjánsson1, Trude Storelvmo1, Mona Johnsrud2, Gunnar Myhre1,2,Frode Stordal1, Ann-Mari Fjæraa2
1 Department of Geosciences, University of Oslo
2 Norwegian Institute for Air Research, Kjeller
Humans influence the climate in various ways, e.g., by releasing so-called greenhouse gases into the atmosphere and by introducing new particles (aerosols) into the atmosphere. In this way the number of cloud condensation nuclei (CCN) is enhanced, leading to smaller and more numerous cloud droplets, which reflect more solar radiation. The impact of this “indirect effect” of aerosols is, by current estimates, only surpassed in magnitude by greenhouse gas forcing, but with opposite sign. At present, there is great uncertainty concerning many aspects of the indirect effect. This is due to a combination of poorly understood physics, insufficient measurements and oversimplified model treatments. In Norway, the modeling aspect has been addressed within the RegClim project, and will be worked on further in AerOzClim. To strengthen the research in this area, we have introduced an integrated effort combining climate modeling and the use of satellite observations. To improve the simulations of the indirect effect, prognostic equations will be developed for cloud droplet number and ice crystal number. The satellite observations will serve to identify and evaluate the magnitude of the indirect effect, as well as to validate crucial model parameters, such as aerosol optical depth, cloud optical depth, liquid water path and CCN. These quantities are obtained from the MODIS instrument onboard the Terra and Aqua satellites.
Deep water ventilation processes
Peter M. Haugan, Tor Eldevik, Bjørn Ådlandsvik on behalf of the ProClim participants
The deep parts of the world oceans are ventilated from the surface in limited areas at high latitudes. Small scale ocean mixing processes, mesoscale variability, sea ice formation and salt release are involved in setting the properties of the deep water and the pathways of circulation between low and high latitudes. Since this circulation is crucial to the ocean heat transport, the surface temperature and the sea ice distribution, there is a need to understand the physics of the processes and their sensitivity to atmospheric conditions. Studies in the Polar Ocean Climate Processes (ProClim) project focusses on process studies in the Storfjord area and thewestern Barents Sea, Norwegian Sea, and Greenland Sea.
The sea ice production and salt release in Storfjorden is primarily determined by the strength of northeasterly winds locally each winter. The resulting dense water volume and properties also depend upon the Arctic and Atlantic water masses advected into the area, i.e. on larger and longer time scale conditions. Mixing in the outflow is primarily determined by shear instability between the dense flow and ambient water above. This first order description based on measurements gives a good basis for modelling based on appropriate atmospheric forcing, although predictive capability for the whole system still remains to be tested.
Deep convection in the open ocean involves small net vertical volume flow but is nevertheless important for deep water properties and large scale pressure fields. The variability in the strength of the different ventilation processes and pathways on shelves and in the deep ocean is large. The possibility for alternation between different modes and shift between different areas in closing the overturning circulation will be addressed in later parts of the project but remains a motivation for the ongoing work.
ECOBE 2003-2006 (Effects of North Atlantic Climate Variability On the Barents Sea Ecosystem) – preliminary results from the first year of the project.
Svein Sundby
Institute of Marine Research and Bjerknes Centre for Climate Research
The over-all goal of this integrated project is to understand and quantify the impacts of Arctic climate variability on trophic transfer and ecosystem structure of the Barents Sea in order to improve the prediction of growth and recruitment on key fish species. Inflow of Atlantic plankton-rich water from the Norwegian Sea onto the Norwegian continental shelves is of major importance for the growth and survival of fish stocks along the Norwegian coast and in the Barents Sea. Additionally, ocean climate parameters as temperature, light conditions, wind-induced mixing and turbulence are important abiotic parameters for individual growth of marine organisms. In the ECOBE project, we use integrated physical-biological models to explore influence of the various processes of importance for growth and recruitment in fish. Laboratory experiments produce important input data to the coupled models. The model results are compared to survey data of pelagic juveniles from the region. Here, we present preliminary results after the first year of the project. A first-generation individual-based model simulates growth and survival of larval fish from the spawning areas along the Norwegian coast till the stage of pelagic juveniles when they are spread out in the Barents Sea.
Ecological and nutrient feedbacks to anthropogenic ocean acidification from rising atmospheric CO2
Richard Bellerby – Bjerknes Centre for Climate Research, University of Bergen
The surface oceans are increasing in carbon dioxide, in concert with rising atmospheric concentrations, and there is a consequentially reduction in the seawater pH. Models show that within this century, the anticipated drop in pH will reach levels not seen for the last 420,000 years. Laboratory and field studies have shown that such pH levels have a considerable effect on plankton physiology and community structure. Further into the next century ocean pH will reduce to levels that severely effect the survival of certain marine organisms, particularly benthic and polar species. Decreased pH results in changes in nutrient utilisation and export production which will have consequences for food web structure and ultimately for fisheries. Such planktonic biogeochemical responses will have pronounced feedback to atmospheric carbon dioxide concentrations.
ECOSYSTEM MANIPULATIONS AS A TOOL IN CLIMATE RESEARCH
Arne Stuanes1, Richard F. Wright2, Heleen de Wit3, Lars Hole4, Øyvind Kaste2 & Jan Mulder1
1 Department of Plant and Environmental Sciences, Agricultural University of Norway,
2 Norwegian Institute for Water Research, 3 Norwegian Institute for Land Inventory,
4 Norwegian Institute for Air Research
Large-scale ecosystem experiments are a powerful tool to study environmental effects on ecosystems. Norway has a long experience with large-scale experiments in forest, lake and heathland ecosystems and has an international reputation in this field. Large-scale ecosystem experiments started in the 1970s with research on effects of acid rain on forest and fish (SNSF project). In the SNSF project large field experiments included addition of artificial acid rain in forests and manipulations in small catchments. This was followed by the RAIN project (1984-93) where a small upland catchment with trees was covered by a roof to study the reversibility of acidification. Later, ecosystem-scale experiments with nitrogen (addition and exclusion) in forest (NITREX) and acidification of lakes (HUMEX) were established. In another large- scale experiment in forest aluminium was added to study the effect of this metal on a closed forest stand. Experiments to study the effects of climate change began in the 1990s with the CLIMEX project (glass house covering a forested catchment where CO2 concentration and air temperature were increased) and the THERMOS project (manipulation of heat budget for a whole lake).
Results and experiences gained from these large-scale ecosystem experiments have led to use of this approach in the new Norwegian climate change effects project “Effect of climate change on flux of N and C: air-land-freshwater-marine links (CLUE)”. In the CLUE project we will manipulate snow cover, freeze-thaw cycles, and soil wetness in mini-catchments to simulate future climate scenarios of increased frequency of freezing and thawing cycles in winter, melting episodes due to increased temperature in winter and increased summer and autumn precipitation.
Such controlled large-scale experiments give direct information on effects of different environmental factors on an ecosystem level. They are necessary for evaluation of long-term effects in a short-term perspective. Such experiments are also essential for testing of models that later can be used for extrapolations in time and space.
Ecosystem process modeling with input data from climate scenarios, preliminary experiences.
Lars Bakken
GCM simulations of the present and future global climate can be downscaled to provide local “weather forecasts”. Such downscaled global warming scenarios are like manna from heaven for ecosystem process modellers because they allow us to explore the effects of future global warming on ecosystem functions, including their feedback on the global warming. These phenomena are not predictable by simple statistical climate information (average temperature, annual precipitation etc), because of various non linear responses of interacting components within the ecosystems. We need real weather scenarios (daily weather information) to run our models! The Norwegian research program Regclim has produced such regionalized weather scenarios for the period 2030-2049, based on the basic global scenario from Max-Planck-Institute (MPI) in Germany.
We have used these “weather forecasts” for 2030-49 (SIM3049) as driving data in a cluster of physical, biological, and economical models for agroecosystems. Such exercises necessarily requires an investigation of validity of the weather forecasts as well as our ecosystem forecasts. As a control, we used downscaled MPI simulations for the period 1980-99 (SIM8099), which were compared to observed weather in the same period (OBS8099). Some problematic characteristics of the SIM8099-weather were identified, which had severe consequences for the simulation of water transport, plant growth and soil erosion. Some of these problems were solved by adjustments based on empirical downscaling, and the RegClim project plans for further improvements in the near future. Other problems experienced were the lack of transparency and a large annual variability (20 years scenarios are too short to test relevant changes).
Assuming that the contrast between SIM3049 and SIM8099 is an adequate prediction of the climate change in response to future global warming, we find that soil erosion will increase dramatically and nitrate leaching may increase substantially. The latter is a result of an altered economic optimum for N-fertilization due to slight changes in the product functions. This was not statistically significant, however.
Fører klimaendring til at fjellreven forsvinner?
Nina E. Eide, John D.C. Linnell, Unni S. Lande, Vidar Grøtan, Olav Strand og Pål Prestrud
Arctic foxpopulations declined rapidly around 1900 throughout Fennoscandia and were close to extinction around the 1920s. Despite more than 70 years of protection there has been no recovery of the arctic foxes. The decline was extremely pronounced in Fennoscandia. Although less pronounced, the decline in arctic foxes was observed throughout the whole Arctic. The changes in population sizes across several continents happen approximately at the same time; around 1900, implying a common change happening at larger spatial scales. Many hypotheses have been put forward to explain the non-recovery of the arctic fox; one of them is indirect effects of a warmer climate. The southerly (and lower altitudinal) distribution of arctic foxes is probably constrained by the distribution of the dominant competitor, the red fox, with arctic foxes only surviving in areas that have too low productivity for red fox to survive. At the same time as arctic foxes declined, there was a general temperature rise from 1900 over the whole northern hemisphere. A general temperature rise is expected to result in a vertical rise in productivity zones; which also lead to the expectation that red fox distribution will expand vertically, leading to a decrease in potential arctic fox habitat. The main objective of this study has been to improve our understanding of possible influences of climate changes on community structure in alpine ecosystems, with main focus on the relationship between the arctic fox (a “polar” species) and the red fox (a “temperate” species). Changes at the level of species could in the long run lead to changes in species diversity, shorter food chains and a simplification of alpine ecosystems. The red fox as a typical generalist predator is also a pronounced keystone species, and an increase and expansion of the red fox population could hence have large influence on both the structure and the dynamic of the alpine ecosystem. We explore coincident changes in the abundance of species having the same specialist food niche as the arctic fox; snowy owl, rough-legged buzzard, long-tailed skua; which could indicate larger changes in the structure of alpine ecosystems, and if these changes relate to the climatic changes that have occurred over the last 100-150 years. Could further climate change result in loss of the arctic fox and typical alpine habitat niches?