New research from last week 32/2012
Posted on 14 August 2012 by Ari Jokimäki
Mankind puts dust to atmosphere and all other sorts of air pollution, which pollutes trees so that we can't do climate reconstructions anymore. Trees emit methane which is then measured from sea by Japanese researchers who also think that tsunamis should be detected by satellites which also measure net primary productivity, which is a good idea because climate did have an effect on ecosystems also in past. Meanwhile, we fiddle with our miniaturized radiance cameras and debate if ice surface is melting over large areas of Greenland, which is in Arctic where there just recently were record ozone loss. I guess Arctic is such a big place that it is easy to lose lot of things there, such as ice and ozone. Anyway, at the end we just feed everything to climate models, which by the way have very good quality software.
Miniaturized radiance cameras measuring underwater multi-spectral radiances in all directions
Abstract: "Miniaturized radiance cameras measuring underwater multi-spectral radiances in all directions at high-radiometric accuracy – the CE600 – are presented. The camera design is described, as well as the main steps of its optical and radiometric characterization and calibration. The results show excellent optical quality of the specifically designed fisheye objective. They also show the low noise and excellent linearity of the Complementary Metal Oxide Semiconductor (CMOS) detector array that is used. Initial results obtained in various oceanic environments demonstrate the potential of this instrument to provide new measurements of the underwater radiance distribution from the sea surface to dim-lighted layers at depth. Excellent agreement is obtained between nadir radiances measured with the camera and commercial radiometers. Comparison of the upwelling radiances distributions measured with the CE600 and those obtained with another radiance camera also show a very close agreement. The CE600 measurements allow all apparent optical properties (AOPs) to be determined from integration of the radiances distributions, and inherent optical properties (IOPs) to be determined from inversion of the AOPs. This possibility represents a significant advance for marine optics, by tying all optical properties to the radiometric standard and avoiding deployment of complex instrument packages to collect AOPs and IOPs simultaneously (except when it comes to partitioning IOPs into their component parts)."
Citation: David Antoine, André Morel, Edouard Leymarie, Amel Houyou, Bernard Gentili, Stéphane Victori, Jean-Pierre Buis, Nicolas Buis, Sylvain Meunier, Marius Canini, Didier Crozel, Bertrand Fougnie, and Patrice Henry, Journal of Atmospheric and Oceanic Technology 2012, doi: http://dx.doi.org/10.1175/JTECH-D-11-00215.1.
Too early to infer a global net primary productivity decline since 2000
Abstract: "The global terrestrial carbon cycle plays a pivotal role in regulating the atmospheric composition of greenhouse gases. It has recently been suggested that the upward trend in net primary production (NPP) seen during the 1980's and 90's has been replaced by a negative trend since 2000 induced by severe droughts mainly on the southern hemisphere. Here we compare results from an individual-based global vegetation model to satellite-based estimates of NPP and top-down reconstructions of net biome production (NBP) based on inverse modelling of observed CO2 concentrations and CO2 growth rates. We find that simulated NBP exhibits considerable covariation on a global scale with interannual fluctuations in atmospheric CO2. Our simulations also suggest that droughts in the southern hemisphere may have been a major driver of NPP variations during the past decade. The results, however, do not support conjecture that global terrestrial NPP has entered a period of drought-induced decline."
Citation: Ahlström, A., P. A. Miller, and B. Smith (2012), Too early to infer a global NPP decline since 2000, Geophys. Res. Lett., 39, L15403, doi:10.1029/2012GL052336.
Air pollution masks climate signals in tree rings
Abstract: "Three sites at about 1400 m a.s.l., were chosen for this study along the Mt. Blanc Motorway in Italy. Chronologies of stable isotope ratios (δ13C, δ18O, δ15N), total N concentration and ring width of Larix decidua Mill. were analyzed to observe changes in growth and climatic signals in tree rings after significant changes in air pollution emissions occurred locally over time. The tunnel opened in 1968 and was closed for three years from March 1999 to March 2002. The obtained series from the three sites (Close = C, High = H and Far = F from the highway) for the analyzed periods, 1950–1970 (only sites H and F) and 1985–2008 (all sites), did not show any particular long-term change except site H that showed significant changes in δ18O (enrichment), δ15N (depletion) and total N (increase). δ13C values at site C were enriched in the first year of the tunnel closure (1999), showing an opposite trend in δ13C at site C, in comparison to the two control sites H and F, which cannot be explained by climatic factors. Since no great differences in δ18O were recorded in 1999, this enrichment in δ13C could be related to an enhancement in photosynthetic rate during periods of low air pollution loads. Opposite to δ15N, total N concentration shows a generally good correlation between sites, and site F was measured as the most N enriched. In a correlation analysis performed on the two study periods between the climatic parameters and ring width, we did not find any clear relationships, whereas for the series of stable isotopes and total N, we found the strongest and most significant relationships only between δ13C and summer (June to August) temperature (positive correlations) and precipitation (negative correlations) at sites H and F. These same relationships at site C were, instead, mostly insignificant, indicating an alteration of the climatic signal recorded in the δ13C chronology, caused by direct exposure to the high level of air pollution at this site. Given that site C is more affected by pollution with respect to the other two sites (whereas the same climatic conditions influence tree growth at all sites), the lack of a climatic signal in the δ13C chronology at this site can be ascribed to air pollution. Few other long-term changes were recorded by tree rings (e.g. at site H), indicating that trees probably record better the pollution events or the worsening of the environmental conditions rather than a lack of pollution for a relatively short time period in a polluted environment."
Citation: Giovanni Leonelli, Giovanna Battipaglia, Rolf T.W. Siegwolf, Matthias Saurer, Umberto Morra di Cella, Paolo Cherubini, Manuela Pelfini, Atmospheric Environment, Volume 61, December 2012, Pages 169–179, http://dx.doi.org/10.1016/j.atmosenv.2012.07.023.
Climate models all have very low defect densities compared to similarly sized open-source projects
Abstract: "A climate model is an executable theory of the climate; the model encapsulates climatological theories in software so that they can be simulated and their implications investigated. Thus, in order to trust a climate model, one must trust that the software it is built from is built correctly. Our study explores the nature of software quality in the context of climate modelling. We performed an analysis of defect reports and defect fixes in several versions of leading global climate models by collecting defect data from bug tracking systems and version control repository comments. We found that the climate models all have very low defect densities compared to well-known, similarly sized open-source projects. We discuss the implications of our findings for the assessment of climate model software trustworthiness."
Citation: Pipitone, J. and Easterbrook, S.: Assessing climate model software quality: a defect density analysis of three models, Geosci. Model Dev., 5, 1009-1022, doi:10.5194/gmd-5-1009-2012, 2012.
Trees produce methane in their cores with assistance of microorganisms
Abstract: "There is intense debate about whether terrestrial vegetation contributes substantially to global methane emissions. Although trees may act as a conduit for methane release from soils to atmosphere, the debate centers on whether vegetation directly produces methane by an uncharacterized, abiotic mechanism. A second mechanism of direct methane production in plants occurs when methanogens – microorganisms in the domain Archaea – colonize the wood of living trees. In the debate this biotic mechanism has largely been ignored, yet conditions that promote anaerobic activity in living wood, and hence potentially methane production, are prevalent across forests. We find average, growing season, trunk-gas methane concentrations >15,000 μL·L−1 in common, temperate-forest species. In upland habitat (where soils are not a significant methane source), concentrations are 2.3-times greater than in lowland areas, and wood cores produce methane in anaerobic, lab-assays. Emission rate estimates from our upland site are 52 ± 9.5 ng CH4 m−2 s−1; rates that are of a similar magnitude to the soil methane sink in temperate forest, and equivalent in global warming potential to ∼18% of the carbon likely sequestered by this forest. Microbial infection of one of the largest, biogenic sinks for carbon dioxide, living trees, might result in substantial, biogenic production of methane."
Citation: Covey, K. R., S. A. Wood, R. J. Warren II, X. Lee, and M. A. Bradford (2012), Elevated methane concentrations in trees of an upland forest, Geophys. Res. Lett., 39, L15705, doi:10.1029/2012GL052361.
Ice surface melt area might cover whole Greenland ice sheet within decade
Abstract: "Greenland ice sheet mass loss has accelerated in the past decade responding to combined glacier discharge and surface melt water runoff increases. During summer, absorbed solar energy, modulated at the surface primarily by albedo, is the dominant factor governing surface melt variability in the ablation area. Using satellite-derived surface albedo with calibrated regional climate modeled surface air temperature and surface downward solar irradiance, we determine the spatial dependence and quantitative impact of the ice sheet albedo feedback over 12 summer periods beginning in 2000. We find that, while albedo feedback defined by the change in net solar shortwave flux and temperature over time is positive over 97% of the ice sheet, when defined using paired annual anomalies, a second-order negative feedback is evident over 63% of the accumulation area. This negative feedback damps the accumulation area response to warming due to a positive correlation between snowfall and surface air temperature anomalies. Positive anomaly-gauged feedback concentrated in the ablation area accounts for more than half of the overall increase in melting when satellite-derived melt duration is used to define the timing when net shortwave flux is sunk into melting. Abnormally strong anticyclonic circulation, associated with a persistent summer North Atlantic Oscillation extreme since 2007, enabled three amplifying mechanisms to maximize the albedo feedback: (1) increased warm (south) air advection along the western ice sheet increased surface sensible heating that in turn enhanced snow grain metamorphic rates, further reducing albedo; (2) increased surface downward shortwave flux, leading to more surface heating and further albedo reduction; and (3) reduced snowfall rates sustained low albedo, maximizing surface solar heating, progressively lowering albedo over multiple years. The summer net infrared and solar radiation for the high elevation accumulation area approached positive values during this period. Thus, it is reasonable to expect 100% melt area over the ice sheet within another similar decade of warming."
Citation: Box, J. E., Fettweis, X., Stroeve, J. C., Tedesco, M., Hall, D. K., and Steffen, K.: Greenland ice sheet albedo feedback: thermodynamics and atmospheric drivers, The Cryosphere, 6, 821-839, doi:10.5194/tc-6-821-2012, 2012.
Methane measurements in the water and sediments of Sea of Japan
Abstract:"This paper presents the results of methane measurements in water and sediments, first performed along the north western continental slope and abyssal plain of the Sea of Japan. Methane concentrations in the study area were very low. However, some features of its distribution are revealed. The highest dissolved methane concentrations (10–14 nmol kg−1) are characteristic of the pycnocline layer at a depth of 30–50 m in the northern shallow stations. With increasing depth, the methane is reduced to minimum values (0.5–1.0 nmol kg−1). The greatest variability in methane concentrations was observed in the layers at 0–500 m, which can be explained by the hydrodynamic conditions of the environment on the slope. Methane plumes (1.7 and 1.3 nmol·kg−1) on the northern section were recorded at the depth of 1,250 and 1,495 m, respectively. Plumes (1.2 nmol kg−1) are also observed on near bottom layers at the deepest (more than 3,000 m) stations. CH4 concentration in bottom sediments is also low (from 1 nmol kg−1 at 7 cm level to 752 nmol kg−1 at the 53 cm level of the core sediment in the northern part). Reduced sediments in the southern part of the study region have maximal methane concentration for sediment (2,549 nmol kg−1) at the horizon 44 cm bsf (below sea floor) with a smell of H2S. These results suppose a close relation of CH4 to sediment properties. A few stations with the maximum methane (86–101 nmol kg−1) in the surface sediment layer are at the foot of a steep slope. Herewith, the highest abundance of some pericarid species was observed at the points with the highest values of methane concentrations in the surface sediment layer. Weak methane seepage can cause anoxic marine waters. Methane emission from water to the atmosphere is low because of its close to equilibrium concentration in surface water. An improved formula for calculating the methane flux of water into the atmosphere, taking into account high wind speeds is presented in the paper."
Citation: Olga F. Vereshchagina, Elena V. Korovitskaya, Galina I. Mishukova, Deep Sea Research Part II: Topical Studies in Oceanography, http://dx.doi.org/10.1016/j.dsr2.2012.08.017.
Tsunami detection from satellite altimetry - 2011 tsunami in Japan as test case
Abstract: "The 2011 Tohoku tsunami devastated Japan and affected coastal populations all around the Pacific Ocean. Accurate early warning of an impending tsunami requires the detection of the tsunami in the open ocean. While the lead-time was not sufficient for use in warning coastal populations in Japan, satellite altimetry observations of the tsunami could have been used to improve predictions and warnings for other affected areas. By comparing to both model results and historical satellite altimeter data, we use near-real-time satellite altimeter measurements to demonstrate the potential for detecting the 2011 Tohoku tsunami within a few hours of the tsunami being generated. We show how satellite altimeter data could be used to both directly detect tsunamis in the open ocean and also improve predictions made by models."
Citation: Hamlington, B. D., R. R. Leben, O. A. Godin, E. Gica, V. V. Titov, B. J. Haines, and S. D. Desai (2012), Could satellite altimetry have improved early detection and warning of the 2011 Tohoku tsunami?, Geophys. Res. Lett., 39, L15605, doi:10.1029/2012GL052386.
25% of dust in Earth's atmosphere is from human actions
Abstract: "Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small-scale features which could account for a large fraction of global emissions. Here we present a global-scale high-resolution (0.1°) mapping of sources based on Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue estimates of dust optical depth in conjunction with other data sets including land use. We ascribe dust sources to natural and anthropogenic (primarily agricultural) origins, calculate their respective contributions to emissions, and extensively compare these products against literature. Natural dust sources globally account for 75% of emissions; anthropogenic sources account for 25%. North Africa accounts for 55% of global dust emissions with only 8% being anthropogenic, mostly from the Sahel. Elsewhere, anthropogenic dust emissions can be much higher (75% in Australia). Hydrologic dust sources (e.g., ephemeral water bodies) account for 31% worldwide; 15% of them are natural while 85% are anthropogenic. Globally, 20% of emissions are from vegetated surfaces, primarily desert shrublands and agricultural lands. Since anthropogenic dust sources are associated with land use and ephemeral water bodies, both in turn linked to the hydrological cycle, their emissions are affected by climate variability. Such changes in dust emissions can impact climate, air quality, and human health. Improved dust emission estimates will require a better mapping of threshold wind velocities, vegetation dynamics, and surface conditions (soil moisture and land use) especially in the sensitive regions identified here, as well as improved ability to address small-scale convective processes producing dust via cold pool (haboob) events frequent in monsoon regimes."
Citation: Ginoux, P., J. M. Prospero, T. E. Gill, N. C. Hsu, and M. Zhao (2012), Global-scale attribution of anthropogenic and natural dust sources and their emission rates based on MODIS Deep Blue aerosol products, Rev. Geophys., 50, RG3005, doi:10.1029/2012RG000388.
Past millennial scale climate variability had profound effect on the terrestrial ecosystems in SE Europe
Abstract: "According to the findings of a complex sedimentological, geochemical, malacological and pollen study implemented on a core sequence of an alkaline lake (Fehér Lake), interstadials in the SE Great Hungarian Plain were characterized by increased boreal woodland cover during Marine Isotope Stage 2 (MIS 2: 29,700-14,500 cal BP). These interstadials were dated to 26,420-27,970, 23,185-24,880, and 18,810-20,770 cal BP, and correlate well with the Dansgaard-Oeschger (DO) interstadials 2 and 3 and the post LGM warm interval seen in the Greenland ice core oxygen isotope records. Intervening cold phases, on the other hand, were found between 24,880-26,420 and 20,770-23,185 cal BP, correlating with Heinrich event 2 and the LGM. These data overall confirm that millennial scale climate variability during Marine Isotope Stage 2 had profound effect on the terrestrial ecosystems in the continental interior of SE Europe, leading to periodic boreal woodland expansions and contractions and wildfires."
Citation: Pál Sümegi, Enikő Magyari, Péter Dániel, Mihály Molnár, Tünde Törőcsik, Quaternary International, http://dx.doi.org/10.1016/j.quaint.2012.07.032.
Record-breaking ozone loss in the Arctic winter 2010/2011
Abstract: "We present a detailed discussion of the chemical and dynamical processes in the Arctic winters 1996/1997 and 2010/2011 with high resolution chemical transport model (CTM) simulations and space-based observations. In the Arctic winter 2010/2011, the lower stratospheric minimum temperatures were below 195 K for a record period of time, from December to mid-April, and a strong and stable vortex was present during that period. Simulations with the Mimosa-Chim CTM show that the chemical ozone loss started in early January and progressed slowly to 1 ppmv (parts per million by volume) by late February. The loss intensified by early March and reached a record maximum of ~2.4 ppmv in the late March–early April period over a broad altitude range of 450–550 K. This coincides with elevated ozone loss rates of 2–4 ppbv sh−1 (parts per billion by volume/sunlit hour) and a contribution of about 30–55% and 30–35% from the ClO-ClO and ClO-BrO cycles, respectively, in late February and March. In addition, a contribution of 30–50% from the HOx cycle is also estimated in April. We also estimate a loss of about 0.7–1.2 ppmv contributed (75%) by the NOx cycle at 550–700 K. The ozone loss estimated in the partial column range of 350–550 K exhibits a record value of ~148 DU (Dobson Unit). This is the largest ozone loss ever estimated in the Arctic and is consistent with the remarkable chlorine activation and strong denitrification (40–50%) during the winter, as the modeled ClO shows ~1.8 ppbv in early January and ~1 ppbv in March at 450–550 K. These model results are in excellent agreement with those found from the Aura Microwave Limb Sounder observations. Our analyses also show that the ozone loss in 2010/2011 is close to that found in some Antarctic winters, for the first time in the observed history. Though the winter 1996/1997 was also very cold in March–April, the temperatures were higher in December–February, and, therefore, chlorine activation was moderate and ozone loss was average with about 1.2 ppmv at 475–550 K or 42 DU at 350–550 K, as diagnosed from the model simulations and measurements."
Citation: Kuttippurath, J., Godin-Beekmann, S., Lefèvre, F., Nikulin, G., Santee, M. L., and Froidevaux, L.: Record-breaking ozone loss in the Arctic winter 2010/2011: comparison with 1996/1997, Atmos. Chem. Phys., 12, 7073-7085, doi:10.5194/acp-12-7073-2012, 2012.
CLASSIC OF THE WEEK: Rubens & Aschkinass (1898)
Abstract: No abstract.
Citation: Rubens, H., Aschkinass, E., Astrophysical Journal, vol. 8, p.176, DOI: 10.1086/140516.
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