New research from last week 16/2012
Posted by Ari Jokimäki on April 23, 2012
I’m sick and tired of coming up something witty and funny week after week for these introductions, so now I’ll just write this boring summary: Themes of this week are mapping, Arctic sea ice, non-Arctic air traffic, greenhouse gases (which by the way has nothing to do with gardener’s stomach problems), paleoclimate, biosphere, groundwater, seawater, groundweather, seaweather, and what else? Oh yes, and climate, of course. All this in just 15 little studies plus one classic.
Using computer tomography for measuring tree rings
Abstract: “The paper describes an evaluation of the applicability of computer tomography in archaeological dendrochronology. Two different computer tomographs were tested, a Siemens Somatom Emotion single slice scanner developed for medical use, and a Nikon Metrology model XT H 225 LC, which is an industrial type scanner. Both scanners were tested against air-dried, archaeological oak wood, and more limited experiments were made with waterlogged archaeological oak wood and archaeological oak wood which had been treated with high-molecular polyethyleneglycol as a conservation treatment. After scanning the resulting imagery were measured and analysed for dendrochronology using off-the-shelf software for handling and measuring on the images and the specialist programme DENDRO for the dendrochronological analyses. The results showed that only the industrial scanner produced sufficiently clear imagery to allow for dendrochronological analyses. In the scans it was possible to separate tree-rings down to 0.2 mm width, and it was possible to identify the sapwood–heartwood border when sufficient sapwood rings were present. It was found, however, that a visual inspection of the object was required to distinguish between sapwood and decayed wood. Comparisons between direct measurements of tree-rings and measurements based on CT-imagery revealed no significant differences. The scanning and subsequent dating of more than 90 objects showed that dendrochronological dating based on CT-scanning has a success rate equal to conventional dating, albeit more time consuming. The attempts to scan waterlogged and PEG-impregnated archaeological oak wood were unsuccessful, due to a low degree of contrast between the water/PEG and the preserved wood. The experiments were too limited to exclude, however, that a successful protocol can be developed also for these types of materials.”
Citation: Jan Bill, Aoife Daly, Øistein Johnsen, Knut S. Dalen, Dendrochronologia, http://dx.doi.org/10.1016/j.dendro.2011.11.002.
Satellite measurements of global carbon dioxide distribution
Abstract: “January 2009 saw the successful launch of the first space-based mission specifically designed for measuring greenhouse gases, the Japanese Greenhouse gases Observing SATellite (GOSAT). We present global land maps (Level 3 data) of column-averaged CO2 concentrations (XCO2) derived using observations from the GOSAT ACOS retrieval algorithm, for July through December 2009. The applied geostatistical mapping approach makes it possible to generate maps at high spatial and temporal resolutions that include uncertainty measures and that are derived directly from the Level 2 observations, without invoking an atmospheric transport model or estimates of CO2 uptake and emissions. As such, they are particularly well suited for comparison studies. Results show that the Level 3 maps for July to December 2009 on a 1° × 1.25° grid, at six-day resolution capture much of the synoptic scale and regional variability of XCO2, in addition to its overall seasonality. The uncertainty estimates, which reflect local data coverage, XCO2 variability, and retrieval errors, indicate that the Southern latitudes are relatively well-constrained, while the Sahara Desert and the high Northern latitudes are weakly-constrained. A probabilistic comparison to the PCTM/GEOS-5/CASA-GFED model reveals that the most statistically significant discrepancies occur in South America in July and August, and central Asia in September to December. While still preliminary, these results illustrate the usefulness of a high spatiotemporal resolution, data-driven Level 3 data product for direct interpretation and comparison of satellite observations of highly dynamic parameters such as atmospheric CO2.”
Citation: Hammerling, D. M., A. M. Michalak, C. O’Dell, and S. R. Kawa (2012), Global CO2 distributions over land from the Greenhouse Gases Observing Satellite (GOSAT), Geophys. Res. Lett., 39, L08804, doi:10.1029/2012GL051203.
Phytoplankton production from melting ponds on Arctic sea ice less than 1% of total Arctic Ocean production
Abstract: “Recently, the areal extent of melt ponds within sea ice has rapidly increased during the Arctic Ocean summer. However, the biological impacts of melt ponds on the Arctic marine ecosystem have rarely been studied. Carbon and nitrogen uptake rates of phytoplankton were measured at 26 different melt ponds in 2005 and 2008, using a 13C-15N dual stable isotope tracer technique. Generally, the open ponds had relatively higher nutrients than closed ponds, but the nutrient concentrations in the open ponds were within a range similar to those in surrounding surface seawaters. Chlorophyll a (Chl a) concentrations in melt ponds ranged from 0.1 to 2.9 mg Chl a m−3 with a mean of 0.6 mg Chl a m−3 (SD = ±0.8 mg Chl a m−3) in the Canada Basin in 2005, whereas the range of the Chl a concentrations was from 0.1 to 0.3 mg Chl a m−3 with a mean of 0.2 mg Chl a m−3 (SD = ±0.1 mg Chl a m−3) in the central Arctic Ocean in 2008. The average annual carbon production in sea ice melt ponds was 0.67 g C m−3 (SD = ±1.03 g C m−3) in the Arctic Ocean. Based on this study, recent annual carbon production of all melt ponds was roughly estimated to be approximately 2.6 Tg C, which is less than 1% of the total production in the Arctic Ocean.”
Citation: Lee, S. H., D. A. Stockwell, H.-M. Joo, Y. B. Son, C.-K. Kang, and T. E. Whitledge (2012), Phytoplankton production from melting ponds on Arctic sea ice, J. Geophys. Res., 117, C04030, doi:10.1029/2011JC007717.
The greenhouse gas that mankind stopped emitting
Abstract: “Long term measurements in background air (Cape Grim, Tasmania) and firn air (NEEM, Greenland) of the potent long-lived greenhouse gas SF5CF3show that emissions declined after the late 1990s, having grown since the 1950s, and became indistinguishable from zero after 2003. The timing of this decline suggests that emissions of this gas may have been related to the production of certain fluorochemicals; production of which have been recently phased out. An earlier observation of closely correlated atmospheric abundances of SF5CF3 and SF6 are shown here to have likely been purely coincidental, as their respective trends diverged after 2002. Due to its long lifetime (ca. 900 yr), atmospheric concentrations of SF5CF3 have not declined, and it is now well mixed between hemispheres, as is also shown here from interhemispheric aircraft measurements. Total cumulative emissions of SF5CF3 amount to around 5 kT.”
Citation: Sturges, W. T., Oram, D. E., Laube, J. C., Reeves, C. E., Newland, M. J., Hogan, C., Martinerie, P., Witrant, E., Brenninkmeijer, C. A. M., Schuck, T. J., and Fraser, P. J.: Emissions halted of the potent greenhouse gas SF5CF3, Atmos. Chem. Phys., 12, 3653-3658, doi:10.5194/acp-12-3653-2012, 2012.
What Atlantic Multidecadal Oscillation was like during the Holocene?
Abstract: “The Atlantic Multidecadal Oscillation (AMO) and its possible change during the Holocene are examined in this study, using long-term simulations of the Earth system model COSMOS. A quasi-persistent ~55- to 80-year cycle characterizing in the North Atlantic sea surface temperature, is highly associated with the multidecadal variability of the Atlantic Meridional Overturning Circulation (AMOC) during the Holocene. This mode can be found throughout the Holocene, indicating that the AMO is dominated by internal climate variability. Stronger-than-normal AMOC results in warmer-than-normal surface temperature, spreading over almost the whole North Hemisphere, in particular the North Atlantic Ocean. During the warm phase of the AMO, more precipitation is detected in the North Atlantic low and high latitudes. It also generates a dipolar seesaw pattern in the sea ice anomaly. Our results reveal that the influence of the AMO can be amplified by a more vigorous AMOC variability during the early Holocene in the presence of a remnant of the Laurentide Ice Sheet and when freshwater entered the North Atlantic Ocean. This conclusion might be applicable to the past AMO reconstruction and the future AMO estimation.”
Citation: Wei Wei and Gerrit Lohmann, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00667.1.
Flooding of wet tundra can lead to increased carbon dioxide loss
Abstract: “Tundra ecosystems are especially sensitive to climate change, which is particularly rapid in high northern latitudes resulting in significant alterations in temperature and soil moisture. Numerous studies have demonstrated that soil drying increases the respiration loss from wet Arctic tundra. And, warming and drying of tundra soils are assumed to increase CO2 emissions from the Arctic. However, in this water table manipulation experiment (i.e., flooding experiment), we show that flooding of wet tundra can also lead to increased CO2 loss. Standing water increased heat conduction into the soil, leading to higher soil temperature, deeper thaw and, surprisingly, to higher CO2 loss in the most anaerobic of the experimental areas. The study site is located in a drained lake basin, and the soils are characterized by wetter conditions than upland tundra. In experimentally flooded areas, high wind speeds (greater than ∼4 m s−1) increased CO2 emission rates, sometimes overwhelming the photosynthetic uptake, even during daytime. This suggests that CO2 efflux from C rich soils and surface waters can be limited by surface exchange processes. The comparison of the CO2 and CH4 emission in an anaerobic soil incubation experiment showed that in this ecosystem, CO2 production is an order of magnitude higher than CH4 production. Future increases in surface water ponding, linked to surface subsidence and thermokarst erosion, and concomitant increases in soil warming, can increase net C efflux from these arctic ecosystems.”
Citation: Zona, D., D. A. Lipson, K. T. Paw U, S. F. Oberbauer, P. Olivas, B. Gioli, and W. C. Oechel (2012), Increased CO2 loss from vegetated drained lake tundra ecosystems due to flooding, Global Biogeochem. Cycles, 26, GB2004, doi:10.1029/2011GB004037.
Where to build wells in Africa
Abstract: “In Africa, groundwater is the major source of drinking water and its use for irrigation is forecast to increase substantially to combat growing food insecurity. Despite this, there is little quantitative information on groundwater resources in Africa, and groundwater storage is consequently omitted from assessments of freshwater availability. Here we present the first quantitative continent-wide maps of aquifer storage and potential borehole yields in Africa based on an extensive review of available maps, publications and data. We estimate total groundwater storage in Africa to be 0.66 million km3 (0.36–1.75 million km3). Not all of this groundwater storage is available for abstraction, but the estimated volume is more than 100 times estimates of annual renewable freshwater resources on Africa. Groundwater resources are unevenly distributed: the largest groundwater volumes are found in the large sedimentary aquifers in the North African countries Libya, Algeria, Egypt and Sudan. Nevertheless, for many African countries appropriately sited and constructed boreholes can support handpump abstraction (yields of 0.1–0.3 l s−1), and contain sufficient storage to sustain abstraction through inter-annual variations in recharge. The maps show further that the potential for higher yielding boreholes ( > 5 l s−1) is much more limited. Therefore, strategies for increasing irrigation or supplying water to rapidly urbanizing cities that are predicated on the widespread drilling of high yielding boreholes are likely to be unsuccessful. As groundwater is the largest and most widely distributed store of freshwater in Africa, the quantitative maps are intended to lead to more realistic assessments of water security and water stress, and to promote a more quantitative approach to mapping of groundwater resources at national and regional level.”
Citation: A M MacDonald et al 2012 Environ. Res. Lett. 7 024009 doi:10.1088/1748-9326/7/2/024009.
Climate change might lead to more frequent environments favorable for severe thunderstorms
Abstract: “As the planet warms, it is important to consider possible impacts of climate change on severe thunderstorms and tornadoes. To further that discussion, the current distribution of severe thunderstorms as a function of large-scale environmental conditions is presented. Severe thunderstorms are much more likely to form in environments with large values of convective available potential energy (CAPE) and deep-tropospheric wind shear. Tornadoes and large hail are preferred in high-shear environments and non-tornadic wind events in low shear. Further, the intensity of tornadoes and hail, given that they occur, tends to be almost entirely a function of the shear and only weakly depends on the thermodynamics. Climate model simulations suggest that CAPE will increase in the future and the wind shear will decrease. Detailed analysis has suggested that the CAPE change will lead to more frequent environments favorable for severe thunderstorms, but the strong dependence on shear for tornadoes, particularly the strongest ones, and hail means that the interpretation of how individual hazards will change is open to question. The recent development of techniques to use higher-resolution models to estimate the occurrence of storms of various kinds is discussed. Given the large interannual variability in environments and occurrence of events, caution is urged in interpreting the observational record as evidence of climate change.”
Citation: H.E. Brooks, Atmospheric Research, http://dx.doi.org/10.1016/j.atmosres.2012.04.002.
Arctic seasonal sea ice has smaller albedo than multiyear ice
Abstract: “There is an ongoing shift in the Arctic sea ice cover from multiyear ice to seasonal ice. Here we examine the impact of this shift on sea ice albedo. Our analysis of observations from four years of field experiments indicates that seasonal ice undergoes an albedo evolution with seven phases; cold snow, melting snow, pond formation, pond drainage, pond evolution, open water, and freezeup. Once surface ice melt begins, seasonal ice albedos are consistently less than albedos for multiyear ice resulting in more solar heat absorbed in the ice and transmitted to the ocean. The shift from a multiyear to seasonal ice cover has significant implications for the heat and mass budget of the ice and for primary productivity in the upper ocean. There will be enhanced melting of the ice cover and an increase in the amount of sunlight available in the upper ocean.”
Citation: Perovich, D. K. and C. Polashenski (2012), Albedo evolution of seasonal Arctic sea ice, Geophys. Res. Lett., 39, L08501, doi:10.1029/2012GL051432.
Recent sea level trend fluctuations in tropical Pacific are dominated by natural variability
Abstract: “In this study we focus on the sea level trend pattern observed by satellite altimetry in the tropical Pacific over the 1993–2009 time span (i.e. 17 yr). Our objective is to investigate whether this 17-yr-long trend pattern was different before the altimetry era, what was its spatio-temporal variability and what have been its main drivers. We try to discriminate the respective roles of the internal variability of the climate system and of external forcing factors, in particular anthropogenic emissions (greenhouse gases and aerosols). On the basis of a 2-D past sea level reconstruction over 1950–2009 (based on a combination of observations and ocean modelling) and multi-century control runs (i.e. with constant, preindustrial external forcing) from eight coupled climate models, we have investigated how the observed 17-yr sea level trend pattern evolved during the last decades and centuries, and try to estimate the characteristic time scales of its variability. For that purpose, we have computed sea level trend patterns over successive 17-yr windows (i.e. the length of the altimetry record), both for the 60-yr long reconstructed sea level and the model runs. We find that the 2-D sea level reconstruction shows spatial trend patterns similar to the one observed during the altimetry era. The pattern appears to have fluctuated with time with a characteristic time scale of the order of 25–30 yr. The same behaviour is found in multi-centennial control runs of the coupled climate models. A similar analysis is performed with 20th century coupled climate model runs with complete external forcing (i.e. solar plus volcanic variability and changes in anthropogenic forcing). Results suggest that in the tropical Pacific, sea level trend fluctuations are dominated by the internal variability of the ocean–atmosphere coupled system. While our analysis cannot rule out any influence of anthropogenic forcing, it concludes that the latter effect in that particular region is stillhardly detectable.”
Citation: Meyssignac, B., Salas y Melia, D., Becker, M., Llovel, W., and Cazenave, A.: Tropical Pacific spatial trend patterns in observed sea level: internal variability and/or anthropogenic signature?, Clim. Past, 8, 787-802, doi:10.5194/cp-8-787-2012, 2012.
Recent sea ice loss is largely caused by Atlantification of the Barents Sea
Abstract: “The recent Arctic winter sea ice retreat is most pronounced in the Barents Sea. Using available observations of the Atlantic inflow to the Barents Sea and results from a regional ice-ocean model we assess and quantify the role of inflowing heat anomalies on sea ice variability. The interannual variability and longer term decrease in sea ice area reflect the variability of the Atlantic inflow, both in observations and model simulations. The last decade (1998-2008) the reduction in annual (July-June) sea ice area was 218·103 km2, or close to 50%. This reduction has occurred concurrent to an increase in observed Atlantic heat transport, due to both strengthening and warming of the inflow. Modelled interannual variations in sea ice area between 1948 and 2007 are associated with anomalous heat transport (r = −0.63) with a 70·103 km2 decrease per 10 TW input of heat. Based on the simulated ocean heat budget we find that the heat transport into the western Barents Sea sets the boundary of the ice-free Atlantic domain and, hence, the sea ice extent. The regional heat content and heat loss to the atmosphere scale with the area of open ocean as a consequence. Recent sea ice loss is thus largely caused by an increasing “Atlantification” of the Barents Sea.”
Citation: M. Årthun, T. Eldevik, L. H. Smedsrud, Ø. Skagseth and R. B. Ingvaldsen, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-11-00466.1.
Foraminifera species cannot maintain populations under next century carbon dioxide levels
Abstract: “Changes in the seawater carbonate chemistry (ocean acidification) from increasing atmospheric carbon dioxide (CO2) concentrations negatively affect many marine calcifying organisms, but may benefit primary producers under dissolved inorganic carbon (DIC) limitation. To improve predictions of the ecological effects of ocean acidification, the net gains and losses between the processes of photosynthesis and calcification need to be studied jointly on physiological and population levels. We studied productivity, respiration, and abundances of the symbiont-bearing foraminifera Marginopora vertebralis on natural CO2 seeps in Papua New Guinea and conducted additional studies on production and calcification on the Great Barrier Reef (GBR) using artificially enhanced pCO2. Net oxygen production increased up to 90% with increasing pCO2, with temperature, light and pH together explaining 61% of the variance in production. Production increased with increasing light and increasing pCO2, and declined at higher temperatures. Respiration was also significantly elevated (~25%), while calcification was reduced (16-39%) at low pH/high pCO2 compared to present day conditions. In the field, M. vertebralis was absent at three CO2 seep sites at pHTotal levels below ~7.9 (pCO2 ~700 μatm), but it was found in densities of over 1000 m−2 at all three control sites. The study showed that endosymbiotic algae in foraminifera benefit from increased DIC availability, and may be naturally carbon limited. The observed reduction in calcification may have been caused either by increased energy demands for proton pumping (measured as elevated rates of respiration), or by stronger competition for DIC from the more productive symbionts. The net outcome of these two competing processes is that M. vertebralis cannot maintain populations under pCO2 exceeding 700 μatm, thus are likely to be extinct in the next century.”
Citation: S. Uthicke, K. Fabricius, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02715.x.
Role of climate in medieval Norway population might have been underestimated
Abstract: “The topic of this paper is the importance of climate for the population and settlement in medieval and early modern times. Were the demographic crises caused by crop failure and famine or by disease? I begin by reviewing European research (particularly English) relating to the issue. The views of Norwegian historians regarding the causes of the agrarian crisis in the late Middle Ages are then examined. Hasund (Hasund S, 1919, 1944, Den store mannedauden. Or Noregs bondesoge. Glytt og granskingar II, Oslo, pp. 82–161. First printed in Beretning om Norges Landbrukshøiskoles virksomhet 1918–1919) claimed it was the plagues, not the climate, that held the population at a low level to the end of the Middle Ages, a view that has been repeated in recent years by such researchers as Lunden (Lunden K, 2002, Norges landbrukshistorie II, 1350–1814. Frå svartedauden til 17. mai. Oslo) and Moseng (Moseng OG, 2006, Den flyktige pesten. Vilkårene for epidemier i Norge i seinmiddelalder og tidlig nytid. Oslo). This paper claims that the role of the climate has been underestimated, in particular that the climatic shock of several bad years in a row directly and indirectly brought appreciable excess mortality in a country situated so far north. ‘Bad’ years demonstrated through dendrochronology are in many cases reflected in documentary evidence concerning poor corn harvests and high mortality.”
Citation: Audun Dybdahl, The Holocene April 16, 2012 0959683612441843, doi: 10.1177/0959683612441843.
Amazonian diversity depends primarily on ability of species to tolerate rising temperatures
Abstract: “Tropical forests are threatened by many human disturbances – two of the most important of which are deforestation and climate change. In order to mitigate the impacts of these disturbances, it is important to understand their potential effects on the distributions of species. In the tropics, such understanding has been hindered by poor knowledge of the current distributions and range limits of most species. Here we use herbarium collection records to model the current and future distributions of ca 3000 Amazonian plant species. We project these distributions into the future under a range of different scenarios related to the magnitude and extent of disturbance as well as the response of species to changes in temperature, precipitation and atmospheric concentrations of CO2. We find that the future of Amazonian diversity will be dependant primarily on the ability of species to tolerate or adapt to rising temperatures. If the thermal niches of tropical plants are fixed and incapable of expanding under rapid warming, then the negative effects of climate change will overshadow the effects of deforestation, greatly reducing the area of suitable habitat available to most species and potentially leading to massive losses of biodiversity throughout the Amazon. If tropical species are generally capable of tolerating warmer temperatures, rates of habitat loss will be greatly reduced but many parts of Amazonia may still experience rapid losses of diversity, with the effects of enhanced seasonal water stress being similar in magnitude to the effects of deforestation.”
Citation: Kenneth J. Feeley, Yadvinder Malhi, Przemyslaw Zelazowski, Miles R. Silman, Global Change Biology, DOI: 10.1111/j.1365-2486.2012.02719.x.
Rerouting Arctic cross-polar flights might be a good idea
Abstract: “Climate data suggest greater warming over the Arctic than lower latitudes, and the most abundant direct source of black carbon and other climate-relevant pollutants over the Arctic is cross-polar flights by international aviation. A relevant question is whether rerouting cross-polar flights to circumnavigate the Arctic Circle reduces or enhances such warming. To study this issue, a model accounting for subgrid exhaust plumes from each individual commercial flight worldwide was used with 2006 global aircraft emission inventories that treated cross-polar flights and flights rerouted around the Arctic Circle (66.56083 °N), respectively. Rerouting increased fuel use by 0.056 % in the global average, mostly right outside the Arctic Circle, but most of the associated black carbon and other emissions were removed faster because they were now over latitudes of greater precipitation and lesser stability. Rerouting also reduced fuel use and emissions within the Arctic Circle by 83 % and delayed pollutant transport to the Arctic. The Arctic reduction in pollutants, particularly of black carbon, decreased Arctic and global temperature and increased Arctic sea ice over 22 years. Although the slight increase in total CO2 emissions due to rerouting may dampen the benefit of rerouting over more decades, rerouting or even partial rerouting (allowing cross-polar flights during polar night only) may delay the elimination of Arctic sea ice, which will otherwise likely occur within the next 2–3 decades due to global warming in general. Rerouting may increase worldwide fuel plus operational costs by only ~$99 million/yr, 47–55 times less than an estimated 2025 U.S.-alone cost savings due to the global warming reduction from rerouting.”
Citation: Mark Z. Jacobson, Jordan T. Wilkerson, Sathya Balasubramanian, Wayne W. Cooper and Nina Mohleji, Climatic Change, DOI: 10.1007/s10584-012-0462-0.
CLASSIC OF THE WEEK: Palmer (1910)
Abstract: No abstract. Quote from the beginning of the paper: “Considerable speculation has been indulged in within recent years as to the terrestrial influence of sun-spots. While few investigations have been made attempting to measure this relation, if such exists, many conjectures of various kinds have been offered from time to time. Certain influences of these solar activities upon the Earth have been perfectly demonstrated. For example,…”
Citation: Palmer, Andrew H., 1910, Popular Astronomy, vol. 18, pp.8-12.
When each paper is published, it is notified in AGW Observer Facebook page and Twitter page. Here’s the archive for the research papers of previous weeks. If this sort of thing interests you, be sure to check out A Few Things Illconsidered. They also have a weekly posting containing lots of links to new research and other climate related news.