New research from last week 49/2012
Posted on 10 December 2012 by Ari Jokimäki
Global warming impacts many things. It's actually quite difficult to come up with things within Earth system that are not affected by global warming. In this week's papers we see that Greenland glaciers accelerate, frequency and intensity of temperature extremes change, air pollution is getting worse, Arctic sea ice amount is decreasing while Siberian snow cover is thickening, Northern Hemisphere thermal growing season is getting longer, corals are trying to expand polewards but ocean acidification doesn't let them to do that, western North America gets dry and vegetation declines, sea level rises, ...
But all this doesn't mean anything because climate has changed in the past, right? Well, also mass extinctions have happened in the past.
Spreading of warm ocean waters around Greenland as a possible cause for glacier acceleration
Abstract:"We examine the pattern of spreading of warm subtropical-origin waters around Greenland for the years 1992-2009 using a high-resolution (4 km horizontal grid) coupled ocean and sea-ice simulation. The simulation, provided by the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project, qualitatively reproduces the observed warming of subsurface waters in the subpolar gyre associated with changes of the North Atlantic atmospheric state that occurred in the mid-1990s. The modeled subsurface ocean temperature warmed by 1.5°C in southeast and southwest Greenland during 1994-2005 and subsequently cooled by 0.5°C; modeled subsurface ocean temperature increased by 2-2.5°C in central and then northwest Greenland during 1997-2005 and stabilized thereafter, while it increased after 2005 by <0.5°C in north Greenland. Comparisons with in situ measurements off the continental shelf in the Labrador and Irminger Seas indicate that the model initial conditions were 0.4°C too warm in the south but the simulated warming is correctly reproduced; while measurements from eastern Baffin Bay reveal that the model initial conditions were 1.0°C too cold in the northwest but the simulated ocean warming brought modeled temperature closer to observations, i.e. the simulated warming is 1.0°C too large. At several key locations, the modeled oceanic changes off the shelf and below the seasonal mixed layer were rapidly transmitted to the shelf within troughs towards (model-unresolved) fjords. Unless blocked in the fjords by shallow sills, these warm subsurface waters had potential to propagate down the fjords and melt the glacier fronts. Based on model sensitivity simulations from an independent study (Xu and others, 2012), we show that the oceanic changes have very likely increased the subaqueous melt rates of the glacier fronts, and in turn impacted the rates of glacier flow."
Citation: Rignot, E.; Fenty, I.; Menemenlis, D.; Xu, Y., Annals of Glaciology, Volume 53, Number 60, November 2012 , pp. 257-266(10), DOI: http://dx.doi.org/10.3189/2012AoG60A136.
Collapse of the terrestrial ecosystem predated that of the marine ecosystem during Permian mass extinction
Highlights:► Eukaryotic algae were very low in abundance in the microbialite interval. ► Cyanobacteria, anaerobic bacteria, archaea and/or acritarchs were the main microbes in the ocean after the main oceanic metazoan mass extinction. ► Collapse of the terrestrial ecosystem predated that of the marine ecosystem. ► Intensive wildfire occurred simultaneously with the collapse of the terrestrial ecosystem but, preceded that of the marine ecosystem.
Abstract: "Microbialites flourished globally immediately following the latest Permian mass extinction. In this study, lipid biomarker records were analyzed in the Cili section (Hunan Province, South China) in order to determine the types of microbes involved in microbialite formation and their response to contemporaneous environmental changes. Various biomarkers were identified in the aliphatic and aromatic fractions using gas chromatography (GC) and GC-mass spectrometry (GC-MS). Low abundance of steranes in the microbialite layer suggests that it did not contain large amounts of algae, in striking contrast to the abundant algal fossils and algal-derived steranes present in the underlying (pre-crisis) skeletal limestone. Although pristine/phytane (Pr/Ph) ratios increased in the microbialite layer, covariation of Pr/Ph with the ratio of low- to high-molecular-weight n-alkanes (C20-/C20 +) suggests that the former proxy was controlled by microbial (particularly cyanobacterial) inputs rather than by redox conditions. The microbialite also yielded low ratios of hopanes to short-chain n-alkanes (HP/Lalk) and high abundances of C21n-alkylcyclohexane, indicating that, in addition to cyanobacteria, anaerobic bacteria, archaea, and possibly acritarchs flourished in the aftermath of the marine extinction event. The upper part of the thinly bedded micritic limestone overlying the microbialite exhibits a bimodal distribution of n-alkanes as well as increased abundances of extended tricyclic terpanes and steranes, suggesting a return of habitable shallow-marine conditions for eukaryotic algae several hundred thousand years after the latest Permian mass extinction. Increases in the dibenzofuran ratio (i.e., DBF/(DBF+DBT+F)) and in the coronene to phenanthrene ratio (Cor/P) in the skeletal limestone immediately below the microbialite are evidence of enhanced soil erosion rates and wildfire intensity, marking the collapse of terrestrial ecosystems. The terrestrial crisis thus slightly preceded the marine biotic crisis in the South China region, to which it may have been a major contributing factor."
Citation: Genming Luo, Yongbiao Wang, Kliti Grice, Steve Kershaw, Thomas J. Algeo, Xiaoyan Ruan, Hao Yang, Chengling Jia, Shucheng Xie, Global and Planetary Change, http://dx.doi.org/10.1016/j.gloplacha.2012.11.015.
Can a decadal forecasting system predict temperature extreme indices?
Abstract:"Daily maximum and minimum summer temperatures have increased throughout the majority of Europe over the past few decades, along with the frequency and intensity of heatwaves. It is essential to learn whether this rise is expected to continue in the future for adaptation purposes. A study of predictability of European temperature indices, with the Met Office Hadley Centre Decadal Prediction System (DePreSys) has revealed significant skill in predictions of 5/10-year average indices of the summer mean and maximum 5-day average temperatures based on daily maximum and minimum temperatures for a large area of Europe, particularly in the Mediterranean. In contrast, the decadal forecasts of winter mean/minimum 5-day average temperature indices show poorer skill than the summer indices. The UK shows significant skill in some cases but less than for the European/Mediterranean regions. Comparison of two parallel ensembles, one initialised with observations, one without initialisation has shown that the skill largely originates from external forcing. However, there were a few cases which had hints of additional skill in forecasts of decadal mean indices due to the initialisation. Model realisations of extreme indices can have large biases compared to observations that are different from those of the mean climate indices. Several methods were tested for correcting biases, as well as for testing the significance and quantifying uncertainty of the results to rule out cases of spurious skill. Bias correction of each index individually is required as biases vary across different extremes."
Citation: Helen M. Hanlon, Gabriele C. Hegerl, and Simon F. B. Tett, Doug M. Smith, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00512.1.
Climate change might increase the frequency of bad ozone days considerably in Germany
Highlights:► Ozone dependence on NOx and temperature at industrial and rural stations. ► Prediction of number of days with ozone exceedances in terms of climate change. ► Frequency of bad ozone days increases by 135% at the industrial station. ► Frequency of bad ozone days increases by 87% at the rural station. ► Ozone forming potential is significantly higher in rural areas than in urban ones.
Abstract: "In this paper, the dependence of ozone-forming potential on temperature was analysed based on data from two stations (with an industrial and rural background, respectively) in North Rhine-Westphalia, Germany, for the period of 1983–2007. After examining the interrelations between ozone, NOx and temperature, a projection of the days with ozone exceedance (over a limit value of a daily maximum 8-h average ≥ 120 μg m−3for 25 days per year averaged for 3 years) in terms of global climate change was made using probability theory and an autoregression integrated moving average (ARIMA) model. The results show that with a temperature increase of 3 K, the frequency of days when ozone exceeds its limit value will increase by 135% at the industrial station and by 87% at the rural background station."
Citation: Ani Melkonyan, Patrick Wagner, Atmospheric Environment, Volume 67, March 2013, Pages 287–295, http://dx.doi.org/10.1016/j.atmosenv.2012.10.023.
Arctic sea ice loss helps to explain Siberian snow cover thickening
Highlights:•Examine a possible causal link between Arctic sea ice and Siberian snow cover, •CAM3 experiments were designed, •Arctic Ocean surface forcing is necessary to induce a Siberian snow signal.
Abstract:"The loss of Arctic sea ice has wide-ranging impacts, some of which are readily apparent and some of which remain obscure. For example, recent observational studies suggest that terrestrial snow cover may be affected by decreasing sea ice. Here, we examine a possible causal link between Arctic sea ice and Siberian snow cover during the past 3 decades using a suite of experiments with the National Center for Atmospheric Research Community Atmospheric Model version 3. The experiments were designed to isolate the influence of surface conditions within the Arctic Ocean from other forcing agents such as low-latitude sea surface temperatures and direct radiative effects of increasing greenhouse gases. Only those experiments that include the observed evolution of Arctic sea ice and sea surface temperatures result in increased snow depth over Siberia, while those that maintain climatological values for Arctic Ocean conditions result in no snow signal over Siberia. In the former, Siberian precipitation and air temperature both increase, but because surface air temperatures remain below freezing during most months, the snowpack thickens over this region. These results suggest that Arctic Ocean surface forcing is necessary and sufficient to induce a Siberian snow signal, and that other forcings in combination can modulate the strength and geographic extent of the response."
Citation: Ghatak, D., C. Deser, A. Frei, G. Gong, A. Phillips, D. A. Robinson, and J. Stroeve (2012), Simulated Siberian snow cover response to observed Arctic sea ice loss, 1979–2008, J. Geophys. Res., 117, D23108, doi:10.1029/2012JD018047.
Northern Hemisphere thermal growing season has become longer but biospheric carbon uptake hasn't
Highlights:•The decade of the 2000s recorded the longest thermal growing seasons since 1950, •The extension has been symmetrical since 2005 due to strong autumn warming, •Thermal growing season length is not correlated with biospheric uptake period.
Abstract: "Gridded daily temperature from 1950 to 2011 and atmospheric CO2 concentration data from high-latitude observing stations and the CarbonTracker assimilation system are used to examine recent spatiotemporal variability of the thermal growing season and its relationship with seasonal biospheric carbon uptake and release in the Northern Hemisphere. The thermal growing season has lengthened substantially since 1950 but most of the lengthening has occurred during the last three decades (2.9 days decade−1, p < 0.01 for 1980–2011), with stronger rates of extension in Eurasia (4.0 days decade−1, p < 0.01) than in North America (1.2 days decade−1, p> 0.05). Unlike most previous studies, which had more limited data coverage over the past decade, we find that strong autumn warming of about 1°C during the second half of the 2000s has led to a significant shift toward later termination of the thermal growing season, resulting in the longest potential growing seasons since 1950. On average, the thermal growing season has extended symmetrically by about a week during this period, starting some 4.0 days earlier and ending about 4.3 days later. The earlier start of the thermal growing season is associated with earlier onset of the biospheric carbon uptake period at high northern latitudes. In contrast, later termination of the growing season is associated with earlier termination of biospheric carbon uptake, but this relationship appears to have decoupled since the beginning of the period of strong autumn warming during the second half of the 2000s. Therefore, owing to these contrasting biospheric responses at the margins of the growing season, the current extension in the thermal growing season length has not led to a concomitant extension of the period of biospheric carbon uptake."
Citation: Barichivich, J., K. R. Briffa, T. J. Osborn, T. M. Melvin, and J. Caesar (2012), Thermal growing season and timing of biospheric carbon uptake across the Northern Hemisphere, Global Biogeochem. Cycles, 26, GB4015, doi:10.1029/2012GB004312.
Global warming will be accelerated with reduced aerosol negative forcing
Distributions and climate effects of atmospheric aerosols from the preindustrial era to 2100 along Representative Concentration Pathways (RCPs) simulated using the global aerosol model SPRINTARS - Takemura (2012) [FULL TEXT]
Abstract:"Global distributions and associated climate effects of atmospheric aerosols were simulated using a global aerosol climate model, SPRINTARS, from 1850 to the present day and projected forward to 2100. Aerosol emission inventories used by the Coupled Model Intercomparison Project Phase 5 (CMIP5) were applied to this study. Scenarios based on the Representative Concentration Pathways (RCPs) were used for the future projection. Aerosol loading in the atmosphere has already peaked and is now reducing in Europe and North America. However, in Asia where rapid economic growth is ongoing, aerosol loading is estimated to reach a maximum in the first half of this century. Atmospheric aerosols originating from the burning of biomass have maintained high loadings throughout the 21st century in Africa, according to the RCPs. Evolution of the adjusted forcing by direct and indirect aerosol effects over time generally correspond to the aerosol loading. The probable future pathways of global mean forcing differ based on the aerosol direct effect for different RCPs. Because aerosol forcing will be close to the preindustrial level by the end of the 21st century for all RCPs despite the continuous increases in greenhouse gases, global warming will be accelerated with reduced aerosol negative forcing."
Citation: Takemura, T.: Distributions and climate effects of atmospheric aerosols from the preindustrial era to 2100 along Representative Concentration Pathways (RCPs) simulated using the global aerosol model SPRINTARS, Atmos. Chem. Phys., 12, 11555-11572, doi:10.5194/acp-12-11555-2012, 2012.
Ocean acidification limits temperature-induced poleward expansion of coral habitats around Japan
Abstract: "Using results from four coupled global carbon cycle-climate models combined with in situ observations, we estimate the effects of future global warming and ocean acidification on potential habitats for tropical/subtropical and temperate coral communities in the seas around Japan. The suitability of coral habitats is classified on the basis of the currently observed regional ranges for temperature and saturation states with regard to aragonite (Ωarag). We find that, under the "business as usual" SRES A2 scenario, coral habitats are projected to expand northward by several hundred kilometers by the end of this century. At the same time, coral habitats are projected to become sandwiched between regions where the frequency of coral bleaching will increase, and regions where Ωarag will become too low to support sufficiently high calcification rates. As a result, the habitat suitable for tropical/subtropical corals around Japan may be reduced by half by the 2020s to 2030s, and is projected to disappear by the 2030s to 2040s. The habitat suitable for the temperate coral communities is also projected to decrease, although at a less pronounced rate, due to the higher tolerance of temperate corals for lowΩarag. Our study has two important caveats: first, it does not consider the potential adaptation of the coral communities, which would permit them to colonize habitats that are outside their current range. Second, it also does not consider whether or not coral communities can migrate quickly enough to actually occupy newly emerging habitats. As such, our results serve as a baseline for the assessment of the future evolution of coral habitats, but the consideration of important biological and ecological factors and feedbacks will be required to make more accurate projections."
Citation: Yara, Y., Vogt, M., Fujii, M., Yamano, H., Hauri, C., Steinacher, M., Gruber, N., and Yamanaka, Y.: Ocean acidification limits temperature-induced poleward expansion of coral habitats around Japan, Biogeosciences, 9, 4955-4968, doi:10.5194/bg-9-4955-2012, 2012.
In western North America climate change comes with droughts and declining vegetation
Abstract:"Rapid and broad-scale forest mortality associated with recent droughts, rising temperature, and insect outbreaks has been observed over western North America (NA). Climate models project additional future warming and increasing drought and water stress for this region. To assess future potential changes in vegetation distributions in western NA, the Community Earth System Model (CESM) coupled with its dynamic global vegetation model (DGVM) was used under the future A2 emissions scenario. In order to better span uncertainties in future climate, eight sea surface temperature (SST) projections provided by CMIP3 (phase 3 of the Coupled Model Intercomparison Project) were employed as boundary conditions. There is a broad consensus amongst the simulations, despite differences in the simulated climate trajectories across the ensemble, that needleleaf evergreen tree coverage will decline by approximately 23% (from 45% to 22%) coincident with a 19% (from 14% to 33%) increase in shrubs and grasses by the end of the 21st century in western NA, with most of the change occurring over the latter half of the 21st century. The net impact is a ~ 6 GtC or about 50% decrease in projected ecosystem carbon storage in this region. The findings suggest a potential for a widespread shift from tree-dominated landscapes to shrub and grass-dominated landscapes in western NA due to future warming and consequent increases in water deficits. These results highlight the need for improved process-based understanding of vegetation dynamics, particularly including mortality and the subsequent incorporation of these mechanisms into Earth System Models in order to better quantify the vulnerability of western NA forests under climate change."
Citation: Xiaoyan Jiang, Sara A. Rauscher, Todd D. Ringler, David M. Lawrence, A. Park Williams, Craig D. Allen, Allison L. Steiner, D. Michael Cai, and Nate G. McDowell, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00430.1 .
Greenland ice sheet mass balance reconstruction (1600-2009) part 1
Abstract: "Ice core data are combined with RACMO2 regional climate model (RCM) output (1958-2010) to develop a reconstruction of the Greenland ice sheet net snow accumulation rate (Ât(G)) spanning years 1600-2009. Regression parameters from RCM output regressed on 86 ice cores are used with available cores in a given year resulting in the reconstructed values. Each core site’s residual variance is used to inversely weight the cores’ respective contributions. The interannual amplitude of the reconstructed accumulation rate is damped by the regressions and is thus calibrated to match that of the RCM data. Uncertainty and significance of changes is measured using statistical models. We find a 12% or 86 Gt y-1 increase in ice sheet accumulation rate from the end of the Little Ice Age in ~1840 to the last decade of the reconstruction. This 1840-1996 trend is 30% higher than that of 1600-2009, suggesting an accelerating accumulation rate. The correlation of Ât(G) with the average surface air temperature in the Northern Hemisphere(SATNHt) remains positive through time, while the correlation of Ât(G) with local near-surface air temperatures or North Atlantic sea surface temperatures is inconsistent, suggesting a hemispheric-scale climate connection. We find an annual sensitivity of Ât(G) to SATNHt of 6.8% K-1 or 51 Gt K-1. The reconstuction, Ât(G), correlates consistently highly with the North Atlantic Oscillation index. Yet, at the 11-year time scale, the sign of this correlation flips four times in the 1870-2005 period."
Citation: Jason E. Box, Noel Cressie, David H. Bromwich, Ji-Hoon Jung, Michiel van den Broeke, J. H. van Angelen, Richard R. Forster, Clement Miège, Ellen Mosley-Thompson, Bo Vinther, and Joseph R. McConnell, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00373.1.
Closing the global mean sea level rise budget for 20th century
Abstract:"Confidence in projections of global-mean sea-level rise (GMSLR) depends on an ability to account for GMSLR during the 20th century. There are contributions from ocean thermal expansion, mass loss from glaciers and ice sheets, groundwater extraction and reservoir impoundment. We have made progress towards solving the “enigma” of 20th-century GMSLR—that is, the observed GMSLR has been found to exceed the sum of estimated contributions, especially for the earlier decades. We propose that: thermal expansion simulated by climate models may previously have been underestimated owing to their not including volcanic forcing in their control state; the rate of glacier mass loss was larger than previously estimated, and was not smaller in the first than in the second half of the century; the Greenland ice-sheet could have made a positive contribution throughout the century; groundwater depletion and reservoir impoundment, which are of opposite sign, may have been approximately equal in magnitude. We show that it is possible to reconstruct the timeseries of GMSLR from the quantified contributions, apart from a constant residual term which is small enough to be explained as a long-term contribution from the Antarctic ice-sheet. The reconstructions account for the approximate constancy of the rate of GMSLR during the 20th century, which shows small or no acceleration, despite the increasing anthropogenic forcing. Semi-empirical methods for projecting GMSLR depend on the existence of a relationship between global climate change and the rate of GMSLR, but the implication of our closure of the budget is that such a relationship is weak or absent during the 20th century."
Citation: J. M. Gregory, N. J. White, J. A. Church, M. F. P. Bierkens, J. E. Box, M. R. van den Broeke, J. G. Cogley, X. Fettweis, E. Hanna, P. Huybrechts, L. F. Konikow, P. W. Leclercq, B. Marzeion, J. Oerlemans, M. E. Tamisiea, Y. Wada, L. M. Wake, and R. S.W. van de Wal, Journal of Climate 2012, doi: http://dx.doi.org/10.1175/JCLI-D-12-00319.1.
Blue mussel species tolerates ocean acidification
Abstract: "Ocean acidification is expected to decrease calcification rates of bivalves. Nevertheless in many coastal areas high pCO2 variability is encountered already today. Kiel Fjord (Western Baltic Sea) is a brackish (12-20 g kg-1) and CO2 enriched habitat, but the blue mussel Mytilus edulis dominates the benthic community. In a coupled field and laboratory study we examined the annual pCO2 variability in this habitat and the combined effects of elevated pCO2 and food availability on juvenile M. edulis growth and calcification. In the laboratory experiment, mussel growth and calcification were found to chiefly depend on food supply, with only minor impacts of pCO2 up to 3350 μatm. Kiel Fjord was characterized by strong seasonal pCO2 variability. During summer, maximal pCO2 values of 2500 μatm were observed at the surface and >3000 μatm at the bottom. However, the field growth experiment revealed seven times higher growth and calcification rates of M. edulis at a high pCO2 inner fjord field station (mean pCO2 ca. 1000 μatm) in comparison to a low pCO2 outer fjord station (ca. 600 μatm). In addition, mussels were able to outcompete the barnacle Amphibalanus improvisus at the high pCO2 site. High mussel productivity at the inner fjord site was enabled by higher particulate organic carbon concentrations. Kiel Fjord is highly impacted by eutrophication, which causes bottom water hypoxia and consequently high seawater pCO2. At the same time, elevated nutrient concentrations increase the energy availability for filter feeding organisms such as mussels. Thus M. edulis can dominate over a seemingly more acidification resistant species such as A. improvisus. We conclude that benthic stages of M. edulis tolerate high ambient pCO2when food supply is abundant and that important habitat characteristics such as species interactions and energy availability need to be considered to predict species vulnerability to ocean acidification."
Citation: Jörn Thomsen, Isabel Casties, Christian Pansch, Arne Körtzinger, Frank Melzner, Global Change Biology, DOI: 10.1111/gcb.12109.
Climate change is projected to increase fine particulate matter in atmosphere
Abstract: "Studies of the effect of climate change on fine particulate matter (PM2.5 air quality using general circulation models (GCMs) show inconsistent results including in the sign of the effect. This reflects uncertainty in the GCM simulations of the regional meteorological variables affecting PM2.5. Here we use the CMIP3 archive of data from fifteen different IPCC AR4 GCMs to obtain improved statistics of 21st-century trends in the meteorological modes driving PM2.5 variability over the contiguous US. We analyze 1999–2010 observations to identify the dominant meteorological modes driving interannual PM2.5 variability and their synoptic periods T. We find robust correlations (r > 0.5) of annual mean PM2.5 with T, especially in the eastern US where the dominant modes represent frontal passages. The GCMs all have significant skill in reproducing present-day statistics for T and we show that this reflects their ability to simulate atmospheric baroclinicity. We then use the local PM2.5-to-period sensitivity (dPM2.5/dT) from the 1999–2010 observations to project PM2.5 changes from the 2000–2050 changes in T simulated by the 15 GCMs following the SRES A1B greenhouse warming scenario. By weighted-average statistics of GCM results we project a likely 2000–2050 increase of ~ 0.1 μg m−3in annual mean PM2.5 in the eastern US arising from less frequent frontal ventilation, and a likely decrease albeit with greater inter-GCM variability in the Pacific Northwest due to more frequent maritime inflows. Potentially larger regional effects of 2000–2050 climate change on PM2.5 may arise from changes in temperature, biogenic emissions, wildfires, and vegetation, but are still unlikely to affect annual PM2.5 by more than 0.5 μg m−3."
Citation: Tai, A. P. K., Mickley, L. J., and Jacob, D. J.: Impact of 2000–2050 climate change on fine particulate matter (PM2.5) air quality inferred from a multi-model analysis of meteorological modes, Atmos. Chem. Phys., 12, 11329-11337, doi:10.5194/acp-12-11329-2012, 2012.
Other studies from last week
Proximate weather patterns and spring green-up phenology effect Eurasian beaver (Castor fiber) body mass and reproductive success: The implications of climate change and topography - Campbell et al. (2012)
CLASSIC OF THE WEEK: White (1907)
Citation: David White, The Journal of Geology, Vol. 15, No. 7 (Oct. - Nov., 1907) (pp. 615-633).
This is a cross-post from AGW Observer. About this series. 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.