Components of near-surface energy balance derived from satellite soundings – Part 1: Noontime net available energy
Summary: This paper demonstrates a novel analytical method for recovering global fields noontime near-surface net available energy (the sum of the sensible and latent heat flux) and ground heat flux using day-night land surface temperature and net radiation combining AIRS and MODIS optical, thermal and atmospheric data. This method could potentially overcome the stumbling blocks associated with the empirical parameterisations for determining the ground heat flux in global evapotranspiration modelling.
Intercomparison of fast response commercial gas analysers for nitrous oxide flux measurements under field conditions
Ü. Rannik, S. Haapanala, N. J. Shurpali, I. Mammarella, S. Lind, N. Hyvönen, O. Peltola, M. Zahniser, P. J. Martikainen, and T. Vesala Biogeosciences, 12, 415-432, 2015 AbstractFinal Revised Paper (PDF, 380 KB)Discussion Paper (BGD)
22 Jan 2015
North America's net terrestrial CO2 exchange with the atmosphere 1990–2009
Atmospheric inversion of surface carbon flux with consideration of the spatial distribution of US crop production and consumption
Summary: The major findings of this article are the following. 1. Atmospheric CO2 observations alone are not sufficient to estimate the spatial distribution of carbon sources and sinks over North America, even though it is one of the most densely observed regions in the world. 2. To improve atmospheric inversion, lateral carbon transfer in agricultural products should be considered in the prior flux used to constrain the inversion.
Satellite observations of the small-scale cyclonic eddies in the western South China Sea
Summary: In this paper, small-scale cyclonic eddies in the western South China Sea were observed during the upwelling season of the year. These small-scale eddies propagated eastward at the speed of 12cm/s. They transported the high level of phytoplankton away from the coastal area. The generation of the small-scale eddies may be associated with the relative movement between the mesoscale anticyclonic eddy and the offshore current.
Emissions from prescribed fires in temperate forest in south-east Australia: implications for carbon accounting
Summary: Emissions from fires are estimated as products of fuel load, burning efficiency, area burnt and emission factors for compounds of interest. Uncertainties in these variables lead to a wide range of estimates. We demonstrate that the probability of estimating true emissions declines strongly as the amount of information available declines. Including coarse woody debris in estimates increased uncertainty in calculations because it was the most variable contributor to fuel load.
Upper ocean mixing controls the seasonality of planktonic foraminifer fluxes and associated strength of the carbonate pump in the oligotrophic North Atlantic
Summary: Planktonic foraminifera are an important component of the marine carbon/carbonate cycle, yet the environmental controls on their abundances are still debated. In our study, we see larger foraminifera fluxes, particularly of heavy species, during winter when nutrients are mixed into the surface waters or during eddy mixing. Climatic factors that control mixing could therefore control the flux of planktonic foraminfera and the carbon/carbonate flux on seasonal and decadal timescales.
Variable C : N : P stoichiometry of dissolved organic matter cycling in the Community Earth System Model
Summary: Marine DOM is known to exhibit stoichiometry depleted in N and P compared with POM, suggesting variable production and remineralization stoichiometry for C, N, and P within marine DOM cycling. We utilize marine DOM observations and an inverse tracer modeling framework to optimize DOM cycling parameters for the BEC biogeochemistry ocean model of the CESM, finding a variable stoichiometry with faster turnover of P > N > C superior to the commonly assumed Redfield stoichiometry for marine DOM.
Evaluating the ocean biogeochemical components of Earth system models using atmospheric potential oxygen and ocean color data
Summary: The observed seasonal cycles in atmospheric potential oxygen (APO) at five surface monitoring sites are compared to those inferred from the air-sea O2 fluxes of six ocean biogeochemistry models. The simulated air-sea fluxes are translated into APO seasonal cycles using a matrix method that takes into account atmospheric transport model (ATM) uncertainty among 13 different ATMs. Net primary production (NPP), estimated from satellite ocean color data, is also compared to model output.
Impacts of soil moisture on de novo monoterpene emissions from European beech, Holm oak, Scots pine, and Norway spruce
Summary: Impacts of soil moisture on de novo monoterpene emissions from several tree species were studied. Mild drought slightly increased MT emissions, but with further progressing drought the emissions decreased to almost zero. Increases of MT emissions were explainable by increases of leaf temperature due to lowered transpirational cooling. The decrease of emissions observed when soil moisture fell below certain thresholds was parameterized, allowing considering impacts of soil moisture in models.
C. Wu, I. Pullinen, S. Andres, G. Carriero, S. Fares, H. Goldbach, L. Hacker, T. Kasal, A. Kiendler-Scharr, E. Kleist, E. Paoletti, A. Wahner, J. Wildt, and Th. F. Mentel Biogeosciences, 12, 177-191, 2015 AbstractFinal Revised Paper (PDF, 3028 KB)Supplement (426 KB)Discussion Paper (BGD)
09 Jan 2015
Deploying four optical UAV-based sensors over grassland: challenges and limitations
Summary: Unmanned aerial vehicles (UAVs) equipped with optical sensors facilitate non-invasive, real-time vegetation analysis. To guarantee robust scientific analysis, protocols need to be developed and sensors must be compared to state-of-the-art instruments. Here we compare four UAV sensors (RGB, NIR, six-band, spectrometer) to evaluate their applicability for vegetation monitoring. By showing the opportunities and pitfalls of UAV-based sensing, we describe ways to gather sound scientific data.
The effects of river inflow and retention time on the spatial heterogeneity of chlorophyll and water–air CO2 fluxes in a tropical hydropower reservoir
Summary: CO2 fluxes in Funil Reservoir (FR) is driven by primary production and river inflow dynamics. Our findings suggest that the lack of spatial data in reservoir C budget calculations can affect regional and global estimates. Our results support the idea that the FR is a dynamic system where the hydrodynamics represented by changes in the river inflow and retention time are potentially a more important force driving both the Chl and pCO2 spatial variability than the in-system ecological factors.
F. S. Pacheco, M. C. S. Soares, A. T. Assireu, M. P. Curtarelli, F. Roland, G. Abril, J. L. Stech, P. C. Alvalá, and J. P. Ometto Biogeosciences, 12, 147-162, 2015 AbstractFinal Revised Paper (PDF, 946 KB)Discussion Paper (BGD)
09 Jan 2015
CO2 fluxes and ecosystem dynamics at five European treeless peatlands – merging data and process oriented modeling
Summary: To identify site specific differences in CO2-related processes in open peatlands, we calibrated a process oriented model to fit to detailed measurements of carbon fluxes and compared the resulting parameter ranges between the sites. For most processes a common configuration could be applied. Site specific differences were identified for soil respiration coefficients, plant radiation-use efficiencies and plant storage fractions for spring regrowth.
Two perspectives on the coupled carbon, water and energy exchange in the planetary boundary layer
Summary: This study investigates the interactions among the carbon, water and heat cycles above a maize field at the diurnal scale. We couple two land-surface schemes, corresponding to two different modelling approaches, to the same atmospheric boundary-layer (ABL) model. We find the simpler meteorological approach best reproduces the surface and upper-air observations. Finally, we show that the interaction of subsidence with ABL dynamics is key to explain the daytime atmospheric CO2 budget.
Technical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters
Summary: We compared pCO2 data calculated from pH and alkalinity from those measured directly in a large array of temperate and tropical freshwaters. This revealed a large overestimation (up to 300%) of calculated pCO2 in the case of acidic and organic-rich waters, due to a contribution of organic acids anions to alkalinity and a lower buffering capacity of the carbonate system at acidic pH. Given the widespread distribution of acidic freshwaters, direct measurements of water pCO2 are encouraged.
G. Abril, S. Bouillon, F. Darchambeau, C. R. Teodoru, T. R. Marwick, F. Tamooh, F. Ochieng Omengo, N. Geeraert, L. Deirmendjian, P. Polsenaere, and A. V. Borges Biogeosciences, 12, 67-78, 2015 AbstractFinal Revised Paper (PDF, 682 KB)Discussion Paper (BGD)
06 Jan 2015
A novel reflectance-based model for evaluating chlorophyll concentrations of fresh and water-stressed leaves
Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes
Summary: Beaded streams have deep elliptical pools connected by narrow runs that we show are common landforms in the continuous permafrost zone. These fluvial systems often initiate from lakes and occur predictably in headwater portions of moderately sloping watersheds. Snow capture along stream courses reduces ice thickness allowing thawed sediment to persist under most pools. Interpool thermal variability and hydrologic regimes provide important aquatic habitat and connectivity in Arctic landscapes.
Spatiotemporal variations of nitrogen isotopic records in the Arabian Sea
Summary: This paper presents a new sedimentary nitrogen isotope record (d15N) of a sediment core from the southeastern Arabian Sea (AS). By compiling the published nitrogen isotope data in the AS, we obtain geographically distinctive bottom-depth effects for the northern and southern AS since 35ka. After eliminating the bottom-depth bias, we observe opposite d15N trends in the Holocene between these two areas, reflecting a special coupling of denitrification to the north and N2-fixation to the south.
Components of near-surface energy balance derived from satellite soundings – Part 2: Noontime latent heat flux
Summary: We have successfully used NASA-AIRS temperature-humidity profiles and associated radiances within a Bowen ratio framework to produce the first ever global sounder latent and sensible heat fluxes (SoLH and SoSH). These SoLH and SoSH estimates do not require any land surface parameterisations of the aerodynamic and stomatal conductances and hence are ideally suited to interrogate or improve the surface paramaterisations embedded in the land components of Earth system models.
Limpets counteract ocean acidification induced shell corrosion by thickening of aragonitic shell layers
Summary: Specimens of the patellogastropod limpet Patella caerulea were collected within and outside a CO2 vent site at Ischia, Italy. The distribution of different crystal structures across shell sections was analysed. Patella caerulea counteracts shell dissolution in corrosive waters by enhanced production of aragonitic parts of the shell. We conclude that it is not possible to predict the dissolution behaviour of a composite biomineral on the basis of the properties of its constituent mineral.
Processes determining the marine alkalinity and calcium carbonate saturation state distributions
Summary: We examine and discuss the portion of ocean alkalinity that varies in response to carbonate cycling and riverine alkalinity inputs using a new tracer, Alk*. We use this tracer to quantify the controls on marine carbonate saturation: at depth, we find carbonate cycling to be a minor control relative to organic matter cycling and pressure changes. In well-equilibrated surface water, we find carbonate cycling to be less important than temperature changes and freshwater cycling.
Biomass burning fuel consumption rates: a field measurement database
T. T. van Leeuwen, G. R. van der Werf, A. A. Hoffmann, R. G. Detmers, G. Rücker, N. H. F. French, S. Archibald, J. A. Carvalho Jr., G. D. Cook, W. J. de Groot, C. Hély, E. S. Kasischke, S. Kloster, J. L. McCarty, M. L. Pettinari, P. Savadogo, E. C. Alvarado, L. Boschetti, S. Manuri, C. P. Meyer, F. Siegert, L. A. Trollope, and W. S. W. Trollope Biogeosciences, 11, 7305-7329, 2014 AbstractFinal Revised Paper (PDF, 722 KB)Discussion Paper (BGD)
19 Dec 2014
iMarNet: an ocean biogeochemistry model intercomparison project within a common physical ocean modelling framework
L. Kwiatkowski, A. Yool, J. I. Allen, T. R. Anderson, R. Barciela, E. T. Buitenhuis, M. Butenschön, C. Enright, P. R. Halloran, C. Le Quéré, L. de Mora, M.-F. Racault, B. Sinha, I. J. Totterdell, and P. M. Cox Biogeosciences, 11, 7291-7304, 2014 AbstractFinal Revised Paper (PDF, 5874 KB)Supplement (2134 KB)Discussion Paper (BGD)
19 Dec 2014
Spring bloom community change modifies carbon pathways and C : N : P : Chl a stoichiometry of coastal material fluxes
Summary: Recent evidence suggests that competition between phytoplankton groups is significantly affected by changing climatic factors. We investigated the effects of phytoplankton community composition on spring bloom carbon flows. The comparison of differing communities showed that community structure significantly affected C accumulation parameters. Climate-driven changes in phytoplankton dominance patterns will have far-reaching consequences for major biogeochemical cycles.
Biogeophysical impacts of peatland forestation on regional climate changes in Finland
Summary: This work studies the biogeophysical impacts of peatland forestation on regional climate conditions in Finland by a regional climate model with two land cover maps produced from Finnish national forest inventories. A warming in spring and a slight cooling in the growing season are found in peatland forestation area, which are mainly induced by the decreased surface albedo and increased ET, respectively. The snow clearance days are advanced. The results are also compared with observational data.
CO2 and nutrient-driven changes across multiple levels of organization in Zostera noltii ecosystems
Summary: We found that the multi-level meadow response to nutrient enrichment was faster and stronger than to CO2 enrichment, being both mediated by shifts in leaf epiphyte or sediment communities. Our findings highlight the relevance of integrative approaches considering not only species interactions and connections between organization levels, but also the effect of interactive stressors, to anticipate the evolution of seagrass meadows in the near future and to endorse conservation efforts.
Methane and nitrous oxide exchange over a managed hay meadow
Summary: The methane (CH4) and nitrous oxide (N2O) exchange of a temperate mountain grassland near Neustift, Austria, was measured during 2010–2012 over a time period of 22 months using the eddy covariance method. The meadow acted as a sink for both compounds during certain time periods, but was a clear source of CH4 and N2O on an annual timescale. Both gases contributed to an increase of the global warming potential (GWP), effectively reducing the sink strength in terms of CO2 equivalents.
Identifying vital effects in Halimeda algae with Ca isotopes
Summary: Halimeda algae were used as a test organism to untangle some of the specific factors that influence skeletal composition, in particular Ca-isotope composition. Algae were stimulated to precipitate both calcite and aragonite by growth in artificial Cretaceous seawater. Comparison of the skeletal Ca-isotope ratios with inorganic carbonate forms indicates the effects of mineralogy and Rayleigh distillation of Ca on the geochemistry of their carbonate skeletons.
Physical and biogeochemical controls on light attenuation in a eutrophic, back-barrier estuary
Summary: Light availability to seagrass is an important factor in their success. We deployed instrumentation to measure light in Barnegat Bay, New Jersey, and found lower availability in the southern bay due to high turbidity (suspended sediment), while the northern bay has higher availability. In the northern bay, dissolved organic material and chlorophyll are most responsible for blocking light to the seagrass canopy. We also found that boat wakes do not have a large effect on sediment resuspension.
Drivers of trophic amplification of ocean productivity trends in a changing climate
Summary: Climate change projections suggest large regional ocean productivity shifts for mesozooplankton, an important food resource for fish, which are amplified relative to changes in phytoplankton production. Amplification is attributed to changes in planktonic food web dynamics under global warming. Results have implications for regional economies and food security. Improved understanding of the response of plankton food webs to climate change is essential to refine amplification estimates.
Multi-factor controls on terrestrial carbon dynamics in urbanized areas
Summary: Based on a comprehensive analysis framework including 15 factors, a factorial analysis scheme was developed to quantify a relative contribution of individual factors to carbon dynamics induced by urbanization. A case study in the southern US showed that land conversion had larger impacts than other factors, causing C loss. Urban managements & the interactive effect among factors compensated for 42% of the C loss in LC. The altered disturbance regime after urbanization enhanced the urban C sink.
I/Ca ratios in benthic foraminifera from the Peruvian oxygen minimum zone: analytical methodology and evaluation as a proxy for redox conditions
Summary: Our study explores the correlation of I/Ca ratios in four benthic foraminiferal species (three calcitic, one aragonitic) from the Peruvian OMZ with bottom water oxygenation ([O2]BW), and evaluates foraminiferal I/Ca ratios as a possible redox proxy. All species have a positive trend in the I/Ca ratios as a function of [O2]BW. Only for the aragonitic species Hoeglundina elegans is this trend not significant. The highest significance has been found for Uvigerina striata.
Biogeochemistry and ecosystems of continental margins in the western North Pacific Ocean and their interactions and responses to external forcing – an overview and synthesis
Summary: This paper provides background info on the East China Sea, Japan/East Sea and South China Sea and highlights major findings in the special issue on their biogeochemical conditions and ecosystem functions. The three seas are subject to strong impacts from human activities and/or climate forcing. Because these continental margins sustain arguably some of the most productive marine ecosystems in the world, changes in these stressed ecosystems may threaten the livelihood of a large human population.