scholarly journals The Macquarie Island [LoFlo2G] high-precision continuous atmospheric carbon dioxide record

2018 ◽  
Author(s):  
Ann R. Stavert ◽  
Rachel M. Law ◽  
Marcel van der Schoot ◽  
Ray L. Langenfelds ◽  
Darren A. Spencer ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Southern Ocean ◽  
High Precision ◽  
New Record ◽  
Large Scale ◽  
Atmospheric Co2 ◽  
Spatial And Temporal Variability ◽  
Co2 Fluxes ◽  
Macquarie Island ◽  
Uncertainty Estimates

Abstract. The Southern Ocean (south of 30° S) is a key global scale sink of carbon dioxide (CO2). However, the isolated and inhospitable nature of this environment has restricted the number of oceanic and atmospheric CO2 measurements in this region. This has limited the scientific community’s ability to investigate trends and seasonal variability of the sink. Compared to regions further north, the near-absence of terrestrial CO2 exchange and strong large-scale zonal mixing demands unusual inter-site measurement precision to help distinguish the presence of mid-to-high latitude ocean exchange from large CO2 fluxes transported southwards in the atmosphere. Here we describe a continuous, in-situ, ultra-high-precision, Southern Ocean region CO2 record, which ran at Macquarie Island (54°37’ S, 158°52’ E) from 2005–2016 using a LoFlo2 instrument, along with its calibration strategy, uncertainty analysis and baseline filtering procedures. Uncertainty estimates calculated for minute and hourly frequency data range from 0.01 to 0.05 μmol mol−1 depending on averaging period and application. Higher precisions are applicable when comparing MQA LoFlo measurements to those of similar instruments on the same internal laboratory calibration scale and more uncertain values are applicable when comparing to other networks. Baseline selection is designed to remove measurements that are influenced by local, Macquarie Island, CO2 sources, with effective removal achieved using a within-minute CO2 standard deviation metric. Additionally, measurements that are influenced by CO2 fluxes from Australia or other southern hemisphere land masses are effectively removed using model-simulated radon concentration. A comparison with flask records of atmospheric CO2 at Macquarie Island highlights the limitation of the flask record (due to corrections for storage time and limited temporal coverage) when compared to the new high-precision, continuous record; the new record shows much less noisy seasonal variations than the flask record. As such this new record is ideal for improving our understanding of the spatial and temporal variability of the Southern Ocean CO2 flux particularly when combined with data from similar instruments at other Southern Hemispheric locations.

scholarly journals The Macquarie Island (LoFlo2G) high-precision continuous atmospheric carbon dioxide record

2019 ◽  
Vol 12 (2) ◽  
pp. 1103-1121 ◽  
Author(s):  
Ann R. Stavert ◽  
Rachel M. Law ◽  
Marcel van der Schoot ◽  
Ray L. Langenfelds ◽  
Darren A. Spencer ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Southern Ocean ◽  
High Precision ◽  
New Record ◽  
Large Scale ◽  
Atmospheric Co2 ◽  
Spatial And Temporal Variability ◽  
Co2 Fluxes ◽  
Macquarie Island ◽  
Uncertainty Estimates

Abstract. The Southern Ocean (south of 30∘ S) is a key global-scale sink of carbon dioxide (CO2). However, the isolated and inhospitable nature of this environment has restricted the number of oceanic and atmospheric CO2 measurements in this region. This has limited the scientific community's ability to investigate trends and seasonal variability of the sink. Compared to regions further north, the near-absence of terrestrial CO2 exchange and strong large-scale zonal mixing demands unusual inter-site measurement precision to help distinguish the presence of midlatitude to high latitude ocean exchange from large CO2 fluxes transported southwards in the atmosphere. Here we describe a continuous, in situ, ultra-high-precision Southern Ocean region CO2 record, which ran at Macquarie Island (54∘37′ S, 158∘52′ E) from 2005 to 2016 using a LoFlo2 instrument, along with its calibration strategy, uncertainty analysis and baseline filtering procedures. Uncertainty estimates calculated for minute and hourly frequency data range from 0.01 to 0.05 µmol mol−1 depending on the averaging period and application. Higher precisions are applicable when comparing Macquarie Island LoFlo measurements to those of similar instruments on the same internal laboratory calibration scale and more uncertain values are applicable when comparing to other networks. Baseline selection is designed to remove measurements that are influenced by local Macquarie Island CO2 sources, with effective removal achieved using a within-minute CO2 standard deviation metric. Additionally, measurements that are influenced by CO2 fluxes from Australia or other Southern Hemisphere land masses are effectively removed using model-simulated radon concentration. A comparison with flask records of atmospheric CO2 at Macquarie Island highlights the limitation of the flask record (due to corrections for storage time and limited temporal coverage) when compared to the new high-precision, continuous record: the new record shows much less noisy seasonal variations than the flask record. As such, this new record is ideal for improving our understanding of the spatial and temporal variability of the Southern Ocean CO2 flux, particularly when combined with data from similar instruments at other Southern Hemispheric locations.

scholarly journals Watermasses as a unifying framework for understanding the Southern Ocean carbon cycle

2010 ◽  
Vol 7 (3) ◽  
pp. 3393-3451 ◽  
Author(s):  
D. Iudicone ◽  
I. Stendardo ◽  
O. Aumont ◽  
K. B. Rodgers ◽  
G. Madec ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Large Scale ◽  
Thermohaline Circulation ◽  
Model Simulation ◽  
Polar Front ◽  
Global Ocean ◽  
Inversion Method ◽  
Co2 Fluxes ◽  
Meridional Transport ◽  
Regional Patterns

Abstract. A watermass-based framework is presented for a quantitative understanding of the processes controlling the cycling of carbon in the Southern Ocean. The approach is developed using a model simulation of the global carbon transports within the ocean and with the atmosphere. It is shown how the watermass framework sheds light on the interplay between biology, air-sea gas exchange, and internal ocean transport including diapycnal processes, and the way in which this interplay controls the large-scale ocean-atmosphere carbon exchange. The simulated pre-industrial regional patterns of DIC distribution and the global distribution of the pre-industrial air-sea CO2 fluxes compare well with other model results and with results from an ocean inversion method. The main differences are found in the Southern Ocean where the model presents a stronger CO2 outgassing south of the polar front, a result of the upwelling of DIC-rich deep waters into the surface layer. North of the subantarctic front the typical temperature-driven solubility effect produces a net ingassing of CO2. The biological controls on surface CO2 fluxes through primary production is generally smaller than the temperature effect on solubility. Novel to this study is also a Lagrangian trajectory analysis of the meridional transport of DIC. The analysis allows to evaluate the contribution of separate branches of the global thermohaline circulation (identified by watermasses) to the vertical distribution of DIC throughout the Southern Ocean and towards the global ocean. The most important new result is that the overturning associated with Subantarctic Mode Waters sustains a northward net transport of DIC (15.7×107 mol/s across 30° S). This new finding, which has also relevant implications on the prediction of anthropogenic carbon redistribution, results from the specific mechanism of SAMW formation and its source waters whose consequences on tracer transports are analyzed for the first time in this study.

scholarly journals Rapid establishment of the CO<sub>2</sub> sink associated with Kerguelen's bloom observed during the KEOPS2/OISO20 cruise

2014 ◽  
Vol 11 (12) ◽  
pp. 17543-17578 ◽  
Author(s):  
C. Lo Monaco ◽  
N. Metzl ◽  
F. D'Ovidio ◽  
J. Llort ◽  
C. Ridame
Keyword(s):  
Southern Ocean ◽  
Vertical Mixing ◽  
Growing Season ◽  
Atmospheric Co2 ◽  
Co2 Fluxes ◽  
Kerguelen Plateau ◽  
Iron Source ◽  
Iron Fertilization ◽  
Co2 Sink ◽  
The Impact

Abstract. Iron and light are the main factors limiting the biological pump of CO2 in the Southern Ocean. Iron fertilization experiments have demonstrated the potential for increased uptake of atmospheric CO2, but little is known about the evolution of fertilized environnements. This paper presents observations collected in one of the largest phytoplankton bloom of the Southern Ocean sustained by iron originating from the Kerguelen Plateau. We first complement previous studies by investigating the mechanisms that control air–sea CO2 fluxes over and downstream of the Kerguelen Plateau at the onset of the bloom based on measurements obtained in October–November 2011. These new observations show the rapid establishment of a strong CO2 sink in waters fertilized with iron as soon as vertical mixing is reduced. The magnitude of the CO2 sink was closely related to chlorophyll a and iron concentrations. Because iron concentration strongly depends on the distance from the iron source and the mode of delivery, we identified lateral advection as the main mechanism controlling air–sea CO2 fluxes downtream the Kerguelen Plateau during the growing season. In the southern part of the bloom, situated over the Plateau (iron source), the CO2 sink was stronger and spatially more homogeneous than in the plume offshore. However, we also witnessed a substantial reduction in the uptake of atmospheric CO2 over the Plateau following a strong winds event. Next, we used all the data available in this region in order to draw the seasonal evolution of air–sea CO2 fluxes. The CO2 sink is rapidly reduced during the course of the growing season, which we attribute to iron and silicic acid depletion. South of the Polar Front, where nutrients depletion is delayed, we suggest that the amplitude and duration of the CO2 sink is mainly controlled by vertical mixing. The impact of iron fertilization on air–sea CO2 fluxes is revealed by comparing the uptake of CO2 integrated over the productive season in the bloom, between 1 and 1.5 mol C m−2 yr−1, and in the iron-poor HNLC waters, where we found a typical value of 0.4 mol C m−2 yr−1. Extrapolating our results to the ice-free Southern Ocean (~50–60° S) suggests that iron fertilization of the whole area would increase the contemporay oceanic uptake of CO2 by less than 0.1 Pg C yr−1, i.e., less than 1% of the current anthropogenic CO2 emissions.

scholarly journals Modelling CO<sub>2</sub> weather – why horizontal resolution matters

2019 ◽  
Vol 19 (11) ◽  
pp. 7347-7376 ◽  
Author(s):  
Anna Agustí-Panareda ◽  
Michail Diamantakis ◽  
Sébastien Massart ◽  
Frédéric Chevallier ◽  
Joaquín Muñoz-Sabater ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
High Resolution ◽  
Greenhouse Gas ◽  
Real Time ◽  
Horizontal Resolution ◽  
Surface Fluxes ◽  
Atmospheric Co2 ◽  
Small Scale ◽  
Co2 Fluxes

Abstract. Climate change mitigation efforts require information on the current greenhouse gas atmospheric concentrations and their sources and sinks. Carbon dioxide (CO2) is the most abundant anthropogenic greenhouse gas. Its variability in the atmosphere is modulated by the synergy between weather and CO2 surface fluxes, often referred to as CO2 weather. It is interpreted with the help of global or regional numerical transport models, with horizontal resolutions ranging from a few hundreds of kilometres to a few kilometres. Changes in the model horizontal resolution affect not only atmospheric transport but also the representation of topography and surface CO2 fluxes. This paper assesses the impact of horizontal resolution on the simulated atmospheric CO2 variability with a numerical weather prediction model. The simulations are performed using the Copernicus Atmosphere Monitoring Service (CAMS) CO2 forecasting system at different resolutions from 9 to 80 km and are evaluated using in situ atmospheric surface measurements and atmospheric column-mean observations of CO2, as well as radiosonde and SYNOP observations of the winds. The results indicate that both diurnal and day-to-day variability of atmospheric CO2 are generally better represented at high resolution, as shown by a reduction in the errors in simulated wind and CO2. Mountain stations display the largest improvements at high resolution as they directly benefit from the more realistic orography. In addition, the CO2 spatial gradients are generally improved with increasing resolution for both stations near the surface and those observing the total column, as the overall inter-station error is also reduced in magnitude. However, close to emission hotspots, the high resolution can also lead to a deterioration of the simulation skill, highlighting uncertainties in the high-resolution fluxes that are more diffuse at lower resolutions. We conclude that increasing horizontal resolution matters for modelling CO2 weather because it has the potential to bring together improvements in the surface representation of both winds and CO2 fluxes, as well as an expected reduction in numerical errors of transport. Modelling applications like atmospheric inversion systems to estimate surface fluxes will only be able to benefit fully from upgrades in horizontal resolution if the topography, winds and prior flux distribution are also upgraded accordingly. It is clear from the results that an additional increase in resolution might reduce errors even further. However, the horizontal resolution sensitivity tests indicate that the change in the CO2 and wind modelling error with resolution is not linear, making it difficult to quantify the improvement beyond the tested resolutions. Finally, we show that the high-resolution simulations are useful for the assessment of the small-scale variability of CO2 which cannot be represented in coarser-resolution models. These representativeness errors need to be considered when assimilating in situ data and high-resolution satellite data such as Greenhouse gases Observing Satellite (GOSAT), Orbiting Carbon Observatory-2 (OCO-2), the Chinese Carbon Dioxide Observation Satellite Mission (TanSat) and future missions such as the Geostationary Carbon Observatory (GeoCarb) and the Sentinel satellite constellation for CO2. For these reasons, the high-resolution CO2 simulations provided by the CAMS in real time can be useful to estimate such small-scale variability in real time, as well as providing boundary conditions for regional modelling studies and supporting field experiments.

scholarly journals Side effects and accounting aspects of hypothetical large-scale Southern Ocean iron fertilization

2010 ◽  
Vol 7 (2) ◽  
pp. 2949-2995 ◽  
Author(s):  
A. Oschlies ◽  
W. Koeve ◽  
W. Rickels ◽  
K. Rehdanz
Keyword(s):  
Carbon Sequestration ◽  
Side Effects ◽  
Southern Ocean ◽  
Atmospheric Carbon Dioxide ◽  
Large Scale ◽  
Climate Model ◽  
N2o Emissions ◽  
Co2 Fluxes ◽  
Iron Fertilization ◽  
Fertilization Experiments

Abstract. Recent suggestions to slow down the increase in atmospheric carbon dioxide have included ocean fertilization by addition of the micronutrient iron to Southern Ocean surface waters, where a number of natural and artificial iron fertilization experiments have shown that low ambient iron concentrations limit phytoplankton growth. Using a coupled carbon-climate model with the marine biology's response to iron addition calibrated against data from natural iron fertilization experiments, we examine biogeochemical side effects of a hypothetical large-scale Southern Ocean Iron Fertilization (OIF) that need to be considered when attempting to account for possible OIF-induced carbon offsets. In agreement with earlier studies our model simulates an OIF-induced increase in local air-sea CO2 fluxes by about 60 GtC over a 100-year period, which amounts to about 40% of the OIF-induced increase in organic carbon export. Offsetting CO2 return fluxes outside the region and after stopping the fertilization at 1, 7, 10, 50, and 100 years are quantified for a typical accounting period of 100 years. For continuous Southern Ocean iron fertilization, the return flux outside the fertilized area cancels about 8% of the fertilization-induced CO2 air-sea flux within the fertilized area on a 100-yr timescale. This "leakage" effect has a similar radiative impact as the simulated enhancement of marine N2O emissions. Other side effects not yet discussed in terms of accounting schemes include a decrease in Southern Ocean oxygen levels and a simultaneous shrinking of tropical suboxic areas, and accelerated ocean acidification in the entire water column in the Southern Ocean on the expense of reduced globally averaged surface water acidification. A prudent approach to account for the OIF-induced carbon sequestration would account for global air-sea CO2 fluxes rather than for local fluxes into the fertilized area only. However, according to our model, this would underestimate the potential for offsetting CO2 emissions by about 20% on a 100 year accounting timescale. We suggest that a fair accounting scheme applicable to both terrestrial and marine carbon sequestration has to be based on emission offsets rather than on changes in individual carbon pools.

scholarly journals Tower and Aircraft Eddy Covariance Measurements of Water Vapor, Energy, and Carbon Dioxide Fluxes during SMACEX

2005 ◽  
Vol 6 (6) ◽  
pp. 954-960 ◽  
Author(s):  
J. H. Prueger ◽  
J. L. Hatfield ◽  
T. B. Parkin ◽  
W. P. Kustas ◽  
L. E. Hipps ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Water Vapor ◽  
Eddy Covariance ◽  
Spatial And Temporal Variability ◽  
Co2 Fluxes ◽  
Sensible Heat ◽  
Carbon Dioxide Fluxes ◽  
Crop Growth Stage ◽  
Aircraft Flux Measurements ◽  
Carbon Dioxide Co2

Abstract A network of eddy covariance (EC) and micrometeorological flux (METFLUX) stations over corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] canopies was established as part of the Soil Moisture–Atmosphere Coupling Experiment (SMACEX) in central Iowa during the summer of 2002 to measure fluxes of heat, water vapor, and carbon dioxide (CO2) during the growing season. Additionally, EC measurements of water vapor and CO2 fluxes from an aircraft platform complemented the tower-based measurements. Sensible heat, water vapor, and CO2 fluxes showed the greatest spatial and temporal variability during the early crop growth stage. Differences in all of the energy balance components were detectable between corn and soybean as well as within similar crops throughout the study period. Tower network–averaged fluxes of sensible heat, water vapor, and CO2 were observed to be in good agreement with area-averaged aircraft flux measurements.

scholarly journals Side effects and accounting aspects of hypothetical large-scale Southern Ocean iron fertilization

2010 ◽  
Vol 7 (12) ◽  
pp. 4017-4035 ◽  
Author(s):  
A. Oschlies ◽  
W. Koeve ◽  
W. Rickels ◽  
K. Rehdanz
Keyword(s):  
Carbon Sequestration ◽  
Side Effects ◽  
Southern Ocean ◽  
Atmospheric Carbon Dioxide ◽  
Large Scale ◽  
Climate Model ◽  
N2o Emissions ◽  
Co2 Fluxes ◽  
Iron Fertilization ◽  
Fertilization Experiments

Abstract. Recent suggestions to slow down the increase in atmospheric carbon dioxide have included ocean fertilization by addition of the micronutrient iron to Southern Ocean surface waters, where a number of natural and artificial iron fertilization experiments have shown that low ambient iron concentrations limit phytoplankton growth. Using a coupled carbon-climate model with the marine biology's response to iron addition calibrated against data from natural iron fertilization experiments, we examine biogeochemical side effects of a hypothetical large-scale Southern Ocean Iron Fertilization (OIF) that need to be considered when attempting to account for possible OIF-induced carbon offsets. In agreement with earlier studies our model simulates an OIF-induced increase in local air-sea CO2 fluxes by about 73 GtC over a 100-year period, which amounts to about 48% of the OIF-induced increase in organic carbon export out of the fertilized area. Offsetting CO2 return fluxes outside the region and after stopping the fertilization at 1, 7, 10, 50, and 100 years are quantified for a typical accounting period of 100 years. For continuous Southern Ocean iron fertilization, the CO2 return flux outside the fertilized area cancels about 20% of the fertilization-induced CO2 air-sea flux within the fertilized area on a 100-yr timescale. This "leakage" effect has a radiative impact more than twice as large as the simulated enhancement of marine N2O emissions. Other side effects not yet discussed in terms of accounting schemes include a decrease in Southern Ocean oxygen levels and a simultaneous shrinking of tropical suboxic areas, and accelerated ocean acidification in the entire water column in the Southern Ocean at the expense of reduced globally-averaged surface-water acidification. A prudent approach to account for the OIF-induced carbon sequestration would account for global air-sea CO2 fluxes rather than for local fluxes into the fertilized area only. However, according to our model, this would underestimate the potential for offsetting CO2 emissions by about 20% on a 100 year accounting timescale. We suggest that a fair accounting scheme applicable to both terrestrial and marine carbon sequestration has to be based on emission offsets rather than on changes in individual carbon pools.

scholarly journals Atmospheric concentrations of carbon dioxide and its isotopic composition in southern Poland: comparison of high-altitude mountain site and a near-by urban environment

2005 ◽  
Vol 2 (6) ◽  
pp. 1849-1865 ◽  
Author(s):  
L. Chmura ◽  
K. Rozanski ◽  
J. M. Necki ◽  
M. Zimnoch ◽  
T. Kuc ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Isotopic Composition ◽  
High Altitude ◽  
Urban Environment ◽  
Carbon Isotopic Composition ◽  
Urban Atmosphere ◽  
Atmospheric Co2 ◽  
Co2 Fluxes ◽  
Mixing Ratios ◽  
Mountain Site

Abstract. The results of regular observations of atmospheric CO2 mixing ratios and its carbon isotope composition (δ13C, Δ14C), carried out at two continental sites located in central Europe are presented and discussed. The sites (Kasprowy Wierch, 49°14' N, 19°59' E, 1989 m a.s.l.; Krakow, 50°04' N, 19°55' E, 220 m a.s.l.), are located in two contrasting environments: (i) high-altitude mountaneous area, relatively free of anthropogenic influences, and (ii) typical urban environment with numerous local sources of carbon dioxide. Despite of relative proximity of those sites (ca. 100 km), substantial differences in both the recorded CO2 levels and their isotopic composition were detected. The CO2 mixing ratios measured in the urban atmosphere revealed quasi-permanent excess concentration of this gas when compared with near-by background atmosphere. The annual mean CO2 concentration recorded in Krakow in 2004 was almost 10% higher than that recorded at high-altitude mountain site (Kasprowy Wierch). Such effect is occuring probably in all urban centers. Carbon isotopic composition of atmospheric CO2 proved to be efficient tool for identification the surface CO2 fluxes into the atmosphere related to fossil fuel burning and their influence on the recorded levels of this gas in the local atmosphere. The available records of Δ14C for Krakow and Kasprowy Wierch suggest gradual reduction of 14C-free CO2 fluxes into the urban atmosphere of Krakow in the past several years.

scholarly journals Spatial and temporal variability of urban fluxes of methane, carbon monoxide and carbon dioxide above London, UK

2016 ◽  
Vol 16 (16) ◽  
pp. 10543-10557 ◽  
Author(s):  
Carole Helfter ◽  
Anja H. Tremper ◽  
Christoforos H. Halios ◽  
Simone Kotthaus ◽  
Alex Bjorkegren ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Air Temperature ◽  
Temporal Variability ◽  
Substantial Contribution ◽  
Spatial And Temporal Variability ◽  
Co2 Fluxes ◽  
Atmospheric Emissions ◽  
Ch4 Emissions ◽  
Emissions Inventories

Abstract. We report on more than 3 years of measurements of fluxes of methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2) taken by eddy-covariance in central London, UK. Mean annual emissions of CO2 in the period 2012–2014 (39.1 ± 2.4 ktons km−2 yr−1) and CO (89 ± 16 tons km−2 yr−1) were consistent (within 1 and 5 % respectively) with values from the London Atmospheric Emissions Inventory, but measured CH4 emissions (72 ± 3 tons km−2 yr−1) were over two-fold larger than the inventory value. Seasonal variability was large for CO with a winter to summer reduction of 69 %, and monthly fluxes were strongly anti-correlated with mean air temperature. The winter increment in CO emissions was attributed mainly to vehicle cold starts and reduced fuel combustion efficiency. CO2 fluxes were 33 % higher in winter than in summer and anti-correlated with mean air temperature, albeit to a lesser extent than for CO. This was attributed to an increased demand for natural gas for heating during the winter. CH4 fluxes exhibited moderate seasonality (21 % larger in winter), and a spatially variable linear anti-correlation with air temperature. Differences in resident population within the flux footprint explained up to 90 % of the spatial variability of the annual CO2 fluxes and up to 99 % for CH4. Furthermore, we suggest that biogenic sources of CH4, such as wastewater, which is unaccounted for by the atmospheric emissions inventories, make a substantial contribution to the overall budget and that commuting dynamics in and out of central business districts could explain some of the spatial and temporal variability of CO2 and CH4 emissions. To our knowledge, this study is unique given the length of the data sets presented, especially for CO and CH4 fluxes. This study offers an independent assessment of "bottom-up" emissions inventories and demonstrates that the urban sources of CO and CO2 are well characterized in London. This is however not the case for CH4 emissions which are heavily underestimated by the inventory approach. Our results and others point to opportunities in the UK and abroad to identify and quantify the "missing" sources of urban methane, revise the methodologies of the emission inventories and devise emission reduction strategies for this potent greenhouse gas.

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