ALBERT

Description: We present observations of CHBr3, CH2Br2, CH3I, CHClBr2, and CHBrCl2 from the Trace Gas Organic Analyzer (TOGA) during the O2/N2 Ratio and CO2 Airborne Southern Ocean (ORCAS) study and the 2nd Atmospheric Tomography mission (ATom-2), in January and February of 2016 and 2017. We also use CH3Br from the University of Miami Advanced Whole Air Sampler (AWAS) on ORCAS and from the UC Irvine Whole Air Sampler (WAS) on ATom-2. We compare our observations with simulations from the Community Atmosphere Model with Chemistry (CAM-Chem). We report regional enrichment ratios of CHBr3 and CH2Br2 to O2 of 0.19 ± 0.01, and 0.07 ± 0.004 pmol : mol, poleward of 60° S between 180° W and 55° W, and of 0.32 ± 0.02, 0.07 ± 0.004 pmol : mol over the Patagonian Shelf, between 40° S and 55° S and between 70° W and 55° W where we also report enrichment ratios of CH3I to O2 of 0.38 ± 0.03 pmol : mol and of CH2ClBr2 to O2 of 0.19 ± 0.04 pmol: mol. Using the Stochastic Time-Inverted Lagrangian Transport (STILT) particle dispersion model, we use correlations between halogenated hydrocarbon mixing ratios and the upwind influences of chlorophyll a, sea ice, solar radiation, and dissolved organic material to investigate previously hypothesized sources of halogenated volatile organic compounds (HVOCs) in the southern high latitudes. Our results are consistent with a biogenic regional source of CHBr3, and both non-biological and biological sources of CH3I over these regions, but do not corroborate a regional sea-ice source of HVOCs in January and February. Based on these relationships, we estimate the average two-month (Jan.-Feb.) emissions poleward of 60° S between 180° W and 55° W of CHBr3, CH2Br2, CH3I, and CHClBr2 to be 91 ± 8, 31 ± 17, 35 ± 29, and 11 ± 4 pmol m−2 hr−1, and regional emissions of these gases over the Patagonian Shelf to be 329 ± 23, 69 ± 5, 392 ± 32, 24 ± 4 pmol m−2 hr−1 respectively.

Description: Ground-based atmospheric observations of CO2, δ(O2∕N2), N2O, and CH4 were used to make estimates of the air–sea fluxes of these species from the Lüderitz and Walvis Bay upwelling cells in the northern Benguela region, during upwelling events. Average flux densities (±1σ) were 0.65±0.4 µmol m−2 s−1 for CO2, -5.1±2.5 µmol m−2 s−1 for O2 (as APO), 0.61±0.5 nmol m−2 s−1 for N2O, and 4.8±6.3 nmol m−2 s−1 for CH4. A comparison of our top-down (i.e., inferred from atmospheric anomalies) flux estimates with shipboard-based measurements showed that the two approaches agreed within ±55 % on average, though the degree of agreement varied by species and was best for CO2. Since the top-down method overestimated the flux density relative to the shipboard-based approach for all species, we also present flux density estimates that have been tuned to best match the shipboard fluxes. During the study, upwelling events were sources of CO2, N2O, and CH4 to the atmosphere. N2O fluxes were fairly low, in accordance with previous work suggesting that the evasion of this gas from the Benguela is smaller than for other eastern boundary upwelling systems (EBUS). Conversely, CH4 release was quite high for the marine environment, a result that supports studies that indicated a large sedimentary source of CH4 in the Walvis Bay area. These results demonstrate the suitability of atmospheric time series for characterizing the temporal variability of upwelling events and their influence on the overall marine greenhouse gas (GHG) emissions from the northern Benguela region.

Description: Ground-based atmospheric observations of CO2, δ(O2/N2), N2O, and CH4 were used to make top-down estimates of the air–sea fluxes of these species from the Lüderitz and Walvis Bay upwelling cells in the northern Benguela region, during upwelling events. Average flux densities (±1σ) were 0.64 ± 0.4 μmol m−2 sec−1 for CO2, −5.1 ± 1.4 μmol m−2 sec−1 for O2 (as APO), 0.57 ± 0.3 nmol m−2 sec−1 for N2O, and 4.3 ± 5.5 nmol m−2 sec−1 for CH4. A comparison of our top-down flux estimates with shipboard-based measurements showed good agreement between both approaches. During the study, upwelling events were sources of CO2, N2O, and CH4 to the atmosphere. N2O fluxes were fairly low, in accordance with previous work suggesting that the evasion of this gas from the Benguela is smaller than for other Eastern Boundary Upwelling Systems (EBUS). Conversely, CH4 release was quite high for the marine environment, a result that supports studies that indicated a large sedimentary source of CH4 in the Walvis Bay area. These results demonstrate the suitability of atmospheric time series for characterizing the temporal variability of upwelling events and their influence on the overall marine GHG emissions from the northern Benguela region.

Description: We have developed in situ and flask sampling systems for airborne measurements of variations in the O2/N2 ratio at the part per million level. We have deployed these instruments on a series of aircraft campaigns to measure the distribution of atmospheric O2 from 0–14 km and 87∘ N to 86∘ S throughout the seasonal cycle. The National Center for Atmospheric Research (NCAR) airborne oxygen instrument (AO2) uses a vacuum ultraviolet (VUV) absorption detector for O2 and also includes an infrared CO2 sensor. The VUV detector has a precision in 5 s of ±1.25 per meg (1σ) δ(O2/N2), but thermal fractionation and motion effects increase this to ±2.5–4.0 per meg when sampling ambient air in flight. The NCAR/Scripps airborne flask sampler (Medusa) collects 32 cryogenically dried air samples per flight under actively controlled flow and pressure conditions. For in situ or flask O2 measurements, fractionation and surface effects can be important at the required high levels of relative precision. We describe our sampling and measurement techniques and efforts to reduce potential biases. We also present a selection of observational results highlighting the individual and combined instrument performance. These include vertical profiles, O2:CO2 correlations, and latitudinal cross sections reflecting the distinct influences of terrestrial photosynthesis, air–sea gas exchange, burning of various fuels, and stratospheric dynamics. When present, we have corrected the flask δ(O2/N2) measurements for fractionation during sampling or analysis with the use of the concurrent δ(Ar/N2) measurements. We have also corrected the in situ δ(O2/N2) measurements for inlet fractionation and humidity effects by comparison to the corrected flask values. A comparison of Ar/N2-corrected Medusa flask δ(O2/N2) measurements to regional Scripps O2 Program station observations shows no systematic biases over 10 recent campaigns (+0.2±8.2 per meg, mean and standard deviation, n=86). For AO2, after resolving sample drying and inlet fractionation biases previously on the order of 10–100 per meg, independent AO2 δ(O2/N2) measurements over six more recent campaigns differ from coincident Medusa flask measurements by -0.3±7.2 per meg (mean and standard deviation, n=1361) with campaign-specific means ranging from −5 to +5 per meg.

Description: Nitrous oxide (N2O) and carbon monoxide (CO) are atmospheric trace gases which significantly influence Earth’s climate through their role as greenhouse gases. In addition, N2O is currently considered to be main ozone-depleting substance of the 21st century. Despite its importance, N2O and CO emission estimates from vast areas of the ocean are associated with large uncertainties mainly due to the lack of adequate temporal and spatial resolution. By making use of a novel technique based upon off-axis integrated cavity output spectroscopy (OA-ICOS) in combination with custom equilibration systems, we developed a method which allows measuring along-track N2O and CO in surface waters and the overlying atmosphere. Performance tests demonstrated the high stability of the analytic system, with low optimal integration times of 2 and 4 min for N2O and CO respectively, as well as detection limits 〈 40 ppt and precision better than 0.3 ppb Hz−1/2. Comparison of our method and well-established discrete methods for dissolved N2O and atmospheric CO evidenced a reliable operation of the setup in the field. The applicability of the system for continuous measurements both in research ships and vessels of opportunity is discussed in light of the results obtained during different deployments carried out in the tropical and North Atlantic.

Description: A new, near-coastal background site was established for observations of greenhouse gases (GHGs) and atmospheric oxygen in the central Namib Desert near Gobabeb, Namibia. The location of the site was chosen to provide observations in a data-poor region in the global sampling network for GHGs. Semi-automated, continuous measurements of carbon dioxide, methane, nitrous oxide, carbon monoxide, atmospheric oxygen, and basic meteorology are made at a height of 21 m a.g.l., 50 km from the coast at the northern border of the Namib Sand Sea. Atmospheric oxygen is measured with a differential fuel cell analyzer. Carbon dioxide and methane are measured with an early-model cavity ring-down spectrometer; nitrous oxide and carbon monoxide are measured with an off-axis integrated cavity output spectrometer. Instrument-specific water corrections are employed for both instruments in lieu of drying. The representativity of the site was assessed within the context of atmospheric transport. During austral summer, strong equatorward winds are present as a result of the Hadley circulation. This brings marine boundary layer air inland to Gobabeb. In austral winter, the descending branch of the southern Hadley cell is at the same latitude as NDAO, which encourages the establishment of anticyclonic conditions over southern Africa. The variability of air mass history during this time of year is quite high, alternating between marine and terrestrial air masses, as well as air that was recently in contact with the surface and air that had descended from heights greater than 2 km. NOAA ask samples taken at Gobabeb from 1996 to the present appeared to respond to these seasonal patterns in atmospheric dynamics, when compared to other marine background sites at the same latitude as NDAO. Two years of data are presented from the observatory. Diurnal variability was noted at times for all species, particularly for atmospheric oxygen. Through stoichiometry and phasing, this was attributed primarily to the local wind system, which features a prominent sea breeze, and daily boundary layer oscillations. Large anomalies in carbon monoxide and methane were observed in the time series on a synoptic time scale, during the ascending portion of the seasonal cycle. These were attributed to an alternation between polluted air masses from the continental interior and marine boundary layer air. The continental air masses were progressively in uenced by biomass burning as the fire season developed. The concentration of re activity close to the station increased throughout the year, peaking in September, a fact re ected in the enhancement ratio of CH4 to CO. During such synoptic events the molar exchange ratio of O2 to CO2 also supported this interpretation. Finally, the NDAO time series was used to make top-down estimates of air-sea fl uxes of the main measurands from the Lüderitz and Walvis Bay upwelling cells in the Benguela Current region, during upwelling events. Flux densities were evaluated using shipboard measurements within the study area, showing good agreement with the top-down estimates. Average flux densities for CO2 were 0.450.4 µmol m-2 sec-1, -3.92.6 µmol m-2 sec-1 for O2, 6.05.0 nmol m-2 sec-1 for CH4, 0.50.4 nmol m-2 sec-1 for N2O, and 2.71.7 nmol m-2 sec-1 for CO. N2O uxes were fairly low, in accord with previous work, suggesting that the evasion of this gas from the Benguela is smaller than in other upwelling systems. Conversely, methane release was very high for the marine environment, which adds to mounting evidence of a large sedimentary source of methane in the Walvis Bay area. Carbon dioxide and oxygen uxes were substantial and probably not accounted for in current budgets.

Description: Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (E-FOS) are based on energy statistics and cement production data, while emissions from land-use change (E-LUC), mainly deforestation, are based on land-use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (G(ATM)) is computed from the annual changes in concentration. The ocean CO2 sink (S-OCEAN) is estimated with global ocean biogeochemistry models and observation-based fCO(2) products. The terrestrial CO2 sink (S-LAND) is estimated with dynamic global vegetation models. Additional lines of evidence on land and ocean sinks are provided by atmospheric inversions, atmospheric oxygen measurements, and Earth system models. The resulting carbon budget imbalance (B-IM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and incomplete understanding of the contemporary carbon cycle. All uncertainties are reported as +/- 1 sigma. For the year 2022, E-FOS increased by 0.9% relative to 2021, with fossil emissions at 9.9 +/- 0.5 GtC yr(-1) (10.2 +/- 0.5 GtC yr(-1) when the cement carbonation sink is not included), and E-LUC was 1.2 +/- 0.7 GtC yr(-1), for a total anthropogenic CO2 emission (including the cement carbonation sink) of 11.1 +/- 0.8 GtC yr(-1) (40.7 +/- 3.2 GtCO(2) yr(-1)). Also, for 2022, G(ATM) was 4.6 +/- 0.2 GtC yr(-1) (2.18 +/- 0.1 ppm yr(-1); ppm denotes parts per million), S-OCEAN was 2.8 +/- 0.4 GtC yr(-1), and S-LAND was 3.8 +/- 0.8 GtC yr(-1), with a B-IM of 0.1 GtC yr(-1) (i.e. total estimated sources marginally too low or sinks marginally too high). The global atmospheric CO2 concentration averaged over 2022 reached 417.1 +/- 0.1 ppm. Preliminary data for 2023 suggest an increase in E-FOS relative to 2022 of +/- 1:1% (0.0% to 2.1 %) globally and atmospheric CO2 concentration reaching 419.3 ppm, 51% above the pre-industrial level (around 278 ppm in 1750). Overall, the mean of and trend in the components of the global carbon budget are consistently estimated over the period 1959-2022, with a near-zero overall budget imbalance, although discrepancies of up to around 1 Gt Cyr(-1) persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows the following: (1) a persistent large uncertainty in the estimate of land-use changes emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living-data update documents changes in methods and data sets applied to this most recent global carbon budget as well as evolving community understanding of the global carbon cycle.