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2. Detection of Local Mixing in Time-Series Data Using Permutation Entropy

Author

Neuder, Michael, Bradley, Elizabeth, Dlugokencky, Edward, White, James W. C., and Garland, Joshua

Subjects
Computer Science - Information Theory
Abstract

While it is tempting in experimental practice to seek as high a data rate as possible, oversampling can become an issue if one takes measurements too densely. These effects can take many forms, some of which are easy to detect: e.g., when the data sequence contains multiple copies of the same measured value. In other situations, as when there is mixing$-$in the measurement apparatus and/or the system itself$-$oversampling effects can be harder to detect. We propose a novel, model-free technique to detect local mixing in time series using an information-theoretic technique called permutation entropy. By varying the temporal resolution of the calculation and analyzing the patterns in the results, we can determine whether the data are mixed locally, and on what scale. This can be used by practitioners to choose appropriate lower bounds on scales at which to measure or report data. After validating this technique on several synthetic examples, we demonstrate its effectiveness on data from a chemistry experiment, methane records from Mauna Loa, and an Antarctic ice core., Comment: Submission for Physical Review E

Published
2020
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3. Seasonal temperatures in West Antarctica during the Holocene

Author

Jones, Tyler R., Cuffey, Kurt M., Roberts, William H. G., Markle, Bradley R., Steig, Eric J., Stevens, C. Max, Valdes, Paul J., Fudge, T. J., Sigl, Michael, Hughes, Abigail G., Morris, Valerie, Vaughn, Bruce H., Garland, Joshua, Vinther, Bo M., Rozmiarek, Kevin S., Brashear, Chloe A., and White, James W. C.

Published
2023
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4. Anomaly Detection in Paleoclimate Records using Permutation Entropy

Author

Garland, Joshua, Jones, Tyler R., Neuder, Michael, Morris, Valerie, White, James W. C., and Bradley, Elizabeth

Subjects
Physics - Data Analysis, Statistics and Probability, Computer Science - Information Theory, Physics - Atmospheric and Oceanic Physics
Abstract

Permutation entropy techniques can be useful in identifying anomalies in paleoclimate data records, including noise, outliers, and post-processing issues. We demonstrate this using weighted and unweighted permutation entropy of water-isotope records in a deep polar ice core. In one region of these isotope records, our previous calculations revealed an abrupt change in the complexity of the traces: specifically, in the amount of new information that appeared at every time step. We conjectured that this effect was due to noise introduced by an older laboratory instrument. In this paper, we validate that conjecture by re-analyzing a section of the ice core using a more-advanced version of the laboratory instrument. The anomalous noise levels are absent from the permutation entropy traces of the new data. In other sections of the core, we show that permutation entropy techniques can be used to identify anomalies in the raw data that are not associated with climatic or glaciological processes, but rather effects occurring during field work, laboratory analysis, or data post-processing. These examples make it clear that permutation entropy is a useful forensic tool for identifying sections of data that require targeted re-analysis---and can even be useful in guiding that analysis., Comment: 15 pages, 7 figures

Published
2018
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5. Climate entropy production recorded in a deep Antarctic ice core

Author

Garland, Joshua, Jones, Tyler R., Bradley, Elizabeth, Neuder, Michael, and White, James W. C.

Subjects
Physics - Geophysics, Physics - Data Analysis, Statistics and Probability
Abstract

Paleoclimate records are extremely rich sources of information about the past history of the Earth system. Information theory, the branch of mathematics capable of quantifying the degree to which the present is informed by the past, provides a new means for studying these records. Here, we demonstrate that estimates of the Shannon entropy rate of the water-isotope data from the West Antarctica Ice Sheet (WAIS) Divide ice core, calculated using weighted permutation entropy (WPE), can bring out valuable new information from this record. We find that WPE correlates with accumulation, reveals possible signatures of geothermal heating at the base of the core, and clearly brings out laboratory and data-processing effects that are difficult to see in the raw data. For example, the signatures of Dansgaard-Oeschger events in the information record are small, suggesting that these abrupt warming events may not represent significant changes in the climate system dynamics. While the potential power of information theory in paleoclimatology problems is significant, the associated methods require careful handling and well-dated, high-resolution data. The WAIS Divide ice core is the first such record that can support this kind of analysis. As more high-resolution records become available, information theory will likely become a common forensic tool in climate science., Comment: 15 pages, 7 figures, 1 table

Published
2018

6. The Greenland spatial fingerprint of Dansgaard-Oeschger events in observations and models.

Author

Buizert, Christo, Sowers, Todd A., Niezgoda, Kyle, Blunier, Thomas, Gkinis, Vasileios, Harlan, Margaret, Chengfei He, Jones, Tyler R., Kjaer, Helle A., Liisberg, Jesper B., Menking, James A., Morris, Valerie, Noone, David, Rasmussen, Sune Olander, Sime, Louise C., Steffensen, Jørgen P., Svensson, Anders, Vaughn, Bruce H., Vinther, Bo M., and White, James W. C.

Abstract

Pleistocene Ice Ages display abrupt Dansgaard-Oeschger (DO) climate oscillations that provide prime examples of Earth System tipping points--abrupt transition that may result in irreversible change. Greenland ice cores provide key records of DO climate variability, but gas-calibrated estimates of the temperature change magnitudes have been limited to central and northwest Greenland. Here, we present ice-core δ15N-N2 records from south (Dye 3) and coastal east Greenland (Renland) to calibrate the local water isotope thermometer and provide a Greenland-wide spatial characterization of DO event magnitude. We combine these data with existing records of δ18O, deuterium excess, and accumulation rates to create a multiproxy "fingerprint" of the DO impact on Greenland. Isotope-enabled climate models have skill in simulating the observational multiproxy DO event impact, and we use a series of idealized simulations with such models to identify regions of the North Atlantic that are critical in explaining DO variability. Our experiments imply that wintertime sea ice variation in the subpolar gyre, rather than the commonly invoked Nordic Seas, is both a sufficient and a necessary condition to explain the observed DO impacts in Greenland, whatever the distal cause. Moisture-tagging experiments support the idea that Greenland DO isotope signals may be explained almost entirely via changes in the vapor source distribution and that site temperature is not a main control on δ18O during DO transitions, contrary to the traditional interpretation. Our results provide a comprehensive, multiproxy, data-model synthesis of abrupt DO climate variability in Greenland. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Thoughtful data analysis.

Author

Bradley, Elizabeth, White, James W. C., and Garland, Joshua

Subjects
*CHOICE (Psychology), *DATA science, *DATA analysis, *INFORMATION sharing, *ARGUMENT
Abstract

The acceleration in the field of data science is well known [see, e.g., D. Donoho, J. Comput. Graph. Stat. 26(4), 745–766 (2017) and references therein]. Improvements in technology for acquisition, storage, and processing have made unheard of amounts of data available to scientists; in parallel with that, the pace of methodological advance has also been rapid; with new techniques and packages becoming available, it seems, every day. With these affordances come many challenges, notably the volume and variety of the data [Fan et al., Natl. Sci. Rev. 1(2), 293–314 (2014)]. In this Perspective piece, we examine a different challenge—how to choose and use the right analysis method—and make an argument for the sharing of raw data. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Shifts in Greenland interannual climate variability lead Dansgaard-Oeschger abrupt warming by hundreds of years

Author

Brashear, Chloe A., primary, Jones, Tyler R., additional, Morris, Valerie, additional, Vaughn, Bruce H., additional, Roberts, William H. G., additional, Skorski, William B., additional, Hughes, Abigail G., additional, Nunn, Richard, additional, Rasmussen, Sune Olander, additional, Cuffey, Kurt M., additional, Vinther, Bo M., additional, Sowers, Todd, additional, Buizert, Christo, additional, Gkinis, Vasileios, additional, Holme, Christian, additional, Jensen, Mari F., additional, Kjellman, Sofia E., additional, Langebroek, Petra M., additional, Mekhaldi, Florian, additional, Rozmiarek, Kevin S., additional, Rheinlænder, Jonathan W., additional, Simon, Margit, additional, Sinnl, Giulia, additional, Smith-Johnsen, Silje, additional, and White, James W. C., additional

Published
2024
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9. Supporting Online Material to the manuscript: 'Water isotope diffusion rates from the NorthGRIP ice core for the last 16,000 years - glaciological and paleoclimatic implications.'

Author

Gkinis, Vasileios, Simonsen, Sebastian B., Buchardt, Susanne L., White, James W. C., and Vinther, Bo M.

Subjects
Physics - Geophysics
Abstract

This is the supporting online material for the manuscript arXiv:1404.4201 "Water isotope diffusion rates from the NorthGRIP ice core for the last 16,000 years - glaciological and paleoclimatic implications."

Published
2014

10. A 120,000-year long climate record from a NW-Greenland deep ice core at ultra-high resolution

Author

Gkinis, Vasileios, Vinther, Bo M., Popp, Trevor J., Quistgaard, Thea, Faber, Anne-Katrine, Holme, Christian T., Jensen, Camilla-Marie, Lanzky, Mika, Lütt, Anine-Maria, Mandrakis, Vasileios, Ørum, Niels-Ole, Pedersen, Anna-Sofie, Vaxevani, Nikol, Weng, Yongbiao, Capron, Emilie, Dahl-Jensen, Dorthe, Hörhold, Maria, Jones, Tyler R., Jouzel, Jean, Landais, Amaëlle, Masson-Delmotte, Valérie, Oerter, Hans, Rasmussen, Sune O., Steen-Larsen, Hans Christian, Steffensen, Jørgen-Peder, Sveinbjörnsdóttir, Árný-Erla, Svensson, Anders, Vaughn, Bruce, and White, James W. C.

Published
2021
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11. Role of atmospheric oxidation in recent methane growth

Author

Rigby, Matthew, Montzka, Stephen A., Prinn, Ronald G., White, James W. C., Young, Dickon, O’Doherty, Simon, Lunt, Mark F., Ganesan, Anita L., Manning, Alistair J., Simmonds, Peter G., Salameh, Peter K., Harth, Christina M., Mühle, Jens, Weiss, Ray F., Fraser, Paul J., Steele, L. Paul, Krummel, Paul B., McCulloch, Archie, and Park, Sunyoung

Published
2017

12. Atmospheric Methane: Comparison Between Methane's Record in 2006–2022 and During Glacial Terminations

Author

Nisbet, Euan G., primary, Manning, Martin R., additional, Dlugokencky, Ed J., additional, Michel, Sylvia Englund, additional, Lan, Xin, additional, Röckmann, Thomas, additional, Denier van der Gon, Hugo A. C., additional, Schmitt, Jochen, additional, Palmer, Paul I., additional, Dyonisius, Michael N., additional, Oh, Youmi, additional, Fisher, Rebecca E., additional, Lowry, David, additional, France, James L., additional, White, James W. C., additional, Brailsford, Gordon, additional, and Bromley, Tony, additional

Published
2023
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13. Global Atmospheric δ13CH4 and CH4 Trends for 2000–2020 from the Atmospheric Transport Model TM5 Using CH4 from Carbon Tracker Europe–CH4 Inversions

Author

Mannisenaho, Vilma, primary, Tsuruta, Aki, additional, Backman, Leif, additional, Houweling, Sander, additional, Segers, Arjo, additional, Krol, Maarten, additional, Saunois, Marielle, additional, Poulter, Benjamin, additional, Zhang, Zhen, additional, Lan, Xin, additional, Dlugokencky, Edward J., additional, Michel, Sylvia, additional, White, James W. C., additional, and Aalto, Tuula, additional

Published
2023
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14. A First Step Toward Quantifying the Climate’s Information Production over the Last 68,000 Years

Author

Garland, Joshua, Jones, Tyler R., Bradley, Elizabeth, James, Ryan G., White, James W. C., Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Boström, Henrik, editor, Knobbe, Arno, editor, Soares, Carlos, editor, and Papapetrou, Panagiotis, editor

Published
2016
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19. Global Atmospheric δ 13 CH 4 and CH 4 Trends for 2000–2020 from the Atmospheric Transport Model TM5 Using CH 4 from Carbon Tracker Europe–CH 4 Inversions.

Author

Mannisenaho, Vilma, Tsuruta, Aki, Backman, Leif, Houweling, Sander, Segers, Arjo, Krol, Maarten, Saunois, Marielle, Poulter, Benjamin, Zhang, Zhen, Lan, Xin, Dlugokencky, Edward J., Michel, Sylvia, White, James W. C., and Aalto, Tuula

Subjects
ATMOSPHERIC transport, ATMOSPHERIC models, ISOTOPIC signatures, WETLANDS, INVERSION (Geophysics), CARBON, COAL
Abstract

This study investigates atmospheric δ 13 CH 4 trends, as produced by a global atmospheric transport model using CH 4 inversions from CarbonTracker-Europe CH 4 for 2000–2020, and compares them to observations. The CH 4 inversions include the grouping of the emissions both by δ 13 CH 4 isotopic signatures and process type to investigate the effect, and to estimate the CH 4 magnitudes and model CH 4 and δ 13 CH 4 trends. In addition to inversion results, simulations of the global atmospheric transport model were performed with modified emissions. The estimated global CH 4 trends for oil and gas were found to increase more than coal compared to the priors from 2000–2006 to 2007–2020. Estimated trends for coal emissions at 30 ∘ N–60 ∘ N are less than 50% of those from priors. Estimated global CH 4 rice emissions trends are opposite to priors, with the largest contribution from the EQ to 60 ∘ N. The results of this study indicate that optimizing wetland emissions separately produces better agreement with the observed δ 13 CH 4 trend than optimizing all biogenic emissions simultaneously. This study recommends optimizing separately biogenic emissions with similar isotopic signature to wetland emissions. In addition, this study suggests that fossil-based emissions were overestimated by 9% after 2012 and biogenic emissions are underestimated by 8% in the inversion using EDGAR v6.0 as priors. [ABSTRACT FROM AUTHOR]

Published
2023
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20. Upward revision of global fossil fuel methane emissions based on isotope database

Author

Schwietzke, Stefan, Sherwood, Owen A., Bruhwiler, Lori M. P., Miller, John B., Etiope, Giuseppe, Dlugokencky, Edward J., Michel, Sylvia Englund, Arling, Victoria A., Vaughn, Bruce H., White, James W. C., and Tans, Pieter P.

Subjects
Fossil fuels -- Chemical properties -- Environmental aspects, Emissions (Pollution) -- Research, Methane -- Chemical properties -- Environmental aspects, Environmental research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Author(s): Stefan Schwietzke (corresponding author) [1, 2]; Owen A. Sherwood [3]; Lori M. P. Bruhwiler [2]; John B. Miller [1, 2]; Giuseppe Etiope [4, 5]; Edward J. Dlugokencky [2]; Sylvia [...]

Published
2016
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22. The Role of Emission Sources and Atmospheric Sink in the Seasonal Cycle of CH4 and δ13-CH4: Analysis Based on the Atmospheric Chemistry Transport Model TM5

Author

Kangasaho, Vilma, primary, Tsuruta, Aki, additional, Backman, Leif, additional, Mäkinen, Pyry, additional, Houweling, Sander, additional, Segers, Arjo, additional, Krol, Maarten, additional, Dlugokencky, Edward J., additional, Michel, Sylvia, additional, White, James W. C., additional, and Aalto, Tuula, additional

Published
2022
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24. High-Resolution Greenland Ice Core Data Show Abrupt Climate Change Happens in Few Years

Author

Steffensen, Jørgen Peder, Andersen, Katrine K., Bigler, Matthias, Clausen, Henrik B., Dahl-Jensen, Dorthe, Fischer, Hubertus, Goto-Azuma, Kumiko, Hansson, Margareta, Johnsen, Sigfús J., Jouzel, Jean, Masson-Delmotte, Valérie, Popp, Trevor, Rasmussen, Sune O., Röthlisberger, Regine, Ruth, Urs, Stauffer, Bernhard, Siggaard-Andersen, Marie-Louise, Sveinbjörnsdóttir, Arný E., Svensson, Anders, and White, James W. C.

Published
2008
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30. Precise interpolar phasing of abrupt climate change during the last ice age

Author

Buizert, Christo, Adrian, Betty, Ahn, Jinho, Albert, Mary, Alley, Richard B., Baggenstos, Daniel, Bauska, Thomas K., Bay, Ryan C., Bencivengo, Brian B., Bentley, Charles R., Brook, Edward J., Chellman, Nathan J., Clow, Gary D., Cole-Dai, Jihong, Conway, Howard, Cravens, Eric, Cuffey, Kurt M., Dunbar, Nelia W., Edwards, Jon S., Fegyveresi, John M., Ferris, Dave G., Fitzpatrick, Joan J., Fudge, T. J., Gibson, Chris J., Gkinis, Vasileios, Goetz, Joshua J., Gregory, Stephanie, Hargreaves, Geoffrey M., Iverson, Nels, Johnson, Jay A., Jones, Tyler R., Kalk, Michael L., Kippenhan, Matthew J., Koffman, Bess G., Kreutz, Karl, Kuhl, Tanner W., Lebar, Donald A., Lee, James E., Marcott, Shaun A., Markle, Bradley R., Maselli, Olivia J., McConnell, Joseph R., McGwire, Kenneth C., Mitchell, Logan E., Mortensen, Nicolai B., Neff, Peter D., Nishiizumi, Kunihiko, Nunn, Richard M., Orsi, Anais J., Pasteris, Daniel R., Pedro, Joel B., Pettit, Erin C., Price, Buford P., Priscu, John C., Rhodes, Rachael H., Rosen, Julia L., Schauer, Andrew J., Schoenemann, Spruce W., Sendelbach, Paul J., Severinghaus, Jeffrey P., Shturmakov, Alexander J., Sigl, Michael, Slawny, Kristina R., Souney, Joseph M., Sowers, Todd A., Spencer, Matthew K., Steig, Eric J., Taylor, Kendrick C., Twickler, Mark S., Vaughn, Bruce H., Voigt, Donald E., Waddington, Edwin D., Welten, Kees C., Wendricks, Anthony W., White, James W. C., Winstrup, Mai, Wong, Gifford J., and Woodruff, Thomas E.

Published
2015
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31. Reconstruction of Temperature, Accumulation Rate, and Layer Thinning From an Ice Core at South Pole, Using a Statistical Inverse Method

Author

Kahle, Emma C., primary, Steig, Eric J., additional, Jones, Tyler R., additional, Fudge, T. J., additional, Koutnik, Michelle R., additional, Morris, Valerie A., additional, Vaughn, Bruce H., additional, Schauer, Andrew J., additional, Stevens, C. Max, additional, Conway, Howard, additional, Waddington, Edwin D., additional, Buizert, Christo, additional, Epifanio, Jenna, additional, and White, James W. C., additional

Published
2021
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34. The Role of Emission Sources and Atmospheric Sink in the Seasonal Cycle of CH 4 and δ 13 -CH 4 : Analysis Based on the Atmospheric Chemistry Transport Model TM5.

Author

Kangasaho, Vilma, Tsuruta, Aki, Backman, Leif, Mäkinen, Pyry, Houweling, Sander, Segers, Arjo, Krol, Maarten, Dlugokencky, Edward J., Michel, Sylvia, White, James W. C., and Aalto, Tuula

Subjects
ATMOSPHERIC chemistry, ATMOSPHERIC transport, CHEMICAL models, SEASONS, ATMOSPHERIC models, ATMOSPHERIC methane, WETLANDS
Abstract

This study investigates the contribution of different CH4 sources to the seasonal cycle of δ 13 C during 2000–2012 by using the TM5 atmospheric transport model, including spatially varying information on isotopic signatures. The TM5 model is able to produce the background seasonality of δ 13 C, but the discrepancies compared to the observations arise from incomplete representation of the emissions and their source-specific signatures. Seasonal cycles of δ 13 C are found to be an inverse of CH4 cycles in general, but the anti-correlations between CH4 and δ 13 C are imperfect and experience a large variation ( p = −0.35 to −0.91) north of 30° S. We found that wetland emissions are an important driver in the δ 13 C seasonal cycle in the Northern Hemisphere and Tropics, and in the Southern Hemisphere Tropics, emissions from fires contribute to the enrichment of δ 13 C in July–October. The comparisons to the observations from 18 stations globally showed that the seasonal cycle of EFMM emissions in the EDGAR v5.0 inventory is more realistic than in v4.3.2. At northern stations (north of 55° N), modeled δ 13 C amplitudes are generally smaller by 12–68%, mainly because the model could not reproduce the strong depletion in autumn. This indicates that the CH4 emission magnitude and seasonal cycle of wetlands may need to be revised. In addition, results from stations in northern latitudes (19–40° N) indicate that the proportion of biogenic to fossil-based emissions may need to be revised, such that a larger portion of fossil-based emissions is needed during summer. [ABSTRACT FROM AUTHOR]

Published
2022
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35. High-frequency climate variability in the Holocene from a coastal-dome ice core in east-central Greenland

Author

Hughes, Abigail G., Jones, Tyler R., Vinther, Bo M., Gkinis, Vasileios, Stevens, C. Max, Morris, Valerie, Vaughn, Bruce H., Holme, Christian, Markle, Bradley R., White, James W. C., Hughes, Abigail G., Jones, Tyler R., Vinther, Bo M., Gkinis, Vasileios, Stevens, C. Max, Morris, Valerie, Vaughn, Bruce H., Holme, Christian, Markle, Bradley R., and White, James W. C.

Abstract

An ice core drilled on the Renland ice cap in eastcentral Greenland contains a continuous climate record dating through the last glacial period. The Renland record is valuable because the coastal environment is more likely to reflect regional sea surface conditions compared to inland Greenland ice cores that capture synoptic variability. Here we present the delta O-18 water isotope record for the Holocene, in which decadal-scale climate information is retained for the last 8 kyr, while the annual water isotope signal is preserved throughout the last 2.6 kyr. To investigate regional climate information preserved in the water isotope record, we apply spectral analysis techniques to a 300-year moving window to determine the mean strength of varying frequency bands through time. We find that the strength of 15-20-year delta O-18 variability exhibits a millennial-scale signal in line with the well-known Bond events. Comparison to other North Atlantic proxy records suggests that the 15-20-year variability may reflect fluctuating sea surface conditions throughout the Holocene, driven by changes in the strength of the Atlantic Meridional Overturning Circulation. Additional analysis of the seasonal signal over the last 2.6 kyr reveals that the winter delta O-18 signal has experienced a decreasing trend, while the summer signal has predominantly remained stable. The winter trend may correspond to an increase in Arctic sea ice cover, which is driven by a decrease in total annual insolation, and is also likely influenced by regional climate variables such as atmospheric and oceanic circulation. In the context of anthropogenic climate change, the winter trend may have important implications for feedback processes as sea ice retreats in the Arctic.

Published
2020

36. West Antarctic Ice Sheet Elevation Changes

Author

Steig, Eric J., primary, Fastook, James L., additional, Zweck, Christopher, additional, Goodwin, Ian D., additional, Licht, Kathy J., additional, White, James W. C., additional, and Ackert, Robert P., additional

Published
2013
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38. Onset of deglacial warming in West Antarctica driven by local orbital forcing

Author

Fudge, T. J., Steig, Eric J., Markle, Bradley R., Schoenemann, Spruce W., Ding, Qinghua, Taylor, Kendrick C., McConnell, Joseph R., Brook, Edward J., Sowers, Todd, White, James W. C., Alley, Richard B., Cheng, Hai, Clow, Gary D., Cole-Dai, Jihong, Conway, Howard, Cuffey, Kurt M., Edwards, Jon S., Edwards, Lawrence R., Edwards, Ross, Fegyveresi, John M., Ferris, David, Fitzpatrick, Joan J., Johnson, Jay, Hargreaves, Geoffrey, Lee, James E., Maselli, Olivia J., Mason, William, McGwire, Kenneth C., Mitchell, Logan E., Mortensen, Nicolai, Neff, Peter, Orsi, Anais J., Popp, Trevor J., Schauer, Andrew J., Severinghaus, Jeffrey P., Sigl, Michael, Spencer, Matthew K., Vaughn, Bruce H., Voigt, Donald E., Waddington, Edwin D., Wang, Xianfeng, and Wong, Gifford J.

Published
2013
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43. An improved estimate for the δ13C and δ18O signatures of carbon monoxide produced from atmospheric oxidation of volatile organic compounds

Author

Vimont, Isaac J., Turnbull, Jocelyn C., Petrenko, Vasilii V., Place, Philip F., Sweeney, Colm, Miles, Natasha, Richardson, Scott, Vaughn, Bruce H., and White, James W. C.

Abstract

Atmospheric carbon monoxide (CO) is a key player in global atmospheric chemistry and a regulated pollutant in urban areas. Oxidation of volatile organic compounds (VOCs) is an important component of the global CO budget and has also been hypothesized to contribute substantially to the summertime urban CO budget. In principle, stable isotopic analysis of CO could constrain the magnitude of this source. However, the isotopic signature of VOC-produced CO has not been well quantified, especially for the oxygen isotopes. We performed measurements of CO stable isotopes on air samples from two sites around Indianapolis, US, over three summers to investigate the isotopic signature of VOC-produced CO. One of the sites is located upwind of the city, allowing us to quantitatively remove the background air signal and isolate the urban CO enhancements. as well as the isotopic signature of these enhancements. In addition, we use measurements of Δ14CO2 in combination with the CO:CO2 emission ratio from fossil fuels to constrain the fossil-fuel-derived CO and thereby isolate the VOC-derived component of the CO enhancement. Combining these measurements and analyses, we are able to determine the carbon and oxygen isotopic signatures of CO derived from VOC oxidation as -32.8‰±0.5‰ and 3.6 ‰±1.2 ‰, respectively. Additionally, we analyzed CO stable isotopes for 1 year at Beech Island, South Carolina, US, a site thought to have large VOC-derived contributions to the summertime CO budget. The Beech Island results are consistent with isotopic signatures of VOC-derived CO determined from the Indianapolis data. This study represents the first direct determination of the isotopic signatures of VOC-derived CO and will allow for improved use of isotopes in constraining the global and regional CO budgets.

Published
2019

47. The CarbonTracker Data Assimilation System for CO2 and delta C-13 (CTDAS-C13 v1.0): retrieving information on land-atmosphere exchange processes

Author

van der Velde, Ivar R., Miller, John B., van der Molen, Michiel K., Tans, Pieter P., Vaughn, Bruce H., White, James W. C., Schaefer, Kevin, Peters, Wouter, and Isotope Research

Subjects
MODEL, CLIMATE, FLUXES, PHOTOSYNTHESIS, STOMATAL CONDUCTANCE, EL-NINO, CARBON-ISOTOPE DISCRIMINATION, INTERANNUAL VARIABILITY, FOREST, DROUGHT
Abstract

To improve our understanding of the global carbon balance and its representation in terrestrial biosphere models, we present here a first dual-species application of the CarbonTracker Data Assimilation System (CTDAS). The system's modular design allows for assimilating multiple atmospheric trace gases simultaneously to infer exchange fluxes at the Earth surface. In the prototype discussed here, we interpret signals recorded in observed carbon dioxide (CO2) along with observed ratios of its stable isotopologues (CO2)-C-13/(CO2)-C-12 (delta C-13). The latter is in particular a valuable tracer to untangle CO2 exchange from land and oceans. Potentially, it can also be used as a proxy for continent-wide drought stress in plants, largely because the ratio of (CO2)-C-13 and (CO2)-C-12 molecules removed from the atmosphere by plants is dependent on moisture conditions. The dual-species CTDAS system varies the net exchange fluxes of both (CO2)-C-13 and CO2 in ocean and terrestrial biosphere models to create an ensemble of (CO2)-C-13 and CO2 fluxes that propagates through an atmospheric transport model. Based on differences between observed and simulated (CO2)-C-13 and CO2 mole fractions (and thus delta C-13) our Bayesian minimization approach solves for weekly adjustments to both net fluxes and isotopic terrestrial discrimination that minimizes the difference between observed and estimated mole fractions. With this system, we are able to estimate changes in terrestrial delta C-13 exchange on seasonal and continental scales in the Northern Hemisphere where the observational network is most dense. Our results indicate a decrease in stomatal conductance on a continent-wide scale during a severe drought. These changes could only be detected after applying combined atmospheric CO2 and delta C-13 constraints as done in this work. The additional constraints on surface CO2 exchange from delta C-13 observations neither affected the estimated carbon fluxes nor compromised our ability to match observed CO2 variations. The prototype presented here can be of great benefit not only to study the global carbon balance but also to potentially function as a data-driven diagnostic to assess multiple leaf-level exchange parameterizations in carbon-climate models that influence the CO2, water, isotope, and energy balance.

Published
2018

48. Interlaboratory comparison of δ¹³C and δD measurements of atmospheric CH₄ for combined use of data sets from different laboratories

Author

Umezawa, Taku, Brenninkmeijer, Carl A. M., Röckmann, Thomas, van der Veen, Carina, Tyler, Stanley C., Fujita, Ryo, Morimoto, Shinji, Aoki, Shuji, Sowers, Todd, Schmitt, Jochen, Bock, Michael, Beck, Jonas, Fischer, Hubertus, Michel, Sylvia E., Vaughn, Bruce H., Miller, John B., White, James W. C., Brailsford, Gordon, Schaefer, Hinrich, Sperlich, Peter, Brand, Willi A., Rothe, Michael, Blunier, Thomas, Lowry, David, Fisher, Rebecca E., Nisbet, Euan G., Rice, Andrew L., Bergamaschi, Peter, Veidt, Cordelia, and Levin, Ingeborg

Subjects
530 Physics, 520 Astronomy, 620 Engineering
Abstract

We report results from a worldwide interlaboratory comparison of samples among laboratories that measure (or measured) stable carbon and hydrogen isotope ratios of atmospheric CH₄ (δ¹³C-CH₄ and δD-CH₄). The offsets among the laboratories are larger than the measurement reproducibility of individual laboratories. To disentangle plausible measurement offsets, we evaluated and critically assessed a large number of intercomparison results, some of which have been documented previously in the literature. The results indicate significant offsets of δ¹³C-CH₄ and δD-CH₄ measurements among data sets reported from different laboratories; the differences among laboratories at modern atmospheric CH₄ level spread over ranges of 0.5 ‰ for δ¹³C-CH₄ and 13 ‰ for δD-CH₄. The intercomparison results summarized in this study may be of help in future attempts to harmonize δ¹³C-CH₄ and δD-CH₄ data sets from different laboratories in order to jointly incorporate them into modelling studies. However, establishing a merged data set, which includes δ¹³C-CH₄ and δD-CH₄ data from multiple laboratories with desirable compatibility, is still challenging due to differences among laboratories in instrument settings, correction methods, traceability to reference materials and long-term data management. Further efforts are needed to identify causes of the interlaboratory measurement offsets and to decrease those to move towards the best use of available δ¹³C-CH₄ and δD-CH₄ data sets.

Published
2018
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