Index Catalog // ScholarsArchive@OSU

Early to Late Holocene Surface Exposure Ages From Two Marine-Terminating Outlet Glaciers in Northwest Greenland

Creator:: Reusche, Melissa M., Marcott, Shaun A., Ceperley, Elizabeth G., Barth, Aaron M., Brook, Edward J., Mix, Alan C., and Caffee, Marc W.
Abstract:: Terrestrial chronologies from southern Greenland provide a detailed deglacial history of the Greenland Ice Sheet (GIS). The northern GIS margin history, however, is less established. Here we present surface exposure ages from moraines associated with two large outlet glaciers, Petermann and Humboldt, in the northwestern sector of the GIS. These...
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Abrupt change in atmospheric CO₂ during the last ice age

Creator:: Ahn, Jinho, Brook, Edward J., Schmittner, Andreas, and Kreutz, Karl
Abstract:: During the last glacial period atmospheric carbon dioxide and temperature in Antarctica varied in a similar fashion on millennial time scales, but previous work indicates that these changes were gradual. In a detailed analysis of one event we now find that approximately half of the CO₂ increase that occurred during...
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Atmospheric CO₂ over the last 1000 years: A high-resolution record from the West Antarctic Ice Sheet (WAIS) Divide ice core

Creator:: Ahn, Jinho, Brook, Edward J., Mitchell, Logan, Rosen, Julia, McConnell, Joseph R., Taylor, Kendrick, Etheridge, David, and Rubino, Mauro
Abstract:: We report a decadally resolved record of atmospheric CO₂ concentration for the last 1000 years, obtained from the West Antarctic Ice Sheet (WAIS) Divide shallow ice core. The most prominent feature of the pre-industrial period is a rapid ∼7 ppm decrease of CO₂ in a span of ∼20–50 years at...
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Modes of Global Climate Variability during Marine Isotope Stage 3 (60–26 ka)

Creator:: Pisias, Nicklas G., Clark, Peter U., and Brook, Edward J.
Abstract:: Recent analysis of 38 globally distributed paleoclimatic records covering Marine Isotope Stage 3 (MIS 3) 60–26 ka demonstrated that the two leading empirical orthogonal functions (EOFs) explaining the data are the Greenland ice-core signal (“northern” signal) and the Antarctic ice-core signal (“southern” signal). Here singular spectral analysis (SSA) is used...
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Chronology reconstruction for the disturbed bottom section of the GISP2 and the GRIP ice cores: Implications for Termination II in Greenland

Creator:: Suwa, Makoto, von Fischer, Joseph C., Bender, Michael L., Landais, Amaelle, and Brook, Edward J.
Abstract:: We have reconstructed chronology for the disturbed bottom parts of the GRIP and GISP2 ice cores using the combined paleoatmospheric records of CH₄ concentration and δ¹⁸O[subscript atm] in the trapped gases. Our reconstructed ages for basal ice samples are based on comparison of published measurements of CH₄ and δ¹⁸O[subscript atm]...
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Multidecadal variability of atmospheric methane, 1000–1800 C.E.

Creator:: Mitchell, Logan E., Brook, Edward J., Sowers, Todd, McConnell, J. R., and Taylor, Kendrick
Abstract:: We present a new high-precision, high-resolution record of atmospheric methane from the West Antarctic Ice Sheet (WAIS) Divide ice core covering 1000–1800 C.E., a time period known as the late preindustrial Holocene (LPIH). The results are consistent with previous measurements from the Law Dome ice core, the only other high-resolution...
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An interlaboratory comparison of techniques for extracting and analyzing trapped gases in ice cores

Creator:: Sowers, Todd, Brook, Edward J., Etheridge, David, Blunier, Thomas, Fuchs, Andreas, Leuenberger, Markus, Chappellaz, Jerome, Barnola, Jean Marc, Wahlen, Martin, Deck, Bruce, and Weyhenmeyer, Connie
Abstract:: We undertook an interlaboratory comparison of techniques used to extract and analyze trapped gases in ice cores. The intercomparison included analyses of standard reference gases and samples of ice from the Greenland Ice Sheet Project 2 (GISP2) site. Concentrations of CO₂, CH₄, the δ¹⁸O of O₂, the δ¹⁵N of N₂,...
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Atmospheric CO₂ and climate from 65 to 30 ka B.P.

Creator:: Ahn, Jinho and Brook, Edward J.
Abstract:: Using new and existing ice core CO₂ data from 65 ∼ 30 ka a new chronology for CO₂ is established and synchronized with Greenland ice core records to study how high latitude climate change and the carbon cycle were linked during the last glacial period. Atmospheric CO₂ rose several thousand...
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Dating the Siple Dome (Antarctica) ice core by manual and computer interpretation of annual layering

Creator:: Taylor, Kendrick C., Alley, Richard B., Meese, Debra A., Spencer, Matthew K., Brook, Edward J., Dunbar, Nelia W., Finkel, Robert C., Gow, Anthony J., Kurbatov, Andrei V., Lamorey, Gregg W., Mayewski, Paul A., Meyerson, Eric A., Nishiizumi, Kunihiko, and Zielinski, Gregory A.
Abstract:: The Holocene portion of the Siple Dome (Antarctica) ice core was dated by interpreting the electrical, visual and chemical properties of the were interpreted manually and with a computer algorithm.The algorithm was adjusted to be consistent with atmospheric methane stratigraphic (Greenland Ice Sheet Project 2) ice core, ¹⁰Be stratigraphic ties...
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BuizertChristoCEOASWAISDivideDeep_Supplement.zip

Creator:: Buizert, C., Cuffey, K. M., Severinghaus, J. P., Baggenstos, D., Fudge, T. J., Steig, E. J., Markle, B. R., Winstrup, M., Rhodes, R. H., Brook, Edward J., Sowers, T. A., Clow, G. D., Cheng, H., Edwards, R. L., Sigl, M., McConnell, J. R., and Taylor, K. C.
Abstract:: The West Antarctic Ice Sheet Divide (WAIS Divide, WD) ice core is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ~68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP) have been dated using annual-layer counting. Here we...
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BuizertChristoCEOASWAISDivideDeep.pdf

Creator:: Buizert, C., Cuffey, K. M., Severinghaus, J. P., Baggenstos, D., Fudge, T. J., Steig, E. J., Markle, B. R., Winstrup, M., Rhodes, R. H., Brook, Edward J., Sowers, T. A., Clow, G. D., Cheng, H., Edwards, R. L., Sigl, M., McConnell, J. R., and Taylor, K. C.
Abstract:: The West Antarctic Ice Sheet Divide (WAIS Divide, WD) ice core is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ~68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP) have been dated using annual-layer counting. Here we...
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The WAIS Divide deep ice core WD2014 chronology - Part 2: Annual-layer counting (0-31 ka BP)

Creator:: Sigl, Michael, Fudge, Tyler J., Winstrup, Mai, Cole-Dai, Jihong, Ferris, David, McConnell, Joseph R., Taylor, Ken C., Welten, Kees C., Woodruff, Thomas E., Adolphi, Florian, Bisiaux, Marion, Brook, Edward J., Buizert, Christo, Caffee, Marc W., Dunbar, Nelia W., Edwards, Ross, Geng, Lei, Iverson, Nels, Koffman, Bess, Layman, Lawrence, Maselli, Olivia J., McGwire, Kenneth, Muscheler, Raimund, Nishiizumi, Kunihiko, Pasteris, Daniel R., Rhodes, Rachael H., and Sowers, Todd A
Abstract:: We present the WD2014 chronology for the upper part (0–2850 m; 31.2 ka BP) of the West Antarctic Ice Sheet (WAIS) Divide (WD) ice core. The chronology is based on counting of annual layers observed in the chemical, dust and electrical conductivity records. These layers are caused by seasonal changes...
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Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation

Creator:: Rhodes, Rachael H., Faïn, Xavier, Brook, Edward J., McConnell, Joseph R., Maselli, Olivia J., Sigl, Michael, Edwards, Jon, Buizert, Christo, Blunier, Thomas, Chappellaz, Jérôme, and Freitag, Johannes
Abstract:: Advances in trace gas analysis allow localised, non-atmospheric features to be resolved in ice cores, superimposed on the coherent atmospheric signal. These high-frequency signals could not have survived the low-pass filter effect that gas diffusion in the firn exerts on the atmospheric history and therefore do not result from changes...
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Precise interpolar phasing of abrupt climate change during the last ice age

Creator:: 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, P. Buford, 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.
Abstract:: The last glacial period exhibited abrupt Dansgaard–Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives¹. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard–Oeschger cycle and vice versa[superscript 2,3], suggesting an interhemispheric redistribution of heat through a mechanism...
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Observing and modeling the influence of layering on bubble trapping in polar firn

Creator:: Mitchell, Logan E., Buizert, Christo, Brook, Edward J., Breton, Daniel J., Fegyveresi, John, Baggenstos, Daniel, Orsi, Anais, Severinghaus, Jeffrey, Alley, Richard B., Albert, Mary, Rhodes, Rachael H., McConnell, Joseph R., Sigl, Michael, Maselli, Olivia, Gregory, Stephanie, and Ahn, Jinho
Abstract:: Interpretation of ice core trace gas records depends on an accurate understanding of the processes that smooth the atmospheric signal in the firn. Much work has been done to understand the processes affecting air transport in the open pores of the firn, but a paucity of data from air trapped...
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The WAIS Divide deep ice core WD2014 chronology – Part 1: Methane synchronization (68–31 kaBP) and the gas age–ice age difference

Creator:: Buizert, C., Cuffey, K. M., Severinghaus, J. P., Baggenstos, D., Fudge, T. J., Steig, E. J., Markle, B. R., Winstrup, M., Rhodes, R. H., Brook, Edward J., Sowers, T. A., Clow, G. D., Cheng, H., Edwards, R. L., Sigl, M., McConnell, J. R., and Taylor, K. C.
Abstract:: The West Antarctic Ice Sheet Divide (WAIS Divide, WD) ice core is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ~68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP) have been dated using annual-layer counting. Here we...
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High-precision dual-inlet IRMS measurements of the stable isotopes of CO₂ and the N₂O/CO₂ ratio from polar ice core samples

Creator:: Bauska, T. K., Brook, E. J., Mix, A. C., Ross, A., and Brook, Edward J.
Abstract:: An important constraint on mechanisms of past carbon cycle variability is provided by the stable isotopic composition of carbon in atmospheric carbon dioxide (δ¹³C-CO₂) trapped in polar ice cores, but obtaining very precise measurements has proven to be a significant analytical challenge. Here we describe a new technique to determine...
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Greenland Temperature Response to Climate Forcing during the Last Deglaciation

Creator:: Buizert, Christo, Gkinis, Vasileios, Severinghaus, Jeffrey P., He, Feng, Lecavalier, Benoit S., Kindler, Philippe, Leuenberger, Markus, Carlson, Anders E., Vinther, Bo, Masson-Delmotte, Valerie, White, James W. C., Liu, Zhengyu, Otto-Bliesner, Bette, and Brook, Edward J.
Abstract:: Greenland ice core water isotopic composition (δ¹⁸O) provides detailed evidence for abrupt climate changes, but is by itself insufficient for quantitative reconstruction of past temperatures and their spatial patterns. We investigate Greenland temperature evolution during the last deglaciation using independent reconstructions from three ice cores and simulations with a coupled...
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Earliest Holocene south Greenland ice sheet retreat within its late Holocene extent

Creator:: Carlson, Anders E., Winsor, Kelsey, Ullman, David J., Brook, Edward J., Hood, Dylan H., Axford, Yarrow, LeGrande, Allegra N., Anslow, Faron S., and Sinclair, Gaylen
Abstract:: Early Holocene summer warmth drove dramatic Greenland ice sheet (GIS) retreat. Subsequent insolation-driven cooling caused GIS margin readvance to late Holocene maxima, from which ice margins are now retreating. We use ¹⁰Be surface exposure ages from four locations between 69.4°N and 61.2°N to date when in the early Holocene south...
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Radiometric ⁸¹Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica

Creator:: Buizert, Christo, Baggenstos, Daniel, Jiang, Wei, Purtschert, Roland, Petrenko, Vasilii V., Lu, Zheng-Tian, Mueller, Peter, Lee, James, Severinghaus, Jeffrey P., and Brook, Edward J.
Abstract:: We present the first successful ⁸¹Kr-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four ~350 kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The ⁸¹Kr radiometric ages agree with independent...
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Response of atmospheric CO₂ to the abrupt cooling event 8200 years ago

Creator:: Ahn, Jinho, Brook, Edward J., and Buizert, Christo
Abstract:: Atmospheric CO₂ records for the centennial scale cooling event 8200 years ago (8.2 ka event) may help us understand climate-carbon cycle feedbacks under interglacial conditions, which are important for understanding future climate, but existing records do not provide enough detail. Here we present a new CO₂ record from the Siple...
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Constraints on the Late Holocene Anthropogenic Contribution to the Atmospheric Methane Budget

Creator:: Mitchell, Logan, Brook, Edward J., Lee, James E., Buizert, Christo, and Sowers, Todd
Abstract:: The origin of the late pre-industrial Holocene (LPIH) increase in atmospheric methane concentrations has been much debated. Hypotheses invoking changes in solely anthropogenic sources or solely natural sources have been proposed to explain the increase in concentrations. Here two high-resolution, high-precision ice core methane concentration records from Greenland and Antarctica...
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Where to find 1.5 million yr old ice for the IPICS “Oldest-Ice” ice core

Creator:: Fischer, H., Severinghaus, J., Brook, Edward J., Wolff, E., Albert, M., Alemany, O., Arthern, R., Bentley, C., Blankenship, D., Chappellaz, J., Creyts, T., Dahl-Jensen, D., Dinn, M., Frezzotti, M., Fujita, S., Gallee, H., Hindmarsh, R., Hudspeth, D., Jugie, G., Kawamura, K., Lipenkov, V., Miller, H., Mulvaney, R., Parrenin, F., Pattyn, F., Ritz, C., Schwander, J., Steinhage, D., van Ommen, T., and Wilhelms, F.
Abstract:: The recovery of a 1.5 million yr long ice core from Antarctica represents a keystone of our understanding of Quaternary climate, the progression of glaciation over this time period and the role of greenhouse gas cycles in this progression. Here we tackle the question of where such ice may still...
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A first chronology for the North Greenland Eemian Ice Drilling (NEEM) ice core

Creator:: Rasmussen, S. O., Abbott, P. M., Blunier, T., Bourne, A. J., Brook, Edward J., Buchardt, S. L., Buizert, Christo, Chappellaz, J., Clausen, H. B., Cook, E., Dahl-Jensen, D., Davies, S. M., Guillevic, M., Kipfstuhl, S., Laepple, T., Seierstad, I. K., Severinghaus, J. P., Steffensen, J. P., Stowasser, C., Svensson, A., Vallelonga, P., Vinther, B. M., Wilhelms, F., and Winstrup, M.
Abstract:: A stratigraphy-based chronology for the North Greenland Eemian Ice Drilling (NEEM) ice core has been derived by transferring the annual layer counted Greenland Ice Core Chronology 2005 (GICC05) and its model extension (GICC05modelext) from the NGRIP core to the NEEM core using 787 match points of mainly volcanic origin identified...
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High-resolution glacial and deglacial record of atmospheric methane by continuous-flow and laser spectrometer analysis along the NEEM ice core

Creator:: Chappellaz, J., Stowasser, C., Blunier, T., Baslev-Clausen, D., Brook, Edward J., Dallmayr, R., Fain, X., Lee, J. E., Mitchell, L. E., Pascual, O., Romanini, D., Rosen, J., and Schuepbach, S.
Abstract:: The Greenland NEEM (North Greenland Eemian Ice Drilling) operation in 2010 provided the first opportunity to combine trace-gas measurements by laser spectroscopic instruments and continuous-flow analysis along a freshly drilled ice core in a field-based setting. We present the resulting atmospheric methane (CH₄) record covering the time period from 107.7...
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Onset of deglacial warming in West Antarctica driven by local orbital forcing

Creator:: 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, R. Lawrence, 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., and Schauer, Andrew J.
Abstract:: The cause of warming in the Southern Hemisphere during the most recent deglaciation remains a matter of debate[superscript 1,2]. Hypotheses for a Northern Hemisphere trigger, through oceanic redistributions of heat, are based in part on the abrupt onset of warming seen in East Antarctic ice cores and dated to 18,000...
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Global climate evolution during the last deglaciation

Creator:: Clark, Peter U., Shakun, Jeremy D., Baker, Paul A., Bartlein, Patrick J., Brewer, Simon, Brook, Edward J., Carlson, Anders E., Cheng, Hai, Kaufman, Darrell S., Liu, Zhengyu, Marchitto, Thomas M., Mix, Alan C., Morrill, Carrie, Otto-Bliesner, Bette L., Pahnke, Katharina, Russell, James M., Whitlock, Cathy, Adkins, Jess F., Blois, Jessica L., Clark, Jorie, Colman, Steven M., Curry, William B., Flower, Ben P., He, Feng, Johnson, Thomas C., Lynch-Stieglitz, Jean, Markgraf, Vera, McManus, Jerry, Mitrovica, Jerry X., Moreno, Patricio I., and Williams, John W.
Abstract:: Deciphering the evolution of global climate from the end of the Last Glacial Maximum approximately 19 ka to the early Holocene 11 ka presents an outstanding opportunity for understanding the transient response of Earth's climate system to external and internal forcings. During this interval of global warming, the decay of...
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In situ cosmogenic radiocarbon production and 2-D ice flow line modeling for an Antarctic blue ice area

Creator:: Buizert, Christo, Petrenko, Vasilii V., Kavanaugh, Jeffrey L., Cuffey, Kurt M., Lifton, Nathaniel A., Brook, Edward J., and Severinghaus, Jeffrey P.
Abstract:: Radiocarbon measurements at ice margin sites and blue ice areas can potentially be used for ice dating, ablation rate estimates and paleoclimatic reconstructions. Part of the measured signal comes from in situ cosmogenic ¹⁴C production in ice, and this component must be well understood before useful information can be extracted...
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A New Method for Analyzing ¹⁴C of Methane in Ancient Air Extracted from Glacial Ice

Creator:: Petrenko, Vasilii V., Smith, Andrew M., Brailsford, Gordon, Riedel, Katja, Hua, Quan, Lowe, Dave, Severinghaus, Jeffrey P., Levchenko, Vladimir, Bromley, Tony, Moss, Rowena, Muhle, Jens, and Brook, Edward J.
Abstract:: We present a new method developed for measuring radiocarbon of methane (¹⁴CH₄) in ancient air samples extracted from glacial ice and dating 11,000–15,000 calendar years before present. The small size (~20 μg CH₄ carbon), low CH₄ concentrations ([CH₄], 400–800 parts per billion [ppb]), high carbon monoxide concentrations ([CO]), and low...
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Rapid Holocene Deglaciation of the Labrador Sector of the Laurentide Ice Sheet

Creator:: Carlson, Anders E., Clark, Peter U., Raisbeck, Grant M., and Brook, Edward J.
Abstract:: Retreat of the Laurentide Ice Sheet (LIS) following the Last Glacial Maximum 21 000 yr BP affected regional to global climate and accounted for the largest proportion of sea level rise. Although the late Pleistocene LIS retreat chronology is relatively well constrained, its Holocene chronology remains poorly dated, limiting our...
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A record of atmospheric CO₂ during the last 40,000 years from the Siple Dome, Antarctica ice core

Creator:: Ahn, Jinho, Wahlen, Martin, Deck, Bruce L., Brook, Edward J., Mayewski, Paul A., Taylor, Kendrick C., and White, James W. C.
Abstract:: We have measured the CO₂ concentration of air occluded during the last 40,000 years in the deep Siple Dome A (hereafter Siple Dome) ice core, Antarctica. The general trend of CO₂ concentration from Siple Dome ice follows the temperature inferred from the isotopic composition of the ice and is mostly...
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CH₄ and δ¹⁸O of O₂ records from Antarctic and Greenland ice: A clue for stratigraphic disturbance in the bottom part of the Greenland Ice Core Project and the Greenland Ice Sheet Project 2 ice cores

Creator:: Jerome Chappellaz, Brook, Edward J., Thomas Blunier, Bruno Malaize, Blunier, Thomas, Chappellaz, Jerome, and Malaize, Bruno
Abstract:: The suggestion of climatic instability during the last interglacial period (Eem), based on the bottom 10% of the Greenland Ice core Project (GRIP) isotopic profile, has been questioned because the bottom record from the neighboring Greenland Ice Sheet Project 2 (GISP2) core (28 km away) is strikingly different over the...
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Atmospheric methane during the last four glacial-interglacial cycles: Rapid changes and their link with Antarctic temperature

Creator:: Delmotte, M., Chappellaz, J., Brook, Edward J., Yiou, P., Barnola, J. M., Goujon, C., Raynaud, D., and Lipenkov, V. I.
Abstract:: Atmospheric methane (CH₄) recorded in Antarctic ice cores represents the closest ice proxy available for Greenland temperature changes beyond times when Greenland climate records are available. The record over four climatic cycles from the Vostok ice core offers the opportunity to study the phase relationship between Greenland and Antarctic climate...
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A global climate model study of CH₄ emissions during the Holocene and glacial-interglacial transitions constrained by ice core data

Creator:: Harder, S. L., Shindell, D. T., Schmidt, G. A., and Brook, Edward J.
Abstract:: Ice core records show atmospheric methane mixing ratio and interpolar gradient varying with climate. Changes in wetland sources have been implicated as the basis for this observed variation in the record, but more recently, modeling studies suggest that changes in the CH₄ sink resulting from changes in sea surface temperature...
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Effective attenuation lengths of cosmic rays producing ¹⁰Be and ²⁶Al in quartz: Implications for exposure age dating

Creator:: Brown, Erik Thorson, Brook, Edward J., Raisbeck, Grant M., Yiou, Francoise, and Kurz, Mark D.
Abstract:: We have measured cosmic ray produced ¹⁰Be (t₁/₂ = 1.5 My) and ²⁶Al (t₁/₂ = 0.72 My) as functions of depth in a core of quartz sandstone bedrock collected in South Victoria Land, Antarctica. These data were used to place limits on the exposure age and erosion rate of the...
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Relative timing and variability of atmospheric methane and GISP2 oxygen isotopes between 68 and 86 ka

Creator:: Grachev, Alexi M., Brook, Edward J., Severinghaus, Jeffrey P., and Pisias, Nicklas G.
Abstract:: The global biogeochemical cycle of methane has received wide attention because of methane's role as a greenhouse gas. Measurements of methane in air trapped in Greenland ice cores provide a high-resolution record of methane levels in the atmosphere over the past ~100 ka, providing clues about what controls the methane...
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On the origin and timing of rapid changes in atmospheric methane during the Last Glacial Period

Creator:: Brook, Edward J., Harder, Susan, Severinghaus, Jeff, Steig, Eric J., and Sucher, Cara M.
Abstract:: We present high resolution records of atmospheric methane from the GISP2 (Greenland Ice Sheet Project 2) ice core for four rapid climate transitions that occurred during the past 50 ka: the end of the Younger Dryas at 11.8 ka, the beginning of the Bølling-Allerød period at 14.8 ka, the beginning...
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Abrupt changes in atmospheric methane at the MIS 5b–5a transition

Creator:: Grachev, Alexi M., Brook, Edward J., and Severinghaus, Jeffrey P.
Abstract:: New ice core analyses show that the prominent rise in atmospheric methane concentration at Dansgaard-Oeschger event 21 was interrupted by a century-long 20% decline, which was previously unrecognized. The reversal was found in a new ∼100-year resolution study of methane in the GISP2 ice core, encompassing the beginning of D-O...
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Accretion of interplanetary dust in polar ice

Creator:: Brook, Edward J., Kurz, Mark D., Curtice, Joshua, and Cowburn, Stuart
Abstract:: Measurements of helium isotopes in particles separated from polar ice demonstrate that extraterrestrial ³He dominates the ³He flux at the GISP2 (Greenland) and Vostok (Antarctica) ice core sites. Replicate measurements of late Holocene ice samples yield ³He fluxes of 0.62±0.27×10⁻¹² cm³ STP cm⁻² ka⁻¹ (GISP2) and 0.77 ± 0.25 ×...
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Ice stratigraphy at the Pakitsoq ice margin, West Greenland, derived from gas records

Creator:: Schaefer, Hinrich, Petrenko, Vasilii V., Brook, Edward J., Severinghaus, Jeffrey P., Reeh, Niels, Melton, Joe R., and Mitchell, Logan
Abstract:: Horizontal ice-core sites, where ancient ice is exposed at the glacier surface, offer unique opportunities for paleo-studies of trace components requiring large sample volumes. Following previous work at the Pâkitsoq ice margin in West Greenland, we use a combination of geochemical parameters measured in the ice matrix (δ¹⁸O[subscript ice]) and...
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Instruments and Methods: A novel method for obtaining very large ancient air samples from ablating glacial ice for analyses of methane radiocarbon

Creator:: Petrenko, Vasilii V., Severinghaus, Jeffrey P., Brook, Edward J., Muhle, Jens, Headly, Melissa, Harth, Christina M., Schaefer, Hinrich, Reeh, Niels, Weiss, Ray F., Lowe, Dave, and Smith, Andrew M.
Abstract:: We present techniques for obtaining large (∼100 L STP) samples of ancient air for analysis of ¹⁴C of methane (¹⁴CH₄) and other trace constituents. Paleoatmospheric ¹⁴CH₄ measurements should constrain the fossil fraction of past methane budgets, as well as provide a definitive test of methane clathrate involvement in large and...
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CO₂ diffusion in polar ice: observations from naturally formed CO₂ spikes in the Siple Dome (Antarctica) ice core

Creator:: Ahn, Jinho, Headly, Melissa, Wahlen, Martin, Brook, Edward J., Mayewski, Paul A., and Taylor, Kendrick C.
Abstract:: One common assumption in interpreting ice-core CO₂ records is that diffusion in the ice does not affect the concentration profile. However, this assumption remains untested because the extremely small CO₂ diffusion coefficient in ice has not been accurately determined in the laboratory. In this study we take advantage of high...
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Geochemical proxies of North American freshwater routing during the Younger Dryas cold event

Creator:: Carlson, Anders E., Clark, Peter U., Haley, Brian A., Klinkhammer, Gary P., Simmons, Kathleen, Brook, Edward J., and Meissner, Katrin J.
Abstract:: The Younger Dryas cold interval represents a time when much of the Northern Hemisphere cooled from ≈12.9 to 11.5 kiloyears B.P. The cause of this event, which has long been viewed as the canonical example of abrupt climate change, was initially attributed to the routing of freshwater to the St....
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Gases in ice cores

Creator:: Bender, Michael, Sowers, Todd, and Brook, Edward J.
Abstract:: Air trapped in glacial ice offers a means of reconstructing variations in the concentrations of atmospheric gases over time scales ranging from anthropogenic (last 200 yr) to glacial/interglacial (hundreds of thousands of years). In this paper, we review the glaciological processes by which air is trapped in the ice and...
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