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2. Eemian interglacial reconstructed from a Greenland folded ice core

Author

Dahl-Jensen, D., Albert, M. R., Aldahan, A., Azuma, N., Balslev-Clausen, D., Baumgartner, M., Berggren, A.-M., Bigler, M., Binder, T., Blunier, T., Bourgeois, J. C., Brook, E. J., Buchardt, S. L., Buizert, C., Capron, E., Chappellaz, J., Chung, J., Clausen, H. B., Cvijanovic, I., Davies, S. M., Ditlevsen, P., Eicher, O., Fischer, H., Fisher, D. A., Fleet, L. G., Gfeller, G., Gkinis, V., Gogineni, S., Goto-Azuma, K., Grinsted, A., Gudlaugsdottir, H., Guillevic, M., Hansen, S. B., Hansson, M., Hirabayashi, M., Hong, S., Hur, S. D., Huybrechts, P., Hvidberg, C. S., Iizuka, Y., Jenk, T., Johnsen, S. J., Jones, T. R., Jouzel, J., Karlsson, N. B., Kawamura, K., Keegan, K., Kettner, E., Kipfstuhl, S., Kjær, H. A., Koutnik, M., Kuramoto, T., Köhler, P., Laepple, T., Landais, A., Langen, P. L., Larsen, L. B., Leuenberger, D., Leuenberger, M., Leuschen, C., Li, J., Lipenkov, V., Martinerie, P., Maselli, O. J., Masson-Delmotte, V., McConnell, J. R., Miller, H., Mini, O., Miyamoto, A., Montagnat-Rentier, M., Mulvaney, R., Muscheler, R., Orsi, A. J., Paden, J., Panton, C., Pattyn, F., Petit, J.-R., Pol, K., Popp, T., Possnert, G., Prié, F., Prokopiou, M., Quiquet, A., Rasmussen, S. O., Raynaud, D., Ren, J., Reutenauer, C., Ritz, C., Röckmann, T., Rosen, J. L., Rubino, M., Rybak, O., Samyn, D., Sapart, C. J., Schilt, A., Schmidt, A. M. Z., Schwander, J., Schüpbach, S., Seierstad, I., Severinghaus, J. P., Sheldon, S., Simonsen, S. B., Sjolte, J., Solgaard, A. M., Sowers, T., Sperlich, P., Steen-Larsen, H. C., Steffen, K., Steffensen, J. P., Steinhage, D., Stocker, T. F., Stowasser, C., Sturevik, A. S., Sturges, W. T., Sveinbjörnsdottir, A., Svensson, A., Tison, J.-L., Uetake, J., Vallelonga, P., van de Wal, R. S. W., van der Wel, G., Vaughn, B. H., Vinther, B., Waddington, E., Wegner, A., Weikusat, I., White, J. W. C., Wilhelms, F., Winstrup, M., Witrant, E., Wolff, E. W., Xiao, C., and Zheng, J.

Published
2013
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3. Estimation and calibration of the water isotope differential diffusion length in ice core records

Author

van der Wel, G., Fischer, H., Oerter, Hans, Meyer, Hanno, Meijer, H. A. J., van der Wel, G., Fischer, H., Oerter, Hans, Meyer, Hanno, and Meijer, H. A. J.

Abstract

Palaeoclimatic information can be retrieved from the diffusion of the stable water isotope signal during firnification of snow. The diffusion length, a measure for the amount of diffusion a layer has experienced, depends on the firn temperature and the accumulation rate. We show that the estimation of the diffusion length using power spectral densities (PSDs) of the record of a single isotope species can be biased by uncertainties in spectral properties of the isotope signal prior to diffusion. By using a second water isotope and calculating the difference in diffusion lengths between the two isotopes, this problem is circumvented. We study the PSD method applied to two isotopes in detail and additionally present a new forward diffusion method for retrieving the differential diffusion length based on the Pearson correlation between the two isotope signals. The two methods are discussed and extensively tested on synthetic data which are generated in a Monte Carlo manner. We show that calibration of the PSD method with this synthetic data is necessary to be able to objectively determine the differential diffusion length. The correlation-based method proves to be a good alternative for the PSD method as it yields precision equal to or somewhat higher than the PSD method. The use of synthetic data also allows us to estimate the accuracy and precision of the two methods and to choose the best sampling strategy to obtain past temperatures with the required precision. In addition to application to synthetic data the two methods are tested on stable-isotope records from the EPICA (European Project for Ice Coring in Antarctica) ice core drilled in Dronning Maud Land, Antarctica, showing that reliable firn temperatures can be reconstructed with a typical uncertainty of 1.5 and 2 °C for the Holocene period and 2 and 2.5 °C for the last glacial period for the correlation and PSD method, respectively.

Published
2015

5. Past local temperatures obtained from the EDML ice core using differential diffusion

Author

van der Wel, G, Oerter, H, Meyer, H, and Fischer, H

Abstract

Since the 1960-s the stable water isotope signal in ice core records has been used as a proxy for palaeotemperatures. However, this direct interpretation of the isotope signal has limitations, as the relationship between the isotope ratio and atmospheric temperature is known to fluctuate both spatially and temporally. One way to circumvent these limitations is the use of diffusion thermometry as pioneered by Johnsen et al (2000). In the firn stage the isotope signal is subject to a smoothing caused by the random movement of water vapour in the pores of the snow. The total amount of diffusion a layer has suffered is measured in terms of the diffusion length. This length is sensitive to changes in firn temperature and the accumulation rate at the site. The diffusion length for Oxygen-18 is higher than that for Deuterium due to a difference in ice-vapour fractionation factors. As these fractionation factors are dependent on the temperature of the firn, the difference in diffusion length can be used to estimate past local temperatures. To apply this differential diffusion method successfully, it is necessary to have high resolution measurements for both Oxygen-18 and Deuterium. We present such measurements for the EDML ice core. In total 400 m of ice was measured with a 5 cm resolution from periods in the mid and early Holocene, the last glacial-interglacial transition and the last glacial period. Application of the differential diffusion method to this dataset shows a decreasing temperature trend during the Holocene and a surface temperature of approximately -55 °C in the interval representing the LGM in the ice (~10 °C colder than present day temperature (not corrected for changes in altitude)). This is, within the error limits, in line with the temperature reconstructed from the stable water isotope proxy itself using the spatial isotope/temperature gradient (EPICA community members, 2006). References: Johnsen, S. et al, 2000. Diffusion of stable isotopes in polar firn and ice: the isotope effect in diffusion. In: Physics of Ice Core Records, Ed: Hondoh, T., p.121-140, Hokkaido Press, Sapporo. EPICA community members, 2006. One-to-one coupling of glacial climate variability in Greenland and Antarctica. Nature 444, p.195-198.

Published
2012

7. Eemian interglacial reconstructed from a Greenland folded ice core

Author

Dahl-Jensen, Dorthe, Albert, M. R., Aldahan, A., Azuma, N., Balslev-Clausen, David Morten, Baumgartner, M., Berggren, A.-M., Bigler, M., Binder, Thomas, Blunier, Thomas, Bourgeois, J.C., Brook, E.J., Buchardt, Susanne Lilja, Buizert, Christo, Capron, E., Chappellaz, J., Chung, J., Clausen, Henrik Brink, Cvijanovic, Ivana, Davies, S.M., Ditlevsen, Peter, Eicher, O., Fischer, H., Fisher, D. A., Fleet, L.G., Gfeller, G., Gkinis, Vasileios, Gogineni, S., Goto-Azuma, K., Grinsted, Aslak, Gudlaugsdottir, H., Guillevic, Myriam, Hansen, S. B., Hansson, M., Hirabayashi, M., Hong, S., Hur, S.D., Huybrechts, P., Hvidberg, Christine Schøtt, Iizuka, Y., Jenk, Theo Manuel, Johnsen, Sigfus Johann, Jones, T.R., Jouzel, J., Karlsson, Nanna Bjørnholt, Kawamura, K., Keegan, K., Kettner, Ernesto, Kipfstuhl, S., Kjær, Helle Astrid, Koutnik, M., Kuramoto, T., Köhler, P., Laepple, T., Landais, A., Langen, Peter Lang, Larsen, Lars Berg, Leuenberger, D., Leuenberger, M., Leuschen, C., Li, J., Lipenkov, V., Martinerie, P., Maselli, O. J., Masson-Delmotte, V., McConnell, J. R., Miller, H., Mini, O., Miyamoto, A., Montagnat-Rentier, M., Mulvaney, R., Muscheler, R., Orsi, A.J., Paden, J., Panton, Christian, Pattyn, F., Petit, J.-R., Pol, K., Popp, Trevor James, Possnert, G., Prié, F., Prokopiou, M., Quiquet, A., Rasmussen, Sune Olander, Raynaud, D., Ren, J., Reutenauer, Corentin, Ritz, C., Röckmann, T., Rosen, J.L., Rubino, Mauro, Rybak, O., Samyn, D., Sapart, C.J., Schilt, A., Schmidt, Astrid Mariah Zelma, Schwander, J., Schüpbach, S., Seierstad, Inger Kathrine, Severinghaus, J. P., Sheldon, S., Simonsen, Sebastian Bjerregaard, Sjolte, Jesper, Solgaard, Anne Munck, Sowers, T., Sperlich, Peter, Steen-Larsen, Hans Christian, Steffen, K., Steffensen, Jørgen Peder, Steinhage, D., Stocker, T.F., Stowasser, Christopher, Sturevik, A.S., Sturges, W.T., Sveinbjörnsdottir, A., Svensson, Anders, Tison, J.-L., Uetake, J., Vallelonga, Paul Travis, Van De Wal, R.S.W., Van Der Wel, G., Vaughn, B.H., Vinther, Bo Møllesøe, Waddington, E., Wegner, A., Weikusat, I., White, J. W. C., Wilhelms, F., Winstrup, Mai, Witrant, E., Wolff, E.W., Xiao, C., Zheng, Jin, Dahl-Jensen, Dorthe, Albert, M. R., Aldahan, A., Azuma, N., Balslev-Clausen, David Morten, Baumgartner, M., Berggren, A.-M., Bigler, M., Binder, Thomas, Blunier, Thomas, Bourgeois, J.C., Brook, E.J., Buchardt, Susanne Lilja, Buizert, Christo, Capron, E., Chappellaz, J., Chung, J., Clausen, Henrik Brink, Cvijanovic, Ivana, Davies, S.M., Ditlevsen, Peter, Eicher, O., Fischer, H., Fisher, D. A., Fleet, L.G., Gfeller, G., Gkinis, Vasileios, Gogineni, S., Goto-Azuma, K., Grinsted, Aslak, Gudlaugsdottir, H., Guillevic, Myriam, Hansen, S. B., Hansson, M., Hirabayashi, M., Hong, S., Hur, S.D., Huybrechts, P., Hvidberg, Christine Schøtt, Iizuka, Y., Jenk, Theo Manuel, Johnsen, Sigfus Johann, Jones, T.R., Jouzel, J., Karlsson, Nanna Bjørnholt, Kawamura, K., Keegan, K., Kettner, Ernesto, Kipfstuhl, S., Kjær, Helle Astrid, Koutnik, M., Kuramoto, T., Köhler, P., Laepple, T., Landais, A., Langen, Peter Lang, Larsen, Lars Berg, Leuenberger, D., Leuenberger, M., Leuschen, C., Li, J., Lipenkov, V., Martinerie, P., Maselli, O. J., Masson-Delmotte, V., McConnell, J. R., Miller, H., Mini, O., Miyamoto, A., Montagnat-Rentier, M., Mulvaney, R., Muscheler, R., Orsi, A.J., Paden, J., Panton, Christian, Pattyn, F., Petit, J.-R., Pol, K., Popp, Trevor James, Possnert, G., Prié, F., Prokopiou, M., Quiquet, A., Rasmussen, Sune Olander, Raynaud, D., Ren, J., Reutenauer, Corentin, Ritz, C., Röckmann, T., Rosen, J.L., Rubino, Mauro, Rybak, O., Samyn, D., Sapart, C.J., Schilt, A., Schmidt, Astrid Mariah Zelma, Schwander, J., Schüpbach, S., Seierstad, Inger Kathrine, Severinghaus, J. P., Sheldon, S., Simonsen, Sebastian Bjerregaard, Sjolte, Jesper, Solgaard, Anne Munck, Sowers, T., Sperlich, Peter, Steen-Larsen, Hans Christian, Steffen, K., Steffensen, Jørgen Peder, Steinhage, D., Stocker, T.F., Stowasser, Christopher, Sturevik, A.S., Sturges, W.T., Sveinbjörnsdottir, A., Svensson, Anders, Tison, J.-L., Uetake, J., Vallelonga, Paul Travis, Van De Wal, R.S.W., Van Der Wel, G., Vaughn, B.H., Vinther, Bo Møllesøe, Waddington, E., Wegner, A., Weikusat, I., White, J. W. C., Wilhelms, F., Winstrup, Mai, Witrant, E., Wolff, E.W., Xiao, C., and Zheng, Jin

Abstract

Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 ± 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 ± 250 metres, reaching surface elevations 122,000 years ago of 130 ± 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.

Published
2013

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