Helle Astrid Kjær

Helle Astrid Kjær

Associate Professor


  1. Published

    The Ross Sea Dipole – Temperature, Snow Accumulation and Sea Ice Variability in the Ross Sea Region, Antarctica, over the Past 2,700 Years

    Bertler, N. A. N., Conway, H., Dahl-Jensen, D., Emanuelsson, D. B., Winstrup, M., Vallelonga, P. T., Lee, J. E., Brook, E. J., Severinghaus, J. P., Fudge, T. J., Keller, E. D., Baisden, W. T., Hindmarsh, R. C. A., Neff, P. D., Blunier, T., Edwards, R., Mayewski, P. A., Kipfstuhl, S., Buizert, C., Canessa, S. & 51 others, Dadic, R., Kjær, Helle Astrid, Kurbatov, A., Zhang, D., Waddington, E. D., Baccolo, G., Beers, T., Brightley, H. J., Carter, L., Clemens-Sewall, D., Ciobanu, V. G., Delmonte, B., Eling, L., Ellis, A. A., Ganesh, S., Golledge, N. R., Haines, S. A., Handley, M., Hawley, R. L., Hogan, C. M., Johnson, K. M., Korotkikh, E., Lowry, D. P., Mandeno, D., McKay, R. M., Menking, J. A., Naish, T. R., Noerling, C., Ollive, A., Orsi, A., Proemse, B. C., Pyne, A. R., Pyne, R. L., Renwick, J., Scherer, R. P., Semper, S., Simonsen, M., Sneed, S. B., Steig, E. J., Tuohy, A., Venugopal, A. U., Valero-Delgado, F., Venkatesh, J., Wang, F., Wang, S., Winski, D. A., Winton, V. H. L., Whiteford, A., Xiao, C., Yang, J. & Zhang, X., 1 Aug 2017, In: Climate of the Past Discussions. 31 p.

    Research output: Contribution to journalJournal articlepeer-review

  2. Published

    The Ross Sea Dipole - temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years

    Bertler, N. A. N., Conway, H., Dahl-Jensen, D., Emanuelsson, D. B., Winstrup, M., Vallelonga, P. T., Lee, J. E., Brook, E. J., Severinghaus, J. P., Fudge, T. J., Keller, E. D., Baisden, W. T., Hindmarsh, R. C. A., Neff, P. D., Blunier, T., Edwards, R., Mayewski, P. A., Kipfstuhl, S., Buizert, C., Canessa, S. & 30 others, Dadic, R., Kjær, Helle Astrid, Kurbatov, A., Zhang, D., Waddington, E. D., Baccolo, G., Beers, T., Brightley, H. J., Carter, L., Clemens-Sewall, D., Ciobanu, V. G., Delmonte, B., Eling, L., Ellis, A., Ganesh, S., Golledge, N. R., Haines, S., Handley, M., Hawley, R. L., Hogan, C. M., Johnson, K. M., Korotkikh, E., Lowry, D. P., Mandeno, D., McKay, R. M., Menking, J. A., Naish, T. R., Noerling, C., Simonsen, M. & Wang, S., 21 Feb 2018, In: Climate of the Past. 14, 2, p. 193-214

    Research output: Contribution to journalJournal articlepeer-review

  3. Published

    New data from the 40 year old Dye3 core

    Blunier, Thomas, Venkatesh, J., Soestmeyer, D. A., Liisberg, J. B., Rhodes, R., Menking, J. A., Severinghaus, J. P., Harlan, Meg, Kjær, Helle Astrid & Vallelonga, P., 23 Mar 2020. 1 p.

    Research output: Contribution to conferenceConference abstract for conferenceResearchpeer-review

  4. Published

    The summer 2012 Greenland heat wave: In situ and remote sensing observations of water vapor isotopic composition during an atmospheric river event

    Bonne, J., Steen-Larsen, H. C., Risi, C., Werner, M., Sodemann, H., Lacour, J., Fettweis, X., Cesana, G., Delmotte, M., Cattani, O., Vallelonga, P. T., Kjær, Helle Astrid, Clerbaux, C., Svienbjörndóttir, Á. E. & Masson-Delmotte, V., 1 Apr 2015, In: Journal of Geophysical Research: Biogeosciences. 120, 7, p. 2970-2989

    Research output: Contribution to journalJournal articlepeer-review

  5. Published

    Climate changes modulated the history of Arctic iodine during the Last Glacial Cycle

    Corella, J. P., Maffezzoli, N., Spolaor, A., Vallelonga, P., Cuevas, C. A., Scoto, F., Müller, J., Vinther, Bo Møllesøe, Kjær, Helle Astrid, Cozzi, G., Edwards, R., Barbante, C. & Saiz-Lopez, A., 2022, In: Nature Communications. 13, 88.

    Research output: Contribution to journalJournal articlepeer-review

  6. Published

    Holocene atmospheric iodine evolution over the North Atlantic

    Corella, J. P., Maffezzoli, N., Cuevas, C. A., Vallelonga, P., Spolaor, A., Cozzi, G., Muller, J., Vinther, Bo Møllesøe, Barbante, C., Kjær, Helle Astrid, Edwards, R. & Saiz-Lopez, A., 18 Dec 2019, In: Climate of the Past. 15, 6, p. 2019-2030

    Research output: Contribution to journalJournal articlepeer-review

  7. Published

    El Niño-Southern Oscillation signal in a new East Antarctic ice core, Mount Brown South

    Crockart, C. K., Vance, T. R., Fraser, A. D., Abram, N. J., Criscitiello, A. S., Curran, M. A. J., Favier, V., Gallant, A. J. E., Kittel, C., Kjær, Helle Astrid, Klekociuk, A. R., Jong, L. M., Moy, A. D., Plummer, C. T., Vallelonga, P. T., Wille, J. & Zhang, L., 9 Sep 2021, In: Climate of the Past. 17, 5, p. 1795-1818 24 p.

    Research output: Contribution to journalJournal articlepeer-review

  8. Published

    Rapid increase in atmospheric iodine levels in the North Atlantic since the mid-20th century

    Cuevas, C. A., Maffezzoli, N., Corella, J. P., Spolaor, A., Vallelonga, P. T., Kjær, Helle Astrid, Simonsen, M. F., Winstrup, M., Vinther, Bo Møllesøe, Horvat, C., Fernandez, R. P., Kinnison, D., Lamarque, J., Barbante, C. & Saiz-Lopez, A., 1 Dec 2018, In: Nature Communications. 9, 1452.

    Research output: Contribution to journalJournal articlepeer-review

  9. Published

    Eemian interglacial reconstructed from a Greenland folded ice core

    Dahl-Jensen, D., Albert, M. R., Aldahan, A., Azuma, N., Balslev-Clausen, D. M., 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. & 113 others, 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, M., Hansen, S. B., Hansson, M., Hirabayashi, M., Hong, S., Hur, S. D., Huybrechts, P., Hvidberg, Christine Schøtt, Iizuka, Y., Jenk, T. M., Johnsen, S. J., Jones, T. R., Jouzel, J., Karlsson, N. B., Kawamura, K., Keegan, K., Kettner, E., Kipfstuhl, S., Kjær, Helle Astrid, 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., Pol, K., Popp, T. J., Possnert, G., Prié, F., Prokopiou, M., Quiquet, A., Rasmussen, Sune Olander, 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. K., Severinghaus, J. P., Sheldon, S., Simonsen, S. B., Sjolte, J., Solgaard, Anne Munck, Sowers, T., Sperlich, P., Steen-Larsen, H. C., Steffen, K., Steffensen, Jørgen Peder, Steinhage, D., Stocker, T. F., Stowasser, C., Sturevik, A. S., Sturges, W. T., Sveinbjörnsdottir, A., Svensson, Anders, Tison, J., Uetake, J., Vallelonga, P. T., 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, M., Witrant, E., Wolff, E. W., Xiao, C. & Zheng, J., 24 Jan 2013, In: Nature. 493, 7433, p. 489-494 6 p.

    Research output: Contribution to journalJournal articlepeer-review

  10. Published

    A High-Resolution Continuous Flow Analysis System for Polar Ice Cores

    Dallmayr, R., Goto-Azuma, K., Kjær, Helle Astrid, Azuma, N., Takata, M., Schüpbach, S. & Hirabayashi, M., 2016, In: Bulletin of Glaciological Research. 34, p. 11-20

    Research output: Contribution to journalJournal articlepeer-review

  11. Published

    High-resolution aerosol concentration data from the Greenland NorthGRIP and NEEM deep ice cores

    Erhardt, T., Bigler, M., Federer, U., Gfeller, G., Leuenberger, D., Stowasser, O., Rothlisberger, R., Schupbach, S., Ruth, U., Twarloh, B., Wegner, A., Goto-Azuma, K., Kuramoto, T., Kjaer, H. A., Vallelonga, P. T., Siggaard-Andersen, M-L., Hansson, M. E., Benton, A. K., Fleet, L. G., Mulvaney, R. & 4 others, Thomas, E. R., Abram, N., Stocker, T. F. & Fischer, H., 16 Mar 2022, In: Earth System Science Data. 14, 3, p. 1215-1231 17 p.

    Research output: Contribution to journalJournal articlepeer-review

  12. Published

    High-resolution aerosol data from the top 3.8 kyr of the East Greenland Ice coring Project (EGRIP) ice core

    Erhardt, T., Jensen, C. M., Adolphi, F., Kjær, H. A., Dallmayr, R., Twarloh, B., Behrens, M., Hirabayashi, M., Fukuda, K., Ogata, J., Burgay, F., Scoto, F., Crotti, I., Spagnesi, A., Maffezzoli, N., Segato, D., Paleari, C., Mekhaldi, F., Muscheler, R., Darfeuil, S. & 1 others, Fischer, H., 17 Nov 2023, In: Earth System Science Data. 15, 11, p. 5079-5091 13 p.

    Research output: Contribution to journalJournal articlepeer-review

  13. Published

    Determination of 129I in Arctic snow by a novel analytical approach using IC-ICP-SFMS

    Ezerinskis, Z., Spolaor, A., Kirchgeorg, T., Cozzi, G., Vallelonga, P., Kjær, Helle Astrid, Sapolaite, J., Barbante, C. & Druteikiene, R., 10 Jan 2014, In: Journal of Analytical Atomic Spectrometry. 29, 10, p. 1827-1834

    Research output: Contribution to journalJournal articlepeer-review

  14. Published

    Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities

    George, T. S., Giles, C. D., Menezes-Blackburn, D., Condron, L. M., Gama-Rodrigues, A. C., Jaisi, D., Lang, F., Neal, A. L., Stutter, M. I., Almeida, D. S., Bol, R., Cabugao, K. G., Celi, L., Cotner, J. B., Krueger, J., Plassard, C., Rosling, A., Darch, T., Fraser, T., Tamburini, F. & 30 others, Audette, Y., Bertrand, I., Beyhaut, E., Boitt, G., Bradshaw, N., Brearley, C. A., Bruulsema, T. W., Cozzolino, V., Duran, P. C., Mora, M. L., de Menezes, A. B., Dodd, R. J., Dunfield, K., Engl, C., Frazao, J. J., Jimenez, J. L. G., Harrison, A. F., Hou, E. Q., Johnes, P. J., Kaiser, K., Kjær, Helle Astrid, Klumpp, E., Lamb, A. L., Macintosh, K. A., Nelson, L. A., Tibbett, M., Wallander, H., Wang, L., Wasaki, J. & Haygarth, P. M., Jun 2018, In: Plant and Soil. 427, 1-2, SI, p. 209-211

    Research output: Contribution to journalJournal articlepeer-review

  15. Published

    Accelerating ice flow at the onset of the Northeast Greenland Ice Stream

    Grinsted, Aslak, Hvidberg, Christine Schøtt, Lilien, D. A., Rathmann, Nicholas Mossor, Karlsson, N. B., Gerber, T., Kjær, Helle Astrid, Vallelonga, P. & Dahl-Jensen, Dorthe, 23 Sep 2022, In: Nature Communications. 13, 1, 4 p., 5589.

    Research output: Contribution to journalJournal articlepeer-review

  16. Published

    Continuous flow analysis of the Mount Brown South ice core

    Harlan, Meg, Kjær, Helle Astrid, Vance, T., Vallelonga, P., Gkinis, Vasileios, Blunier, Thomas, Svensson, Anders, Moy, A., Plummer, C., Jackson, S., Peensoo, K. & Campo, A. D., 9 Apr 2021, 1 p. Copernicus/EGU.

    Research output: Other contributionResearch

  17. Published

    Surface velocity of the Northeast Greenland Ice Stream (NEGIS): assessment of interior velocities derived from satellite data by GPS

    Hvidberg, Christine Schøtt, Grinsted, Aslak, Dahl-Jensen, Dorthe, Khan, S. A., Kusk, A., Andersen, Jonas Kvist, Neckel, N., Solgaard, Anne Munck, Karlsson, N. B., Kjær, Helle Astrid & Vallelonga, P., 22 Oct 2020, In: Cryosphere. 14, 10, p. 3487-3502 16 p.

    Research output: Contribution to journalJournal articlepeer-review

  18. Published

    Past perspectives on the present era of abrupt Arctic climate change

    Jansen, E., Christensen, Jens Hesselbjerg, Dokken, T., Nisancioglu, K. H., Vinther, Bo Møllesøe, Capron, E., Guo, C., Jensen, M. F., Langen, P. L., Pedersen, R. A., Yang, S., Bentsen, M., Kjær, Helle Astrid, Sadatzki, H., Sessford, E. & Stendel, M., 1 Aug 2020, In: Nature climate change. 10, 8, p. 714-721 8 p.

    Research output: Contribution to journalJournal articlepeer-review

  19. Published

    Canadian forest fires, Icelandic volcanoes and increased local dust observed in six shallow Greenland firn cores

    Kjær, Helle Astrid, Zens, P., Black, S., Lund, K. H., Svensson, Anders & Vallelonga, P., 10 Oct 2022, In: Climate of the Past. 18, 10, p. 2211-2230 20 p.

    Research output: Contribution to journalJournal articlepeer-review

  20. Published

    Forty years later: High resolution continuous flow analysis of the Dye3 ice core

    Kjær, Helle Astrid, Harlan, Meg, Vallelonga, P., Svensson, Anders, Blunier, Thomas, Sowers, T., Menking, J. A., Campo, A. D., Venkatesh, J., Liisberg, J., Soestmeyer, D., Morris, V., Vaughn, B. & Vinther, Bo Møllesøe, 4 Mar 2021, 2 p. Copernicus/EGU.

    Research output: Other contributionResearch

  21. Assessment of the temperature, precipitation and snow in the RCM HIRHAM4 at 25 km resolution: Danish Climate Centre Report 09-08

    Kjær, Helle Astrid, 2009, Assessment of the temperature, precipitation and snow in the RCM HIRHAM4 at 25 km resolution: Danish Climate Centre Report 09-08. Danmarks Meterologiske Institut (DMI)

    Research output: Chapter in Book/Report/Conference proceedingReport chapterResearch

  22. Published

    Continuous Flow Analysis Method for Determination of Dissolved Reactive Phosphorus in Ice Cores

    Kjær, Helle Astrid, Vallelonga, P. T., Svensson, Anders, Elleskov L. Kristensen, M., Tibuleac, C. & Bigler, M., 5 Nov 2013, In: Environmental Science & Technology (Washington). 47, 21, p. 12325-12332

    Research output: Contribution to journalJournal articlepeer-review

  23. Published

    An Optical Dye Method for Continuous Determination of Acidity in Ice Cores

    Kjær, Helle Astrid, Vallelonga, P. T., Svensson, Anders, Kristensen, M. E., Tibuleac, C., Winstrup, M. & Kipfstuhl, S., 1 Sep 2016, In: Environmental Science & Technology. 50, 19, p. 10485-10493

    Research output: Contribution to journalJournal articlepeer-review

  24. Published

    Continuous Chemistry in Ice Cores: Phosphorus, pH and the Photolysis of Humic Like Substances

    Kjær, Helle Astrid, 2014, The Niels Bohr Institute, Faculty of Science, University of Copenhagen.

    Research output: Book/ReportPh.D. thesis

  25. Published

    A portable lightweight in situ analysis (LISA) box for ice and snow analysis

    Kjær, Helle Astrid, Lolk Hauge, L., Simonsen, M., Yoldi, Zuriñe, Koldtoft, Iben, Hörhold, M., Freitag, J., Kipfstuhl, S., Svensson, Anders & Vallelonga, P., 2021, In: Cryosphere. 15, 8, p. 3719-3730

    Research output: Contribution to journalJournal articlepeer-review

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ID: 33355865