Helle Astrid Kjær

Helle Astrid Kjær

Associate Professor


  1. Published

    Initial results from geophysical surveys and shallow coring of the Northeast Greenland Ice Stream (NEGIS)

    Vallelonga, P. T., Christianson, K., Alley, R. B., Anandakrishnan, S., Dahl-Jensen, D., Gkinis, V., Holme, C. T., Jacobel, R. W., Karlsson, N. B., Keisling, B. A., Kipfstuhl, S., Kjær, H. A., Kristensen, M. E., Muto, A., Peters, L. E., Popp, T. J., Riverman, K. L., Svensson, A., Tibuleac, C., Vinther, B. M. & 2 others, Weng, Y. & Winstrup, M., 10 Jan 2014, In: The Cryosphere Discussions. 8, p. 1275-1287

    Research output: Contribution to journalJournal articlepeer-review

  2. Published

    Ice core evidence for a 20th century increase in surface mass balance in coastal Dronning Maud Land, East Antarctica

    Philippe, M., Tison, J., Fjosne, K., Hubbard, B., Kjær, Helle Astrid, Lenaerts, J. T. M., Drews, R., Sheldon, S. G., De Bondt, K., Claeys, P. & Pattyn, F., 2016, In: Cryosphere. 10, 5, p. 2501-2516 16 p.

    Research output: Contribution to journalJournal articlepeer-review

  3. 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

  4. 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

  5. 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

  6. Published

    Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene

    Schupbach, S., Fischer, H., Bigler, M., Erhardt, T., Gfeller, G., Leuenberger, D., Mini, O., Mulvaney, R., Abram, N. J., Fleet, L., Frey, M. M., Thomas, E., Svensson, A., Dahl-Jensen, D., Kettner, E., Kjaer, H., Seierstad, I., Steffensen, J. P., Rasmussen, S. O., Vallelonga, P. & 30 others, Winstrup, M., Wegner, A., Twarloh, B., Wolff, K., Schmidt, K., Goto-Azuma, K., Kuramoto, T., Hirabayashi, M., Uetake, J., Zheng, J., Bourgeois, J., Fisher, D., Zhiheng, D., Xiao, C., Legrand, M., Spolaor, A., Gabrieli, J., Barbante, C., Kang, J. -., Hur, S. D., Hong, S. B., Hwang, H. J., Hong, S., Hansson, M., Iizuka, Y., Oyabu, I., Muscheler, R., Adolphi, F., Maselli, O. & McConnell, J., 16 Apr 2018, In: Nature Communications. 9, 1476.

    Research output: Contribution to journalJournal articlepeer-review

  7. Published

    Greenland ice cores constrain glacial atmospheric fluxes of phosphorus

    Kjær, Helle Astrid, Dallmayr, R., Gabrieli, J., Goto-Azuma, K., Hirabayashi, M., Svensson, Anders & Vallelonga, P. T., 29 Oct 2015, In: Journal of Geophysical Research: Biogeosciences. 120, 20

    Research output: Contribution to journalJournal articlepeer-review

  8. Published

    Greenland 2012 melt event effects on CryoSat-2 radar altimetry

    Nilsson, J., Vallelonga, P., Simonsen, S. B., Sorensen, L. S., Forsberg, R., Dahl-Jensen, Dorthe, Hirabayashi, M., Goto-Azuma, K., Hvidberg, Christine Schøtt, Kjær, Helle Astrid & Satow, K., 28 May 2015, In: Geophysical Research Letters (Online). 42, 10, p. 3919-3926

    Research output: Contribution to journalJournal articlepeer-review

  9. 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

  10. Published

    Five thousand years of fire history in the high North Atlantic region: natural variability and ancient human forcing

    Segato, D., Villoslada Hidalgo, M. D. C., Edwards, R., Barbaro, E., Vallelonga, P., Kjær, Helle Astrid, Simonsen, M., Vinther, Bo Møllesøe, Maffezzoli, N., Zangrando, R., Turetta, C., Battistel, D., Vesteinsson, O., Barbante, C. & Spolaor, A., 20 Jul 2021, In: Climate of the Past. 17, 4, p. 1533-1545 13 p.

    Research output: Contribution to journalJournal articlepeer-review

  11. 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

  12. 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

  13. Published

    Editorial: Impure Snow and Ice in Remote Areas: Arctic, Antarctica and High Mountains

    Ming, J., Lee, K., Wang, F., Zhang, T. & Kjær, Helle Astrid, 20 Jan 2022, In: Frontiers in Earth Science. 9, 2 p., 780068.

    Research output: Contribution to journalEditorialpeer-review

  14. Published

    East Greenland ice core dust record reveals timing of Greenland ice sheet advance and retreat.

    Simonsen, M. F., Baccolo, G., Blunier, Thomas, Borunda, A., Delmonte, B., Frei, Robert, Goldstein, S., Grinsted, Aslak, Kjær, Helle Astrid, Sowers, T., Svensson, Anders, Vinther, Bo Møllesøe, Vladimirova, D., Winckler, G., Winstrup, M. & Vallelonga, P., 3 Oct 2019, In: Nature Communications. 10, 8 p., 4494.

    Research output: Contribution to journalJournal articlepeer-review

  15. Published

    Duration of Greenland Stadial 22 and ice-gas Δage from counting of annual layers in Greenland NGRIP ice core

    Vallelonga, P. T., Bertagna, G., Blunier, Thomas, Kjær, Helle Astrid, Popp, T. J., Rasmussen, Sune Olander, Steffensen, Jørgen Peder, Stowasser, C., Svensson, Anders, Warming, E., Winstrup, M., Bigler, M. & Kipfstuhl, S., 20 Nov 2012, In: Climate of the Past. 8, 6, p. 1839-1847 8 p.

    Research output: Contribution to journalJournal articlepeer-review

  16. 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

  17. 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

  18. 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

  19. 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

  20. Published

    Constraining Glacial input of phosphorus to the oceans based on Greenland ice core evidence

    Kjær, Helle Astrid, Gotto-Azuma, K., Dallmayr, R., Hirabayashi, M., Vallelonga, P. T. & Svensson, Anders, 27 Apr 2014, European Geosciences Union General Assembly 2014, 16, 27 April – 02 May 2014. European Geosciences Union ed. Vienna, Austria, 1524

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

  21. 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

  22. 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

  23. Published

    Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period

    Svensson, A., Dahl-Jensen, D., Steffensen, J. P., Blunier, T., Rasmussen, S. O., Vinther, B. M., Vallelonga, P. T., Capron, E., Gkinis, V., Cook, E., Kjær, H. A., Muscheler, R., Kipfstuhl, S., Wilhelms, F., Stocker, T. F., Fischer, H., Adolphi, F., Erhardt, T., Sigl, M., Landais, A. & 6 others, Parrenin, F., Buizert, C., McConnell, J. R., Severi, M., Mulvaney, R. & Bigler, M., 19 Aug 2020, In: Climate of the Past. 16, p. 1565-1580 15 p.

    Research output: Contribution to journalJournal articlepeer-review

  24. 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

  25. Published

    Assessing surface-exposed old ice along the Greenland Ice Sheet margin as an analogue for the Northern Polar Layered Deposits on Mars

    Yoldi, Zuriñe, Hvidberg, Christine Schøtt, Svensson, Anders, Vallelonga, P. T. & Kjær, Helle Astrid, 8 Oct 2020, 3 p. Göttingen, Germany : Europlanet Science Congress.

    Research output: Other contributionResearch

ID: 33355865