Helle Astrid Kjær

Helle Astrid Kjær

Assistant professor


  1. Published

    A 2700-year annual timescale and accumulation history for an ice core from Roosevelt Island, West Antarctica

    Winstrup, M., Vallelonga, P., Kjær, Helle Astrid, Fudge, T. J., Lee, J. E., Riis, M. H., Edwards, R., Bertler, N. A. N., Blunier, Thomas, Brook, E. J., Buizert, C., Ciobanu, G., Conway, H., Dahl-Jensen, Dorthe, Ellis, A., Emanuelsson, B. D., Hindmarsh, R. C. A., Keller, E. D., Kurbatov, A. V., Mayewski, P. A., Neff, P. D., Pyne, R. L., Simonsen, M. F., Svensson, Anders, Tuohy, A., Waddington, E. D. & Wheatley, S., 10 Apr 2019, In : Climate of the Past. 15, 2, p. 751-779 29 p.

    Research output: Contribution to journalJournal articleResearchpeer-review

  2. 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 articleResearchpeer-review

  3. 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, Dorthe, Gkinis, Vasileios, Holme, C. T., Jacobel, R. W., Karlsson, N. B., Keisling, B. A., Kipfstuhl, S., Kjær, Helle Astrid, Kristensen, M. E., Muto, A., Peters, L. E., Popp, T. J., Riverman, K. L., Svensson, Anders, Tibuleac, C., Vinther, Bo Møllesøe, Weng, Y. & Winstrup, M., 10 Jan 2014, In : The Cryosphere Discussions. 8, p. 1275-1287

    Research output: Contribution to journalJournal articleResearchpeer-review

  4. Published

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

    Svensson, Anders, Dahl-Jensen, Dorthe, Steffensen, Jørgen Peder, Blunier, Thomas, Rasmussen, Sune Olander, Vinther, Bo Møllesøe, Vallelonga, P. T., Capron, E., Gkinis, Vasileios, Cook, Eliza, Kjær, Helle Astrid, Muscheler, R., Kipfstuhl, S., Wilhelms, F., Stocker, T. F., Fischer, H., Adolphi, F., Erhardt, T., Sigl, M., Landais, A., 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 articleResearchpeer-review

  5. Published

    Afslørende kemi i Grønlands og Antarktis' iskerner

    Svensson, Anders & Kjær, Helle Astrid, 1 Jun 2018, In : Dansk Kemi. 9, p. 18-21 3 p.

    Research output: Contribution to journalJournal articleResearchpeer-review

  6. Published

    On the occurrence of annual layers in Dome Fuji ice core early Holocene ice

    Svensson, Anders, Fujita, S., Bigler, M., Braun, M., Dallmayr, R., Gkinis, Vasileios, Goto-Azuma, K., Hirabayashi, M., Kawamura, K., Kipfstuhl, S., Kjær, Helle Astrid, Popp, T., Simonsen, M., Steffensen, Jørgen Peder, Vallelonga, P. & Vinther, Bo Møllesøe, 2015, In : Climate of the Past. 11, 9, p. 1127-1137

    Research output: Contribution to journalJournal articleResearchpeer-review

  7. Published

    Seasonality of halogen deposition in polar snow and ice

    Spolaor, A., Vallelonga, P., Gabrieli, J., Martma, T., Bjorkman, M. P., Isaksson, E., Cozzi, G., Turetta, C., Kjær, Helle Astrid, Curran, M. A. J., Moy, A. D., Schoenhardt, A., Blechschmidt, A. -., Burrows, J. P., Plane, J. M. C. & Barbante, C., 10 Jan 2014, In : Atmospheric Chemistry and Physics. 14, 18, p. 9613-9622

    Research output: Contribution to journalJournal articleResearchpeer-review

  8. Published

    Particle shape accounts for instrumental discrepancy in ice core dust size distributions

    Simonsen, M. F., Cremonesi, L., Baccolo, G., Bosch, S., Delmonte, B., Erhardt, T., Kjær, Helle Astrid, Potenza, M., Svensson, Anders & Vallelonga, P., 3 May 2018, In : Climate of the Past. 14, 5, p. 601-608

    Research output: Contribution to journalJournal articleResearchpeer-review

  9. 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, R., Goldstein, S., Grinsted, Aslak, Kjær, Helle Astrid, Sowers, T. A., Svensson, Anders, Vinther, Bo Møllesøe, Vladimirova, D., Winckler, G., Winstrup, M. & Vallelonga, P. T., 3 Oct 2019, In : Nature Communications. 10, 8 p., 4494.

    Research output: Contribution to journalJournal articleResearchpeer-review

  10. 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, Anders, Dahl-Jensen, Dorthe, Kettner, E., Kjær, Helle Astrid, Seierstad, I., Steffensen, Jørgen Peder, Rasmussen, Sune Olander, Vallelonga, P., 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 articleResearchpeer-review

  11. Published

    Rapid reductions and millennial-scale variability in Nordic Seas sea ice cover during abrupt glacial climate changes

    Sadatzki, H., Maffezzoli, N., Dokken, T. M., Simon, M. H., Berben, S. M. P., Fahl, K., Kjær, Helle Astrid, Spolaor, A., Stein, R., Vallelonga, P., Vinther, Bo Møllesøe & Jansen, E., 24 Nov 2020, In : Proceedings of the National Academy of Sciences of the United States of America. 117, 47, p. 29478-29486 9 p.

    Research output: Contribution to journalJournal articleResearchpeer-review

  12. Published

    A novel approach to process brittle ice for continuous flow analysis of stable water isotopes

    Pyne, R. L., Keller, E. D., Canessa, S., Bertler, N. A., Pyne, A. R., Pyne, A. R., Mandeno, D., Vallelonga, P. T., Semper, S., Kjær, Helle Astrid, Hutchison, E. & Baisden, W. T., 16 Mar 2018, In : Journal of Glaciology. 64, 243, p. 1-11

    Research output: Contribution to journalJournal articleResearchpeer-review

  13. 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 articleResearchpeer-review

  14. 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 articleResearchpeer-review

  15. Published

    A first chronology for the East Greenland Ice-core Project (EGRIP) over the Holocene and last glacial termination

    Mojtabavi, S., Wilhelms, F., Cook, Eliza, Siwan M., D., Sinnl, Giulia, Skov Jensen, M., Dahl-Jensen, Dorthe, Svensson, Anders, Vinther, Bo Møllesøe, Kipfstuhl, S., Gwydion, J., Karlsson, N. B., Henrique Faria, S., Gkinis, Vasileios, Kjær, Helle Astrid, Erhardt, T., Berben, S. M. P., Nisancioglu, K. H., Koldtoft, Iben & Rasmussen, Sune Olander, 27 Sep 2020, In : Climate of the Past. 16, 6, p. 2359-2380 21 p.

    Research output: Contribution to journalJournal articleResearchpeer-review

  16. Published

    A 120 000-year record of sea ice in the North Atlantic?

    Maffezzoli, N., Vallelonga, P., Edwards, R., Saiz-Lopez, A., Turetta, C., Kjær, Helle Astrid, Barbante, C., Vinther, Bo Møllesøe & Spolaor, A., 19 Dec 2019, In : Climate of the Past. 15, 6, p. 2031-2051

    Research output: Contribution to journalJournal articleResearchpeer-review

  17. 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

  18. Published

    Laboratory supervision of MSc projects -Qualitative interviews, thematic analysis, and recommendations for the supervisor

    Kjær, Helle Astrid, 23 May 2018, Improving University Science Teaching and Learning Pedagogical Projects 2018. Institut for Naturfagenes Didaktik ed. København, Danmark: Københavns Universitet, Vol. 12. p. 91-105 (Improving University Science Teaching and Learning - Pedagogical Projects).

    Research output: Chapter in Book/Report/Conference proceedingBook chapterEducation

  19. Published

    Iskerner-et indblik i fortidens klimaforandringer

    Kjær, Helle Astrid & Balslev-Clausen, D., 2 Apr 2011, Aspekter af dansk kemi i det 20. og 21. århundrede. 1 ed. København: Kemi Forlaget, p. 65-70 5 p.

    Research output: Chapter in Book/Report/Conference proceedingBook chapterCommunication

  20. 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: Earth Surface. 120, 20

    Research output: Contribution to journalJournal articleResearchpeer-review

  21. Published

    A novel method for the detection of acidity in ice cores

    Kjær, Helle Astrid, 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, 1526

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

  22. 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

  23. 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

  24. 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 articleResearchpeer-review

  25. 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 articleResearchpeer-review

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