Helle Astrid Kjær

Helle Astrid Kjær

Associate Professor


  1. 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 articlepeer-review

  2. Published

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

    Winstrup, M., Vallelonga, P., Kjaer, H. A., Fudge, T. J., Lee, J. E., Riis, M. H., Edwards, R., Bertler, N. A. N., Blunier, T., Brook, E. J., Buizert, C., Ciobanu, G., Conway, H., Dahl-Jensen, D., Ellis, A., Emanuelsson, B. D., Hindmarsh, R. C. A., Keller, E. D., Kurbatov, A. V., Mayewski, P. A. & 7 others, 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 articlepeer-review

  3. 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

  4. 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 articlepeer-review

  5. 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 articlepeer-review

  6. 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

  7. Published

    A portable Lightweight In Situ Analysis (LISA) box for ice and snow analysis

    Kjær, Helle Astrid, Hauge, L. L., Simonsen, M., Yoldi, Zuriñe, Koldtoft, Iben, Hörholdt, M., Freitag, J., Kipfstuhl, S., Svensson, Anders & Vallelonga, P., 2 Mar 2021, In: The Cryosphere Discussions. 19 p.

    Research output: Contribution to journalJournal articlepeer-review

  8. 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

  9. 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

  10. 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 articlepeer-review

  11. Published

    An Age Scale for the First Shallow (Sub-)Antarctic Ice Core from Young Island, Northwest Ross Sea

    Moser, D. E., Jackson, S., Kjær, Helle Astrid, Markle, B., Ngoumtsa, E., Pedro, J. B., Segato, D., Spolaor, A., Tetzner, D., Vallelonga, P. & Thomas, E. R., Sep 2021, In: Geosciences. 11, 9, 18 p., 368.

    Research output: Contribution to journalJournal articlepeer-review

  12. 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

  13. Published

    Antarctic evidence for an abrupt northward shift of the Southern Hemisphere westerlies at 32 ka BP

    Venugopal, A. U., Bertler, N. A. N., Severinghaus, J. P., Brook, E. J., Cortese, G., Lee, J. E., Blunier, Thomas, Mayewski, P. A., Kjær, Helle Astrid, Carter, L., Weber, M. E., Levy, R. H., Pyne, R. L. & Vandergoes, M. J., 5 Sep 2023, In: Nature Communications. 14, 1, 8 p., 5432.

    Research output: Contribution to journalJournal articlepeer-review

  14. Published

    Arctic mercury flux increased through the Last Glacial Termination with a warming climate

    Segato, D., Saiz-Lopez, A., Mahajan, A. S., Wang, F., Corella, J. P., Cuevas, C. A., Erhardt, T., Jensen, C. M., Zeppenfeld, C., Kjær, Helle Astrid, Turetta, C., Cairns, W. R. L., Barbante, C. & Spolaor, A., 4 May 2023, In: Nature Geoscience. 16, p. 439-445 9 p.

    Research output: Contribution to journalJournal articlepeer-review

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  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

    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

  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

    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

  24. 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

  25. 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

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