Willi Dansgaard

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Willi Dansgaard (born August 30, 1922 in Copenhagen ; † January 8, 2011 there ) was a Danish paleoclimatologist . Until his retirement in 1992 he was Professor of Geophysics at the University of Copenhagen . He made significant contributions to the application of isotope studies in climate research, especially the reconstruction of past climate changes , and is considered by many to be one of the founders of modern climate research using ice cores .

Dansgaard was a member of the Royal Danish Academy of Sciences , the Royal Swedish Academy of Sciences , the Icelandic Academy of Sciences, the Danish Society for Geophysics and the Academia Europaea .

Studies and Meteorological Institute

Dansgaard grew up in Vesterbro in the center of Copenhagen, where his parents had an engraving business. In 1947 he finished his studies in physics, mathematics and astronomy at the University of Copenhagen . He was awarded a gold medal for his thesis at the university's biophysical laboratory on the measurement of X-rays .

In the years 1947–1951 he worked at the Danish Meteorological Institute on geomagnetism and meteorology . As part of this work he spent 1947-1948 a year at the geomagnetic observatory in Qeqertarsuaq , East Greenland. The year made a deep impression on him, Greenland should not let go of him.

Isotope studies on precipitation

In 1951 Dansgaard went back to the biophysical laboratory, where he was henceforth responsible for setting up and operating the mass spectrometry . He developed a mass spectrometer for the isotope analysis of water. In June 1952 he succeeded in discovering a connection between the isotopic composition of rainwater and temperatures in rain clouds. It shaped his further career and was the foundation stone for one of his decisive scientific contributions - the "perhaps only good idea that I ever had", as he wrote: from the conditions of stable isotopes in rainwater, including layers of snow and ice (where it concerns past precipitation) to draw conclusions about past climatic conditions (→ climatic proxy ).

Linear relationship between the annual mean values ​​of δ 18 O and temperature at different locations, according to data from Dansgaard

Over the next twelve years, Dansgaard had water samples sent from many parts of the world. He also undertook research trips to Greenland himself in order to obtain further samples from snow and icebergs: In 1958 he took part in a Greenland expedition of the Arctic Institute of North America , in the same year he drove four months along the west coast of Greenland with Norwegian researchers. The analysis of these samples was the subject of his doctoral thesis , which he completed in 1961 at the University of Copenhagen, and his 1964 published article Stable isotopes in precipitation , which was described as a milestone in geophysics .

In 1961, the American geochemist Harmon Craig reported a linear relationship between the isotope ratios δ 18 O and δD in precipitation, the meteoric water line . Dansgaard defined the Y-axis intercept as the deuterium excess and examined its dependence on geographical parameters such as latitude, altitude, distance from the coast and amount of precipitation. He was the first to notice the excess deuterium in glacier ice compared to the typical 18 O- 2 H ratio in the world's oceans (→ SMOW ). For δ 18 O Dansgaard gave a linear relationship with temperature that is valid for the North Atlantic region. He found that the differences in the relationship between deuterium and common hydrogen are due to the temperature of the water and the global average humidity .

Ice core research

In 1964, Dansgaard was at Camp Century , Northeast Greenland, in the United States , and learned of a program by the US Cold Regions Research and Engineering Laboratory (CRREL), the aim of which was to pierce the Greenland ice sheet (→ Project Iceworm ). He started in 1967, in cooperation a. a. with the American glaciologist Chester Langway and the Swiss climate researcher Hans Oeschger to systematically investigate the stable isotopes of the ice core . The isotope investigation of the Antarctic Byrd ice core was added later. The ice turned out to be a climate archive that stores earlier oxygen isotope ratios δ 18 O. Dansgaard and his team found δ 18 O fluctuations, which indicated abrupt, large climate changes over the course of the last glacial . However, the significance of these events was not yet recognized at the time.

In 1972 Dansgaard became head of the Geophysical Isotope Laboratory at the University of Copenhagen. The facility, managed by Dansgaard, has grown to become a world leader in ice core mining and research. In the following years, the drilling technology developed there, in addition to the projects up to 1992 with Dansgaard's participation, later also enabled the important European ice core projects EPICA and NGRIP. This laid the foundation for the reconstruction of the composition of the atmosphere, the fluctuations in temperature and precipitation and a better understanding of the climate up to the middle Pleistocene around 1 million years ago.

The extraction of the Dye-3 ice core in southern Greenland, which was initiated by Dansgaard in 1979–1981, was the first ice core project carried out for climate science reasons. The results of the project were dealt with in more than 80 publications, with which ice core research achieved the breakthrough to worldwide scientific attention. Abrupt fluctuations lasting several hundred years were particularly noticeable ; they resembled the fluctuations in the ice from the Camp Century borehole , which had not been taken into account until then . Hans Oeschger also found a correlation in Swiss lake sediments . These climatic fluctuations of the past 100,000 years, which were mainly visible in the North Atlantic area, became known as the Dansgaard-Oeschger events .

From 1989 until his retirement in 1992, Dansgaard drove further ice core projects, including the European Greenland Ice Core Project (GRIP), which was carried out at the highest point of the ice sheet and allowed a look back 105,000 years, almost to the Eem warm period .

Honors

Publications (selection)

  • Niels Bohr Institute , University of Copenhagen (Ed.): Frozen Annals, Greenland Ice Sheet Research . 2005 ( ku.dk [PDF; 6.8 MB ] autobiographical book on the exploration of the Greenland ice sheet and ice core research).
  • with SJ Johnsen, HB Clausen, D. Dahl-Jensen, NS Gundestrup, CU Hammer, CS Hvidberg, JP Steffensen, AE Sveinbjörnsdottir, J. Jouzel, G. Bond : Evidence for general instability of past climate from a 250-kyr ice- core record . In: Nature . July 1993, doi : 10.1038 / 364218a0 .
  • with SJ Johnsen, HB Clausen, D. Dahl-Jensen, N. Gundestrup, CU Hammer, H. Oeschger: North Atlantic climatic oscillations revealed by deep Greenland ice cores . In: James E. Hansen , Taro Takahashi (Ed.): Climate Processes . 1984, doi : 10.1029 / GM029p0288 .
  • with HB Clausen, N. Gundestrup, CU Hammer, SF Johnsen, PM Kristinsdottir, N. Reeh: A new Greenland deep ice core . In: Science . December 1982, doi : 10.1126 / science.218.4579.1273 (on the ice core project at the Dye-3 station, describes abrupt climatic fluctuations that became known as the Dansgaard-Oeschger events).
  • with SJ Johnsen, N. Reeh, N. Gundestrup, HB Clausen, CU Hammer: Climatic changes, Norsemen and modern man . In: Nature . May 1975, doi : 10.1038 / 255024a0 .
  • with SJ Johnsen, HB Clausen, CC Langway: Climatic record revealed by the Camp Century ice core . In: K. Turekian, Richard Foster Flint (Eds.): The Late Cenozoic Glacial Ages . Yale University Press, 1971 (results of his research on Camp Century ice core).
  • Stable isotopes in precipitation . In: Tellus . November 1964, doi : 10.1111 / j.2153-3490.1964.tb00181.x .
  • University of Copenhagen (Ed.): The isotopic composition of natural waters: with special reference to the Greenland Ice Cap . 1961, OCLC 313298583 (Dansgaard's dissertation).
  • The O 18 abundance in fresh water . In: Geochimica et Cosmochimica Acta . December 1954, doi : 10.1016 / 0016-7037 (54) 90003-4 (already contains the idea of extracting the isotopic composition of past precipitation from glacier ice and thus information about past climatic conditions).
  • The Abundance of O 18 in Atmospheric Water and Water Vapor . In: Tellus . November 1953, doi : 10.1111 / j.2153-3490.1953.tb01076.x .

Web links

Individual evidence

  1. ↑ a b c d En stor pionér i klimaforskning er gået bort. Center for Is og Klima, Nils Bohr Institute, January 10, 2011, accessed on January 29, 2019 .
  2. ↑ a b c d e f Jørgen Peder Steffensen: Obituaries - Willi Dansgaard . In: Polar Record . 2012, doi : 10.1017 / S0032247411000155 .
  3. ↑ Frozen Annals (2005), p. 11.
  4. ↑ a b c Douglas Martin: Willi Dansgaard Dies at 88; Read climates in old ice. In: nytimes.com. January 28, 2011, accessed January 29, 2019 .
  5. ↑ Frozen Annals (2005), p. 16.
  6. ^ A b Wallace Broecker: The Great Ocean Conveyor: Discovering the Trigger for Abrupt Climate Change . Princeton University Press, 2010, ISBN 978-1-4008-3471-6 , pp. 20-34 .
  7. ↑ sketched after Broecker: The Great Ocean Conveyor: Discovering the Trigger for Abrupt Climate Change (2010), p. 20, Fig. 2-1.
  8. ^ Ian D. Clark, Peter Fritz: Environmental Isotopes in Hydrogeology . CRC Press, 2013, ISBN 978-1-4822-4291-1 , pp. 45 ( limited preview in Google Book search).
  9. ↑ Peter Fritz (Ed.): Handbook of Environmental Isotope Geochemistry: A The Terrestrial Environment . Elsevier, 2016, ISBN 978-1-4832-8961-8 , pp. 30-32 .
  10. ↑ Aant Elzinga: Some Aspects in the History of Ice Core Drilling and Science from IGY to EPICA . In: Byrd Polar Research Center, Ohio State University (Ed.): National and Trans-National Agendas in Antarctic Research from the 1950s and Beyond - Proceedings of the 3rd Workshop of the SCAR Action Group on the History of Antarctic Research (=  BPRC Technical Report . no. 2011-01 ). 2011.
  11. ^ Chester C. Langway: Willi Dansgaard (1922-2011) . In: Arctic . September 2011, doi : 10.14430 / arctic4135 .
  12. ↑ Spencer Wheart: The Discovery of Global Warming. February 2017, accessed January 30, 2019 .
  13. ^ Jean Jouzel : A brief history of ice core science over the last 50 yr . In: Climate of the Past . November 2013, doi : 10.5194 / cp-9-2525-2013 .
personal data
SURNAME Dansgaard, Willi
BRIEF DESCRIPTION Danish paleoclimatologist
DATE OF BIRTH August 30, 1922
PLACE OF BIRTH Copenhagen
DATE OF DEATH January 8, 2011
Place of death Copenhagen