Eem warm period

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Average July temperatures in the Eem warm period
Average January temperatures in the Eem warm period
Average annual precipitation in the Eem warm period

The Eem warm period (synonym Eem interglacial ), often referred to as Eem for short , was the last warm period before the current one, the Holocene . It began about 126,000 years ago, ended 115,000 years ago and is named after the river Eem in the Netherlands .

The Eem warm period is also known as the Riss / Würm interglacial in the Alpine region , as it represents the warm period between the Riss and Würm glaciers . It corresponds to the Ipswichian Stage on the British Isles , the Mikulin Interglacial in the Eastern European Plain , the Sangamonian Stage in North America and the Valdivia Interglacial in Chile , although the exact dates differ in the individual regions. In the international classification of the Pleistocene , which is based on the separation of oxygen isotope levels , the Eem is classified in level 5 and there as the fifth sub-level e .

Research history on the Eem warm period

Bittium reticulatum ,viewedby Pieter Harting as a key fossil for the Eem warm period, drawn by himself (published 1886)

The Eem warm period was recognized as an independent stratigraphic unit in 1874 after Pieter Harting unearthed fossil-rich material while drilling in the area of Amersfoort ( Netherlands ) , the species composition of which was far from that of the present-day North Sea . Many very similar species of snails and clams have been found in the Atlantic south of the Dover Strait . Their distribution area extends today from the coasts of Portugal ( Lusitan Faunal Province ) to the Mediterranean ( Mediterranean Faunal Province ). For Harting, this was an indication that at the time when the sediments with the fossils were deposited, the temperatures must have been much higher than today at this latitude. Harting named the deposits "Système Eémien" after the river Eem near Amersfoort.

The composition of the Dutch mollusc fauna from the Eem warm period was later investigated. Guide fossils were established, with the help of which stratigraphic layers of the same age could be identified. It turned out that the layers of the Eem warm period are often deposited on the ground moraines of the Saale Ice Age and that local river gravel or aeolian deposits from the Vistula Ice Age can be found above them . This suggests a warm period between these two cold periods. In the Netherlands, however, the Eem warm period deposits are never overlaid by ground moraines from the Vistula Ice Age.

Van Voorthuysen published a paper on the foraminifera of the type locality in 1958 and Zagwijn a few years later the palynology with the pollen zones . At the end of the twentieth century, the type locality was examined again, this time in a multidisciplinary manner, using old and new data. At the same time a parastratotype was named, this is in the glacial basin of Amsterdam . In the course of drilling the Amsterdam Terminal , this type was described in an interdisciplinary manner. The authors also published a uranium-thorium dating of the late interglacial deposits from this borehole with an age of 118,200 years (± 6300 years).

Bosch, Cleveringa and Meijer gave a historical overview of the Dutch Eem studies in 2000.

Duration and climate development

Fossil coral reef from the Eem - Great Inagua, Bahamas.

The Eem warm period lasted about 11,000 years. It began about 126,000 years ago, after the Saale Glacial or Riss Ice Age, and ended about 115,000 years ago with the beginning of the last glacial period . The Eem warm period was characterized by relatively stable climatic conditions. The temperature at the optimum of the warm period in Europe was several degrees above the pre-industrial mean temperature (up to around 1850). One of the consequences of this was that the sea level was higher than it is now and many plains and basins were flooded ( transgression ).

The beginning of the Eem warm period coincides with the beginning of the Young Pleistocene . This includes the Eem warm period and the last cold period . Then, with the Holocene, began the warm period in which we live today. As a characteristic point for the beginning of the Eem warm period, the change in the ratio of the oxygen isotopes around 126,000 years ago is given on the geological time scale . This change can be seen in the shells of microorganisms in marine debris from this period.

With the help of palynological investigations of drill cores from Eifel maars it was possible to show that a dry phase of 468 years occurred during the transition between the Eem warm period and the last cold period . Forest fires and dust storms affected the forests in the Eifel and left their mark on the sediments . Possibly due to changes in the ocean currents, there was a lack of precipitation. Fresh water was bound in the ice of the advancing glaciers. The drought came abruptly, and within 100 years the predominant forests had to give way to a steppe. After that, the trees in the Eifel apparently returned, while the conditions further north were colder. In the Eifel, the mixed forests were able to hold out for around 8,000 years until the next cold pulse of the ice age climatic fluctuations only allowed tundra vegetation . However, this mixed forest period no longer belongs to the Eem warm period in the narrower sense.

Climate fluctuations during the Eem warm period - findings from ice cores

Climate research has gained a lot of knowledge about the climate of the past in recent years. The Summit ice core (72 ° 34 'N, 37 ° 37' W), which was taken by the European Ice Core Project ( GRIP ) between 1990 and 1992 , and the NGRIP (North Greenland Ice Core Project) in Ice core drilled between 1996 and 2003.

Among other things, the oxygen isotope ratio 18 O / 16 O was investigated in both drill cores , which is mainly determined by the cloud temperature at the time of snow formation and can thus provide direct information about the temperature.

Determining the time scales is extremely difficult. For the Summit ice core, after a comparison with other climate proxies (ice cores, sediment cores, etc.), this has been considered to be sufficiently precise, at least for the last 130,000 years before today, mainly due to the fact that the ice sheet is folding and flowing in the area of ​​the Summit Station was largely excluded.

The fluctuations in the oxygen-isotope ratio in this ice core indicated that climatic fluctuations ( Dansgaard-Oeschger events , Heinrich events ) were not limited to the last ice age, but also run through the profile before this glacial (Eem warm period , Saale Ice Age). This is in contrast to the relatively high climatic stability of the current warm period ( Holocene , since about 11,700 cal BP ). It has therefore been suggested that the stability of the current warm period is the exception rather than the rule.

The violent oscillations in the Summit ice core during the Eem warm period could not be found either in the Vostok ice core (Antarctica) or in sediment cores of the deep sea. It was therefore initially assumed that the Greenland ice reflects short-term fluctuations in the atmospheric and ocean circulation of the North Atlantic region.

It soon became clear, however, that the bottom 10 percent of the ice core was exposed to various processes of change. The chronology of the Eem warm period was significantly disturbed, which is why the NGRIP ice core was used for comparison. Previously, in order to get a clearer picture of the Eem warm period, the bottom end of the drill core had been made sure that there were no impairments or fault patterns.

The evaluation of the proxy data confirmed that the climatic conditions during the Eem warm period were consistently stable. The summer temperatures in the northern hemisphere were about two degrees above the pre-industrial temperature level, in Greenland it was even 5 ° C warmer. More recent work indicates that it was only a few tenths of a degree warmer globally than today (2013). In comparison with other ice cores in the north-west (Camp Century, 77.2 ° N, 61.1 ° W) and south-east (Renland, 71.3 ° N, 26.7 ° W) of Greenland, it has been shown that only part of the South Greenland ice sheet melted during the entire warm period, the central and north Greenland ice sheet, on the other hand, remained stable despite higher temperatures.

Most current studies assume that the sea level in the Eem was about 6 to 9 meters above the current level. According to corresponding calculations, the Greenland Ice Sheet accounted for a proportion of meltwater with an approximate mean value in the range of 1.5 to 2.5 meters, the rest of the increase was distributed between the thermal expansion of seawater and the melting of mountain glaciers (∼1 m) as well as in larger extent to the substantial reduction of the West Antarctic ice cover. According to this, the Greenland Ice Sheet lost 20 to 30 percent of its mass during this period. These findings are of great importance when extrapolating the expected future sea ​​level rise .

The NGRIP ice core also revealed that the cold period following the Eem warm period began only gradually (with a transition period of around 7,000 years) and that a relatively weak Dansgaard-Oeschger event (DO 25) took place before the change to a glacial climate (with an amplitude of 25 percent of the subsequent DO events), which, however, was very similar in its course to the following events.

Eem warm period archeology

The Eem is the time of the Middle Paleolithic, during which time Neanderthals settled large parts of Europe and Western Asia. Outstanding findings are hunted forest elephants (see Lance von Lehringen or Gröbern open-cast mine ) as evidence of a successful big game hunt.

Web links

literature

  • P. Harting: De bodem van het Eemdal. Verslag Koninklijke Akademie van Wetenschappen, Afdeling N, II, Deel VIII, 1874, pp. 282–290.
  • P. Harting: Le système Éemien. In: Archives Néerlandaises Sciences Exactes et Naturelles de la Societé Hollandaise des Sciences (Harlem). 10, 1875, pp. 443-454.
  • P. Harting: Het Eemdal en het Eemstelsel In: Album der Natuur. 1886, pp. 95-100.
  • H. Müller: Pollen analysis and annual shift counts on the Eemzeit diatomaceous earth from Bispingen / Luhe. In: Geological Yearbook. A 21, Hanover 1974, pp. 149-169.
  • Greenland Ice-core Project Members: Climate instability during the last interglacial period recorded in the GRIP ice core. In: Nature. Volume 364, 1993, pp. 203-207.
  • Dansgaard et al: Evidence for general instability of past climate from a 250-kyr ice-core record. In: Nature. Volume 364, 1993, pp. 218-220, nature.com .
  • SJ Johnsen et al: The Eem Stable Isotope Record along the GRIP Ice Core and Its Interpretation. In: Quaternary Research. Vol 43, 1995, pp. 117-124, doi: 10.1006 / qres.1995.1013 .
  • George J Kukla: The Last Interglacial. In: Science . 287, February 2000, pp. 987-988 doi: 10.1126 / science.287.5455.987 .
  • Kurt M. Cuffey: Substantial contribution to sea-level rise during the last interglacial contribution from the Greenland ice sheet. In: Nature . Volume 404, April 2000, pp. 591-594, doi: 10.1038 / 35007053 .
  • Charles Turner: Problems of the Duration of the Eemian Interglacial in Europe North of the Alps. In: Quaternary Research . 58, 2002, pp. 45-48.
  • NGRIP Members: High-resolution record of the Northern Hemisphere climate extending into the last interglacial period. In: Nature. Volume 431, 2004, pp. 147-151, nature.com .
  • Frank Kaspar, Norbert Kühl, Ulrich Cubasch, Thomas Litt: A model ‐ data comparison of European temperatures in the Eemian interglacial . In: Geophysical Research Letters . tape 32 , no. 11 . American Geophysical Union, June 2005, ISSN  1944-8007 (English, online ).
  • F. Sirocko, K. Seelos, K. Schaber, B. Rein, F. Dreher, M. Diehl, R. Lehne, K. Jäger, M. Krbetschek, D. Degering: A late Eemian aridity pulse in central Europe during the last glacial inception. In: Nature. Volume 436, August 2005, pp. 833-836, doi: 10.1038 / nature03905 .

Individual evidence

  1. ^ J. Lorié: Contributions a la géologie des Pays Bas III. Le Diluvium plus récent ou sableux et le système Eémien. In: Archives Teyler. Ser. II, Vol. III, 1887, pp. 104-160.
  2. ^ G. Spaink: De Nederlandse Eemlagen, I: Algemeen overzicht. (= Wetenschappelijke Mededelingen Koninklijke Nederlandse Natuurhistorische Vereniging. 29). 1958.
  3. ^ JH Van Voorthuysen: Foraminifera from the Eemien (Riss-Würm-Interglacial) in the Amersfoort I borehole (Locus Typicus). In: Mededelingen Geologische Stichting. NS 11, 1957, pp. 27-39.
  4. ^ WH Zagwijn: Vegetation, climate and radiocarbon datings in the Late Pleistocene of the Netherlands. Part 1: Eemian and Early Weichselian. In: Mededelingen Geologische Stichting. NS 14, 1961, pp. 15-45.
  5. ↑ P. Cleveringa, T. Meijer, RJW van Leeuwen, H. de Wolf, R. Pouwer, T. Lissenberg, AW Burger: The Eemian stratotype locality at Amersfoort in the central Netherlands: a re-evaluation of old and new data. In: Geologie & Mijnbouw / Netherlands Journal of Geosciences. 79 (2/3), 2000, pp. 197-216. njgonline.nl ( Memento of the original dated November 10, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 348 kB) @1@ 2Template: Webachiv / IABot / www.njgonline.nl
  6. ↑ RJ Van Leeuwen, D. Beets, JHA Bosch, AW Burger, P. Cleveringa, D. van Harten, GFW Herngreen, CG Langereis, T. Meijer, R. Pouwer, H. de Wolf: Stratigraphy and integrated facies analysis of the Saalian and Eemian sediments in the Amsterdam-Terminal borehole, the Netherlands. In: Geologie en Mijnbouw / Netherlands Journal of Geosciences. 79, 2000, pp. 161-196. njgonline.nl ( Memento of the original dated November 10, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 762 kB) @1@ 2Template: Webachiv / IABot / www.njgonline.nl
  7. ^ JHA Bosch, P. Cleveringa, T. Meijer: The Eemian stage in the Netherlands: history, character and new research. In: Geologie & Mijnbouw / Netherlands Journal of Geosciences. 79 (2/3), 2000, pp. 135-145. njgonline.nl ( Memento of the original dated December 22, 2009 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 287 kB) @1@ 2Template: Webachiv / IABot / www.njgonline.nl
  8. ↑ Niklaus Merz, Andreas Born, Christoph C. Raible, Thomas F. Stocker: Warm Greenland during the last interglacial: the role of regional changes in sea ice cover . (PDF) In: Climate of the Past . 12, October 2016, pp. 2011–2031. doi : 10.5194 / cp-12-2011-2016 .
  9. ↑ L. Bazin, A. Landais, B. Lemieux-Dudon, H. Toyè Mahamadou Kele, D. Veres, F. Parrenin, P. Martinerie, C. Ritz, E. Capron, V. Lipenkov, M.-F. Loutre, D. Raynaud, B. Vinther, A. Svensson, SO Rasmussen, M. Severi, T. Blunier, M. Leuenberger, H. Fischer, V. Masson-Delmotte, J. Chappellaz, E. Wolff: An optimized multi -proxy, multi-site Antarctic ice and gas orbital chronology (AICC2012): 120–800 ka . (PDF) In: Climate of the Past . 9, August 2013, pp. 1715-1731. doi : 10.5194 / cp-9-1715-2013 .
  10. ↑ New ice core study: Greenland's ice sheet shrank only minimally during the Eem warm period. Press release. Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, January 23, 2013, accessed on February 16, 2020 .
  11. ^ EJ Stone, PD. J. Lunt, JD Annan, JC Hargreaves: Quantification of the Greenland ice sheet contribution to Last Interglacial sea level rise . (PDF) In: Climate of the Past . 9, March 2013, pp. 621-639. doi : 10.5194 / cp-9-621-2013 .
  12. ↑ Chris SM Turney, Christopher J. Fogwill, Nicholas R. Golledge, Nicholas P. McKay, Erik van Sebille, Richard T. Jones, David Etheridge, Mauro Rubino, David P. Thornton, Siwan M. Davies, Christopher Bronk Ramsey, Zoë A. Thomas, Michael I. Bird, Niels C. Munksgaard, Mika Kohno, John Woodward, Kate Winter, Laura S. Weyrich, Camilla M. Rootes, Helen Millman, Paul G. Albert, Andres Rivera, Tas van Ommen, Mark Curran , Andrew Moy, Stefan Rahmstorf, Kenji Kawamura, Claus-Dieter Hillenbrand, Michael E. Weber, Christina J. Manning, Jennifer Young, Alan Cooper: Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica . In: PNAS . February 2020. doi : 10.1073 / pnas.1902469117 .
  13. ^ A. Dutton, K. Lambeck: Ice Volume and Sea Level During the Last Interglacial . (PDF) In: Science . 337, No. 6091, July 2012, pp. 216-219. doi : 10.1126 / science.1205749 .
  14. ↑ Michael J. O'Leary, Paul J. Hearty, William G. Thompson, Maureen E. Raymo, Jerry X. Mitrovica, Jody M. Webster: Ice sheet collapse following a prolonged period of stable sea level during the last interglacial . (PDF) In: Nature Geoscience . 6, July 2013, pp. 796-800. doi : 10.1038 / ngeo1890 .