Gerzensee fluctuation

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The Gerzensee fluctuation was a striking, deadly period of cooling . It took place between 11200 and 10950 BC. Chr. Instead.

Etymology and history

The Gerzensee fluctuation, engl. Gerzensee oscillation , was named after the Gerzensee in Switzerland ( Canton Bern ). Eicher and Siegenthaler became aware of them in 1976 while investigating the sampling in the lake sediments. However, they were not the first, because as early as 1954, Krog and 1977 Usinger had noticed a noticeable decrease in the δ 18 O values in Danish pollen analyzes . The same trend was evident in Wales . Since then, the Gerzensee fluctuation has been found in numerous other investigations in the North Atlantic region. Eicher (1980) and Lotter et al. (1992) then interpreted the results as a return to cold climatic conditions during the Alleröds. A correlation of the Gerzensee fluctuation with other proxy data also suggested the same conclusion. The ice cores from Greenland such as Camp Century , Dye 3 and Renland also show a significant decrease in the δ 18 O values.

stratigraphy

The Gerzensee fluctuation, engl. Inter Allerød Cold Period (IACP), corresponds to Greenland Interstadial 1b (GI-1b). It joins the Greenland Interstadial 1c (GI 1c), the first period of the Alleröds. It is followed by the Greenland Interstadial 1a (GI 1a), engl. pre Younger Dryas Warm Period , a warm phase before the start of the cold Younger Dryas.

In North America , the Killarney fluctuation should be equivalent to the Gerzensee fluctuation. It has been dated to be 11,160-10,910 carbon years.

Dating

Lowe et al. (2008) put the Gerzense fluctuation in the period 11311 to 11099 BC. A very similar period from 11324 to 11039 BC. Also found van Raden et al. (2012). Björck et al. (1998) found slightly different values ​​from 11180 to 10930 BC. Chr.

Environmental parameters

Temperatures

The Gerzensee fluctuation caused a maximum difference in the summer average temperatures (July) of 2 ° C compared to the other two periods of the Alleröd, determined using cladocers . However, data obtained by pollen analysis only indicate 1 ° C.

Oxygen isotopes

The δ 18 O values ​​show a fluctuation range of around 2 ‰ VPDB (from −39 to −41 ‰ VPDB). The minimum is 11100 BC. Chr.

Volcanic eruption

In the midst of the Gerzensee fluctuation, the phonolithic " Laacher See " volcano erupted, dated by van Raden (2012) to 11084 BC. Chr.

Effects

The Gerzensee fluctuation had significant effects on terrestrial and limnic ecosystems and led to upheavals in vegetation, increased soil erosion and reduced aquatic biomass.

vegetation

Characteristic of the vegetation history (for example in Denmark) during the Gerzensee fluctuation are:

The cooling phase is usually followed by a maximum of bushes composed of juniper (Juniperus), willow (Salix) and / or empetrum . This means that the cooling during the Gerzensee fluctuation resulted in a clearing of the birch forests. During the subsequent heating, shrubs requiring light could benefit from the openings.

See also

Individual evidence

  1. ^ H. Krog: Pollen analytical investigation of a 14C-dated Allerød-section from Ruds-Vedby . In: Danmarks Geologiske Undersøgelse . tape II / 80 , 1954, pp. 120-140 .
  2. ↑ H. Usinger: Bølling-Interstadial and Laacher Bimstuff in a new late glacial profile from Vallensgård Mose / Bornholm. With pollen size statistical separation of the birch trees . In: Årbog Danmarks Geologiske Undersøgelse . 1977, p. 5-29 .
  3. ^ MJC Walker, DD Harkness: Radiocarbon dating the Devensian Lateglacial in Britain: new evidence from Llanilid, South Wales . In: Journal of Quaternary Science . tape 5 , 1990, pp. 135-144 .
  4. ↑ U. Eicher: Pollen and oxygen isotope analyzes on late glacial profiles from the Gerzensee, Faulenseemoos and the rain moss near Boltigen . In: Mitteilungen Naturforschende Gesellschaft Bern NF Volume 37 , 1980, pp. 65-80 .
  5. ↑ AF Lotter, U. Eicher, U. Siegenthaler, HJB Birks: Late-glacial climatic oscillations as recorded in Swiss lake sediments . In: Journal of Quaternary Science . tape 7 , 1992, pp. 187-204 .
  6. ^ SJ Johnsen, among others: Irregular glacial interstadials recorded in a new Greenland ice core . In: Nature . tape 359 , September 24, 1992, pp. 311-314 , doi : 10.1038 / 359311a0 .
  7. ^ AJ Levesque: A previously unrecognized late-glacial cold event in eastern North America . In: Nature . tape 361 , February 18, 1993, p. 623-626 , doi : 10.1038 / 361623a0 .
  8. ^ JJ Lowe, inter alia: Synchronization of palaeoenvironmental events in the North Atlantic region during the Last Termination: a revised protocol recommended by the INTIMATE group . In: Quaternary Science Reviews . tape 27 , no. 1–2 , 2008, pp. 6-17 , doi : 10.1016 / j.quascirev.2007.09.016 .
  9. ↑ Ulrike J. van Raden ,: High-resolution late-glacial chronology for the Gerzensee lake record (Switzerland): δ 18 O correlation between a Gerzensee-stack and NGRIP, Palaeogeography, Palaeoclimatology, Palaeoecology . 2012, doi : 10.1016 / j.palaeo.2012.05.017 .
  10. ↑ S. Björck, among others: An event stratigraphy for the Last Termination in the North Atlantic region based on the Greenland Ice Core record: a proposal by the INTIMATE group . In: Journal of Quaternary Science . tape 13 , 1998, pp. 283-292 .
  11. ↑ AF Lotter: Younger Dryas and Allerød summer temperatures at Gerzensee (Switzerland) inferred from fossil pollen and cladoceran assemblages . In: Palaeogeography, Palaeoclimatology, Palaeoecology . tape 159 , 2000, pp. 49-361 .