Subatlantic

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series Climate level Pollen
zone 		Period
Holocene Subatlantic X 450 BC Until today
IX
Subboreal VIII 3,710-450 BC Chr.
Atlantic VII 7,270-3,710 BC Chr.
VI
Boreal V 8,690-7,270 BC Chr.
Preboreal IV 9,610-8,690 BC Chr.
Pleistocene
Younger dryas period III 10,730-9,700 ± 99 BC Chr.

The Subatlantic is Blytt-Sernander classification the last and present current climate phase of the Holocene in Northern Europe. It has been going on for around 2500 years. Its average temperatures are slightly lower than in the preceding Subboreal and Atlantic . During its course, several temperature fluctuations occurred , the direct ecological effects of which on flora and fauna also influenced the development history of human civilization. With increasing industrialization , however, human society has overlaid natural climate cycles with rapidly increasing greenhouse gas emissions over the past two centuries .

Conceptual history and stratigraphic position

The term subatlantic (ie below the Atlantic ), often referred to as the warming period , was coined by Rutger Sernander to distinguish it from Axel Blytts Atlantic . The subatlantic follows the immediately preceding subboreal . According to the scheme of Franz Firbas (1949) and Litt et al. a. (2001) pollen zones IX and X or, according to Fritz Theodor Overbeck, pollen zones XI and XII.

In terms of climatic stratigraphy, the subatlantic is usually divided into an older subatlantic (pollen zone IX or XI - early warmth period or also beech season or oak-beech season ) and a younger subatlantic (pollen zone X or XII - late warmth period ). The subatlantic belongs to or forms the sub-epoch of the Young Holocene .

Dietrich Franke even shows the following four levels for East Germany (from young to old):

Chronological order

Mesolithikum Neolithikum Bronzezeit Eisenzeit Yoldia-Meer Ancylussee Littorinameer Flandrische Transgression Dünkirchen-Transgression Präboreal Boreal (Klimastufe) Subboreal

Note: Only the borders marked with a black dividing line are more or less exact; they are based on annual layers in lake sediments in north-central Europe and, strictly speaking, only apply to the climatic stages. The other boundaries are uncertain and not rigidly set. In particular, the boundary between the Middle and Young Holocene is very variable. Regarding the cultural levels, the regionally different development must be taken into account.

Age

The beginning of the subatlantic is usually 2400 calendar years BP or 450 BC. Dated. However, this limit is not to be regarded as absolutely rigid. Some authors prefer to set the beginning of the subatlantic at 2500 radiocarbon years , which is around 625 BC. Corresponds to. Occasionally the beginning is also up to 1200 BC. Moved back.

According to Franz Firbas, the transition from the subboreal (pollen zone VIII) to the older sub-Atlantic (pollen zone IX) is characterized by the decline in hazel and linden trees with simultaneous anthropogenic expansion of hornbeam . However, the decline did not occur at the same time everywhere. For this event, for example, in the western lower Oder valley 930 to 830 BC. Determined, in south-western Poland ( Lower Silesia ) this transition took place between 1170 and 1160 BC. Instead of.

The beginning of the Younger Subatlantic (1250 AD) coincides with the medieval population expansion and is marked by increasing proportions of pine and increasing settlement indicators. For him, values ​​between 1,050 and 1,270 AD were found in Lower Silesia. However, if the beginning of the Younger Subatlantic is linked to the appearance of the beeches (1st beech maximum), it must be brought forward to the Carolingian period (700 AD) .

Climate history in Europe

Summer temperature anomalies in Europe, 138 BC u. Z -2003 n. U. Z

The summer temperatures of the subatlantic were cooler and up to 1.0 ° C lower than in the subboreal, the annual average temperatures by up to 0.7 ° C. However, winter precipitation has increased by up to 50% at the same time; the climate therefore tends towards cold and wet. The average lower limit of glaciers in Scandinavia fell by 100 to 200 meters during the subatlantic.

The subatlantic began in the middle of the 1st millennium BC. BC still with the so-called optimum of Roman times , which lasted until the beginning of the 4th century . Classical antiquity almost exactly falls into this period . This optimum is characterized by a temperature spike that is centered at 2500 years BP. In Europe it is expressed in particular by winter temperatures that are 0.6 ° C higher than in the rest of the sub-Atlantic, but it was still 0.3 ° C below the values ​​in the previous subboreal region. Drill cores from the Greenland ice sheet show a significant temperature increase compared to the Younger Subboreal.

The subsequent, comparatively short and weakly pronounced cold period is called the pessimum of the migration period . A temperature drop of 0.2 ° C in average temperatures and 0.4 ° C in winter temperatures is centered at 350 AD and 1600 years BP, respectively. This change to a drier and colder climate may have prompted the Huns, native to Central Asia, to migrate west, which in turn triggered the migrations of the Germanic peoples . At the same time, the Byzantine Empire experienced its first heyday and Christianity established itself in Europe as a formative monotheistic religion .

After this brief pessimum, the climate warmed up again to the level of the Roman optimum from around 800 to 1200. In this time falls the High Middle Ages , which is why the period as Medieval Warm Period ( English Medieval Warm Period ) is called. The warmer climate with maxima around the year 850 and 1050 AD (temperatures determined on the basis of sediments in the North Atlantic) caused the tree line in Scandinavia and Russia to rise by 100 to 140 meters and made it possible to a. the Vikings settled on Iceland and Greenland . It was during this period that most of the Crusades took place, and the Byzantine Empire was pushed back by the growing Ottoman Empire .

The end of the medieval warm period is dated to the beginning of the 14th century (temperature minimum at 1350 AD). During this period there were numerous documented famines and the great plague epidemic (the " Black Death "). Numerous settlements were abandoned during this period and became deserted . It is believed that Central Europe's population has decreased dramatically (perhaps by 50%).

Much longer and in places colder the subsequent Pessimum that had its peak after a brief warming by the year 1500, from 1550 to 1860 and as was the Little Ice Age ( English Little Ice Age ) is known. The snowline declined during this period in the northern hemisphere by 100 to 200 meters. Several revolutionary events occurred during this period ( Thirty Years War , French Revolution ). The later part of the Renaissance took place in parallel and culminated in the Enlightenment . The industrialization began here.

The Little Ice Age ended in the 19th century with global warming, mainly caused by human greenhouse gas emissions. Summer temperatures in Europe over the past three decades are likely to be higher than any other period of equal length since at least 138 BC. u. Z.

the atmosphere

Concentrations of important greenhouse gases, years 0–2016
Ghgs-lawdome-2000yr-CO2-asof2010-de.svg
Ghgs-lawdome-2000yr-CH4-asof2010-de.svg
Ghgs-lawdome-2000yr-N2O-asof2010-de.svg

Measurements on ice cores from the Antarctic and Greenland show a development for atmospheric greenhouse gases that is comparable to one another. After a temporary minimum in the preceding Subboreal and Atlantic, the concentrations of carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (laughing gas, N 2 O) gradually increased during the subatlantic , but this increased more from the year 1800 onwards or less dramatically in parallel with the temperature profile. The CO 2 concentration rose from 280 ppm to the current value of around 400 ppm , CH 4 from 700 to 1800 ppb and N 2 O from 265 to 320 ppb.

An event of this magnitude roughly comparable had already taken place during the transition to the Holocene, but this process took more than 5000 years. The short-term anthropogenic greenhouse emissions represent a unique experiment in the history of the earth. The release of juvenile water from fossil fuels such as hard coal , lignite , natural gas and crude oil is often completely ignored .

Sea level

The postglacial sea level rise

In the roughly 2500 years of the subatlantic, the global sea ​​level had risen constantly but only by 1 meter. However, this rather low rate of 0.4 millimeters / year changed drastically from the end of the 19th century. For the period from 1880 to 2000, an increase of 22 centimeters was measured, which corresponds to a rate of 1.83 millimeters / year. For the last 20 years alone, 50 millimeters have been recorded using satellites , which corresponds to a new rate of 2.5 millimeters / year and thus a six-fold increase in speed. However, these statements are controversial in the professional world, as land masses and sea floors rise or fall over certain periods of time due to plate tectonics and thus also influence the sea level and its reference to measurements.

Development in the Baltic Sea Region

With the 3rd Littorina transgression , today's sea level was reached in the oldest subatlantic in the Baltic Sea region . The sea level rise was up to 1 meter, since then it has been swinging around the zero line. The Limnaea Sea established itself ( postlittorine phase ). The Limnaea Sea had a lower salt content than the previous Littorina Sea , which was caused by an isostatic flattening of the Danish sea ​​routes Little Belt , Great Belt and Oresund . As a result, the snail Littorina littorea was gradually displaced by the freshwater snail Limnaea ovata . About 1300 years ago there was another slight rise in sea level in the Central Subatlantic. However, the salinity continued to decline and new freshwater taxa could immigrate. Thus, in the Younger and Youngest Subatlantic, the Limnaea Sea was finally replaced by the Mya Sea (immigration of the sand clam Mya arenaria around 400 years ago) and thus by today's Baltic Sea.

Development in the North Sea region

In the older subatlantic, the slight decline in sea level or the sea level standstill during the subboreal with the Dunkirk transgression was followed by a renewed rise to today's level.

Vegetation-historical development tendencies

The damp and cool older subatlantic (pollen zone IX a) is characterized in Central Europe by the mixed oak forest, in which beeches increasingly established themselves (mixed oak forests with linden and elm or mixed oak forests with ash and beech). Alder- ash forests settled on wet locations. The mixed oak forest still held during the humid temperate Middle Subatlantikums (pollen zone IX b), but had optima of beech and hornbeam (mixed oak forest with beech and oak mixed forests with elm, hornbeam and beech). During the humid and temperate Younger Subatlantic (pollen zone X a), which is very similar to today's climate, the mixed beech forest or a pure beech forest established itself. However, the anthropogenic use of arable land, meadows, pastures and forests, which began in the Bronze Age, now dominates. The current youngest subatlantic (pollen zone X b) also has a humid, temperate climate with a clear annual precipitation gradient that decreases from west to east . Natural, pristine forests hardly exist anymore and have given way to a cultivated forest floor.

In north-west Germany the mixed oak forest (EMW) remained the determining element during the older subatlantic with around 40% of the tree pollen, but showed a decline in the younger subatlantic with strong fluctuations. Elms and linden trees as part of the mixed oak forest, however, remained constant. The alder stocks decreased from an initial 30% to 10%. The pines were also in decline, but showed an enormous forest- related expansion in the youngest subatlantic . Hazel (15%), birch (5%) and willow (<1%) roughly retained their populations. However, the significant expansion of beech (from 5 to 45%) and hornbeam (from 1 to 15%) was significant. According to HM Müller, it was due to the increase in humidity from approx. 550 BC. And then favored by the decline in settlement activities during the migration period.

The proportion of herbs (including cornflowers , wild plants , sorrel and plantain ) in the total pollen also increased very significantly (from 15 to 65%). Also Getreidetaxa were detected multiplies; with an increase from 5 to 30%, they demonstrate the increased arable farming in the Younger Subatlantic.

In northern Germany ( Ostholstein ) the vegetation-historical development was very similar. The rapid increase in non-tree pollen from 30 to over 80% in the Younger Subatlantic (including an increase in grain from 2 to over 20%) is also remarkable. The mixed oak forest was able to maintain its position among the tree pollen with 30%. The alder also recorded a decline here (from 40 to 25%). Birch, beech and hornbeam remained roughly the same (with smaller fluctuations) (the latter, however, had a clear optimum at the beginning of the Younger Subatlantic). Here, too, the increase in pine trees in the Youngest Subatlantic is striking.

The following key horizons could be eliminated in Ostholstein (from young to old):

  • Rise of pine trees (K) - around 1800 AD - due to forestry
  • Beech summit 2 (F 2)
  • Beech summit 1 (F 1) - around 1300 AD, in Lower Saxony as early as 800 AD.
  • Hazel maximum 5 (C 5) - due to climatic conditions - 200 to 400 AD

fauna

The faunal biodiversity by the mid-18th century promoted industrialization and the concomitant environmental degradation grasped strongly in decline. This development assumed alarming proportions from 1985 onwards. The Living Planet Index shows a 40% decline in vertebrate species diversity up to the year 2000 . Animals in freshwater ecosystems, whose biodiversity (mainly due to loss of biotopes and water pollution) have declined by 50%, are particularly hard hit.

Summary

The influence of humans on their environment, which had already become noticeable in the Atlantic since the Neolithic Revolution, increased noticeably in the course of the sub-Atlantic. The youngest subatlantic is likely to represent the first time in the history of the earth in which anthropogenically forced spikes (environmental impulses) by far push natural control cycles into the background. It remains to be seen whether and to what extent these anthropogenic inputs will compete with catastrophic events in the geological past.

See also

Web links

Commons : Climatic Variations in the Young Holocene  - Album with pictures, videos and audio files

Individual evidence

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  2. ↑ A. BIytt: Immigration of the Norvegian Flora . Alb. Cammermeyer, Christiania (Oslo) 1876, p. 89 .
  3. ↑ F. Firbas: Late and post-glacial climatic history of Central Europe north of the Alps. I. General forest history . Jena 1949, p. 480 .
  4. ↑ T. Litt et al .: Correlation and synchronization of Lateglacial continental sequences in northern central Europe based on annually laminated lacustrine sediments . In: Quaternary Science Reviews . tape 20 , 2001, p. 1233-1249 .
  5. ^ Overbeck, F .: The moors of Lower Saxony. In: Publ. D. Lower Saxony. Office f. State planning u. Statistics, AI series, Bremen-Horn department . 2nd Edition. tape 3, 4 , 1950.
  6. ^ D. Franke: Regional geology of East Germany - A dictionary . 2010.
  7. ↑ J. Mangerud, inter alia: Quaternary stratigraphy of Norden, a proposal for terminology and classification . In: Boreas . tape 3 . Oslo 1974, p. 109-128 .
  8. ↑ S. Jahns: Late-glacial and Holocene woodland dynamics and land-use history of the Lower Oder valley, north-eastern Germany, based on two, AMS 14C-dated, pollen profiles . In: Vegetation History and Archaeobotany . tape 9 , no. 2 , 2000, pp. 111-123 .
  9. ^ A b C. M. Herking: Pollen analysis of the Holocene vegetation history along the eastern lower Oder valley and southern lower Warta valley in north-western Poland. Dissertation . Göttingen, Georg August University 2004.
  10. ↑ a b J Luterbacher u. a .: European summer temperatures since Roman times . In: Environmental Research Letters . 2016, doi : 10.1088 / 1748-9326 / 11/2/024001 .
  11. ↑ SO Dahl, A. Nesje: A new approach to calculating Holocene winter precipitation by combining glacier equilibrium line altitudes and pine-tree limits: a case study from Hardangerjøkulen central southern Norway . In: The Holocene . tape 6 , 1996, pp. 381-398 .
  12. ^ WS Broecker: Was the Medieval Warm Period global? In: Science . 291, N ° 5508, 2001, p. 1497-1499 .
  13. ↑ G. Bond: Persistent Solar Influence on North Atlantic Climate During the Holocene . In: Science . tape 294 , no. 5594 , 2001, pp. 2130-2136 .
  14. ↑ a b Elena Xoplaki: The Medieval Climate Anomaly and Byzantium: A review of the evidence on climatic fluctuations, economic performance and societal change . In: Quaternary Science Reviews . 2015, doi : 10.1016 / j.quascirev.2015.10.004 .
  15. ↑ LD Keigwin: The Little Ice Age and Medieval Warm Period in the Sargasso Sea . In: Science . tape 274 , 1996, pp. 1504-1508 .
  16. ↑ A. Hiller, T. Boettger, C. Kremenetski: Medieval climatic warming recorded by radiocarbon dated alpine tree-line shift on the Kola Peninsula, Russia . In: Holocene . tape 11 , no. 4 , 2001, p. 491 .
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  18. ↑ E. Jansen, among others: Palaeoclimate. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change . Ed .: S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, KB Averyt, M. Tignor, HL Miller. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA 2007.
  19. ↑ Peter Hupfer: The Baltic Sea - small sea with big problems . BSB BG Teubner Verlagsgesellschaft, Leipzig 1981.
  20. ^ H. Hyvärinen, among others: The Litorina Sea and Limnea Sea in the northern and central Baltic . In: J. Donner, A. Razier (ed.): Problems of the Baltic Sea History (=  Annales Academiae Scientiarum Fennicae, Series A, III. Geologica-Geographica . Volume 148 ). 1988, p. 25-35 .
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  22. ↑ Heinz Kliewe: Geological Development in the Holocene . In: Klaus Duphorn, among others (Hrsg.): The German Baltic Sea Coast . Borntraeger Brothers, Berlin 1995, p. 32-50 .
  23. ↑ H. Schmitz: The pollen analysis of the post-glacial structure in the northwestern German lowlands . In: Ice Age and the Present . tape 6 , 1956, pp. 52-59 .
  24. ^ HM Müller: The late Pleistocene and Holocene vegetation development in the eastern lowlands of the GDR between the northern and southern ridges . tape 10 , 1969, p. 155-165 .
  25. ^ H. Schmitz: The forest history of Ostholstein and the temporal course of the postglacial transgression on the Holstein Baltic Sea coast . In: Ber. German. Bot. Ges. Band 66 , no. 3 , 1953, pp. 151-166 ( onlinelibrary.wiley.com ).
  26. ↑ VM Mikkelsen: Pollenanalytiske undersogelser ved Bolle, et bidrag til vegetation histories i subatlantisk tid . In: National Museum 3. afd. Arkaeologic Landsbyundersegelser . tape 1 . Copenhagen 1952, p. 109-132 .
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