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Featured researches published by Leeli Amon.


Nature Communications | 2014

Validation of climate model-inferred regional temperature change for late-glacial Europe

Oliver Heiri; Stephen J. Brooks; H. Renssen; Alan Bedford; Marjolein Hazekamp; Boris P. Ilyashuk; Elizabeth S. Jeffers; Barbara Lang; Emiliya Kirilova; Saskia Kuiper; Laurent Millet; Stéphanie Samartin; Mónika Tóth; F. Verbruggen; Jenny E. Watson; Nelleke Van Asch; Emmy Lammertsma; Leeli Amon; Hilary H. Birks; H. John B. Birks; Morten Fischer Mortensen; Wim Z. Hoek; Enikö Magyari; Castor Muñoz Sobrino; Heikki Seppä; Willy Tinner; Spassimir Tonkov; Siim Veski; André F. Lotter

Comparisons of climate model hindcasts with independent proxy data are essential for assessing model performance in non-analogue situations. However, standardized paleoclimate datasets for assessing the spatial pattern of past climatic change across continents are lacking for some of the most dynamic episodes of Earths recent past. Here we present a new chironomid-based paleotemperature dataset designed to assess climate model hindcasts of regional summer temperature change in Europe during the late-glacial and early Holocene. Latitudinal and longitudinal patterns of inferred temperature change are in excellent agreement with simulations by the ECHAM-4 model, implying that atmospheric general circulation models like ECHAM-4 can successfully predict regionally diverging temperature trends in Europe, even when conditions differ significantly from present. However, ECHAM-4 infers larger amplitudes of change and higher temperatures during warm phases than our paleotemperature estimates, suggesting that this and similar models may overestimate past and potentially also future summer temperature changes in Europe.


Nature Communications | 2015

Plant macrofossil evidence for an early onset of the Holocene summer thermal maximum in northernmost Europe

Minna Väliranta; J. S. Salonen; Maija Heikkilä; Leeli Amon; Karin F. Helmens; A. Klimaschewski; Peter Kuhry; Seija Kultti; Anneli Poska; Shyhrete Shala; Siim Veski; Hilary H. Birks

Holocene summer temperature reconstructions from northern Europe based on sedimentary pollen records suggest an onset of peak summer warmth around 9,000 years ago. However, pollen-based temperature reconstructions are largely driven by changes in the proportions of tree taxa, and thus the early-Holocene warming signal may be delayed due to the geographical disequilibrium between climate and tree populations. Here we show that quantitative summer-temperature estimates in northern Europe based on macrofossils of aquatic plants are in many cases ca. 2 °C warmer in the early Holocene (11,700–7,500 years ago) than reconstructions based on pollen data. When the lag in potential tree establishment becomes imperceptible in the mid-Holocene (7,500 years ago), the reconstructed temperatures converge at all study sites. We demonstrate that aquatic plant macrofossil records can provide additional and informative insights into early-Holocene temperature evolution in northernmost Europe and suggest further validation of early post-glacial climate development based on multi-proxy data syntheses.


Vegetation History and Archaeobotany | 2014

Tree taxa immigration to the eastern Baltic region, southeastern sector of Scandinavian glaciation during the Late-glacial period (14,500–11,700 cal. b.p.)

Leeli Amon; Siim Veski; Jüri Vassiljev

The eastern Baltic region is situated in the southeastern part of the area which was covered by the last Scandinavian glaciation. Four well-dated sediment profiles from sites distributed along a ~330-km north–south transect were analysed for their macrofossil contents. The immigration of tree taxa during the Late-glacial (LG) period, which was the time of environmental change from tundra to woodland in previously glaciated areas, can be determined from these data. The pioneer vegetation in the study area was treeless dwarf shrub tundra with various dominant taxa. The so-called Allerød hemispheric warming permitted the Post-glacial immigration of trees into the southern part of the eastern Baltic region; however, these most probably disappeared during the following cold period, the Younger Dryas/GS-1. The local presence of Betula sect. Albae, Pinus sylvestris, Populus tremula and Picea abies during the LG period in the southern part of the region was confirmed. The northern part of the area presumably remained treeless for the entire LG period. Therefore, until the beginning of the Holocene, the tree line in the eastern Baltic region did not reach beyond 58°N.


Journal of Paleolimnology | 2018

Late glacial and early Holocene climate and environmental changes in the eastern Baltic area inferred from sediment C/N ratio

Merlin Liiv; Tiiu Alliksaar; Leeli Amon; Rene Freiberg; Atko Heinsalu; Triin Reitalu; Leili Saarse; Heikki Seppä; Normunds Stivrins; Ilmar Tõnno; Jüri Vassiljev; Siim Veski

Abstract We assessed the utility of using the sediment total organic carbon/total nitrogen (C/N) ratio as an indicator of paleoclimate changes in the eastern Baltic area during the late glacial and early Holocene. The C/N ratio in sediments from Lake Lielais Svētiņu, eastern Latvia, was compared with other sediment variables that are used as proxies of past climate and environment. Analysis revealed that although the organic matter (OM) content in late glacial sediments was extremely low, the C/N ratio captured information about OM origin, and fluctuations in the ratio tracked climate oscillations. The C/N ratio was significantly positively correlated with pollen-inferred mean summer temperature. Therefore, C/N ratio was lower under colder conditions, indicating a predominantly phytoplankton origin of OM, and was higher during warmer conditions, when there was more vegetation around the lake. A strong positive correlation between C/N ratio and the paleopigment beta carotene suggested that elevated phytoplankton production resulted from higher nutrient availability that was controlled largely by the input of terrestrial OM to the lake during warmer climate episodes. Thus, C/N ratio was a good indicator of paleoclimate changes, at least for the late glacial period, when generally cold conditions prevailed. This study also demonstrates the power of multi-proxy paleolimnological analyses for investigating past environmental changes in lakes and their watersheds.


Quaternary Science Reviews | 2012

Lateglacial vegetation dynamics in the eastern Baltic region between 14,500 and 11,400 cal yr BP: A complete record since the Bølling (GI-1e) to the Holocene

Siim Veski; Leeli Amon; Atko Heinsalu; Triin Reitalu; Leili Saarse; Normunds Stivrins; Jüri Vassiljev


Estonian Journal of Earth Sciences | 2009

Development of the late glacial Baltic basin and the succession of vegetation cover as revealed at Palaeolake Haljala, northern Estonia

Leili Saarse; Eve Niinemets; Leeli Amon; Atko Heinsalu; Siim Veski; Kadri Sohar


Journal of Quaternary Science | 2012

Timing of Lateglacial vegetation dynamics and respective palaeoenvironmental conditions in southern Estonia: evidence from the sediment record of Lake Nakri

Leeli Amon; Siim Veski; Atko Heinsalu; Leili Saarse


Estonian Journal of Earth Sciences | 2010

Late glacial multiproxy evidence of vegetation development and environmental change at Solova, southeastern Estonia

Leeli Amon; Atko Heinsalu; Siim Veski


Quaternary International | 2015

Quantitative summer and winter temperature reconstructions from pollen and chironomid data between 15 and 8 ka BP in the Baltic–Belarus area

Siim Veski; Heikki Seppä; Migle Stančikaitė; Valentina Zernitskaya; Triin Reitalu; Gražyna Gryguc; Atko Heinsalu; Normunds Stivrins; Leeli Amon; Jüri Vassiljev; Oliver Heiri


Geological Quarterly | 2010

Postglacial palaeoenvironmental changesin the area surrounding Lake Udriku in North Estonia

Leeli Amon; Leili Saarse

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Siim Veski

Tallinn University of Technology

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Atko Heinsalu

Tallinn University of Technology

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Leili Saarse

Tallinn University of Technology

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Jüri Vassiljev

Tallinn University of Technology

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Triin Reitalu

Tallinn University of Technology

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Normunds Stivrins

Tallinn University of Technology

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Hilary H. Birks

Bjerknes Centre for Climate Research

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