Suzanne Leroy

Dr. Suzanne Leroy

orcid

Research Focus & Metrics

Academic Career Length

14Years (2013-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 October 2014 in Quaternary Science Reviews
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Journal Article
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SLSuzanne Leroy
Suzanne Leroy
LLLourdes López-Merino
Lourdes López-Merino
ATAlina Tudryn
Alina Tudryn
FCFrançoise Chalié
Françoise Chalié
FGFrançoise Gasse
Françoise Gasse
Late Pleistocene and/or Holocene high-resolution palynological studies are available for the south basin of the Caspian Sea (CS), the world's largest lake. However, the north and middle basins have not been the object of high-resolution palynological reconstructions. This new study presents the pollen, spores and dinoflagellate cysts records obtained from a 10 m-long sediment core recovered in the middle basin, which currently has brackish waters and is surrounded by arid and semi-arid vegetation.An age–depth model built based on six radiocarbon dates on ostracod shells indicates that the sequence spans the period from 14.47 to 2.43 cal. ka BP. The present palaeoenvironmental study focuses on the top 666 cm, or from 12.44 to 2.43 cal. ka BP.At the vegetation level, the Younger Dryas is characterised by an open landscape dominated by desert vegetation composed by Amaranthaceae with shrubs and salt-tolerant plants. However, although the Early Holocene is also characterised by desert vegetation, it is enriched in various shrubs such as Ephedra and Calligonum, but tree expansion is not important at the Holocene onset. After a major shift at 8.19 cal. ka BP, the Middle Holocene displays now both the character of desert and of steppe, although some trees such as Quercus and Corylus slightly spread. The Late Holocene records steppe vegetation as dominant, with more tree diversity.Regarding the lacustrine signal, the dinocyst assemblage record fluctuates between slightly brackish conditions highlighted by Pyxidinopsis psilata and Spiniferites cruciformis, and more brackish ones – similar to the present day – with the dominance of Impagidinium caspienense. The Late Pleistocene is characterised by low salinities, related to the Khvalynian highstand. From 11.56 cal. ka BP, slightly more saline waters are reconstructed with an increase of I. caspienense for a period of 1000 years, which could be attributed to the Mangyshlak lowstand. From 10.55 cal. ka BP, low salinity conditions return with remains such as Anabaena and Botryococcus abundant until 8.83 cal. ka BP, followed by a slow, progressive decrease of P. psilata and S. cruciformis until 4.11 cal. ka BP, which is the main assemblage change at lacustrine scale. Since then, higher salinities, similar to the present one, are reconstructed. Finally, Lingulodinium machaerophorum starts its development only at 2.75 cal. ka BP, in the Late Holocene.The present research revealed fundamental differences from previously published sea-level curves, in that a 6000 yr-long highstand suggested by low salinities is shown between 10.55 and 4.11 cal. ka BP. Amongst other arguments, using a comparison to a similar palynological regard but in the south basin, a N–S salinity gradient that is the reverse of the present one across the CS, suggests that the Amu Darya was flowing in the CS. Hence the CS levels during the Late Pleistocene and Holocene were influenced by a combination of precipitation over the high European latitudes and the indirect influence of the Indian summer monsoon over the Pamirs

9 October 2020 in Earth System Science Data
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BDBasil A. S. Davis
Basil A. S. Davis
MCManuel Chevalier
Manuel Chevalier
PSPhilipp Sommer
Philipp Sommer
VCVachel A. Carter
Vachel A. Carter
WFWalter Finsinger
Walter Finsinger
MZMarcelina Zimny
Marcelina Zimny
The Eurasian (née European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60 % from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https://doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019).

29 July 2013 in Climate of the Past
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Journal Article
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ABA. Naderi Beni
A. Naderi Beni
HLH. Lahijani
H. Lahijani
RHR. Mousavi Harami
R. Mousavi Harami
KAK. Arpe
K. Arpe
SLSuzanne Leroy
Suzanne Leroy
PRP. J. Reimer
P. J. Reimer
Historical literature may constitute a valuable source of information to reconstruct sea-level changes. Here, historical documents and geological records have been combined to reconstruct Caspian sea-level (CSL) changes during the last millennium. In addition to a comprehensive literature review, new data from two short sediment cores were obtained from the south-eastern Caspian coast to identify coastal change driven by water-level changes and to compare the results with other geological and historical findings. The overall results indicate a high-stand during the Little Ice Age, up to −21 m (and extra rises due to manmade river avulsion), with a −28 m low-stand during the Medieval Climate Anomaly, while presently the CSL stands at −26.5 m. A comparison of the CSL curve with other lake systems and proxy records suggests that the main sea-level oscillations are essentially paced by solar irradiance. Although the major controller of the long-term CSL changes is driven by climatological factors, the seismicity of the basin creates local changes in base level. These local base-level changes should be considered in any CSL reconstruction.

4 April 2019 in Geophysical Research Letters
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WJWenying Jiang
Wenying Jiang
SLSuzanne Leroy
Suzanne Leroy
SYShiling Yang
Shiling Yang
EZEnlou Zhang
Enlou Zhang
LWLuo Wang
Luo Wang
Patrick RioualPatrick Rioual
Patrick Rioual
The responses of the Indian and East Asian summer monsoons (ISM and EASM) to warming since the last deglaciation are controversial. Pollen results from a subalpine lake in the ISM area show that the Tsuga dumosa forest zone migrated at least 650 m upward during 18.6–7.1 kyr BP, indicating a gradual rise in mean annual temperature exceeding 3.9 °C. In response, grasses and deciduous and evergreen broad‐leaved trees successively colonized the mountainous environment. By contrast, the area around a lake in the EASM area was gradually occupied by temperate deciduous trees. In both areas, the maximum monsoonal precipitation occurred during 7.1–6.4 kyr BP, coinciding with peak Holocene warmth, but lagging the peak in Northern Hemisphere summer insolation by 3.9–4.6 kyr, due to delayed ice melting in northern high latitudes. Our results indicate the synchronous strengthening of the ISM and EASM in response to warming‐induced northward shifts in the Intertropical Convergence Zone.

24 March 2020 in International Journal of Climatology
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Journal Article
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KAklaus arpe
klaus arpe
MMMahboubeh Molavi-Arabshahi
Mahboubeh Molavi-Arabshahi
SLSuzanne Leroy
Suzanne Leroy
Newly available time series of 10‐m winds over last 60 years in the South Caspian Sea (CS) region show a remarkable shift in wind speed in 1995, that is also the year of maximum elevation of the Caspian Sea level (CSL). Our aim is to find the mechanisms linking these two features. This change is not only seen in the wind observations along the Southern CS coast, but also in the European Centre for Medium‐Range Weather Forecasts (ECMWF) reanalysis covering the Southern CS, leading there to an increase of evaporation after 1995. Due to wind increase, evaporation increases but does not lead to enhanced precipitation over the CS catchment area, the water seems to be lost to the east of the drainage basin for the water budget of the CS after 1995. This stopped the CSL rise and caused its post‐1995 fall. The connection between the wind speed and the trend of the CSL can also be seen for the 1977 low stand. Before 1977, the CSL was slightly dropping with relatively strong wind, then the wind speed fell and the CSL started to rise. The change of the wind seems to be induced by a teleconnection from El Niño‐Southern oscillation (ENSO). It is shown that ENSO impact is much stronger than that of North Atlantic oscillation (NAO), not only for the change of the CSL, but also for several key components of the CS water budget, like the Volga river discharge and wind speed. The wind speed is induced by ENSO, which is demonstrated by a shift of the jet stream over the CS area. This could be an explanative link between ENSO and CSL variability, but still needs further understanding. The NAO has a similar impact but to a lesser degree. When NAO and ENSO are working in the same direction, the CSL change is enhanced like from 1990 to 1995.

12 May 2020
Verified
Book Chapter
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SLSuzanne Leroy
Suzanne Leroy
HLHamid A. K. Lahijani
Hamid A. K. Lahijani
JCJean-Francois Crétaux
Jean-Francois Crétaux
NANikolai V. Aladin
Nikolai V. Aladin
IPIgor S. Plotnikov
Igor S. Plotnikov