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Katrantsiotis, Christos
Publikasjoner (8 av 8) Visa alla publikasjoner
Katrantsiotis, C., Haberle, S., Ekblom, A., Smittenberg, R. H., Risberg, J., Rule, S., . . . Norström, E. (2024). Late Quaternary hydroclimate variability in Madagascar and its connection to atmospheric circulation patterns. Palaeogeography, Palaeoclimatology, Palaeoecology, 649, Article ID 112336.
Åpne denne publikasjonen i ny fane eller vindu >>Late Quaternary hydroclimate variability in Madagascar and its connection to atmospheric circulation patterns
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2024 (engelsk)Inngår i: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 649, artikkel-id 112336Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Large uncertainties still exist about the long-term mechanisms influencing the hydroclimate variability of southeast Africa where proxy data and model simulations indicate rainfall dipoles between subtropical and tropical areas. The topography of Madagascar, located off the southeastern coast of Africa, modulates these dipoles while its climate is influenced by the position of the Intertropical Convergence Zone (ITCZ) and the Subtropical High as well as the sea surface temperature (SST) of SW Indian Ocean. The island can thus be considered a key location for the understanding of the tropical SE African climatic variability and the interplay between atmospheric patterns. However, the scarcity of continuous records from Madagascar has made the evolution of regional late Quaternary climate and its driving mechanisms difficult to assess. Here, we present a 26-kyr record of the deuterium/hydrogen isotope ratio (δD) of biomarkers (n-alkanes) from the central eastern part of the island at Antananarivo at around 1250 m a.s.l. Preliminary summary pollen data are also presented as a comparison. The δD profiles of aquatic plant and terrestrial plant-derived n-alkanes generally exhibit similar trends implying that they all record changes in the isotope composition of source water, namely meteoric water that recharges soil and lake waters. In this tropical region, the δD variability of precipitation is mainly influenced by the amount effect reflecting the intensity of precipitation associated with the monsoon. We observe: (i) stable and wet conditions during the Last Glacial Maximum, (ii) drier conditions from 18.5 to 15 ka (ka before present) during the Heinrich Stadial 1 (iii) high humidity after 15 ka culminating at the Younger Dryas (YD), (iv) drier conditions from 11.7 ka to 8.2 ka, (v) a return to humid climate until 2.8 ka, and (vi) an arid phase followed by increased wetness after 0.9 ka, although the record is likely influenced by human-induced vegetation changes the last 1.2 ka. This climate signal is similar to other records from the Mozambique Channel but opposite to records from the East African mainland and the subtropical southern Africa, especially between 20 and 25°S. Although there is a good correspondence of our record with insolation- driven migrations of ITCZ during the LGM and the early Holocene, the dipoles are largely consistent with the modern rainfall anomaly and are best explained by the interlinked effects of the SST changes and the variability of the Mozambique Channel Trough.

sted, utgiver, år, opplag, sider
Elsevier, 2024
Emneord
Madagascar, Indian Ocean, Hydrogen isotopes, Climate variability, Intertropical Convergence Zone
HSV kategori
Forskningsprogram
klimatförändringar; miljöförändringar
Identifikatorer
urn:nbn:se:umu:diva-227672 (URN)10.1016/j.palaeo.2024.112336 (DOI)2-s2.0-85197068042 (Scopus ID)
Forskningsfinansiär
Australian Research Council, DP0986991Swedish Research Council, 2019-05054
Tilgjengelig fra: 2024-07-03 Laget: 2024-07-03 Sist oppdatert: 2024-07-09bibliografisk kontrollert
Yahiaoui, N., Mansour, B., Katrantsiotis, C., Risberg, J., Reimer, P. J. & Mahboubi, M. (2023). Early to Middle Holocene hydroclimate changes in the Guern El Louläilet depressions, Algerian Sahara. Journal of Paleolimnology, 69, 161-183
Åpne denne publikasjonen i ny fane eller vindu >>Early to Middle Holocene hydroclimate changes in the Guern El Louläilet depressions, Algerian Sahara
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2023 (engelsk)Inngår i: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 69, s. 161-183Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Fossil diatoms and litho-stratigraphic changes in the Guern El Louläilet depressions, NW of the Great Western Erg, Algeria, were analysed to infer paleoenvironmental changes in the northern Algerian Sahara during the Early and Middle Holocene. Analysis was based on calcareous diatomite collected from four outcrops within the depressions. The diatom flora consists of brackish and epiphytic taxa, such as Epithemia argus, with percentages of some freshwater and planktonic species, mainly Cyclotella distinguenda. Results provide evidence for two Holocene lacustrine episodes related to the African Humid Period. The first episode (Early to Middle Holocene) was characterized by abrupt development of shallow-water conditions, with extensive littoral zones and evaporative periods that coincided with high salt concentrations in warm, alkaline water (swampy conditions). A second episode (Middle to Late Holocene?), with brackish water and alkaline conditions, coincided with a decline in lake water level that is attributed to drier conditions. Our findings are consistent with those of other studies from the area and demonstrate similar environmental changes occurred after 9300 cal yr BP at sites within the region. The main drivers of the African Humid Period were the northward shift of the Intertropical Convergence Zone (ITCZ) and expansion of summer monsoonal rains. Our study sites were located in the northern Sahara, where variations in the position of the Intertropical Convergence Zone (ITCZ) did not affect rainfall. Early and Middle Holocene climate fluctuations detected in this study may have been caused by intensification of winter precipitation in the south-central Mediterranean and its penetration southward.

sted, utgiver, år, opplag, sider
Springer, 2023
Emneord
Diatoms, Paleolakes, Great Western Erg, African Humid Period, Shallow lake, Holocene
HSV kategori
Forskningsprogram
naturgeografi; klimatförändringar
Identifikatorer
urn:nbn:se:umu:diva-199336 (URN)10.1007/s10933-022-00267-4 (DOI)000852117700001 ()2-s2.0-85137767864 (Scopus ID)
Tilgjengelig fra: 2022-09-13 Laget: 2022-09-13 Sist oppdatert: 2023-06-08bibliografisk kontrollert
Katrantsiotis, C., Dahl, M., Palm, V., Rönnby, J., Andrén, T. & Andrén, E. (2023). Holocene relative sea level changes in the Västervik‐Gamlebyviken region on the southeast coast of Sweden, southern Baltic Sea. Boreas, 52(2), 206-222
Åpne denne publikasjonen i ny fane eller vindu >>Holocene relative sea level changes in the Västervik‐Gamlebyviken region on the southeast coast of Sweden, southern Baltic Sea
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2023 (engelsk)Inngår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 52, nr 2, s. 206-222Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We reconstruct the Holocene shore displacement of the Västervik-Gamlebyviken area on the southeast coast of Sweden, characterised by a maritime cultural landscape and archaeological significance since the Mesolithic. Sediment cores were retrieved from four lake basins that have been raised above sea level due to the postglacial land uplift and eustatic sea level changes after the melting of the Fennoscandian Ice Sheet. The cores were radiocarbon dated and analysed for loss on ignition and diatoms. The isolation thresholds of the basins were determined using LiDAR data. The results provide evidence for the initiation of the first Littorina Sea transgression in this area at 8.5 thousand calibrated years before present (cal. ka BP). A relative sea level rise by ∼7 m a.s.l. is recorded between 8.0 and 7.5 cal. ka BP with a highstand at ∼22 m a.s.l. between 7.5 and 6.2 cal. ka BP. These phases coincide with the second and third Littorina Sea transgressions, respectively, in the Blekinge area, southern Sweden and are consistent with the final deglaciation of North America. After 6.2 cal. ka BP, the relative sea level dropped below 22 m a.s.l., and remained at ∼20 m a.s.l. until 4.6 cal. ka BP coinciding with the fourth Littorina Sea transgression in Blekinge. From 4.6 to 4.2 cal. ka BP, the shore displacement shows a regression rate of 10 mm a−1 followed by a slowdown with a mean value of 4.6 mm a−1 until 1.6 cal. ka BP, when the relative sea level dropped below 3.3 m a.s.l. The Middle to Late Holocene highstand and other periods of minor sea level transgressions and/or higher salinity between 6.2 and 1.7 cal. ka BP are attributed to a combination of warmer climate and higher inflow of saline waters in the southern Baltic Sea due to stronger westerlies, caused by variations in the North Atlantic atmospheric patterns.

sted, utgiver, år, opplag, sider
John Wiley & Sons, 2023
Emneord
Baltic Sea, diatoms, Glacial isostatic adjustment, Shore displacement, sediments
HSV kategori
Forskningsprogram
miljöarkeologi; klimatförändringar; naturgeografi
Identifikatorer
urn:nbn:se:umu:diva-200048 (URN)10.1111/bor.12605 (DOI)000864284500001 ()2-s2.0-85139201509 (Scopus ID)
Forskningsfinansiär
The Foundation for Baltic and East European Studies, 21-PD2-0002The Foundation for Baltic and East European Studies, 3146-3.1.1-2017
Tilgjengelig fra: 2022-10-06 Laget: 2022-10-06 Sist oppdatert: 2023-06-08bibliografisk kontrollert
Emmanouilidis, A., Katrantsiotis, C., Dotsika, E., Kokkalas, S., Unkel, I. & Avramidis, P. (2022). Holocene paleoclimate variability in the eastern Mediterranean, inferred from the multi-proxy record of Lake Vouliagmeni, Greece. Palaeogeography, Palaeoclimatology, Palaeoecology, 595, Article ID 110964.
Åpne denne publikasjonen i ny fane eller vindu >>Holocene paleoclimate variability in the eastern Mediterranean, inferred from the multi-proxy record of Lake Vouliagmeni, Greece
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2022 (engelsk)Inngår i: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 595, artikkel-id 110964Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This study presents a Holocene multi-proxy record from Lake Vouliagmeni, eastern Gulf of Corinth, Greece. The lake is subjected to intense climatic and tectonic forces causing stratigraphic variations with laminated sediments frequently interrupted by homogenous sections and event deposits. Lamination couplets consist of aragonite layers alternating with detrital and organic residues formed during periods of seawater intrusion and stratification of the lake water. The discontinuous occurrence of laminated deposits excludes a varve based chronology from being established but highlights the susceptibility of the lake to record environmental and climatic changes. Our synthesis model for regional climatic reconstruction and local environmental changes derives from δ18O and δ13C data from laminated and homogenous sediments studied separately and depending on the dominant carbonate mineral. This is further strengthened by high-resolution geochemical proxies, diatom and sedimentological data. Regional climatic signals from key sites and possible links to the Lake Vouliagmeni record are explored in response to atmospheric circulation patterns. Phases of overall humid conditions are recorded by increased inflow of siliciclastic material to the lake and negative δ18Obulk values. In contrast, periods of marine intrusion and enhanced evaporation are recorded by aragonite precipitation, positive δ18OAr values and laminations. The laminations formed in the lake seem to occur during periods of sea water intrusion into the lake, which led to pycnocline stabilization and stratified lake waters.

sted, utgiver, år, opplag, sider
Elsevier, 2022
Emneord
Paleoenvironment, Stable isotopes, Laminations, XRF scanning, Aragonite
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-193516 (URN)10.1016/j.palaeo.2022.110964 (DOI)000795155300004 ()2-s2.0-85127743013 (Scopus ID)
Tilgjengelig fra: 2022-04-05 Laget: 2022-04-05 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Vignola, C., Hättestrand, M., Bonnier, A., Finné, M., Izdebski, A., Katrantsiotis, C., . . . Masi, A. (2022). Mid-late Holocene vegetation history of the Argive Plain (Peloponnese, Greece) as inferred from a pollen record from ancient Lake Lerna. PLOS ONE, 17(7), Article ID e0271548.
Åpne denne publikasjonen i ny fane eller vindu >>Mid-late Holocene vegetation history of the Argive Plain (Peloponnese, Greece) as inferred from a pollen record from ancient Lake Lerna
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2022 (engelsk)Inngår i: PLOS ONE, E-ISSN 1932-6203, Vol. 17, nr 7, artikkel-id e0271548Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This study provides a high-resolution reconstruction of the vegetation of the Argive Plain (Peloponnese, Greece) covering 5000 years from the Early Bronze Age onwards. The well dated pollen record from ancient Lake Lerna has been interpreted in the light of archaeological and historical sources, climatic data from the same core and other regional proxies. Our results demonstrate a significant degree of human impact on the environments of the Argive Plain throughout the study period. During the Early Bronze Age evidence of a thermophilous vegetation is seen in the pollen record, representing the mixed deciduous oak woodland of the Peloponnesian uplands. The plain was mainly used for the cultivation of cereals, whereas local fen conditions prevailed at the coring site. Towards the end of this period an increasing water table is recorded and the fen turns into a lake, despite more arid conditions. In the Late Bronze Age, the presence of important palatial centres modified the landscape resulting in decrease of mixed deciduous oak woodland and increase in open land, partly used for grazing. Possibly, the human management produced a permanent hydrological change at Lake Lerna. From the Archaic period onwards the increasing human pressure in association with local drier conditions caused landscape instability, as attested by a dramatic alluvial event recorded in the Pinus curve at the end of the Hellenistic Age. Wet conditions coincided with Roman times and favoured a forest regeneration pattern in the area, at the same time as we see the most intensive olive cultivation in the pollen record. The establishment of an economic landscape primarily based on pastures is recorded in the Byzantine period and continues until modern times. Overgrazing and fires in combination with arid conditions likely caused degradation of the vegetation into garrigue, as seen in the area of the Argive Plain today.

sted, utgiver, år, opplag, sider
Public Library of Science, 2022
HSV kategori
Forskningsprogram
arkeologi; miljöarkeologi
Identifikatorer
urn:nbn:se:umu:diva-198212 (URN)10.1371/journal.pone.0271548 (DOI)000944166200029 ()2-s2.0-85134358971 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 621-2012-4344Swedish Research Council, 421-2014-1181Swedish Research Council, 2019-02868
Tilgjengelig fra: 2022-07-20 Laget: 2022-07-20 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Norström, E., West, J., Kouli, K., Katrantsiotis, C., Hättestrand, M. & Smittenberg, R. (2021). Evaluation of anhydrosugars as a molecular proxy for paleofire activity: A case study on a Holocene sediment core from Agios Floros, Peloponnese, Greece. Organic Geochemistry, 153
Åpne denne publikasjonen i ny fane eller vindu >>Evaluation of anhydrosugars as a molecular proxy for paleofire activity: A case study on a Holocene sediment core from Agios Floros, Peloponnese, Greece
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2021 (engelsk)Inngår i: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 153Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The anhydrosugars levoglucosan, mannosan and galactosan have been regarded a suitable molecular indicator of natural biomass combustion. Here we evaluate the summed anhydrosugars (SAS) as paleofire indicator in a 6000 year-long fossil core from Agios Floros fen, Peloponnese, Greece, by analyzing charcoal fragments in parallel throughout the sediment sequence. Modern surface soil samples from the same region were analysed for presence of SAS, confirming the biomarker as an indicator of recent fire activity. The highest SAS concentrations in the fossil core were found in sections representing periods of wet conditions both on local and regional scale, and regionally widespread arboreal vegetation. Low or absence of SAS in the fossil core is associated with periods of dryness, regional dominance of non-arboreal vegetation and a fen rather than lake ecosystem at the site. Micro-charcoal fragments were generally more abundant under these conditions. This suggests that SAS yield and deposition may vary with fuel availability and fire behavior which in turn is affected by climate, local moisture and vegetation type. Forest fires result in more SAS compared to grass fires. SAS yield is also favored by low-temperature fires sustained under wet climate conditions. Preservation of SAS is likely to be compromised in the only seasonally wet fen ecosystem under the dry and warm Mediterranean climate conditions. The moist and shallow conditions in the wetland during hot summer months are probably promoting oxidation and biodegradation of the labile SAS molecules compared to the more robust charcoal fragments. Thus, a multiproxy approach - using several proxies, both for fire, hydroclimate and vegetation change - is preferred when aiming to reconstruct past biomass burning from wetland ecosystems in a Mediterranean environment. The micro-charcoal record from Agios Floros reveals significant fire activity between 4400-2800 cal yr BP. This partly overlaps the Bronze Age period, associated with intense human environmental interaction and climate change in this area of Peloponnese, Greece.

sted, utgiver, år, opplag, sider
Elsevier, 2021
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-179661 (URN)10.1016/j.orggeochem.2021.104193 (DOI)000754942900005 ()2-s2.0-85102028741 (Scopus ID)
Tilgjengelig fra: 2021-02-05 Laget: 2021-02-05 Sist oppdatert: 2023-09-05bibliografisk kontrollert
Helmens, K., Katrantsiotis, C., Kuosmanen, N., Luoto, T., Salonen, S. & Väliranta, M. (2021). Prolonged interglacial warmth during the Last Glacial in northern Europe. Boreas, 50(2), 331-350
Åpne denne publikasjonen i ny fane eller vindu >>Prolonged interglacial warmth during the Last Glacial in northern Europe
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2021 (engelsk)Inngår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 50, nr 2, s. 331-350Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Few fossil‐based environmental and climate records in northern Europe are dated to Marine Isotope Stage (MIS) 5a around 80 ka BP. We here present multiple environmental and climate proxies obtained from a lake sequence of MIS 5a age in the Sokli basin (northern Finland). Pollen/spores, plant macrofossils, NPPs (e.g. green algae), bryozoa, diatoms and chironomids allowed an exceptionally detailed reconstruction of aquatic and telmatic ecosystem successions related to the development of the Sokli Ice Lake and subsequent infilling of a relatively small and shallow lake confined to the Sokli basin. A regional vegetation development typical for the early half of an interglacial is recorded by the pollen, stomata and plant macrofossil data. Reconstructions of July temperatures based on pollen assemblages suffer from a large contribution of local pollen from the lake's littoral zone. Summer temperatures reaching present‐day values, inferred for the upper part of the lake sequence, however, agree with the establishment of pine‐dominated boreal forest indicated by the plant fossil data. Habitat preferences also influence the climate record based on chironomids. Nevertheless, the climate optima of the predominant intermediate‐ to warm‐water chironomid taxa suggest July temperatures exceeding present‐day values by up to several degrees, in line with climate inferences from a variety of aquatic and wetland plant indicator species. The disequilibrium between regional vegetation development and warm, insolation‐forced summers is also reported for Early Holocene records from northern Fennoscandia. The MIS 5a sequence is the last remaining fossil‐bearing deposit in the late Quaternary basin infill at Sokli to be studied using multi‐proxy evidence. A unique detailed climate record for MIS 5 is now available for formerly glaciated northern Europe. Our studies indicate that interglacial conditions persisted into MIS 5a, in agreement with data for large parts of the European mainland, shortening the Last Glacial by some 50 ka to MIS 4‐2.

sted, utgiver, år, opplag, sider
John Wiley & Sons, 2021
HSV kategori
Identifikatorer
urn:nbn:se:umu:diva-178155 (URN)10.1111/bor.12495 (DOI)000601101800001 ()2-s2.0-85097935817 (Scopus ID)
Tilgjengelig fra: 2021-01-04 Laget: 2021-01-04 Sist oppdatert: 2023-06-08bibliografisk kontrollert
Katrantsiotis, C., Norström, E., Smittenberg, R. H., Salonen, J. S., Plikk, A. & Helmens, K. (2021). Seasonal variability in temperature trends and atmospheric circulation systems during the Eemian (Last Interglacial) based on n-alkanes hydrogen isotopes from Northern Finland. Quaternary Science Reviews, 273, 107250-107250, Article ID 107250.
Åpne denne publikasjonen i ny fane eller vindu >>Seasonal variability in temperature trends and atmospheric circulation systems during the Eemian (Last Interglacial) based on n-alkanes hydrogen isotopes from Northern Finland
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2021 (engelsk)Inngår i: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 273, s. 107250-107250, artikkel-id 107250Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The Last Interglacial warm period, the Eemian (ca. 130–116 thousand years ago), serves as a reference for projected future climate in a warmer world. However, there is a limited understanding of the seasonal characteristics of interglacial climate dynamics, especially in high latitude regions. In this study, we aim to provide new insights into seasonal trends in temperature and moisture source location, linked to shifts in atmospheric circulation patterns, for northern Fennoscandia during the Eemian. Our study is based on the distribution and stable hydrogen isotope composition (δD) of n-alkanes in a lake sediment sequence from the Sokli paleolake in NE Finland, placed in a multi-proxy framework. The δD values of predominantly macrophyte-derived mid-chain n-alkanes are interpreted to reflect lake water δD variability influenced by winter precipitation δD (δDprec), ice cover duration and deuterium (D)-depleted meltwater. The δD values of terrestrial plant-derived long-chain n-alkanes primarily reflect soil water δD variability modulated by summer δDprec and by the evaporative enrichment of soil and leaf water. The δDprec variability in our study area is mostly attributed to the temperature effect and the moisture source location linked to the relative dominance between D-depleted continental and polar air masses and D-enriched North Atlantic air masses. The biomarker signal further corroborates earlier diatom-based studies and pollen-inferred January and July temperature reconstructions from the same sediment sequence. Three phases of climatic changes can be identified that generally follow the secular variations in seasonal insolation: (i) an early warming trend succeeded by a period of strong seasonality (ii) a mid-optimum phase with gradually decreased seasonality and cooler summers, and (iii) a late climatic instability with a cooling trend. Superimposed on this trend, two abrupt cooling events occur in the early and late Eemian. The Sokli δD variability is generally in good agreement with other North Atlantic and Siberian records, reflecting major changes in the atmospheric circulation patterns during the Eemian as a response to orbital and oceanic forcings.

sted, utgiver, år, opplag, sider
Elsevier, 2021
Emneord
EemianMIS 5, Last Interglacial, Biomarkers, Hydrogen isotopes, Climate variability, Seasonality changes, Finland
HSV kategori
Forskningsprogram
kvartärgeologi
Identifikatorer
urn:nbn:se:umu:diva-189113 (URN)10.1016/j.quascirev.2021.107250 (DOI)000723161400004 ()2-s2.0-85118512240 (Scopus ID)
Tilgjengelig fra: 2021-11-04 Laget: 2021-11-04 Sist oppdatert: 2023-09-05bibliografisk kontrollert
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