ABSTRACTS OF THE FIRST CONFERENCE OF THE NORDIC NETWORK OF PALAEOCLIMATOLOGY (NEPAL)

Palmse, Estonia, May 10-12, 2007

Oxygen isotope palaeoclimatology of the woolly mammoth in Sweden Laura Arppe Department of Geology, P.O. Box 64, FIN-00014, University of Helsinki, Finland The oxygen isotope composition (δ18O) of skeletal apatite of homeothermal land mammals serve as a proxy for past rainfall isotope compositions. Due to the strong correlation between the long-term means of precipitation δ18O and temperature (e.g. Rozanski et al., 1992) the δ18O of skeletal bioapatite can be used to reconstruct past atmospheric temperatures. Tooth enamel from ten mammoth molar specimens discovered from Sweden, radiocarbon dated to ca. 25 – 41 BP (26-48 kyr), was analysed. The δ18Ow(=water) of Late Pleistocene precipitation in Sweden, calculated from enamel δ18Op(=phosphate) of samples dated to the Middle Weichselian ice free period ca. 26-44 kyrs ago, has a mean value of -13.4‰ ± 1.2. This corresponds to a mean annual temperature of 0.7 °C using the δ18Ow-T –correlation of Burgman et al. (1987). Today the δ18Ow in the areas of the find localities varies from -9 … -10‰ in southern to -13 … -14‰ in central Sweden. No corresponding spatial gradient could be detected in Late Pleistocene δ18Ow. Due to the lack of north-south variation, a more pronounced shift between glacial and modern climatic conditions is indicated for southern Sweden. 0-1°C lower mean annual temperatures are implied for the Middle Weichselian ice-free period in central Sweden, whereas the equivalent temperature decrease for southern Sweden is 5-7°C. This study was part of a collaboration aimed at investigating all the mammoth skeletal remains of Sweden to reconstruct the occurrence and paleoenvironment of mammoths, and to discuss their implications for the area’s glaciation chronology (Ukkonen et al., subm.). References Burgman, J.O., Calles, B. & Westman, F., 1987. Conclusions from a ten year study of

oxygen-18 in precipitation and runoff in Sweden. In: Isotope Techniques in Water Resources Development, IAEA-SM-299/107, 579–590.

Rozanski, K., Araguás-Araguás, L. & Gonfiantini, R., 1992. Relation between long-term trends of oxygen-18 isotope composition of precipitation and climate. Science, 258, 981-985.

Ukkonen, P., Arppe, L. Houmark-Nielsen, M., Kjær, K. & Karhu, J.A. Middle Weichselian mammoth remains from Sweden - implications for faunal history, palaeoclimate and glaciation chronology. Submitted to Quaternary Science Reviews.

Temperature and precipitation changes around the 8200 cal yr BP event in western and northern Norway – pollen evidence Anne E. Bjune1, John Birks2,1 & Atle Nesje3,1

1) Bjerknes Centre for Climate Research, University of Bergen, Allégaten 55, N-5007 Bergen, Norway.

2) Department of Biology, University of Bergen, Allégaten 41, N-5007 Bergen, Norway 3) Department of Earth Science, University of Bergen, Allégaten 41, N-5007 Bergen,

Norway Reconstructions of mean July temperature (Tjul), mean January temperature (Tjan), and mean annual precipitation (Pann) have been performed at three sites indicating changes in these parameters around the 8200 cal yr BP event. Indications of changes were first detected in the loss-on-ignition (LOI) signal with marked declines in the organic content at this time corresponding with melting of the glaciers in the catchment. The reconstructions of climate parameters are based on the pollen record from lake sediments from three lakes; Trettetjørn and Vanndalsvatnet, western Norway (Bjune et al. 2005, Nesje et al. 2006) and Svanåvatnet, northern Norway (Bjune & Birks, in prep).

Prior to the decrease in LOI at 8200 cal yr BP, Tjul were increasing and relatively high at all sites and during 8300 – 7900 cal yr BP decreases in Tjul are inferred. At both Svanåvatnet and Trettetjørn inferred Tjan decreases sharply at the time of the event. At Vanndalsvatnet a decline is observed at 8250 cal yr BP followed by increased Tjan until 7900 cal yr BP. At Vanndalsvatnet and Svanåvatnet Pann increased at the time of the event, whereas at Trettetjørn a short-lived decrease is inferred. The changes around the 8200 cal yr BP event are more pronounced at Vanndalsvatnet than the two other sites, possibly indicating that this site is situated closer to the distribution limits for the species driving the temperature signal in the pollen content.

A palaeoenvironmental reconstruction of Middle Patagonia, Tierra del Fuego and Isla de los Estados during the first human settlement

M. Fernandez 1,2, I. Unkel 1), S. Björck 1) J. Rabassa 2), B. Wolfarth 3)

1) Geobiosphere Science Centre, Quaternary Sciences, Lund University 2) Centro Austral de Investigaciones Científicas (CADIC) 3) Department of Geology and Geochemistry, Stockholm University

Climate change since the Last Glacial Maximum (c. 20,000 years B.P.) has modified the environments of Patagonia, Tierra del Fuego and Isla de los Estados. Many palynological studies from south Patagonia describe a fluctuating climate since the deglaciation beginning with cool and dry conditions and with the onset of more humid conditions in the early Holocene (Rabassa et al., 1989a, b). The first hunter-gatherer societies that arrived in this southernmost part of the world had to adapt to the complexity and dynamics of this landscape (Borrero et al, 1998; Miotti and Salemme, 1999). The mobility of these groups was limited by the availability of natural resources, mainly water. In order to understand the variability of the archaeological record on a local and regional scale, we will use lake sediments from Isla de los Estados to create a continuous and detailed environmental reconstruction based on changing diatom assemblages from lake sediments deposited since the last deglaciation. This type of study is the first to be carried out in this part of South America. By using diatom analysis we will be able to reconstruct past variations in pH, salinity, nutrient status, water level changes and marine transgressions. These results will be combined with other paleoecological techniques such as geochemistry. The chronology is based on 14C dating. Preliminary results show the frequent occurrence of Fragillaria construens var. venter at the transition from varved clays to organic lake sediments around 16.000 cal. yrs BP, indicating shallow water depths/arid conditions around this time.

Holocene hydroclimate dynamics in northern Fennoscandia inferred from cellulose δ18O records from lake sediments in northernmost Sweden and Finland. D. Hammarlund1,2, N.A. St. Amour2, T.W.D. Edwards1,2, H. Seppä3, and B.B. Wolfe2,4

1 GeoBiosphere Science Centre, Quaternary Sciences, Lund University, Sölvegatan 12, SE-

223 62 Lund, Sweden 2 Department of Earth Sciences and Quaternary Sciences Institute, University of Waterloo,

Waterloo, ON N2L 3G1, Canada 3 Department of Geology, University of Helsinki, P.O. Box 64, FIN-00014 Helsinki,

Finland 4 Department of Geography and Environmental Studies, Wilfrid Laurier University,

Waterloo, ON N2L 3C5, Canada A rather consistent and well-constrained climate history is emerging for Fennoscandia, based mainly on quantitative temperature reconstructions using biological transfer functions. Subsequent to a Holocene thermal maximum around 7500-5500 cal. BP, a general cooling trend is inferred. In contrast, the earliest part of the Holocene shows clearly diverging trends in the reconstructions and frequent non-analogous ecological assemblages, probably as a consequence of markedly different ocean and atmosphere circulation patterns in the northern North Atlantic region.

Here we present complementary information on changing hydroclimatic conditions based on oxygen-isotope analysis of aquatic cellulose extracted from Holocene lake-sediment sequences at two sites in the vicinity of Naimakka in northernmost Sweden. Monitoring of seasonal changes in lake-water isotopic composition and access to isotopic data on modern precipitation from a local meteorological station enable quantification of past hydrological changes and inference of atmospheric circulation dynamics. Changes in lake-water δ18O inferred from the cellulose records reflect regional variations in δ18O of precipitation, partly modified by local evaporation effects. Comparison is made with pollen-based climate records from a nearby Finnish site. Our data indicate a relatively moist and cool climate with enhanced cyclonic circulation across the northern part of the Scandes Mountains during the earliest millennia of the Holocene. At c. 7900-6800 cal. BP declining westerlies and increasing summer temperatures led to a minimum in effective moisture. The remaining part of the Holocene was characterized by a long-term progressive cooling and considerable hydroclimatic variations, with particularly wet events centred at c. 5500, c. 3000, c. 1900, and c. 1000 cal. BP.

Did diatoms respond to the possible cooling event around 8000 years ago: high-resolution case studies of annually laminated sediments in southern Estonia and central southern Finland

Atko Heinsalu Institute of Geology, Tallinn University of Technology Diatoms were analysed from varved sediment sequence of Lake Nautajärvi (central southern Finland) at 30 stratigraphic levels in the core section spanning a period of 500 years from 8300 to 7800 yr BP, each sub-sample including 3 to 8 years and annually laminated sediment sequence of Lake Rõuge Tõugjärv (southern Estonia) at 47 stratigraphic levels in the core section spanning a period of 1000 years from 8700 to 7760 yr BP, each sub-sample including 10 years. Lake environment reaction in south to north longitudinal direction to 8.2 ka climatic cooling event are discussed.

Present-day temperatures at Sokli (northern Finland) during MIS 3 recorded by high-resolution multi-proxy analysis and climate modeling

K.F. Helmens1, J.A.A. Bos2, S. Engels2, C.J. Van Meerbeeck2, H. Seppä3, H.J.B. Birks4, S.J. Brooks5, J. Risberg1 & B. Wohlfarth6 1Department of Physical Geography and Quaternary Geology, Stockholm University, SE-106 91 Stockholm, Sweden. 2Department of Paleoclimatology and Geomorphology, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, NL-1081 HV Amsterdam, The Netherlands. 3Department of Geology, P.O. Box 64, FIN-00014 Helsinki, University of Helsinki, Finland. 4Department of Biology and Bjerknes Centre for Climate Research, University of Bergen, Allégaten 41, N-5007 Bergen, Norway. 5Department of Entomology, The Natural History Museum, Cromwell Road, London, SW7 5BD, U.K. 6Department of Geology and Geochemistry, Stockholm University, Stockholm, SE-106 91 Sweden. A near continuous sediment sequence that spans the last interglacial-glacial cycle and the present interglacial (last ~130 ka) has been recovered from a sedimentary basin in the Sokli Carbonatite Massif in Finnish Lapland. The sequence consists of tills, glacio-fluvial and fluvial beds, inter-layered with a series of fossil-rich lacustrine sediments. A first study of the entire sequence has indicated that the non-glacial sediment intercalations each have a charateristic lithological and palynological content, and represent individual and successive developments both in terms of depositional and vegetational change. The sequence shows progressively colder conditions as the last glacial cycle evolves in agreement with the marine oxygen-isotope record and the chrono-stratigraphic scheme of the northwest European mainland. We here present the results of a high-resolution, multi-proxy analysis (pollen, macrofossils, chironomids, diatoms) carried out on a 2 m thick lacustrine interval of laminated silts/clays dated to the early part of MIS 3 (ca. 50 ka). A climate model experiment with a MIS-3 interstadial set-up was performed in order to test our proxy-based, quantitative climate reconstructions. Our data reveal not only significant response in the northeastern (continental) sector of the Scandinavian Ice Sheet to warming during MIS 3, but also indicate rapid climate warming to surprisingly high, present-day temperatures in this ice-free period. Major part of the silt-clay sequence was deposited in an ice-dammed lake. The margin of the ice-sheet remained in the region most probably even during the warmest interval.

Holocene forest decline on the Tibetan Plateau – climate or human activity?

Ulrike Herzschuh 1 and John Birks2

1Alfred Wegener Institute for Polar and Marine Research, Potsdam and Department of Geosciences, University of Potsdam

2Department of Biology and Bjerknes Centre for Climatic Research, University of Bergen and Jesus College, Oxford Pollen records from the eastern Tibetan Plateau reveal a major decline in tree pollen beginning at about 6000 years B.P., suggesting a major reduction in forest cover. From the available archaeological information, it is known that Neolithic people were in the area at this time. Several Tibetan lake records provide a range of proxy evidence for decreasing moisture availability starting in the mid-Holocene that can be attributed to reduced monsoon intensity as a result of decreasing solar insolation in the Northern Hemisphere. A vigorous debate has developed about the cause of the decline in Tibetan Plateau tree cover – was it a response to climate change or a result of human activity? A pollen-based precipitation reconstruction from Qinghai Lake parallels moisture changes inferred from a stable oxygen-isotope record from ostracods in the same core. This reconstruction of decreasing moisture agrees with precipitation changes simulated by a transient climate model using a coupled atmosphere-ocean general circulation model, and by an Earth System model of intermediate complexity. In light of our reconstructions and the model results, we propose that the most parsimonious explanation for the mid-Holocene tree decline on the eastern Tibetan Plateau is that it was a widespread response to climate change, in particular decreasing moisture availability.

Holocene climate variability in northwestern Russia – activities within the CARBO-North project Steffen Holzkämper and Peter Kuhry

Department of Physical Geography and Quaternary Geology Stockholm University 106 91 Stockholm, Sweden Steffen.holzkamper@natgeo.su.se The outlines of the EU-funded 6th framework project CARBO-North, which started in November 2006 and runs until April 2010, will be presented. The consortium consists of 16 European institutions and it aims at quantifying the carbon budget in northern Russia across temporal and spatial scales. Activities address rates of ecosystem change, effects on the carbon budget (radiative forcing), and global climate and policy implications. One aspect of the project is the reconstruction of Holocene climate and environmental conditions in the investigation area, the northeastern European Russian Arctic (Usa-basin). A wide range of proxies will be used to evaluate rates of ecosystem change under past climatic changes. Both classical and new methods will be applied. New proxies like the stable oxygen and carbon isotope composition of the cellulose fraction of peat deposits and tree rings in combination with “classical analyses” of peat profiles, dendroclimatology and paleolimnology will enable us to get deeper insights into the climatic and environmental development on a local and region scale than any single climate proxy can give. The talk will focus on the methodological approach and the planned activities to achieve a meaningful, quantitative reconstruction of past climate changes in this sensitive region.

Variability and seasonality of North Atlantic climate during the early Holocene: evidence from Faroe Island lake sediments.

Catherine Jessen

GeoBiosphere Science Centre, Quaternary Sciences, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden

Based on their position in relation to major ocean currents, palaeoclimatic archives in the Faroe Islands are expected to be sensitive recorders of variations in North Atlantic circulation. The multi-proxy analysis (magnetic susceptibility, total carbon, nitrogen and sulphur, biogenic silica, grains >255μm) of a lacustrine record with both winter and summer climate indicators illustrates the variability of Faroese climate during the early Holocene (ca. 11,300 – 10,240 cal yr B.P.) and allows comparison with other records in the region. Our high-resolution record shows a period of predominantly winter cooling and increased storminess centred at ca. 11,150 cal yr B.P. followed by a period of stability between ca. 11,000 and 10,680 cal yr B.P., which correlates to a time when the North Atlantic was particularly free of meltwater incursions. After ca. 10,680 cal yr B.P., both winter and summer indicators show a major increase in variability broadly synchronous with increased variability at other North Atlantic sites. Within this time period, a predominantly winter cooling centred at ca. 10,600 cal yr B.P., a winter/summer cooling centred at ca. 10,450 cal yr B.P. and a winter/summer cooling centred at ca. 10,300 cal yr B.P. are recorded. These distinctive coolings correspond to periods of ice core δ18O inferred lowered atmospheric temperatures over Greenland and the reoccurrence of meltwater outbursts at ca. 10,600, 10,500 and 10,350 cal yr B.P.

Humidity and storminess reconstructions from south-west Sweden - a regional record of climate during the past 6500 years?

Rixt de Jong Geobiosphere Science Centre, Quaternary Sciences, Lund University The coastal zone of Halland, south-west Sweden, is situated in the region that is strongly affected by extra-tropical cyclones. To study past changes in the position of the North Atlantic cyclone track, two ombrotrophic peat bogs, the Undarsmosse and Store Mosse bogs, were examined for their mineral sand grain content. This was used as a proxy for aeolian activity. In addition, organic bulk density (OBD) analysis was carried out at both study sites. At the Undarsmosse bog testate amoebae analysis was used to provide more detailed information on humidity shifts during the last 1700 years. The OBD and testate amoebae records reflect variations in surface wetness of the bogs, which can be used to infer changes in the ratio evaporation/precipitation. The results show a highly similar sand influx pattern for both study sites, suggesting that the aeolian sediment influx (ASI) records reflect regional scale changes in storm activity. A comparison between the results from this study to other records shows that the humidity and storminess reconstructions from Halland are generally in good agreement with e.g. dune re-activation phases in Denmark and lake level fluctuations recorded in south-central Sweden. The results may therefore be used to propose a regional scale reconstruction of climatic changes. A detailed comparison between ASI peak events and the testate amoebae wetness reconstruction shows an enigmatic pattern of increased storm activity during hydrological shifts.

A biogenic silica δ18O record from lake sediment in northern Fennoscandia

Christina Jonsson a, Gunhild, C. Rosqvist a, Dan Hammarlund b, Melanie, J. Leng c a) Department of Physical Geography and Quaternary Geology, Stockholm University, 106 91 Stockholm, Sweden b) GeoBiosphere Science centre, Quaternary Sciences, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden c) NERC Isotope Geosciences Laboratory, British Geological Survey, Nottingham NG12 5GG, UK Reconstructions of past variations in the composition of oxygen isotopes in lake waters in northern Sweden have recently been used to infer changes in atmospheric circulation. There is an interest in the 18O/16O ratio of diatom silica, particularly for lakes in areas where carbonates are absent and the oxygen isotope composition of lacustrine biogenic silica (diatoms) (δ18Osi) is being increasingly used in paleoclimate studies. Here we present a record of oxygen isotopes in biogenic silica from Lake Oikojärvi covering the last c. 2500 years. Lake Oikojärvi (68º41'N, 22º21'E; 455 m a.s.l.) is located in northern Lapland, 25 km northwest of the GNIP station in Naimakka. The δ18Osi signal depends on the ambient water temperature and the lake water isotopic composition (δ18Ow). Previous studies have shown that the effect of changes in δ18O of the lake water overwhelms the effect of temperature. The Oikojärvi δ18Osi values vary between 30.4 and 26.2‰. There is a gradual decrease towards more depleted values during the last 1000 years from 29 ‰ to the modern value of 26.2 ‰ with the exception of a period around 500 cal years BP when δ18O becomes enriched. This trend towards more depleted values over the last 1000 years has also been detected in other δ18O-records from northern Fennoscandia derived from both diatom and CaCO3. We argue that this depletion most likely is caused by an increase in δ18O depleted precipitation. This explanation is supported by other climate reconstructions from the area, which show decreasing temperatures during the same time period.

Late Holocene Peatland and Lake Responses to Climate Change and Permafrost Conditions: Results from Multi-proxy Studies in Subarctic Sweden Ulla Kokfelt1*, Dan Hammarlund1, Nina Reuss1, Mats Rundgren1, Peter Rosén2, Mats Sonesson3, Kristian Schoning4, Göran Skog1, Johannes Förster2 1GeoBiosphere Science Centre, Lund University; 2CIRC, Umeå University; 3Plant Ecology and Systematics, Lund University; 4Institute of Physical Geography and Quaternary Geology, Stockholm University *Author for correspondence (ulla.kokfelt@geol.lu.se) The Stordalen mire in northernmost Sweden is situated in a zone characterized by discontinuous permafrost. The permafrost underlying the mire has been melting throughout the last decades, and mire communities have changed from a dominance of frost-heaved ombrotrophic areas (palsas) towards an increase in wet minerotrophic areas (Christensen et al, 2004). Decades of intense research on the mire system and relatively long meteorological monitoring series from a nearby station made the site a natural choice for studies of both recent and late Holocene responses to changes in climate and permafrost conditions. We compare results from multi-proxy studies of peat and lake sediments at Stordalen in order to date and characterize catchment-scale ecological changes. 210Pb dated profiles are compared to meteorological data, and long proxy records covering the later part of the Holocene are compared to regional reconstructions. The results from the analyzed peat sequence show that peat growth started around 4600 cal BP, and that a transition from minerotrophic to wet ombrotrophic conditions was initiated at ca. 2800 cal BP and lasted until 1350 cal BP when Sphagnum (group Cuspidata) became dominant. During the transition to ombrotrophic conditions a continuous increase in organic content and a corresponding decrease in minerogenic content indicate an upheaval of the mire, consistent with a change from a high energy environment to the onset of stable organic sedimentation in the lake at ca. 2650 cal BP. This indicates a rapid isolation of the lake basin, and probably reflects the onset of permafrost formation in response to late Holocene cooling in northern Fennoscandia.

Dunes, wind & fire – a 11 ka record of aeolian sedimentation in Finnish Lapland Mia Kotilainen Department of Geology, P.O. Box 64, FIN-00014, University of Helsinki, Finland Dune reactivation history during the last 11 000 years in northern Finnish Lapland was reconstructed by studying a total of 75 dune sections from two dune fields, which are situated 70 km apart from each other. One of the study areas is located in the present coniferous forest zone while the other dune field lies in the present mountain birch forest zone.

Study methods included stratigraphical interpretation of the dune sections, sedimentological analyses for grain size distribution and parameters (249 samples), binocular microscopy for grain roundness and surface texture (225 samples). Study methods also included Scanning electron microscopy for quartz grain surface texture (175 quartz grains), thin sections (52) for grain mineralogical composition and microprobe analysis (117) for the chemical composition of garnet grains. Conventional radiocarbon dating (54), AMS dating (4) and TL/OSL dating (15) were used for reconstructing the chronostratigraphy.

Three lithostratigraphical units were detected on both dune fields. Paleoenvironmental model of the Holocene development was based on grain property data and dating results respective for each unit.

Unit 1, the initial dune building period, took place in the early Holocene at circa 10 800 to 8 700 yrs before present. Unit 1 is characterised by high wind velocities and transportation rates with effective aeolian processes (sorting and grinding) during the deposition. The morphological frame of the dune fields originates from the deposition of Unit 1 and met only minor modification at the deposition of Units 2 and 3. Unit 2 represents on both dune fields the longest accumulation series with several stabilization-reactivation cycles and shifting wind directions. Four dune reactivation phases were recognised in connection with the deposition of Unit 2. The data suggests a dune advance with moderate wind velocities and transportation rates with effective aeolian processes and aeolian maturation of quartz particles during the deposition. Unit 3 accommodates dune reactivation phase R5 (since 500 yrs BP), which is detected at the Ijjävri dune field. The lithostratigraphy is characterised by unstratified, deformed strata. The data suggests moderate to weak wind velocities and transportation rates with effective aeolian processes and aeolian maturation of quartz particles during the deposition of Unit 3.

The data suggests a climate control on the duration of the active phases on both the dune fields during early- and mid-Holocene. However, the climate variability can not explain the reactivation processes during late-Holocene, for the last 4 500 yrs before present. Human activity as a promoter for dune reactivation prior 1 000 yrs before present is improbable on the studied dune fields. The latest reactivation phenomena at the Ijjävri dune field, from circa 500 yrs BP to the present is promoted by both climate and human impact. The LIA event provided the triggering factor for the beginning of the phase and the continuous aeolian activity has been supported by human activity including reindeer husbandry and off road vehicles. New results provided by this study give an improved picture of the Holocene development of the northern dune areas. The results indicate that stratigraphical interpretation with adequate number of dune sections is vital for understanding the reactivation phenomenon in these areas.

Chydorid ephippia – a promising tool for climate reconstruction Seija Kultti, Kaarina Sarmaja-Korjonen and Liisa Nevalainen

Department of Geology, P.O.Box 64, FI-00014 University of Helsinki (seija.kultti@helsinki.fi) Ephippium analysis, a recent palaeolimnological method, uses the two reproduction strategies of littoral water fleas of the family Chydoridae (chydorids) to estimate the past length of open-water season in cold-temperate lakes. In northern lakes chydorids reproduce asexually during most of the open-water season until the oncoming winter triggers sexual reproduction. This results in the appearance of males and sexual females, and after fertilization, the formation of a modified female shell (carapace), the ephippium, which protects the resting eggs. Chitinous chydorid remains, including ephippia, preserve well in lake sediments and can be identified to species level. In a mild climate (long open-water season) the period of asexual reproduction is long compared to the period of sexual reproduction, resulting in a higher proportion of shells of asexual females being deposited in sediments than in cold climates where the proportion of ephippia (shells of sexual females) increases.

Surface sediment samples were collected from 90 Finnish lakes. The lakes are situated along a transect across Finland where the average open-water season varies from 213 days in the south to 137 days in the north and where annual temperatures vary from +5° C to -2° C, respectively. We tested with statistical methods the relationship between the present ephippium proportions and the present climate normals (1970 – 2000). The preliminary results indicate a clear increase of ephippium proportions from N 60º to N 70º. The linear correlation is highest between ephippium proportion and June temperature (-0.84***). The aim of the study is to provide a model for climate reconstructions on the basis of the analysed data to be applied on past sediments

Holocene glacial fluctuations in Norway Atle Nesjea,c, Jostein Bakkeb,c, Svein Olaf Dahlb,c, Øyvind Liec and John A. Matthewsd a Department of Earth Science, University of Bergen, Allégaten 41, N-5007 Bergen, Norway b Department of Geography, University of Bergen, Fosswinckelsgate 6, N-5007 Bergen c Bjerknes Centre for Climate Research, Allégaten 55, N-5007 Bergen, Norway d Department of Geography University of Wales at Swansea, Singleton Park, Swansea, SA2 8PP, United Kingdom Documentation of glacier changes is a key element for reconstruction of past climate variability and early detection of global climate change. Records of Holocene glacier variations in different regions in Norway have been synthesised. During the period from approximately 8000-4000 cal. yr BP, most glaciers in Norway were completely melted away at least once due to high summer temperatures and/or reduced winter precipitation. Lichenometrically and historically dated moraines at Jostedalsbreen, in Jotunheimen, at Hardangerjøkulen, and at Folgefonna were used to extend records of glacier-length variations back to their maximum position during the ‘Little Ice Age’. The timing of the maximum ‘Little Ice Age’ glacial advance in different parts of southern Norway varied considerably, ranging from the early 18th century to the late 19th century. Cumulative glacier length variations of glaciers in southern Norway show an overall retreat from ~AD 1750 to the 1930s-40s. Thereafter, most Norwegian glaciers retreated significantly. Short maritime outlet glaciers with a short response time (<10-15 years) started to advance in the mid 1950s, whereas long outlet glaciers with longer frontal time lag (>15-20 years) continued their retreat to the 1980s. In the 1990s, however, several of the maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s. Since 2000 most of the observed glaciers have retreated remarkably fast (annual frontal retreat >100 m) mainly due to high summer temperatures.

The Holocene climate effects on chironomids - examples of possible indirect mechanisms Marjut Nyman P.O. Box 65, Department of Biological and Environmental Sciences, 00014 University of Helsinki, Finland Aquatic midge larvae provide valuable information on the past environmental change in the north. The climate has been the ultimate driving force for change in chironomid assemblages in most cases, but the effects of climate are reflected through various mechanisms in different lakes, which makes quantitative chironomid-based temperature reconstructions sometimes difficult to understand. The response of Chironomidae to Holocene climate change will be illustrated using lakes from Lapland as an example. Lower temperature values than expected based on the presence of pine in the catchment during the mid-Holocene were reconstructed from a lake with great water volume and depth. The lake provided a thermal refuge for profundal, cold adapted taxa during the warm period, which was mainly reflected in the changes in the abundances of littoral and sublittoral taxa. In a shallow oligotrophic lake, a decrease in the reconstructed temperatures during the late Holocene may reflect the indirect response of the midges to climate change through pH change. The results from these lakes show that the response of the midge communities to climate change seems to be more or less indirect. The reconstructions should always be evaluated using the techniques for this purpose and checked against other information/proxies for environmental change. To understand the mechanisms behind the assemblage change and resultant reconstructions, we need to refine the subfossil taxonomy, develop the calibration sets further, and improve the ecological understanding of different taxa.

The Pecularities of diatom distribtion in surface sediments in Northern part of the Curonian lagoon

Ieva Paunksnyte Institute of Botany, Zaliuju ezeru 49, LT-08406 Vilnius, Lithuania, e-mail: ieva.paunksnyte@gmail.com

The study focused on diatom assemblages taken in northern part of the Curonian Lagoon, a semi-closed water basin of the SE Baltic Sea. Species composition and abundance were performed on the diatom flora from the eight surface sediments samples and five short sediment cores (up to 10 cm). The diatom groups were distinguished with respect to their tolerance for environmental conditions such as salinity, trophic conditions. The diatom flora of the lagoon proved to be highly variable, corresponding to the general environmental status. The species composition of diatom assemblages showed a very wide range of environmental conditions from freshwater to brackish and different trophy zones.

Changes in the diatom assemblages species enabled a reconstruction of environmental conditions in the lagoon during the last decades. The lowermost sediments were characterized by freshwater and brackish diatoms (e.g. Fragilaria brevistriata, Navicula scutelloides, Aulacoseira islandica), occasional marine taxa were observed. Anomalous occurrence of marine diatoms was evidence for short-lived periods of elevated salinity in the lagoon. In the uppermost layers freshwater, brackish species were complemented by dominants Actinocyclus normanii, the abundance of marine taxa in different parts of the lagoon increased. Eutrophication and pollution of the Curonian Lagoon showed the development of a specific ‘anthropogenic’ diatom assemblage, primarily represented by Stephanodiscus hantzschii, S. minutulus, Cyclotella meneghiniana, Aulacoseira ambigua.

Studies on contemporary land ecosystem – atmosphere interactions

Janne Rinne1, Timo Vesala1, Mika Aurela2, Tuomas Laurila2, Hannele Hakola2, Virpi Taivainen2, Terhi Riutta3, Ilona Riipinen1, Pertti Hari3, Eeva-Stiina Tuittila3, Markku Kulmala1

1) Department of Physical Sciences, University of Helsinki, Finland 2) Finnish Meteorological Institute, Helsinki, Finland 3) Department of Forest Ecology, University of Helsinki, Finland

Current atmospheric trace gas concentrations are to a large extent determined by exchange processes between biosphere and atmosphere. Thus the biosphere can have an effect on the physico-chemical climate through the radiative and chemical effects of the biogenic trace compounds. The exchange processes can be studied in a range of spatial and temporal scales using a variety of different techniques. For example, an important process determining the atmospheric carbon dioxide concentration is the exchange between land ecosystems and the atmosphere. This exchange is studied in leaf scale by enclosure methods, in ecosystem scale by micrometeorological flux measurement techniques, and in regional scales by inversion techniques. In this presentation examples of studies on biosphere-atmosphere exchange conducted in boreal region by the University of Helsinki. Examples include the exchange of methane and carbon dioxide between boreal wetlands and atmosphere, emission of chemically reactive hydrocarbons from boreal ecosystems, and formation of secondary aerosol particles in boreal regions.

Early Holocene environment variations in the NE Lithuania: a pilot study Miglė Stančikaitė, Petras Šinkūnas (Institute of Geology and Geography, Ševčenkos 13, LT-03223, Vilnius, Lithuania; e-mails: stancikaite@geo.lt; sinkunas@geo.lt) Dagfinn Moe (Bergen Museum, Allegated 41, N-5007, Bergen, Norway) Giedrė Vaikutienė (Vilnius University, Čiurlionio21/27, LT-03223, Vilnius, Lithuania; e-mail: giedre.vaikutiene@gf.vu.lt) This study focuses on the characteristics and chronology of early Holocene environmental changes in the northeastern Lithuania. The reconstruction of environmental variations is based on new multiproxy data (geological-geomorphological, lithological, pollen, diatoms, isotope investigations (14C, δO

18‰, δC

13 ‰) and loss-on-ignition) obtained from the sediment sequence of Petrašiūnai Lake. Responding to early Holocene climatic amelioration formation of the tree cover started on the morainic relief deposited by the Weichselian Glaciation. Together with Betula and Pinus that were typical for the vegetation composition in the surrounding territories, Picea established around the oxygen-rich, alkaline water basin and culminated at about 10650 cal. BP. Increasing density of the vegetation cover was confirmed by the rising number of the organic imput in to the sedimentary basin. Later, changing environmental situation was recorded as a repeating strong depression in the number of the particular taxa e.g. Pinus and culmination of other’s e.g. Betula or Picea. The diatom composition indicating some rise of the water depth confirms changing sedimentation regime that may have been related with the fluctuations of the environmental parameters also. Instability of the isotope composition (δO

18‰, δC

13 ‰) indicates some changes in the climatic parameters (temperature and precipitation) that took place in area.

Speleothems from northwestern Sweden as recorder of environmental change during the Holocene

Hanna S. Sundqvist Department of Physical Geography and Quaternary Geology Stockholm University S-10691 Stockholm hanna.sundqvist@natgeo.su.se The main aim of the study was to contribute with detailed information of regional environmental change during the Holocene through studies of speleothems and their growth environments from two caves, Korallgrottan and Labyrintgrottan in northwestern Sweden. This was done through studies of stable isotopes and the speleothems in combination with a detailed monitoring study in Korallgrottan. The monitoring study suggests that stalagmites fed by stalactites with slow and stable drip rates from deep inside the cave may be suitable as palaeoclimate archives. Similarities between oxygen isotope signals of contemporary samples from Labyrintgrottan and Korallgrottan emphasize the potential of speleothems from Labyrintgrottan to also provide high resolution regional palaeoclimate information. Except for a number of cold events stalagmite δ18O records from northern Scandinavia indicate that temperatures were warmer than today between 9500 and 6000 years ago. During this period the interval between 7800 and 6000 years ago seems to have been the warmest. The area above Labyrintgrottan was most likely covered by much denser vegetation than today at the time of stalagmite growth (9500-7500 years ago) and was, unlike today, probably situated below the local tree-limit between 9000 and 8000 years ago. The δ18O record of a stalagmite from Korallgrottan covering the last 4000 years agrees with the concept of a warmer period, the so called Medieval Warm Period, centred around AD1000 and a colder period, the so called Little Ice Age, somewhere between AD1000 and today.

Isla de los Estados (Patagonia) - island at the end of the world. Preliminary palaeoclimate data over the last 15 ka based on 14C and XRF analyses

Ingmar Unkel1, Svante Björck1, Barbara Wohlfahrt2, Marilen Fernandez1

1 GeoBiosphere Science Centre, Quaternary Sciences, Lund University, Sölvegatan 12, S-223 62 Lund (Sweden), 2 Dept. of Geology and Geochemistry, Stockholm University, 10691 Stockholm, Sweden Contact email: ingmar.unkel@geol.lu.se One key question of palaeoclimatic research is the dynamics behind the Atlantic heat transport from South to North, i.e. from equatorial regions to higher latitudes. What are the driving mechanisms of this complex climate system, and how do the northern and southern hemispheres respond during phases of climate change? A widely unexplored source of information on Quaternary climate data are the Atlantic islands. The basic idea is to obtain terrestrial proxy data which record atmospheric condition but within a complete ocean setting. Here we present first radiometric and geochemical analyses from two lake sites on Isla de los Estados (Argentina, 55.8°S, 64.25°W). The two cores of 7,50 m (Lago Galvarne Bog) and 5,25 m (Laguna Cascada), which are currently under investigation, provide a continuous record of the last 15-16 ka years. Their stratigraphy consists of glacial clay, peat and gyttja sequences, indicating changes between cooler/wet and warmer/dry conditions throughout the end of the last glacial and the Holocene.

The island is on of the best palaeoclimatic “anchoring points” between Antarctic, South American and Atlantic records. Thus, it may play a key role for a better understanding of the Atlantic data within the context of changes of global circulation patterns, both atmospheric and marine. The work on Isla de los Estados is part of the ATLANTIS project, in which various islands through the North and South Atlantic have been sampled and investigated since 2000.

Towards a Holocene tephrochronology for Scandinavia and adjacent areas Stefan Wastegård Department of Physical Geography and Quaternary Geology, Stockholm University, SE-10691 Stockholm, Sweden. Tephra horizons are now found routinely in a range of palaeoclimate archives in the North Atlantic region. These time-synchronous markers offer a unique possibility to test hypotheses regarding synchronous or non-synchronous response to climate forcing. There is an increasing demand for exact time markers in the palaeoclimate community as more investigations now aim at high temporal resolutions. Tephrochronology has the potential to provide these, but the full potential has not yet been exploited. For example, dating of many tephras from the last glacial cycle relies on marine radiocarbon dates which suffer from unknown variations in the marine radiocarbon effect. Holocene tephras are usually more securely dated, but some regularly reported ages are indeed based on very few dates. Here I report on the state of the art of the Holocene tephrochronology in Scandinavia and adjacent areas. A series of maps show the known distribution of some widespread horizons including the Early Holocene 10-ka Askja tephra (c. 10,900 cal. yr BP) and the Saksunarvatn tephra (c. 10,200 cal yr BP). The most significant middle and late Holocene isochrones are Lairg-A (c. 7000 cal yr BP), Hekla-4 (c. 4260 cal. yr BP), Hekla-Selsund/Kebister (c. 3720 cal. yr BP), Hekla-3 (c. 3000 cal. yr BP) and Askja-1875 (AD 1875). A recent record of the Hekla-4 tephra from the Mustjärve bog in NW Estonia confirms that this tephra probably is the most widespread Holocene tephra in the North Atlantic region. Several other tephra horizons have been identified in single sites or in restricted areas and are so far less valuable as marker horizons, but are potentially important for the future.

Diatom inferred summer temperatures of the past eight centuries in northern Fennoscandia J. Weckström (1), A. Korhola (1), P. Erästö (2), L. Holmström (3) (1) Department of Biological and Environmental Sciences, University of Helsinki, Finland (jan.weckstrom@helsinki.fi), (2) National Public Health Institute, Finland, (3) Department of Mathematical Sciences, University of Oulu, Finland Establishing natural climate variability becomes particularly important in remote Polar regions in anticipation of higher than average warming. We present a high-resolution record of temperature variability of the past 800 years based on sedimentary diatoms from a treeline lake in northwestern Finnish Lapland. BSiZer multiscale smoothing technique is applied to the data to identify significant features in the record at different temporal levels. The overall reconstruction shows a relatively large multi-centennial temperature variability with a total range of about 0.6-0.8ºC. At a millennial perspective the temperatures exhibit a statistically significant long-term cooling trend prior to industrialisation (∂T = -0.03ºC/century). At a centennial time scale three warm intervals were identified around AD 1200-1300 (terminal phase of the Medieval Warm Period), AD 1380-1550 and from AD 1920 until the present. Pronounced coolness occurred between AD 1600 and 1920, indicative of the Little Ice Age. At a decadal level certain shorter-term climate excursions were revealed. The warmest ∼10-30 year, non-overlapping periods occurred in AD 1220-1250, 1470-1500 and 1970-2000, respectively. The classic events of Medieval Warm Period (MVP) and Little Ice Age (LIA) are evident in our record, as is also the 20th century warming.

Palaeobotanical and lithological review of a 7-m-thick sediment sequence, dated to MIS 5d-c, from Sokli, southern Finnish Lapland – preliminary results and interpretation

M. Väliranta1 & K.F. Helmens2 1 Department of Biological and Environmental Sciences, P.O. Box 65, 00014 University of Helsinki, Finland 2Department of Physical Geography and Quaternary Geology, Stockholm University, SE-106 91 Stockholm, Sweden. Lithological description and preliminary palaeobotanical results of a sediment sequence dated to MIS 5d-c (ca. 110-95 ka) from Sokli, southern Finnish Lapland, are presented. This continuous and unusually long sediment sequence shows that despite the fact that Sokli area was repeatedly covered by the Scandinavian Ice Sheet during the last glacial period, till beds and ice-marginal fluvial sediments as well as fossil-rich lacustrine and fluvial sediments were not eroded. The lithology is very diverse and indicates prominent changes in deposition conditions. The bottom sequence consists of high-power fluvial gravels and sands and above there is a layer of quiet fluvial/shallow lacustrine sands and silts, which are overlain by finely laminated gyttja. On top of these layers, there is gyttja which is inter-layered by woody material and sand, indicating floodplain environment. Above gyttja there is a layer of sands and gravels and at the very top laminated sandy gyttja is recorded. The sequence is capped by basal till. Low-resolution pollen analysis has revealed open (steppe-)tundra vegetation gradually developing towards birch forest with possible stands of pine (birch/pine forest) and back to open tundra. Preliminary macrofossil results suggest two warmer periods, during which for instance tree-type birches and conifers were locally present. According to macrobotanical analysis, especially the latter period is floristically very rich. In near future high-resolution pollen and chironomid analyses will be carried out and. a transfer functions based on modern-day plant/animal-climate calibrations sets will be applied to quantitatively infer mean July temperatures. Minimum mean July temperatures will also be estimated based on the fossil plant/animal assemblages and detailed information on the present distribution of the species in northern Europe.