Veli-Pekka Salonen

The effect of Holocene treeline fluctuations on the sediment chemistry of Lake Kilpisjärvi, Finland

The sediments of Lake Kilpisjärvi were described and analysed for element chemistry and pollen to study the effects of treeline fluctuations in the catchment. Lake Kilpisjärvi is one of the largest lakes in Finnish Lapland, with its catchment partly above the treeline and partly covered with mountain birch woodland. Although the presence of subfossil pine shows that the catchment was previously covered with mountain birch woodland during the Holocene, the present pine treeline has receded 70 km from the lake. Pollen analysis results show that pine immigrated to the area during the Atlantic chrone and that ∼7000 BP pine forests occupied much of the catchment. Pine started to decline around 3500 BP and vegetation in the catchment became more open. Alkaline and alkaline earth metals and some transition metals document the change from glaciolacustrine clay to more organic sediment. However, these geochemical trends give no indication of changes in erosion rate resulting from changes in catchment vegetation. These changes were detected by plotting suitable element ratios. In addition to the conventional Si/Al and Na/K ratios, the Calabile/Si ratio and especially the ratio of labile Ca to K were found to be useful. Of all the elements analysed, potassium showed the strongest reaction to changes in the balance between weathering and erosion. During the phase of denser forests, chemical weathering was dominant, whereas during phases of open catchment, physical erosion prevailed. The effects of changing climate and catchment vegetation were distinguished from other signals. For instance, iron and manganese were enriched at the top of the core due to diffusion and, at the same time, old precipitate layers persisted after burial to deeper levels in the sediment. These iron and manganese rich layers had an effect on the distributions of cobalt, zinc, and vanadium, showing increased concentrations of these elements. Other effects that made the interpretation of chemical records difficult were the effect of ongoing mineralization of organic matter in the top layers of sediment and the effect of biogenic silicon. Owing to the stable conditions of the lake, the desired chemical signals were detected, despite the masking trends.

LATE QUATERNARY ECOLOGICAL TURNOVER IN HIGH ARCTIC LAKE EINSTAKEN, NORDAUSTLANDET, SVALBARD (80° N)

Luoto, T.P., Nevalainen, L., Kubischta, F., Kultti, S., Knudsen, K.L. and Salonen, V.‐P., 2011: Late Quaternary ecological turnover in high arctic Lake Einstaken, Nordaustlandet, Svalbard (80° N). Geografiska Annaler: Series A, Physical Geography, 93, 337–354. DOI:10.1111/j.1468‐0459.2011.00435.x Abstract Multiproxy palaeolimnological analyses of a sediment core record from Lake Einstaken, Nordaustlandet, give insight into long‐term ecological and environmental dynamics in the High Arctic Svalbard during the last c. 13-000 cal yr bp. Fossil remains of foraminifera, chironomidae, cladocera and diatoms (Bacillariophyta) revealed several distinct ecological turnovers during the late Quaternary. The foraminiferal assemblages in a marine interval in the lower part of the core indicated one distinct faunal turnover and two subsequent minor changes. The foraminiferal assemblages reflected high‐arctic, shallow‐water conditions in an area of changing salinity conditions. A development of gradually more restricted marine conditions, presumably related to a decrease in water depth during the isostatic uplift, was evident from the foraminiferal assemblages. The Holocene was characterized by a freshwater environment in the isolated Lake Einstaken. The cladoceran assemblages experienced two complete faunal turnovers in the early part of the lacustrine sediment sequence, most likely related to inlake processes. The chironomid assemblages went through five distinct Holocene faunal changes that were probably mostly related to climate development and changes in nutrient conditions. The freshwater diatoms revealed four distinct episodes of change in their assemblages that could be related to their sensitivity to pH and nutrient status. The most distinct common feature in the Holocene faunal and floral assemblages was the pioneer phase during the early Holocene. The recent environmental changes, which were most visibly reflected in the chironomid records, are possibly related to a coupled effect of elevated nutrient conditions and increased temperatures.

HOLOCENE BENTHIC FORAMINIFERAL RECORD FROM A HIGH-ARCTIC FJORD, NORDAUSTLANDET, SVALBARD

Kubischta, F., Knudsen, K.L., Ojala, A.E.K. and Salonen, V.‐P., 2011. Holocene benthic foraminiferal record from a high‐arctic fjord, Nordaustlandet, Svalbard. Geografiska Annaler: Series A, Physical Geography, 93, 227–242. DOI: 10.1111/j.1468‐0459.2011.00434.x Abstract This study presents the results of benthic foraminiferal analyses of a marine core record from about 100 m water depth in the fjord environment of Isvika bay, Nordaustlandet, Svalbard. During the Last Glacial Maximum, the bay was glaciated by the north‐western sector of the Svalbard‐Barents Sea Ice Sheet. The foraminiferal assemblages reflect glaciomarine conditions during deglaciation and early Holocene (about 11-250–9640 cal. yr bp) followed by glacier‐distal environment in an open fjord with relatively high influence of Atlantic waters from the open ocean (9640–7430-cal. yr bp). A subsequent foraminiferal indication of a glacial advance was followed by deposition of a diamicton unit within a short time period at 5800–5700 cal. yr bp. The mid‐ and late Holocene were characterized by assemblages indicating restricted open‐ocean connection and gradually more severe conditions, which are considered to be caused partly by a gradual cooling and freshening of the Atlantic water inflow to the shelf area and partly by a continuous isostatic uplift of the area. The foraminiferal record shows that the environmental changes in Murchisonfjorden are not just an effect of changes in solar insolation but are also influenced by local processes, as well as changes in the Atlantic water inflow to the northern Svalbard shelf and to the fjord via Hinlopenstretet.

Ecological responses to climate change in a bird-impacted High Arctic pond (Nordaustlandet, Svalbard)

A 28-cm sediment core from an Arctic pond (Nordaustlandet, Svalbard), which is currently subjected to the fertilizing effect of bird guano, was analysed for fossil invertebrates and the physical properties of the sediment. The objective was to examine aquatic community responses to climate warming. Our record reveals that faunal changes have occurred. Initially chironomid assemblages were dominated by a cold-indicating oligotrophic community but this was replaced by a community typical of more nutrient-enriched conditions and warmer water temperature at around AD 1,700–1,800. After AD 1,800, ostracods and Daphnia increase suggesting that a nutrient enrichment threshold was crossed, probably related to increased planktonic algal productivity. In the early twentieth century, organic content markedly increases and magnetic susceptibility values suddenly drop, indicating a further increase in nutrient input and lake productivity. Since the most likely source of nutrients in the lake is goose guano, this suggests that the size of the bird colony may also have increased over this period. These changes coincide with climate warming suggesting a positive feedback in which climate change is the primary driver of the increasing geese abundance and lake productivity. Our results further suggest that the predicted future warming in the Arctic will continue to have cascading effects on freshwater ecosystems in the region.

Fossil remains of an unknown Alona species (Chydoridae, Aloninae) from a high arctic lake in Nordaustlandet (Svalbard) in relation to glaciation and Holocene environmental history

We analyzed a lacustrine sediment core covering the Holocene from Lake Einstaken, Nordaustlandet, for its fossil Cladocera (Crustacea) with an aim to reconstruct past aquatic communities in this environmentally extreme and unexplored region. In the analysis, we encountered remains (carapaces, ephippia, headshields, and postabdomens) of an unknown chydorid (Chydoridae, Aloninae) species during two separate periods in the early Holocene. The remains had some comparable morphological characters with the European Alona guttata s.str. Sars, 1862 and with the glacial relict Alona werestschagini Sinev, 1999, but they differed clearly from the previous species; the headshield had broadly rounded rostrum and narrow fornices, the ephippium was heavily pigmented and reticulated, and the postabdomen had convex dorsal and ventral margins. The postabdomen had evidently similar morphology with Alona bergi Røen, 1992, which has been described, although inadequately, from arctic Canada and northern Greenland. We conclude, based on the morphology of the postabdomen, that the unknown remains belong to species closely resembling A. bergi, named here Alona cf. bergi, and assume that the species, whether the true A. bergi or some other cryptic species of the A.guttata group, is a postglacial relict of the high arctic adapted to cold climate. Herewith, we emphasize the need for extensive biogeographical investigations into both fossil and intact specimens of chydorids in the arctic.

Late Quaternary foraminiferal record in Murchisonfjorden, Nordaustlandet, Svalbard

Benthic foraminiferal assemblages from Nordaustlandet, Svalbard, are described for the first time with the objective of reconstructing the palaeoenvironmental conditions in the area during the late Quaternary. Investigations were carried out on marine deposits exposed along the southern shores of Murchisonfjorden. Five foraminiferal assemblages (A1–A5), representing different palaeoenvironmental conditions, were identified from the marine intervals, i.e., the Cassidulina reniforme–Elphidium albiumbilicatum assemblage (A1) from the Early Weichselian, the Islandiella helenae–Cibicides lobatulus assemblage (A2) from the Early Weichselian, the Cibicides lobatulus–Cassidulina reniforme assemblage (A3) from marine isotope stage 3, the Elphidium albiumbilicatum assemblage (A4) from the early Holocene and the Astrononion gallowayi assemblage (A5) from the mid-Holocene. Assemblages A1–A5 are compared with modern and fossil Quaternary assemblages from Arctic regions. Particularly notable is the fact that a well-defined Middle Weichselian assemblage in Svalbard is described for the first time, i.e., the Cibicides lobatulus– Cassidulina reniforme assemblage. All the assemblages from Nordaustlandet represent glacier-distal, inner-shelf environments with an open connection to the ocean. The results reveal the occurrence of three marine intervals (ice-free periods) in the north-western part of Nordaustlandet during the Weichselian, as well as ice-free conditions during most of the Holocene. A comparison of the assemblages from Nordaustlandet with previously published foraminiferal zones from onshore sections elsewhere in Svalbard show some degree of similarity, but also show considerable variation in species compositions, presumably caused by local environmental differences.

Pro- and postglacial invertebrate communities of Pingualuit Crater Lake, Nunavik (Canada), and their paleoenvironmental implications

Abstract.  Zoological remains were examined from the sediments of the Pingualuit Crater Lake, Nunavik, Canada. Our objective was to describe past climate events in the area of delayed deglaciation in northernmost Ungava Peninsula. Our record covers 3 separate sections of deglacial and postglacial invertebrate dynamics interrupted by laminated proglacial sediments and a basin-scale erosive slumping event. The abundance of animal remains in the ultra-oligotrophic and extremely deep arctic lake was low, but distinct faunal assemblages were found among the intervals, results implying that they were environmentally heterogeneous. The lowermost fine-grained interval (before 6850 calibrated years before present [cal BP]), revealed that Cladocera Chydorus sphaericus-type and Bosmina (Eubosmina) longispina-type were common in the lake, whereas Chironomidae were relatively rare. The dominance of B. longispina-type showed that planktonic communities were successful at the time, probably indicating more favorable climatic conditions than today soon after the last deglaciation (∼7000 cal BP). In the middle interval (between ∼6850 and 5750 cal BP), chironomids became more common and were dominated by Heterotrissocladius subpilosus-type and Protanypus, taxa that are characteristic of oligotrophic lakes. The extirpation of B. longispina-type suggests that planktonic invertebrate communities were not successful, probably because of predation by Arctic char. The presence of the chironomid Oliveridia tricornis-type during the late Holocene (between ∼4200 and 600 cal BP) suggested general climate cooling. Our paleoclimatic conclusions on the regional environmental history suggest a stationary ice front in the initial stages of the Holocene, favorable climatic conditions in the mid-Holocene and a general late-Holocene cooling. Our records also indicate a subtle increase in nutrient availability throughout the Holocene. The paleoecological record from Pingualuit Crater Lake is valuable in describing the faunal history and biotic resilience in this environmentally extreme lake, which presently contains one of the worlds softest and most transparent waters.

Observations on groundwater‐surface water interactions at River Vantaa, Finland

Purpose – The purpose of this paper is to emphasize the importance of groundwater‐surface water interaction when studying, modeling and assessing climate change impacts on river water management.Design/methodology/approach – The investigations were focused on River Vantaa and its tributaries in southern Finland. The main methods used involved aerial infrared photography, thermal profiling of river sediments, water quality measurements, isotopic composition of oxygen and hydrogen δ18O, δ2H and river water temperature measurements. The authors present the first results of the field measurements targeted to identify the groundwater recharge and discharge zones within the river system.Findings – Groundwater discharge zones were found to have a significant impact on water quality and volume in River Vantaa and its tributaries. In the drainage basin, the aerial infrared photography seemed to be a feasible and cost‐effective method to identify areas of groundwater discharge across the entire river basin. Around ...

First direct age determination for the Baltic Ice Lake/Yoldia Sea transition in Finland

The drainage of the Baltic Ice Lake (BIL) to the Yoldia Sea level occurred at around 11 600 years ago and can be considered as one of the most important events in the Late-Glacial Baltic Basin history. Distinctive sandy deposits were formed as a result of the water-level fall. These deposits form a marker horizon at the Pleistocene–Holocene boundary, which has been used as the 0-varve in Finnish clay varve chronology. These sandy deposits have not been dated, and in general, there is lack of direct age determinations from the Pleistocene–Holocene transition. Sediments from three localities: backshore, beachface and upper shoreface environments, interpreted to be connected with BIL drainage, were sampled and dated with an optically stimulated luminescence (OSL) method. Only the beachface deposit appeared to be the suitable material, giving the expected dates of 11 400 ± 1100 and 11 200 ± 1300 years BP for the water-level fall. The other samples were interpreted as only partially bleached, or they represented a mixture of different age generations. This is the first direct dating of a Yoldia shore deposit in Finland and provides a reference for shore displacement studies in Finland. The results also verify the potential of the OSL method in dating ancient shorelines or land uplift history.

Depositional evidence of water-level changes of the Baltic Ice Lake in southern Finland during the Younger Dryas/Holocene transition

Two natural clay sections were described from southern Finland. The sites, Jokela and Koria, are located 5-10 km south of the 1st Salpausselkä end moraine. Six sedimentary units were identified and interpreted: (1) Baltic Ice Lake (BIL) varved sediments – interbedded, laminated clay and silt with load structures and sand layers in places; (2) homogenous, partly deformed clay; (3) BIL varved sediments, deposited in slightly shallower water – interbedded, laminated clay and silt; (4) BIL drainage from Billingen and the 25-m base-level fall 11 600-11 700 BP – homogenous clay with sand pods and discontinuous sand layers; (5) freshwater varves – clay and silt couplets with lenticular and flaser bedding and load structures and (6) brackish water varves – thick clay and thin silt couplets. These units can be associated with previously described units of the Finnish clay-varve chronology. The results confirm the importance of the drainage unit as a basin-wide key horizon and illustrate the differences in sedimentation in different parts of the Baltic Sea basin. This is evidenced by the diachronous nature of the incursion of brackish water and associated facies change in sediments.