Jon Y. Landvik

Frequent Long-Distance Plant Colonization in the Changing Arctic

The ability of species to track their ecological niche after climate change is a major source of uncertainty in predicting their future distribution. By analyzing DNA fingerprinting (amplified fragment-length polymorphism) of nine plant species, we show that long-distance colonization of a remote arctic archipelago, Svalbard, has occurred repeatedly and from several source regions. Propagules are likely carried by wind and drifting sea ice. The genetic effect of restricted colonization was strongly correlated with the temperature requirements of the species, indicating that establishment limits distribution more than dispersal. Thus, it may be appropriate to assume unlimited dispersal when predicting long-term range shifts in the Arctic.

FLUCTUATIONS OF THE SVALBARD–BARENTS SEA ICE SHEET DURING THE LAST 150 000 YEARS

Abstract On Spitsbergen, western Svalbard, three major glacial advances have been identified during the Weichselian. All three reached the continental shelf west of the Svalbard archipelago. Radiocarbon, luminescence and amino acid dating of interbedded interstadial and interglacial sediments indicate that these glacial advances have Early (Isotope Stage 5d), Middle (Stage 4), and Late Weichselian ages (Stage 2). An additional, more local, advance has been dated to Isotope Stage 5b. The Late Weichselian ice sheet expanded across the entire Barents Sea. However, in the south-western Barents Sea, the Late Weichselian till is the only till above Eemian sediments, indicating that the Early- and Middle Weichselian ice advances were restricted to the Svalbard archipelago and the northern Barents Sea. A major problem with the onshore sites is the dating of events beyond the range of the radiocarbon method. To overcome this, the onshore record has been correlated with marine cores from the continental slope and the deep-sea west of Svalbard, where a chronology has been established by oxygen isotope stratigraphy. Ice rafted detritus (IRD) was used as the main monitor of glaciation. The IRD record closely mirrors the glaciation history as interpreted from the onshore sections. During the Late Weichselian, the largest IRD peak occurred during deglaciation, a pattern also postulated for the earlier events. Given this, the results from the marine cores indicate that the ages for the first glacial advances during the Weichselian were a few thousand years older than interpreted from the onshore stratigraphy.

Late Cenozoic history of the Scandinavian and Barents Sea ice sheets

Abstract The oldest ice rafted material (IRD) on the Voring Plateau is dated to about 11 Ma, and is regarded as evidence that glaciers extended to sea level somewhere around the Nordic Sea at this time. We estimate that the major glaciations of Scandinavia and the Barents Sea-Svalbard area started at 2.5–2.8 Ma, when the amount of IRD on the Voring Plateau increased strongly, the deep sea δ18O curves indicate that onset of Northern Hemisphere glaciations, and the climate in The Netherlands was so cold that a major glaciation of Scandinavia is inferred. Most of the time until 0.9 Ma, the ice sheets were of intermediate size; they probably reached the coastal zone of western Norway for long periods. The center of glaciation is inferred to have been further north than during the later glaciations, and we speculate that this was the period of maximum glacial erosion of the Barents Sea. The largest glaciations, and also the warmest interglacials occurred during the last 900 kyrs, when the 100 kyr astronomic cycle became important. For the last glaciation, the Weichselian, the glacial fluctuations are known in greater detail both for Scandinavia and the Svalbard-Barents Sea region. In Scandinavia the glacial fluctuations apparently followed the 23 kyr precession cycle, whereas in the Barents Sea they followed the 41 kyr tilt cycle. In both areas more than one advance reached beyond the coast. We use the Weichselian record to “calibrate” the interpretation of more indirect evidences of glacial fluctuations, and apply the latter to the Scandinavian and Barents Sea glacial history since 2.5 Ma.

Configuration, history and impact of the Norwegian Channel Ice Stream

The Norwegian Channel between Skagerrak, in the southeast, and the continental margin of the northern North Sea, in the northwest, is the result of processes related to repeated ice stream activity through the last 1.1 m yr. In such periods the Skagerrak Trough (700 m deep) has acted as a confluence area for glacial ice from southeastern Norway, southern Sweden and parts of the Baltic. Possibly related to the threshold in the Norwegian Channel off Jaeren (250 m deep), the ice stream, on a number of occasions over the last 400 ka, inundated the coastal lowlands and left an imprint of NW-oriented ice directional features (drumlins, stone orientations in tills and striations). Marine interstadial sediments found up to 200 m a.s.l. on Jaeren have been suggested to reflect glacial isostasy related to the Norwegian Channel Ice Stream (NCIS). In the channel itself, the ice stream activity is evidenced by mega-scale glacial lineations on till surfaces. As a result of subsidence, the most complete sedimentary records of early phases of the NCIS are preserved close to the continental margin in the North Sea Fan region. The strongest evidence for ice stream erosion during the last glacial phase is found in the Skagerrak. On the continental slope the ice stream activity is evidenced by the large North Sea Fan, which is mainly a result of deposition of glacial-fed debris flows. Northwards of the North Sea Fan, rapid deposition of meltwater plume deposits, possibly related to the NCIS, is detected as far north as the Voring Plateau. The NCIS system offers a unique possibility to study ice stream related processes and the impact the ice stream development had on open ocean sedimentation and circulation.

Northwest Svalbard during the last glaciation: Ice-free areas existed

The possibility that ice-free areas existed during the late Weichselian glaciation of the Svalbard archipelago has been debated for several decades. This study reveals the first geologic evidence that nunataks existed on the islands of northwest Svalbard. Several 10 Be exposure ages were obtained from bedrock and glacial erratics on Danskoya and Amsterdamoya Islands. Exposure ages for glacial erratics laid down in block-field‐covered plateaus .300 m above sea level show that the last ice sheet that completely covered the islands deglaciated .80 k.y. ago. Dating of marine sediments close to sea level reveals that full ice-free conditions were achieved by ca. 50 ka. During the late Weichselian, the coastal lowlands were glaciated, and the major fjords and troughs controlled glacier flow. The existence of nunataks at this time opens the possibility for glacial survival of plant species.

Glacial History of the Barents Sea Region

Abstract The major achievement during the later years has been the increased understanding of the number and extent of glaciations, and the ice sheet dynamics. There is no indications of any Barents Ice Sheet until the Pliocene glaciations (3.5-2.4 my). During 2.4-1.0 Ma ice sheets over the northern Barents Sea expanded southward, and during Middle Pleistocene eight full scale glaciations occurred. During the Late Weichselian glaciers reached the shelf break in the west and north, but reached the Russian mainland in the White Sea area only.

Sedimentary ancient DNA from Lake Skartjørna, Svalbard: Assessing the resilience of arctic flora to Holocene climate change

Reconstructing past vegetation and species diversity from arctic lake sediments can be challenging because of low pollen and plant macrofossil concentrations. Information may be enhanced by metabarcoding of sedimentary ancient DNA (sedaDNA). We developed a Holocene record from Lake Skartjørna, Svalbard, using sedaDNA, plant macrofossils and sediment properties, and compared it with published records. All but two genera of vascular plants identified as macrofossils in this or a previous study were identified with sedaDNA. Six additional vascular taxa were found, plus two algal and 12 bryophyte taxa, by sedaDNA analysis, which also detected more species per sample than macrofossil analysis. A shift from Salix polaris-dominated vegetation, with Koenigia islandica, Ranunculaceae and the relatively thermophilic species Arabis alpina and Betula, to Dryas octopetala-dominated vegetation ~6600–5500 cal. BP suggests a transition from moist conditions 1–2°C warmer than today to colder/drier conditions. This coincides with a decrease in runoff, inferred from core lithology, and an independent record of declining lacustrine productivity. This mid-Holocene change in terrestrial vegetation is broadly coincident with changes in records from marine sediments off the west coast of Svalbard. Over the Holocene sedaDNA records little floristic change, and it clearly shows species persisted near the lake during time intervals when they are not detected as macrofossils. The flora has shown resilience in the presence of a changing climate, and, if future warming is limited to 2°C or less, we might expect only minor floristic changes in this region. However, the Holocene record provides no analogues for greater warming.

Saalian to Weichselian stratigraphy and sedimentation along the Lågjæren – Høgjæren escarpment, southwest Norway

Quaternary sediments along a profile crossing the southern part of the Jaeren escarpment, southwestern Norway, have been investigated with regard to their glacial history and sea-level variations. Deposits from at least three glaciations and two ice-free periods between Oxygen Isotope Stage 6 and the Late Weichselian have been identified. Subglacial till directly overlain by a glaciomarine regressional succession indicates a deglaciation, and amino acid ratios in Elphidium excavatum between 0.083 and 0.118 date this event to Oxygen Isotope Stage 6. Sea-level dropped from 130 to below 110 m a.s.l. Subsequently, a short-lived ice advance deposited a marginal moraine and a sandur locally on the escarpment. Stratigraphical position and luminescence dates around 148 ka BP suggest deposition during the final stage 6 deglaciation. A Late Weichselian till covers most of the surface of Jaeren. In addition to a well documented westerly ice flow, glaciotectonic indications of ice flow towards the north have been found. Ice flow directions and a hiatus between Oxygen Isotope Stage 6 and the Weichselian indicate enhanced erosion along the escarpment and the influence of a Norwegian Channel ice-stream. Copyright

Sediments of MIS 5e age suggested by new OSL dates from the Skilvika section, west Svalbard

ABSTRACT The sediment succession at Skilvika, west Svalbard, represents one of the key stratigraphic records of the Late Quaternary palaeoenvironments and glaciation history of the Svalbard/Barents Sea area. A formation of raised marine sediments, interfingering with and capped by glacial deposits of local origin, have previously been assumed to be of an Early Weichselian age, likely marine isotope stage (MIS) 5c. Here we present a new series of optically stimulated luminescence (OSL) ages that suggest the events took place in MIS 5e. This advocates a revision of the correlation with other key stratigraphic sites on Svalbard.