Siberian shelf sediments contain clues to paleoclimate forcing

Bauch, Henning A.; Cremer, Holger; Kunz-Pirrung, Martina

doi:10.1029/00eo00162

Cited by 20 publications

(13 citation statements)

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“…Biogenic components, including particulate organic matter (POM), may be characterised by geochemical and micropalaeontological tracers such as fatty acids, n-alkanes, diatoms, macerals and palynomorphs (e.g. Boucsein and Stein 2000;Cremer 1999;Stein 1997, 1999;Kunz-Pirrung 1998;Mudie 1992;Polyakova 1999;Bauch et al 2000). However, geochemical characterization of POM influx is limited by selective preservation of organic compounds and difficulties in sourcing biological origin and environments (e.g.…”

Section: Introductionmentioning

confidence: 99%

Freshwater chlorophycean algae in recent marine sediments of the Beaufort, Laptev and Kara Seas (Arctic Ocean) as indicators of river runoff

Matthießen

Kunz-Pirrung

Mudie

2000

International Journal of Earth Sciences

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Freshwater chlorophycean algae in recent marine sediments of the Beaufort, Laptev and Kara Seas (Arctic Ocean) as indicators of river runoff Abstract Freshwater chlorophycean algae are characteristic organic-walled microfossils in recent coastal and shelf sediments from the Beaufort, Laptev and Kara seas (Arctic Ocean). The persistent occurrence of the chlorophycean algae Pediastrum spp. and Botryococcus cf. braunii in marine palynomorph assemblages is related to the discharge of freshwater and suspended matter from the large Siberian and North American rivers into the Arctic shelf seas. The distribution patterns of these algae in the marine environments reflect the predominant deposition of riverine sediments and organic matter along the salinity gradient from the outer estuaries and prodeltas to the shelf break. Sedimentary processes overprint the primary distribution of these algae. Resuspension of sediments by waves and bottom currents may transport sediments in the bottom nepheloid layer along the submarine channels to the shelf break. Bottom sediments and microfossils may be incorporated into sea ice during freeze-up in autumn and winter leading to an export from the shelves into the deep sea. The presence of these freshwater algae in sea-ice and bottom sediments in the central Arctic Ocean confirm that transport in sea ice is an important process which leads to a redistribution of shallow water microfossils.Keywords Arctic Ocean´Beaufort Sea´Laptev SeaḰ ara Sea´Recent sediments´Chlorophyte distribution´Freshwater discharge J. Matthiessen ( ) )´M. Kunz-Pirrung

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Section: Introductionmentioning

confidence: 99%

Freshwater chlorophycean algae in recent marine sediments of the Beaufort, Laptev and Kara Seas (Arctic Ocean) as indicators of river runoff

Matthießen

Kunz-Pirrung

Mudie

2000

International Journal of Earth Sciences

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“…The predominance of freshwater diatoms along most of the core sequence but near the surface indicates that the study area has been affected by intensive river runoff throughout the investigated time period. The fact that the variability remains above 60% implies that salinities were never higher than 10±15 (Bauch et al 2000). However, it may well be that these high proportions in freshwater diatoms are to some extent also the result of variations in the total amount of allochthonous sediment material (including riverine and lacustrine-bog diatoms) supplied to the coastal zone through the main delta channels (Ivanov and Piskun 1999) and/or due to changes in productivity of marine diatom coenoses alone.…”

Section: Late Holocene Changes In Freshwater Runoff and Sea-ice Regimementioning

confidence: 90%

“…The total sed- Bauch et al 2000). Also shown are the main rivers draining into the Laptev Sea as well as the main channels within the Lena River delta (1 Trofimovskaya; 2 Bykovskaya; 3 Tumatskaya; 4 Olenekskaya).…”

Section: Methodsmentioning

confidence: 99%

“…Although the species diversity occurring here is relatively high (~200 species), only few species (Aulacoseira subarctica, Asterionella formosa, and Diatoma tenuis) are dominant (Cremer 1998). The (Bauch et al 2000). Away from the marginal zone of the delta, in areas with salinities larger than 10±15, the relative abundance of freshwater diatoms steeply decreases (see also Fig.…”

Section: Diatom Distribution In Surface Sedimentsmentioning

confidence: 94%

“…7). As shown by the distribution of diatoms in surface sediments, the freshwater group has proportions higher than 70% in close proximity of the Lena River delta where surface salinities are below 6 Bauch et al 2000;see also Fig. 2).…”

Section: Late Holocene Changes In Freshwater Runoff and Sea-ice Regimementioning

confidence: 96%

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Late Holocene variations in Arctic shelf hydrology and sea-ice regime: evidence from north of the Lena Delta

Bauch

Polyakova

2000

International Journal of Earth Sciences

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Diatom assemblage studies are used to interpret past changes in river runoff (salinity) and sea-ice regime in the vicinity of the vast Lena River delta, southern Laptev Sea shelf. On the basis of their distribution in surface sediments, the shelf region outside the strong influence of riverine waters is characterized by a dominance in sea-ice diatoms and other marine species. Their numbers increase steeply (>20%) within the area of drifting pack ice. In contrast, the marginal zone of the delta, where exceedingly low salinities prevail, is marked by freshwater diatoms showing values higher than 70%. Using the environmental information from the surface sediments, the downcore distribution patterns of the main ecological groups of diatoms were investigated on a sediment core that covers the past 2800 cal. years BP. Although the freshwater group indicates some temporal variations in salinities, the study site north of the Lena River delta remained under a dominantly riverine influence for most of the three recognized phases. In contrast, the relative abundance of sea-ice species gives evidence that pack-ice conditions were more severe during the oldest phase (older than~2700 cal. years BP). The most significant changes are observed in the uppermost core section (younger thañ 300 cal. years BP) when the relative abundance of freshwater diatoms decreases from 80% down to below 20%. This dramatic decrease is interpreted as a major shift from a more northward-directed to the modern, dominantly eastern outflow pattern. Because the dispersal and fate of riverine waters and its role on the ice regime as well as on water mass properties is a central issue in understanding short-and longerterm climatic changes in the Arctic and beyond, it needs to be tested using more cores if this most recent change in outflow pattern from the delta is connected to climate change or simply a result of channel migration within the delta.

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Composition and Flux of Holocene Sediments on the Eastern Laptev Sea Shelf, Arctic Siberia

et al. 2001

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A 467-cm-long core from the inner shelf of the eastern Laptev Sea provides a depositional history since 9400 cal yr. B.P. The history involves temporal changes in the fluvial runoff as well as postglacial sea-level rise and southward retreat of the coastline. Although the core contains marine fossils back to 8900 cal yr B.P., abundant plant debris in a sandy facies low in the core shows that a river influenced the study site until ∼8100 cal yr B.P. As sea level rose and the distance to the coast increased, this riverine influence diminished gradually and the sediment type changed, by 7400 cal yr B.P., from sandy silt to clayey silt. Although total sediment input decreased in a step-like fashion from 7600 to 4000 cal yr B.P., this interval had the highest average sedimentation rates and the greatest fluxes in most sedimentary components. While this maximum probably resulted from middle Holocene climate warming, the low input of sand to the site after 7400 cal yr B.P. probably resulted from further southward retreat of the coastline and river mouth. Since about 4000 cal yr B.P., total sediment flux has remained rather constant in this part of the Laptev Sea shelf due to a gradual stabilization of the depositional regime after completion of the Holocene sea-level rise.

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Siberian shelf sediments contain clues to paleoclimate forcing

Cited by 20 publications

References 10 publications

Freshwater chlorophycean algae in recent marine sediments of the Beaufort, Laptev and Kara Seas (Arctic Ocean) as indicators of river runoff

Freshwater chlorophycean algae in recent marine sediments of the Beaufort, Laptev and Kara Seas (Arctic Ocean) as indicators of river runoff

Late Holocene variations in Arctic shelf hydrology and sea-ice regime: evidence from north of the Lena Delta

Composition and Flux of Holocene Sediments on the Eastern Laptev Sea Shelf, Arctic Siberia

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