Publikationsdatum:
2024-04-27
Beschreibung:
High-resolution stable oxygen and carbon isotope analyses and detailed sedimentological and geochemical investigations were performed in order to i) reconstruct the paleoclimate and paleoceanography of the Greenland Sea associated with late Quaternary glacial-interglacial cycles, and ii) to link the terrestrial and deep-sea climatic records. The reconstruction of the paleoenvironmental history of the East Greenland margin and the correlation between the terrestrial and deep sea records are major objectives of the ESF-PONAM-Programme (European Science Foundation - Polar North Atlantic Margins). For this study 16 gravity and 2 box cores were recovered along the East Greenland continental margin between 69°N and 72°N on three W-E transects running from the shelf to the deep sea.
The glaciomarine sediments recovered from the heavily ice-covered East Greenland continental margin reflect changes associated with the glacial/interglacial climatic cycles of the last 240 ka. The glaciomarine sediments are characterised by a dominance of terrestrially derived components and a lower content of biogenic components. Glaciomarine sedimentation processes, terrigenous sediment input, and biogenic productivity in the study area are strongly influenced by fluctuations in the extent of the Greenland Ice Sheet, extent of the sea-ice cover, rate of iceberg drifting, meltwater input, and changes in the East Greenland Current (EGC).
The relatively low carbonate content (〈10 %) and the dominant occurrence of N. pachyderma sin. (〉95 %) throughout the sediment sequences indicate a low biological productivity in the surface water resulting from the extensive sea-ice cover and the strong influence of cold and low-saline polar waters of the EGC. An increase in the surface-water productivity, on the other hand, occurred during certain periods within interglacial and glacial stages. This indicates that the sea ice along the Western margin of the Greenland Sea was at least seasonally reduced during these time intetvals.
Based on the accumulation rates of the coarse terrigenous matter (〉63 µm) and amounts of IRD, the advance and retreat of East Greenland glaciers over the past 200 ka can be correlated with those postulated from the terrestrial records. At least five repeated advances and retreats of glaciers beyond the coastline are proposed between the late Early to Middle Weichselian (65-61, 59-51, 48-42, 35-31, and 28-25 ka). Maximum fluxes of IRD recorded along the continental margin between 21 and 16 ka, reflect the maximum extent of East Greenland glaciers probably reaching the shelf break at that time.
The stable oxygen isotope records measured on the planktonic foraminifer N. pachyderma sin. reveal some excursions from the global climate record due to a local andlor regional overprint through meltwater supply andlor cold water masses of the EGC. Distinct meltwater events are documented during Terminations II and l and at the beginning of Stage 3 resulting from the collapse of the Greenland Ice Sheet. The early period of all glacial stages (i.e. 716, 514, and 312) was subjected to an abrupt and rapid build-up of a sea-ice cover. Hence, a distinct decrease in the carbonate content, the low number of planktonic foraminifers, and light d13C values reflect the strong reduction in the C02 exchange between the atmosphere and ocean, and the surface-water productivity, resulting from a meltwater cap andlor an extensive sea-ice cover. The onset of Termination l is characterised by a distinct shift towards light d180 values, a dramatic decrease in the IRD-flux, and a marked increase in organic matter, indicating the rapid retreat of East Greenland glaciers and a reduced sea-ice cover. According to distinct shifts toward light d180 and heavy d13C values of N. pachyderma sin. and O. umbonatus, the present-day circulation Patterns of surface- and deep-water masses were probably established between 7.4 and 6.1 ka. This is very similar to the timing estimated from studies On microfossil assemblages of the Greenland Sea.
In particular, the distinct IRD peaks correlate with the fluctuations of the Greenland Ice Sheet during the last two glacial-interglacial cycles. Most of the major IRD peaks correspond to periods of cooling of air temperatures over Greenland. During the interval between 225 and 60 ka, the IRD peaks are in phase (at the 23-kyr orbital processional cycle) with maximum Summer Insolation at 70°N This suggests that the Greenland Ice Sheet may have experienced a predominantly 23-kyr cycle of growth and decay, and therefore, collapsed and discharged large volumes of icebergs to the Greenland Sea when Summer insolation reached its maxima.
During the last glacial period, there is a strong correlation between major pulses in the supply of IRD, and the Bond Cycles and the Heinrich Events recorded in the GRIP ice core and North Atlantic deep-sea sediments. Furthermore, the higher frequency of IRD events on millennial scales matches the cooling phase of the abrupt Dansgaard-Oeschger Cycles recorded in the GRIP ice core. Consequently, the apparent evidence of millennial scale IRD events in the North Atlantic and the GIN Sea suggests coherent fluctuations of the large northern hemisphere ice sheets (i.e. the Fennoscandian/Barents Sea and Laurentide/Greenland ice sheets) during the last glacial period.
Schlagwort(e):
ARK-V/3b; ARK-VII/3b; AWI_Paleo; Giant box corer; GIK21723-1 PS13/187; GIK21724-2 PS13/191; GIK21725-2 PS13/192; GIK21726-1 PS13/193; GIK21726-2 PS13/193; GIK21730-1 PS13/224; GIK21730-2 PS13/224; GKG; Gravity corer (Kiel type); Greenland Sea; Greenland Shelf; Greenland Slope; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Polarstern; PS13 GRÖKORT; PS17; PS17/247; PS17/248; PS17/249; PS17/250; PS17/251; PS17/285; PS17/286; PS17/287; PS17/288; PS17/289; PS17/290; PS1723-1; PS1724-2; PS1725-2; PS1726-1; PS1726-2; PS1730-1; PS1730-2; PS1923-2; PS1924-1; PS1925-2; PS1926-1; PS1927-2; PS1946-2; PS1947-1; PS1948-2; PS1949-1; PS1950-2; PS1951-1; Quaternary Environment of the Eurasian North; QUEEN; Scoresby Sund; SL
Materialart:
Dataset
Format:
application/zip, 63 datasets
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