Late Quaternary growth and decay of the Svalbard/Barents Sea ice sheet and paleoceanographic evolution in the adjacent Arctic Ocean (original) (raw)
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Boreas, 2015
We have investigated gravity core HH11-09GC from 488 m water depth at the northern 6 Svalbard margin in order to reconstruct changes in Atlantic Water (AW) inflow to the Arctic 7 Ocean. The study is based on the distribution patterns of benthic and planktic foraminifera, 8 benthic and planktic oxygen and carbon isotopes, lithology and physical properties of the 9 sediments. The core contains sediments from Marine Isotope Stage (MIS) 5a to 1. MIS 4 was 10 characterised by glacial conditions with advance of the Svalbard-Barents Sea Ice Sheet (SBIS) at 11 c. 65 ka and formation of a polynya in front of the SBIS at c. 62 ka. During late MIS 3 (32-29 ka) 12 and MIS 2 (22-20 ka), strong influence of AW resulted in high productivity of both planktic and 13 benthic foraminiferal faunas. During 23-22 ka, the SBIS advanced to the shelf edge. The last 14 deglaciation began at 18.5 ka and at 16.9 ka 'a maximum' in influx of meltwater from the 15 retreating SBIS caused a weakening of the ocean circulation. At the start of the Bølling-Allerød 16 interstadial c. 15.5 ka, inflow of relatively warm AW probably intensified the release of 17 meltwater at 14 ka and 12.8 ka.
Global and Planetary Change, 2001
Three cores recovered off the northwest of Svalbard were studied with respect to glacialrinterglacial changes of clay and Ž . bulk mineralogy, lithology and organic geochemistry. The cores cover the Late Quaternary Marine Isotope Stages MIS 6-1 Ž . ca. 170,000 years and are located in the vicinity of the Polar Front which separates the warm Atlantic water of the Westspitsbergen Current and the cold Polar Water of the Transpolar Drift. Globally driven changes in the paleoenvironment like the variable advection of warm Atlantic water into the Arctic Ocean can be distinguished from regional events by means of source mineral signatures and organic geochemistry data. In particular, a combination of high organic carbon and low carbonate contents, high CrN-ratios, a particular lithology and a distinct bulk and clay mineral assemblage can be related to Svalbard ice sheet developments between 23,000 and 19,500 14 C years. This complex sediment pattern has been traced to the northwest of Spitsbergen as far north as 828N. Additionally, the same signature has been recognized in detail in upper MIS 5 sediments. The striking similarity of the history of the SvalbardrBarents Sea Ice Sheet during the late and earlyrmiddle Weichselian is elaborated. Both sediment horizons are intercalated between biogenic calcite rich core sequences which contain the so-called AHigh Productivity ZonesB or ANordway EventsB related to the increased advection of warm Atlantic water to the Arctic Ocean. This study provides further evidence that the meridional circulation pattern has been present during most of the Weichselian and that the ice cover was often reduced in the northeastern Fram Strait and above the Yermak Plateau. Our findings contradict the widely used reconstructions in modelling of the last glaciation cycle and reveal a much more dynamic system in the Fram Strait and southwestern Eurasian Basin of the Arctic Ocean. q
Paleoceanography of the Last Interglacial/Glacial Cycle in the Polar North Atlantic
Quaternary Science Reviews, 1998
Using to its position close to the sites of waxing and waning of the major northern hemisphere ice sheets during the Late Quaternary climatic cycles, the Polar North Atlantic plays a key role in driving global change. Therefore, analyzing the present-day sedimentation processes and reconstructing the Late Quaternary paleoceanography in this region has been a focus of major scientific interest through the last fifteen years. This paper aims to combine the vast amount of new results about modern sediment fluxes, surface sediment distribution and the paleoceanographic record and to present a comprehensive overview of the paleoceanography in the Polar North Atlantic through the last 200,000 years, which is based on the basinwide analysis of carbonate and ice-rafted detritus records. During the last fifteen years the CLIMAP paleoceanographic view of the glacial Polar North Atlantic as an almost permanently isolated sea covered by heavy sea ice throughout the year has been shifted to a much more dynamic view of the environmental conditions. A meridional current system similar to the present-day conditions secured the exchange of water, ice and heat between the Polar North Atlantic and the Alantic and Arctic Oceans. Although affected by variations in strength and intensity this meridional current pattern resulted in an almost permanent presence of at least some seasonally ice-free areas, with all the consequences for e.g. marine life and deep water formation. In addition, the development of the continental ice sheets, namely the Fennoscandian and the Barents Sea ice sheets, is closely related to this dynamic circulation pattern. During the so-called Nordway events the pronounced inflow of temperate waters from the south provided moisture for the growth of the ice sheets. The most prominent of these events (Stage 6, Stage 4 and Substage 3.1/2) ended in major glaciations, reflected in the terrestrial sequences and in the deep-sea IRD records.
Glacial and Oceanic History of the Polar North Atlantic Margins: An Overview
Quaternary Science Reviews, 1998
The five-year PONAM (Polar North Atlantic Margin: Late Cenozoic Evolution) programme was launched by the European Science Foundation in 1989. Its aim was to study the major climate-driven environmental variations in the Norwegian-Greenland (also Nordic) Sea and its continental margins over the last 5 milliion years. The programme has provided substantial new insights into the contrasting behaviour of the ice sheets covering the Svalbard-Barents Sea and East Greenland over the last glacial-interglacial cycle in particular. The highly dynamic Svalbard-Barents Sea Ice Sheet, after reaching the shelf edge during each stadial, almost vanished during subsequent interstadials. By contrast, the East Greenland Ice Sheet showed only minor advances confined to fjord basins or ending on the inner shelf. Although there is a striking correspondence in the timing and duration of the first post-Eemian ice advance in East Greenland and on Svalbard, their chronology and dynamics have been very different since about 65 ka. The Svalbard-Barents Sea Ice Sheet showed well-defined Middle and Late Weichselian ice advances, whereas the East Greenland Ice Sheet was characterised by a 55 kyr-long period with a relatively stable ice margin located in fjords or the inner shelf. The contrasting behaviour of the two ice sheets is probably linked to the palaeoceanographic circulation pattern in the Polar North Atlantic. East Greenland is under the influence of the cold East Greenland Current, whereas the development and behaviour of ice in the Barents Sea is influenced by the continuous, but highly variable. North Atlantic meridional current system that has resulted in a northward inflow of relatively warm waters of Atlantic origin on the eastern side of the Polar North Atlantic. Of particular interest are the so-called ''Nordway events'' in glacial stages 6 and 4 to 2. These represented periods of pronounced inflow of temperate waters from the south and an associated increase in seasonally open waters, providing moisture for ice-sheet growth. The largest of these events ended in major glaciations, which were reflected in terrestrial glacial sequences and in deep-sea records of ice-rafted debris. Differences in ice extent and dynamics around the Polar North Atlantic are expressed in the evolution and architecture of its east and west continental margins. The Svalbard-Barents Sea Ice Sheet developed much later than the East Greenland Ice Sheet, in the Late Pliocene as compared with the Middle/Late Miocene. The Svalbard-Barents Sea margin is characterised by major prograding fans, built mainly of stacked debris flows. These fans are interpreted as products of rapid sediment delivery from fast-flowing ice streams reaching the shelf break during full glacial conditions. Such major submarine fans are not found north of the Scoresby Sund Fan off East Greenland, where ice seldom reached the shelf break, sedimentation rates were relatively low and sediment transport appears to have been localised in several major deep-sea submarine channel systems. Few debris flows are present and more uniform, acoustically-stratified sediments predominate. In general, the Greenland Ice Sheet has been more stable than those on the European North Atlantic margin, which reflect greater variability in heat and moisture transfer at timescale varying from 100,000 year glacial cycles to millennial-scale fluctuations.
Proceedings of the Ocean Drilling Program, 1996
Three sites from Leg 151 were selected for a study of orbital-and millennial-scale climate variability during the last 140,000 years. This interval, from marine isotope Stage (MIS) 6 to the present, includes the last large climate cycle of the Quaternary. Sites 907, 909, and 910 constitute a transect, roughly north-south, from the Iceland Plateau, through the Fram Strait, to the Yermak Plateau. Sediment cores from these sites were analyzed for the abundance and diversity of planktonic foraminifers and the quantity and composition of ice-rafted debris (IRD). Leg 151 drilling was successful in recovering young sediments. This is best demonstrated in Hole 907A, which has a sedimentation rate of 1.7 cm/k.y., where an 11,000-year-old volcanic ash is disseminated at a depth of 0.2 meters below seafloor (mbsf), indicating good recovery of the overlying Holocene section. The last climate cycle in Hole 907A is well defined by faunal assemblages and abundances, which indicate that mild conditions were limited to peak interglacials. Ice-rafted debris is abundant at all other times, although discrete peaks in the ratio of ice-rafted grains to foraminifers, perhaps analogous to the Heinrich events of the North Atlantic, occur only during MIS 2-4 and 6. Site 909 in the Fram Strait has a sedimentation rate of 3.4 cm/k.y., and is characterized by variability in the abundance of ice-rafted debris and clastic rock fragments. Sharp increases in the weight percentage of coarse sediment and the occurrence of detrital coal mark MIS 6, and contrast with the last (MIS 2) glaciation. Site 910 on the Yermak Plateau has a sedimentation rate of 2.7 cm/k.y., and is dominated by detrital sediments. The abundance of coarse sediment remains high with little variation throughout the study interval. Ice-rafted clastic rock fragments are relatively less important on the Yermak Plateau than in the Fram Strait, implying different glacial source areas. The similarity between the last two glacial and interglacial pairs seen on the Iceland Plateau (as in the subpolar North Atlantic) is less evident in our high latitude cores.
Palaeoceanographic evolution of the SW Svalbard shelf over the last 14 000 years
Boreas, 2017
The palaeoceanographic evolution of the SW Svalbard shelf west of Hornsund over the last 14 000 years was reconstructed using benthic foraminiferal assemblages, stable oxygen and carbon isotopes, and grain-size and icerafted debris data. The results reveal the complexity of the feedbacks influencing the shelf environment: the inflow of Atlantic and Arctic waters (AWand ArW, respectively), and the influence of sea ice and tidewater glaciers. The inflow of subsurface AW onto the shelf gradually increased with the first major intrusion at the end of the Bølling-Allerød. During the Younger Dryas, the shelf was affected by fresh water originating from sea ice and glacier discharge. Glaciomarine conditions prevailed until the earliest Holocene with the intense deliveries of icebergs and meltwater from retreating glaciers and the occasional penetration of AWonto the shelf. Other major intrusions of AWoccurred before and after the Preboreal oscillation (early Holocene), which resulted in more dynamic and open-water conditions. Between 10.5 and 9.7 cal. ka BP, the shelf environment transformed from glaciomarine to open marine conditions. Between c. 9.7 and 6.1 cal. ka BP the AW advection reached its maximum, resulting in a highly dynamic and productive environment. At c. 6.1 cal. ka BP, the inflow of AW onto the Svalbard shelf decreased due to the intensification of the Greenland Gyre and the subduction of AW under the sea-ice-bearing ArW. Bioproductivity decreased over the next c. 5500 years. During the Little Ice Age, bioproductivity increased due to favourable conditions in the marginal sea-ice zone despite the effects of cooling. The renewed advection of AW after AD 1850 started the climate warming trend observed presently. Our findings show that d 18 O can be used to reconstruct the dominances of different water-masses and, with some caution, as aproxy for the presence of sea ice in frontal areas over the northwestern Eurasian shelves.
Boreas, 2009
The fjords of southwestern Spitsbergen (European Arctic) are a climatically sensitive area neighbouring the mixing zone of warm northward-flowing Atlantic water-masses and cold Arctic Water. Owing to reasonably high accumulation rates, these settings are especially suitable for providing high-resolution sedimentary records of regional hydrological and environmental changes. A sediment core spanning the last millennium was retrieved from the outer Hornsund fjord basin, 14C dated and analysed for sediment grain size, ice-rafted debris (IRD), the distribution of benthic foraminifera and their oxygen and carbon stable isotope composition. The record of sub-centennial resolution reveals three distinctive periods: the Medieval Warm Period, the Little Ice Age (∼AD 1600–1900) and 20th-century warming. The marine record obtained is well correlated with regional high-resolution ice-core records as well as with atmospheric palaeotemperature reconstructions and sea-ice data. The colder periods stay in phase with the greater influence of less saline, cold Arctic Water indicated by subtle changes in benthic foraminifera assemblages and the δ18O signal, which is dominated by changes in salinity. The IRD record clearly indicates that tidewater glaciers were present in SW Spitsbergen throughout the last millennium, and most actively from the late 16th century until the end of the 19th century.
Three sites from Leg 151 were selected for a study of orbital-and millennial-scale climate variability during the last 140,000 years. This interval, from marine isotope Stage (MIS) 6 to the present, includes the last large climate cycle of the Quaternary. Sites 907, 909, and 910 constitute a transect, roughly north-south, from the Iceland Plateau, through the Fram Strait, to the Yermak Plateau. Sediment cores from these sites were analyzed for the abundance and diversity of planktonic foraminifers and the quantity and composition of ice-rafted debris (IRD).
Reflection of continental ice sheets in late Quarternary sediments from the Nordic Seas
1993
Late Pleistocene climatic and paleoceanographic changes in the Norwegian-Greenland Sea are reflected in eleven long sediment cores by variations in calcium carbonate content and calcareous biogenic components versus coarse terrigenous ice-rafted detritus (IRD). High contents of IRD in glacial sequences are evidence for an enhanced melting of sea ice and icebergs. In contrast, high calcium carbonate contents indicate the inflow of warm Atlantic surface waters. The petrographic IRD composition in cores from the eastern and central Norwegian-Greenland Sea shows that the terrigenous material was predominantly derived from Scandinavia. Thus, it can be concluded that changes in the terrigenous input were caused by oscillations of the Late Pleistocene Scandinavian ice sheet. Changes in the extension of this ice sheet during the last 130 ky correlate well with our IRD data.