No abstract

No abstract

Records of iceberg-rafting and palaeohydrography from two East Greenland shelf cores (JM96-1206/1-GC and JM96-1207/1-GC) are reported. Benthic foraminifera, stable isotopes and IRD uxes indicate a shift toward colder, lower-salinity 'polar' conditions c. 5 cal. ka. A new proxy of iceberg-rafting on the East Greenland Shelf is the ux of calcium carbonate (TIC) thought to be derived from glacial erosion of Cretaceous calcareous mudstones. A change in the regularity and spacing of carbonate ux peaks at c. 4.7 cal. ka in JM96-1207 coincides with the onset of Neoglacial cooling in the Renland ice core d 18 O record. We propose that the carbonate ux peaks between 4.7 and 0.4 cal. ka are related to sea-surface coolings associated with increased ux of polar water and sea ice in the East Greenland Current. These peaks are synchronous with sea-surface coolings interpreted from North Atlantic deep-sea cores, but additional peaks centred around 2.4 and 3.8 cal. ka in JM96-1207 suggest that the shelf site captures higher-frequency events. The data indicate that severe Arctic sea-ice events began in the Neoglacial interval, and that earlier-Holocene cool events in deep-sea records are associated with other processes, such as release of meltwater from residual glacier ice and glacial lakes.

Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector.

No abstract

Past environmental changes in the Baltic area are discussed on the basis of foraminifera and ostracods as well as pollen and spores in marine sediments in cliff sections at Ristinge Klint, Langeland, southern Denmark. The sediment succession represents Jessen & Milthers' (1928) pollen zones d–g or Andersen's (1961, 1975) zones E2–E5, and a correlation with the annually laminated Bispingen sequence indicates that the sequence spans about 3400 years. Marine conditions seem to have occurred at c. 300–365 years after the beginning of the Eemian Interglacial, close to fully marine conditions developing by c. 2500 years. This early date of the marine ingression pre‐dates that of most previous studies in the region by several hundred years, but it postdates the initial marine ingression in the easternmost Baltic. A marked change in salinity at c. 650 years after the beginning of the Eemian was presumably caused by an opening of the Danish Belts. An indication of a major alteration in current activity is registered at c. 3000 years after the beginning of the interglacial. The recognition of the relative timing of these events may be significant for the understanding of the opening of connections between the North Sea, the Baltic and the White Sea.

A multiproxy study of palaeoceanographic and climatic changes in northernmost Baffin Bay shows that major environmental changes have occurred since the deglaciation of the area at about 12 500 cal. yr BP. The interpretation is based on sedimentology, benthic and planktonic foraminifera and their isotopic composition, as well as diatom assemblages in the sedimentary records at two core sites, one located in the deeper central part of northernmost Baffin Bay and one in a separate trough closer to the Greenland coast. A revised chronology for the two records is established on the basis of 15 previously published AMS 14 C age determinations. A basal diamicton is overlain by laminated, fossil-free sediments. Our data from the early part of the fossiliferous record (12 300-11 300 cal. yr BP), which is also initially laminated, indicate extensive seasonal sea-ice cover and brine release. There is indication of a cooling event between 11 300 and 10 900 cal. yr BP, and maximum Atlantic Water influence occurred between 10 900 and 8200 cal. yr BP (no sediment recovery between 8200 and 7300 cal. yr BP). A gradual, but fluctuating, increase in sea-ice cover is seen after 7300 cal. yr BP. Sea-ice diatoms were particularly abundant in the central part of northernmost Baffin Bay, presumably due to the inflow of Polar waters from the Arctic Ocean, and less sea ice occurred at the near-coastal site, which was under continuous influence of the West Greenland Current. Our data from the deep, central part show a fluctuating degree of upwelling after c. 7300 cal. yr BP, culminating between 4000 and 3050 cal. yr BP. There was a gradual increase in the influence of cold bottom waters from the Arctic Ocean after about 3050 cal. yr BP, when agglutinated foraminifera became abundant. A superimposed short-term change in the sea-surface proxies is correlated with the Little Ice Age cooling.

Ocean variability at decadal time-scales remains poorly described partly because of the scarcity of high temporal resolution marine records. Here, we present a reconstruction of Sea Surface