HR: 1340h
AN: PP33B-1571    [Abstracts]
TI: The Holocene Thermal Optimum in the Barents Sea
AU: Murdmaa, I
EM: murdmaa@mail.ru
AF: Shirshov Institute of Oceanology, Russian Academy of Sciences , 36 Nakhimovsky Prosp., Moscow, 117997 Russian Federation
AU: * Ivanova, E
PP33B-1571 AF: Shirshov Institute of Oceanology, Russian Academy of Sciences , 36 Nakhimovsky Prosp., Moscow, 117997 Russian Federation
AU: Risebrobakken, B
PP33B-1571 AF: Bjerknes Centre for Climate Research, University of Bergen , All‚gaten 55, Bergen, 5007 Norway
AU: Akhrimenko, N
PP33B-1571 AF: Geology Department, Lomonosov Moscow State University, Vorobyevy Gory, Moscow, 119992 Russian Federation
AU: Yamskova, E
PP33B-1571 AF: Geology Department, Lomonosov Moscow State University, Vorobyevy Gory, Moscow, 119992 Russian Federation
AB: AMS 14C-dated oxygen isotope records on planktic and benthic foraminifer in our Core ASV 880 from the eastern branch of the Franz Victoria Trough (Northern Barents Sea) shows the Holocene thermal optimum at 7.8 - 6.9 cal ka BP (Duplessy et al., 2001) manifested by low oxygen isotope values as a result of warming of subsurface to bottom waters related to the increased Atlantic water input. Benthic foraminiferal assemblages during this optimum are enriched in the species indicating rather long ice-free season. We test here a hypothesis that the optimum can also be identified by foraminiferal assemblages in other parts of the sea with present water column structure indicating subsurface Atlantic water. We studied the Holocene benthic and planktic foraminiferal assemblages at several locations within the passage of the Atlantic water in surface and subsurface layers,and tried to identify the timing of assumed optimum by the interpolation between AMS 14C-dates when available, and using a level of polychaetas appearance in the Barents Sea at about 5 cal ka BP. The base of the Holocene layer is legibly distinguished in our cores by pronounced changes in sediment color, grain size, sedimentary structures, and an appearance of numerous foraminiferal tests. These two levels provide us with the tick-points for the age control in undated cores. An increase in abundance of species related to Atlantic-derived water is found at the end of Early Holocene in the south-western branch of the Franz Victoria Trough, whereas any faunal indication of the optimum are absent in other cores. On the contrary, our new oxygen isotope data clearly demonstrate the optimum at some locations. The maximum content of so-called "atlantic" benthic species occurs at different time levels in specific cores, and the same is true for planktic foraminifers generally considered to be related to the Atlantic water in the Barents Sea. Therefore, the above hypothesis is not confirmed by our data. It means that besides the water mass properties foraminifer distribution in the region is strongly controlled by food supply.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1637 Regional climate change
DE: 3030 Micropaleontology (0459, 4944)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005