ALBERT

Description: In the light of rapidly diminishing sea ice cover in the Arctic during the present atmospheric warming, it is imperative to study the distribution of sea ice in the past in relation to rapid climate change. Here we focus on glacial millennial scale climatic events (Dansgaard/Oeschger events) using the new sea ice proxy IP25 in combination with phytoplankton proxy data and quantification of diatom species in a record from the SE Norwegian Sea. We demonstrate that expansion and retreat of sea ice varied consistently in pace with the rapid climate changes 90 ka to present, and with this present the first IP25 sea ice proxy record resolving the D/O cyclicity going back in time into Marine Isotope Stage 5a. Sea ice retreated abruptly at the start of warm interstadials, but spread rapidly during the cooling phase of the interstadials and became near-perennial and perennial during cold stadials and Heinrich events, respectively. Low salinity surface water and the sea ice edge spread to the Greenland-Scotland Ridge, and during the largest Heinrich events, probably far into the Atlantic Ocean.

Description: This is the ostracods census data from 157 sub-samples from two marine sediment cores, JM10-10GC and JM10-12GC, from Storfjorden, Svalbard. Cores were taken in October 2010 by RV 'Jan Mayen'. JM10-10GC is 402 cm long, sampled at 5-cm intervals. JM10-12GC is 320 cm long, sampled at 4-cm intervals. The cores comprise the last 13500 years. Cores were split in two halves and one half of each core was cut up in 1 cm thick sample slices. Each sample slice at 5 cm (core JM10-10GC) and 4 cm (cores JM10-12GC) interval was wet sieved with mesh sizes of 63, 100 and 1000 μm, oven dried, and then dry sieved with mesh-size of 150 μm. The size fraction 〉150 μm was analyzed for the content of benthic ostracods. All species were identified to species level.

Description: Ocean circulation changes along the continental shelf of the Nordic and Barents Seas have been investigated in order to reconstruct regional changes in the inflow of Atlantic Water (AW) through the last 16,000 calibrated (cal) years (yr) B.P. We have selected five time-slices representing the late glacial (16,000-15,000 cal yr B.P.), the Bølling-Allerød warm interstadials (14,500-13,500 cal yr B.P.), the Younger Dryas cold stadial (12,500-11,500 cal yr B.P.), the early Holocene (9500-7500 cal yr B.P.) and the late Holocene (4000-2000 cal yr B.P.). Twelve previously published records of the distribution of benthic foraminifera faunas and ice-rafted debris have been compiled. The earliest sign of Atlantic Water inflow was recorded at the northern Iceland shelf at 16,000-15,000 cal yr B.P. The inflow of warm AW to the Nordic Seas shelf has been persistent since, but with variable strength and geographic pattern. An apparent zonal seesaw pattern in the strength of the Norwegian Atlantic Current (NwAC) and the Irminger Current (IC) during the late glacial, Bølling-Allerød and Younger Dryas periods was found. During the Holocene, no zonal differences in the inflows of NwAC and IC were found. A strong meridional gradient with warmer conditions at lower latitudes and relatively cold conditions at high northern latitudes existed.

Description: A high-resolution piston core, ENAM93-21, from a water depth of 1020 m near the Faeroe-Shetland Channel is investigated for variations in magnetic susceptibility, surface oxygen isotopes, grain size distribution, content of ice-rafted detritus (IRD), and distribution of planktonic and benthic foraminifera. The core, covering the last 58,000 years, is correlated with the Greenland ice cores and compared with paleorecords from the Norwegian Sea and the North Atlantic Ocean. All fifteen Dansgaard-Oeschger climatic cycles recognized from the investigated time period in the Greenland ice cores have been identified in the ENAM93-21 core. Each cycle is subdivided into three intervals on the basis of characteristic benthic and planktonic faunas. Interstadial intervals contain a relatively warm planktonic fauna and a benthic fauna similar to the modern fauna in the Norwegian Sea. This indicates thermohaline convection as at present, with a significant contribution of deep water to the North Atlantic Deep Water (NADW). Transitional cooling intervals are characterized by more cold water planktonic foraminfera and ice-related benthic species. The benthic fauna signifies restricted bottom water conditions and a reduced contribution to the NADW. The peak abundance of N. pachyderma (s.) and the coldest surface water conditions are found in the stadial intervals. The benthic fauna is dominated by species with an association to Atlantic Intermediate Water, suggesting an increased Atlantic influence in the Norwegian Sea, and there was probably no contribution to the NADW through the Faeroe-Shetland Channel. The three different modes of circulation can be correlated to paleoceanographic events in the Norwegian Sea and the North Atlantic Ocean.

Description: A number of short-lasting warm periods (interstadials) interrupted the otherwise cold climate of the last glacial period. These events are supposedly linked to the inflow of the warm Atlantic surface water to the Nordic seas. However, previous investigations of planktonic foraminifera from the Nordic seas have not been able to resolve any significant difference between the interstadials and intervening cold stadials, as the faunas are continuously dominated by the polar species Neogloboquadrina pachyderma s. Here we examine the planktonic foraminifera assemblages from a high-resolution core, LINK17, taken at 1500 m water depth off northern Scotland below the warmest part of the inflowing Atlantic water. The core comprises the time period 34–10 calibrated ka B.P., the coldest period of the last glaciation and the deglaciation. The results reveal a hitherto unknown faunistic variability indicating significant fluctuations in both surface water inflow and in summer sea surface temperatures. During the interstadials, relatively warm Atlantic surface water (4–7°C) flowed north into the eastern Norwegian Sea. During the stadials and Heinrich events the surface inflow stopped and the temperatures in the study area dropped to 〈2°C. The Last Glacial Maximum was nearly as warm as the interstadials, but the inflow was much more unstable. The data reveal two previously unrecognized warming events each lasting more than 1600 years and preceding Heinrich events HE3 and HE2, respectively. By destabilizing the ice sheets on the shelves the warmings may have played a crucial role for the development of Heinrich events HE2 and HE3.