Description: NW African climate shows orbital and millennial-scale variations, which are tightly connected to changes in marine productivity. We present an organic-walled dinoflagellate cyst (dinocyst) record from a sediment core off Cape Yubi at about 27°N in the Canary Basin covering the time period from 47 to 3 ka before present (BP). The dinocyst record reflects differences in upwelling intensity and seasonality as well as the influence of fluvial input. Sea-level changes play an important role for the upwelling pattern and productivity signals at the core site. Within the studied time interval, four main phases were distinguished. (1) From 45 to 24 ka BP, when sea-level was mostly about 75 m lower than today, high relative abundances of cysts of heterotrophic taxa point to enhanced upwelling activity, especially during Heinrich Events, while relatively low dinocyst accumulation rates indicate that filament activity at the core location was strongly reduced. (2) At sea-level lowstand during the LGM to H1, dinocyst accumulation rates suggest that local filament formation was even more inhibited. (3) From the early Holocene to about 8 ka BP, extraordinary high accumulation rates of most dinocyst species, especially of Lingulodinium machaerophorum, suggest that nutrient supply via fluvial input increased and rising sea-level promoted filament formation. At the same time, the upwelling season prolongated. (4) A relative increase in cysts of photoautotrophic taxa from about 8 ka BP onwards indicates more stratified conditions while fluvial input decreased. Our study shows that productivity records can be very sensitive to regional features. From the dinocyst data we infer that marine surface productivity off Cape Yubi during glacial times was within the scale of modern times but extremely enhanced during deglaciation.

Description: Here we present an improvement of paleotemperature reconstructions for the Southern Ocean by combining new diatom data from the Pacific sector with published Atlantic and Indian sector reference data. The statistical analysis of 336 surface sediment samples recovered from a wide area of Southern Ocean environments defines a supra-regional reference data set for quantitative summer sea surface temperature (SSST) estimations. In situ temperature measurements covering the time span from approx. 1900 to 1991 were used as reference instead of more recent time series of satellite-derived data, possibly biased by ocean warming. Different transfer function (TF) models for the Imbrie and Kipp Method (IKM), the Modern Analog Technique (MAT), Weighted Averaging (WA), and Weighted Averaging Partial Least Squares (WAPLS) were tested. Best performance for IKM was obtained using the D336 set with 29 diatom taxa and three factors, resulting in root mean square error of prediction (RMSEP) of 0.833°C for SSST. MAT estimates were best with six analogs resulting in the lowest RMSEP of 0.812°C. WAPLS applied to D336 resulted in a RMSEP of 0.782°C. WA performed less well, expressed by a RMSEP of 0.974°C. Furthermore, two subsets for the Atlantic (D151) and the Pacific sectors (D107) were applied with IKM to test for the advantages of localized TFs. IKM-D151 and IKM-D107 performed comparably good as IKM-D336, with RMSEP of 0.71°C and 0.68°C, respectively. Application of the augmented reference data sets on two Pleistocene sediment records from the Atlantic (PS1768-8) and Pacific (PS58/271-1) sectors led to the best performance of IKM with D336, expressed by high overall communalities (〉0.75) and fewer (PS1768-8) to no (PS58/271-1) no-analogs, compared to the regional data sets, proving IKM-D336 to deal better with higher assemblage variability. SSST estimates for both cores exhibit similar glacial/interglacial patterns for all four applied D336-based TF methods, with the best concordance between IKM and WAPLS.

Description: Following a report of supposed fragments of calcareous dinoflagellate cysts from a Pleistocene drill core (CRP-1) recovered in the Ross Sea, Antarctica, sediments of the same core were re-investigated for their microfossil content. Besides common foraminifera and other microfossils, rare complete cysts of calcareous dinoflagellates were found. All cysts belong to the species Caracomia arctica (Gilbert & Clark, 1983) Streng, Hildebrand-Habel & Willems, 2002, a taxon characteristic of late Neogene high latitude, coldwater environments. Two morphotypes can be distinguished, C. arctica f. arctica and C. arctica f. rossensis, of which the latter is described as a new form. The presence of C. arctica strengthens diatom-based palaeoenvironmental reconstructions of periodical sea ice-free conditions at the time of deposition. Accordingly, cysts of C. arctica are interpreted as resting cysts that allow survival during harsh intervals of the high latitude environment. Previously reported calcareous dinoflagellates cyst fragments from these sediments are re-interpreted as test fragments of bilamellar foraminifera, which represent the most common group of foraminifers in the sediments.

Description: In the scope of the International Polar Year 2007/2008, marine sediment cores were retrieved with RV Polarstern offshore the Prydz Bay to gain insight into land-ocean linkages of East Antarctic Ice Sheet (EAIS) dynamics, sea-ice formation, and regional palaeooceanography during the late Cenozoic. The scientific conception is based on the reconstruction of glaciomarine processes, comprising variations in ice-rafting, ice-shelf dynamics, and coastal bottom-water productivity. From our oldest sediment record, reaching back to 4.0 Ma, the results suggest a persistent presence of the EAIS in the Prydz Bay area during that time. The strongest glacial influence in the adjacent ocean appeared around the Plio-/Pleistocene boundary and during the mid-Pleistocene, consistent with maximum glaciation in the hinterland. The EAIS also fluctuated at glacial-interglacial timescales, documented by repeated stages of sediment reworking along the continental slope, prior to interglacials. The most apparent glacial retreat during the late Pleistocene took place after climate termination II, some 130 kyr ago. Another postglacial retreat event is evident from the inner shelf and commenced around 12 ka BP in agreement with ice shrinkage in adjacent onshore regions and global sea-level rise towards the Holocene. The variability of bottom-water formation in coastal polynyas reveals strong affinities to climate change that controls sea-ice extension. Strongest bottom-water activity apparently is related to intermediate interglacial stages, while it diminishes during both glacial stages and peak warmth. During glacial stages the permanent presence of near-shore sea-ice prevents the formation of polynyas, while during very warm stages the seasonal waxing and waning of sea ice is reduced and retards the brine-release effect needed for dense-water formation. The latter phenomenon in conjunction with glacial retreat was well expressed during climate termination II, which is also documented as an exceptionally warm event in Antarctic ice cores.

Description: Diatom assemblages preserved in 18 sediment cores recovered in the eastern Indian, Atlantic and Pacific sectors of the Southern Ocean are used for the reconstruction of the variability of summer sea surface temperature (SSST) and sea ice concentration during the Last Interglacial (LIG) or Marine Isotope Stage 5 (MIS 5). The large coverage of the core sites allows for reconstructions on latitudinal and longitudinal transects across the Southern Ocean and thus for the comparison of the environmental signal evolution in different sedimentary basins of the Southern Ocean. Such information is crucial for the understanding of climate signal propagation in the Southern Ocean and on inter-hemispheric scale. The quantitative temperature and sea ice records are derived with newly established diatom-based transfer functions at millennial to centennial resolution. Stratigraphic age assignment relies on a combination of oxygen isotope stratigraphy, biostratigraphy, core-core correlation using physical, geochemical and microfossil abundance pattern together with a tuning of sediment core signals with climate records in Antarctic ice cores. All records display a rapid transition from glacial (MIS 6) to MIS 5 conditions to reach maximum temperatures in the latest MIS 6/MIS 5 transition (Termination II) and the early LIG attributed to MIS 5.5. The amplitude of the SSST change is up to 5°C, with generally smaller values in the Pacific sector. During this period Southern Ocean temperature may exceed modern surface temperatures by up to 3°C and the winter sea ice edge is located south of the modern ice edge. Higher resolution cores display short-term temperature rebounds during the Termination II warming. Such cold rebounds are not discerned in the ice core records. The Southern Ocean warming could be triggered by precessional changes influencing high latitude summer insolation and potentially be accelerated by feedback mechanisms such as the reduction of surface albedo (sea ice), CO2 outgassing of the Southern Ocean and changes in meridional overturning circulation. The new set of data fills a gap in information in the global evolution of Earth climate during the Last Interglacial and will be used for the testing of numerical modeling results of the last distinctly warmer and higher sea level than present climate period.

Description: Diatom assemblages preserved in 16 sediment cores recovered in the eastern Indian, Atlantic and Pacific sectors of the Southern Ocean are used for the reconstruction of the variability of summer sea surface temperature (SSST) and sea ice concentration during the Last Interglacial (LIG) or Marine Isotope Stage 5 (MIS 5). The large coverage of the core sites allows for reconstructions on latitudinal and longitudinal transects across the Southern Ocean and thus for the comparison of the environmental signal evolution in different sedimentary basins of the Southern Ocean. Such information is crucial for the understanding of climate signal propagation in the Southern Ocean and on inter-hemispheric scale. The quantitative temperature and sea ice records are derived with newly established diatom-based transfer functions at millennial to centennial resolution. Stratigraphic age assignment relies on a combination of oxygen isotope stratigraphy, biostratigraphy, core-core correlation using physical, geochemical and microfossil abundance pattern together with a tuning of sediment core signals with climate records in Antarctic ice cores. All records display a rapid transition from glacial (MIS 6) to MIS 5 conditions to reach maximum temperatures in the latest MIS 6/MIS 5 transition (Termination II) and the early LIG attributed to MIS 5.5. The amplitude of the SSST change is up to 5◦C, with generally smaller values in the Pacific sector. During this period Southern Ocean temperature may exceed modern surface temperatures by up to 3◦C and the winter sea ice edge is located south of the modern ice edge. Higher resolution cores display short-term temperature rebounds during the Termination II warming. Such cold rebounds are not discerned in the ice core records. The Southern Ocean warming could be triggered by precessional changes influencing high latitude summer insolation and potentially be accelerated by feedback mechanisms such as the reduction of surface albedo (sea ice), CO2 outgassing of the Southern Ocean and changes in meridional overturning circulation. The new set of data fills a gap in information in the global evolution of Earth climate during the Last Interglacial and will be useful for the testing of numerical modeling results of the last distinctly warmer and higher sea level than present climate period.