Surface temperature reconstruction using alkenones from sediment core B0406 retreived in the Peru upwelling area

We reconstructed a high-resolution, alkenone-based sea surface temperature (SST) record spanning the last ca. 150 years, from a sediment core retrieved within the main upwelling zone off Peru. A conspicuous SST decline is evidenced since the 1950s despite interdecadal SST variability. Instrumental SST data and reanalysis of ECMWF ERA 40 winds suggest that the recent coastal cooling corresponds mainly to an intensification of alongshore winds and associated increase of upwelling in spring. Consistently, both proxy and instrumental data evidence increased productivity in phase with the SST cooling. Our data expand on previous reports on recent SST cooling in other Eastern Boundary upwelling systems and support scenarios that relate coastal upwelling intensification to global warming. Yet, further investigations are needed to assess the role of different mechanisms and forcings (enhanced local winds vs. spin-up of the South Pacific High Pressure cell).

(Appendix B) Benthic foraminifera in Indian Ocean surface sediments

Multivariate analysis was performed on percentages of 46 species of unstained deep-sea benthic foraminifera from 131 core-top to near-core-top samples (322-5013 m) from across the Indian Ocean. Faunal data are combined with GEOSECS geochemical data to investigate any relationship between benthic foraminifera (assemblages and species) and deep-sea properties. In general, benthic foraminifera show a good correlation to surface productivity, organic carbon flux to the sea floor, deep-sea oxygenation and, to a lesser extent, to bottom temperature, without correlation with the water depths. The foraminiferal census data combined with geochemical data has enabled the division of the Indian Ocean into two faunal provinces. Province A occupies the northwestern Indian Ocean (Arabian Sea region) where surface primary production has a major maximum during the summer monsoon season and a secondary maximum during winter monsoon season that leads to high organic flux to the seafloor, making the deep-sea one of the most oxygen-deficient regions in the world ocean, with a pronounced oxygen minimum zone (OMZ). This province is dominated by benthic foraminifera characteristic of low oxygen and high organic food flux including Uvigerina peregrina, Robulus nicobarensis, Bolivinita pseudopunctata, Bolivinita sp., Bulimina aculeata, Bulimina alazanensis, Ehrenbergina carinata and Cassidulina carinata. Province B covers southern, southeastern and eastern parts of the Indian Ocean and is dominated by Nuttallides umbonifera, Epistominella exigua, Globocassidulina subglobosa, Uvigerina proboscidea, Cibicides wuellerstorfi, Cassidulina laevigata, Pullenia bulloides, Pullenia osloensis, Pyrgo murrhina, Oridorsalis umbonatus, Gyroidinoides (= Gyroidina) soldanii and Gyroidinoides cf. gemma suggesting well-oxygenated, cold deep water with low (oligotrophic) and pulsed food supply.

Benthic foraminifera in eastern equatorial Indian Ocean surface sediments

Study of Recent abyssal benthic foraminifera from core-top samples in the eastern equatorial Indian Ocean has identified distinctive faunas whose distribution patterns reflect the major hydrographic features of the region. Above 3800 m, Indian Deep Water (IDW) is characterized by a diverse and evenly-distributed biofacies to which Globocassidulina subglobosa, Pyrgo spp., Uvigerina peregrina, and Eggerella bradyi are the major contributors. Nuttalides umbonifera and Epistominella exigua are associated with Indian Bottom Water (IBW) below 3800 m. Within the IBW fauna, N. umbonifera and E. exigua are characteristic of two biofacies with independent distribution patterns. Nuttalides umbonifera systematically increases in abundance with increasing water depth. The E. exigua biofacies reaches its greatest abundance in sediments on the eastern flank of the Ninetyeast Ridge and in the Wharton-Cocos Basin. The hydrographic transition between IDW and IBW coincides with the level of transition from waters supersaturated to waters undersaturated with respect to calcite and with the depth of the lysocline. Carbonate saturation levels, possibly combined with the effects of selective dissolution on the benthic foraminiferal populations, best explain the change in faunas across the IDW/IBW boundary and the bathymetric distribution pattern of N. umbonifera. The distribution of the E. exigua fauna cannot be explained with this model. Epistominella exigua is associated with the colder, more oxygenated IBW of the Wharton-Cocos Basin. The distribution of this biofacies on the eastern flank of the Ninetyeast Ridge agrees well with the calculated bathymetric position of the northward flowing deep boundary current which aerates the eastern basins of the Indian Ocean.

Stable isotope ratios on planktonic foraminifer N. pachyderma of surface sediments from the Arctic Ocean (Table 1)

Planktic foraminifers Neogloboquadrina pachyderma (sin.) from 87 eastern and central Arctic Ocean surface sediment samples were analyzed for stable oxygen and carbon isotope composition. Additional results from 52 stations were taken from the literature. The lateral distribution of delta18O (18O/16O) values in the Arctic Ocean reveals a pattern of roughly parallel, W-E stretching zones in the Eurasian Basin, each ~0.5 per mil wide on the delta18O scale. The low horizontal and vertical temperature variability in the Arctic halocline waters (0-100 m) suggests only little influence of temperature on the oxygen isotope distribution of N. pachyderma (sin.). The zone of maximum delta18O values of up to 3.8 per mil is situated in the southern Nansen Basin and relates to the tongue of saline (> 33%.) Atlantic waters entering the Arctic Ocean through the Fram Strait. delta18O values decrease both to the Barents Shelf and to the North Pole, in accordance with the decreasing salinities of the halocline waters. In the Nansen Basin, a strong N-S delta18O gradient is in contrast with a relatively low salinity change and suggests contributions from different freshwater sources, i.e. salinity reduction from sea ice meltwater in the south and from light isotope waters (meteoric precipitation and river-runoff) in the northern part of the basin. North of the Gakkel Ridge, delta18O and salinity gradients are in good accordance and suggest less influence of sea ice melting processes. The delta13C (13C/12C) values of N. pachyderma (sin.) from Arctic Ocean surface sediment samples are generally high (0.75-0.95 per mil). Lower values in the southern Eurasian Basin appear to be related to the intrusion of Atlantic waters. The high delta13C values are evidence for well ventilated surface waters. Because the perennial Arctic sea ice cover largely prevents atmosphere-ocean gas exchange, ventilation on the seasonally open shelves must be of major importance. Lack of delta13C gradients along the main routes of the ice drift from the Siberian shelves to the Fram Strait suggests that primary production (i.e. CO2 consumption) does probably not change the CO2 budget of the Arctic Ocean significantly.

(Table 2) Chemical element contents in the surface sediment layer on the submeridional section through the Eastern Pacific

Paper devoted to geochemistry of antimony in metalliferous and transitional sediments from the Southeast Pacific.

Diatom abundance in surface sediments of the northern North Pacific

In order to map the modern distribution of diatoms and to establish a reliable reference data set for paleoenvironmental reconstruction in the northern North Pacific, a new data set including the relative abundance of diatom species preserved in a total of 422 surface sediments was generated, which covers a broad range of environmental variables characteristic of the subarctic North Pacific, the Sea of Okhotsk and the Bering Sea between 30° and 70°N. The biogeographic distribution patterns as well as the preferences in sea surface temperature of 38 diatom species and species groups are documented. A Q-mode factor analysis yields a three-factor model representing assemblages associated with the Arctic, Subarctic and Subtropical water mass, indicating a close relationship between the diatom composition and the sea surface temperatures. The relative abundance pattern of 38 diatom species and species groups was statistically compared with nine environmental variables, i.e. the summer sea surface temperature and salinity, annual surface nutrient concentration (nitrate, phosphate, silicate), summer and winter mixed layer depth and summer and winter sea ice concentrations. Canonical Correspondence Analysis (CCA) indicates 32 species and species groups have strong correspondence with the pattern of summer sea surface temperature. In addition, the total diatom flux data compiled from ten sediment traps reveal that the seasonal signals preserved in the surface sediments are mostly from spring through autumn. This close relationship between diatom composition and the summer sea surface temperature will be useful in deriving a transfer function in the subarctic North Pacific for the quantitative paleoceanographic and paleoenvironmental studies. The relative abundance of the sea-ice indicator diatoms Fragilariopsis cylindrus and F. oceanica of >20% in the diatom composition is used to represent the winter sea ice edge in the Bering Sea. The northern boundary of the distribution of F. doliolus in the open ocean is suggested to be an indicator of the Subarctic Front, while the abundance of Chaetoceros resting spores may indicate iron input from nearby continents and shelves and induced productivity events in the study area.

(Table 1) Planktonic foraminifera counts and stable oxygen isotope ratios of Pacific Ocean surface sediments

Core-top samples from the eastern tropical Pacific (10°N to 20°S) were used to test whether the ratio between Globorotalia menardii cultrata and Neogloboquadrina dutertrei abundance (Rc/d) and the oxygen isotope composition (?18O) of planktonic foraminifera can be used as proxies for the latitudinal position of the Equatorial Front. Specifically, this study compares the ?18O values of eight species of planktonic foraminifera (Globigerinoides ruber sensu stricto (ss) and sensu lato (sl), Globigerinoides sacculifer, Globigerinoides triloba, Pulleniatina obliquiloculata, Neogloboquadrina dutertrei, Globorotalia menardii menardii, Globorotalia menardii cultrata and Globorotalia tumida) with the seasonal hydrography of the region, and evaluates the application of each species or combination of species for paleoceanographic reconstructions. The results are consistent with sea surface temperature and water column stratification patterns. We found that in samples north of 1°N, the Rc/d values tend to be higher and d18O values of G. ruber, G. sacculifer, G. triloba, P. obliquiloculata, N. dutertrei, and G. menardii cultrata tend to be lower than those from samples located south of 1°N. We suggest that the combined use of Rc/d and the d18O difference between G. ruber and G. tumida or between P. obliquiloculata and G. tumida are the most suitable tools for reconstructing changes in the latitudinal position of the Equatorial Front and changes in the thermal stratification of the upper water column in the eastern tropical Pacific.

(Appendix B) Dinoflagellate cysts in Southeast Pacific Ocean surface sediments

orty-eight surface sediment samples from the southeast (SE) Pacific (25-53°S) are investigated for the determination of the spatial distribution of organic-walled dinoflagellate cysts along the western South American continental margin. Fifty-five different taxa are recorded and reflect oceanic or coastal assemblages. The oceanic assemblages are characterised by low cyst concentrations and the dominance of autotrophs, while the coastal assemblages generally contain a higher number of cysts, which are mainly produced by heterotrophic species. Highest cyst concentrations are observed in the active upwelling system offshore Concepción (35-37°S). Brigantedinium spp., Echinidinium aculeatum, Echinidinium granulatum/delicatum and cysts of Protoperidinium americanum dominate assemblages related to upwelling. Echinidinium aculeatum appears to be the best indicator for the presence of all year round active upwelling cells. Other protoperidinioid cysts may also occur in high relative abundances in coastal regions outside active upwelling systems, if the availability of nutrients, co-responsible for the presence/absence of their main food sources such as diatoms and other protists, is sufficient. The importance of nutrient availability as a determining environmental variable influencing cyst signals on a regional scale (SE Pacific) is demonstrated through statistical analyses of the data. Because of the importance of nutrients, uncertainties about the outcomes of quantitative sea-surface temperature (SST) reconstructions (Modern Analogue Technique) based on dinoflagellate cysts may arise, since no interaction between different hydrographical variables is considered in this approach. The combination of the SE Pacific surface sample dataset with other published cyst data from the Southern Hemisphere resulted in a database which includes 350 samples: the 'SH350 database'. This database is used to test the accuracy of the quantitative reconstructions by calculating and comparing the estimated versus observed values for each site. An attempt to perform quantitative SST reconstructions on the last 25 cal ka of site ODP1233 (41°S; 74°27'W) is made and again stresses the importance of other environmental variables such as nutrient availability in determining the dinoflagellate cyst assemblages.

Granulometry of surface sediments from the Panama Basin (Table 2, 3)

Panama Basin sediment surface coarse fractions are dominantly composed of planktonic foraminiferal remains. Textural studies of these coarse fractions by means of a large diameter settling tube system reveal characteristics grain size spectra with important modes at 2.0-2.25 phi, 2.3-2.45 phi, 2.5-2.75 phi, 3.0-33 phi, and 3.4-3.75 phi. The coarser modes consist of large Globoquadrina dutertrei and Globorotalia menardii shells, the finer ones of small planktonic foraminiferal species and of shell fragments of the larger species. Analyses of samples from the Carnegie Gap provide sufficient information such that the extent of the high energy environment close to the sill depth can be mapped; the textural analyses also seem to indicate south and northward flowing components of the bottom currents which transport particle assemblages with distinct textural characteristics. The samples bear evidence for large scale removal of calcareous fines from the crest of structural highs; the fines are then dumped on the flanks of these elevations.

Mineralogy of northern Indian Ocean surface sediments and of suspended sediments of Indian rivers (Table 2 and 5)

The solid phases from surface sediments, atmospheric dusts, and rivers of the Indian Ocean environment have been analyzed for their clay minerals and quartz. Such data have been used to delimit the transport paths and sources of the detrital minerals in the oceanic deposits. Diagnostic in distinguishing fluvial and eolian inputs to the northern Indian Ocean is a combination of the clay mineral assemblages and of their geographic distributions. River borne solids are the primary components of the Bay of Bengal deposits. The eastern part receives its continental input through the Ganges-Brahmaputra river system, while drainage of the Indian Peninsula by rivers introduces solids to the western part. The former materials are characterized by high illite and chlorite in the clay mineral assemblages; the latter by montmorillonite. The winds over the Bay bear distinctive dust burdens based upon their directions. However, their contributions to the sediments are insignificant. The eastern sector of the Arabian Sea receives major contributions of continental debris from the rivers and the high montmorillonite levels clearly indicate a source in the Indian Peninsula. The rest of the Sea appears to receive most of its land-derived materials from the north, perhaps the desert regions of northern India and West Pakistan, and they are wind-borne. These materials are also transported to the equatorial regions of the Indian Ocean. A gradient in attapulgite, just north of the equator, may indicate an eolian contribution to the Arabian Sea from the African continent. The halogenated hydrocarbon pesticides were assayed in the southwest monsoon winds and enter the Bay of Bengal at levels of a half ton per month, an amount comparable to those introduced by other wind and river systems to the marine environment.

Planktic foraminiferal and sea surface temperature record during the last 1 Myr across the Subtropical Front, Southwest Pacific

Planktic foraminiferal faunas and modern analogue technique estimates of sea surface temperature (SST) for the last 1 million years (Myr) are compared between core sites to the north (ODP 1125, 178 faunas) and south (DSDP 594, 374 faunas) of the present location of the Subtropical Front (STF), east of New Zealand. Faunas beneath cool subtropical water (STW) north of the STF are dominated by dextral Neogloboquadrina pachyderma, Globorotalia inflata, and Globigerina bulloides, whereas faunas to the south are strongly dominated by sinistral N. pachyderma (80-95% in glacials), with increased G. bulloides (20-50%) and dextral N. pachyderma (15-50%) in interglacials (beneath Subantarctic Water, or SAW). Canonical correspondence analysis indicates that at both sites, SST and related factors were the most important environmental influences on faunal composition. Greater climate-related faunal fluctuations occur in the south. Significant faunal changes occur through time at both sites, particularly towards the end of the mid-Pleistocene climate transition, MIS18-15 (e.g., decline of Globorotalia crassula in STW, disappearance of Globorotalia puncticulata in SAW), and during MIS8-5. Interglacial SST estimates in the north are similar to the present day throughout the last 1 Myr. To the south, interglacial SSTs are more variable with peaks 4-7 °C cooler than present through much of the early and middle Pleistocene, but in MIS11, MIS5.5, and early MIS1, peaks are estimated to have been 2-4 °C warmer than present. These high temperatures are attributed to southward spread of the STF across the submarine Chatham Rise, along which the STF appears to have been dynamically positioned throughout most of the last 1 Myr. For much of the last 1 Myr, glacial SST estimates in the north were only 1-2 °C cooler than the present interglacial, except in MIS16, MIS8, MIS6, and MIS4-2 when estimates are 4-7 °C cooler. These cooler temperatures are attributed to jetting of SAW through the Mernoo Saddle (across the Chatham Rise) and/or waning of the STW current. To the south, glacial SST estimates were consistently 10-11 °C cooler than present, similar to temperatures and faunas currently found in the vicinity of the Polar Front. One interpretation is that these cold temperatures reflect thermocline changes and increased Circumpolar Surface Water spinning off the Subantarctic Front as an enhanced Bounty Gyre along the south side of the Chatham Rise. For most of the last 1 Myr, the temperature gradient across the STF has been considerably greater than the present 4 °C. During glacial episodes, the STF in this region did not migrate northwards, but instead there was an intensification of the temperature gradient across it (interglacials 4-11 °C; glacials 8-14 °C).

(Table 1) Relarive abundance of foraminiferal species in the surface layer of bottom sediments from the Atlantic Ocean

Quantitative ratios of tests of planktonic foraminiferal species in thanatocoenoses within the surface layer of bottom sediments from Iceland to the Equator are described. Subarctic, boreal, subtropical and tropical types of thanatocoenoses and their subtypes are distinguished. Each subtype corresponds to a 2-3°C interval of mean annual temperature of the upper layer of ocean water. Comparison of fossil thanatocoenoses from Quaternary sediment cores with recent thanatocoenoses offers new potentials for paleotemperature analysis.

Ostracode relative abundances and geochemistry in surface sediments from Lake Ohrid

Understanding the ecology of bioindicators such as ostracods is essential in order to reconstruct past environmental and climate change from analysis of fossil assemblages preserved in lake sediment cores. Knowledge of the ecology of ancient Lake Ohrid's ostracod fauna is very limited and open to debate. In advance of the Ohrid ICDP-Drilling project, which has potential to generate high-resolution long-term paleoenvironmental data of global importance in paleoclimate research, we sampled Lake Ohrid and a wide range of habitat types in its surroundings to assess 1) the composition of ostracod assemblages in lakes, springs, streams, and short-lived seasonal water bodies, 2) the geographical distribution of ostracods, and 3) the ecological characteristics of individual ostracod species. In total, 40 species were collected alive, and seven species were preserved as valves and empty carapaces. Of the 40 ostracod species, twelve were endemic to Lake Ohrid. The most common genus in the lake was Candona, represented by 13 living species, followed by Paralimnocythere, represented by five living species. The most frequent species was Cypria obliqua. Species with distinct distributions included Heterocypris incongruens, Candonopsis kingsleii, and Cypria lacustris. The most common species in shallow, flooded areas was H. incongruens, and the most prominent species in ditches was C. kingsleii. C. lacustris was widely distributed in channels, springs, lakes, and rivers. Statistical analyses were performed on a "Lake Ohrid" dataset, comprising the subset of samples from Lake Ohrid alone, and an "entire" dataset comprising all samples collected. The unweighted pair group mean average (UPGMA) clustering was mainly controlled by species-specific depth preferences. Canonical Correspondence Analysis (CCA) with forward selection identified water depth, water temperature, and pH as variables that best explained the ostracod distribution in Lake Ohrid. The lack of significance of conductivity and dissolved oxygen in CCA of Ohrid data highlight the uniformity across the lake of the well-mixed waters. In the entire area, CCA revealed that ostracod distribution was best explained by water depth, salinity, conductivity, pH, and dissolved oxygen. Salinity was probably selected by CCA due to the presence of Eucypris virens and Bradleystrandesia reticulata in short-lived seasonal water bodies. Water depth is an important, although indirect, influence on ostracod species distribution which is probably associated with other factors such as sediment texture and food supply. Some species appeared to be indicators for multiple environmental variables, such as lake level and water temperature.