Radiation balance of the tropical ocean surface measured during Atlantic Expedition GARP 1974 (Table 1)

The net flux of all irreversible fluxes of radiation and heat crossing the ocean surface is determined for phase III of GATE at position no. 27 (WFS "Planet", FRG). The radiation fluxes have been measured directly, while the heat fluxes have been parameterized with the bulk formula however with bulk coefficients depending on stability. The heat loss of the ocean due to warming of the cooler precipitation is included for the determination of the net flux at the ocean surface. Some examples of hourly mean values of different fluxes during different weather conditions are additionally shown.

(Table 1) Age control points and of sediment core MD01-2444

The marine isotopic stage 3 (MIS3) at Ocean Drilling Program (ODP) Site 1060 (Gulf Stream) shows both sharp onset and end of interstadials, the existence of very short lived warm events during stadials, and points to differences in detail between the sea surface temperature (SST) record from the western North Atlantic and the atmospheric temperature record inferred from d18O in Greenland ice. Investigating MIS3 and obtaining comparable data from other locations appears crucial. The eastern Atlantic provides well-documented records of climate changes. We have selected a core from off Portugal and use it to examine Dansgaard/Oeschger events (D/O) at centennial-scale resolution (139 years on average between two data points). We have obtained a faunal data set for core MD01-2444, 37°N, 10°W, 2600 m water depth and use a group of species (Globigerina bulloides + Globigerinita glutinata) as a proxy of upwelling intensity driven by trade winds intensity changes. We tentatively relate the variation of this group to a North Atlantic Oscillation-like phenomenon (NAO) off Portugal. We observe that it resembles the rainfall index in the Caribbean as recorded at ODP Site 1002 (Cariaco Basin) which traces the Intertropical Convergence Zone (ITCZ) location through changes of terrigenous inputs. The driest intervals (ITZC to the south) at Site 1002 correspond to intervals of increased upwelling in MD01-2444 as well as the driest periods identified during stadials on similar cores in the area. Because the ITZC to the south is consistent with an El Niño-Southern Oscillation (ENSO+) situation, our study suggests a positive correlation between ENSO-like conditions and NAO-like conditions at a millennial timescale. During interstadial intervals when increased wetness over Cariaco is recorded (ITCZ to the north) and the upwelling in MD01-2444 is decreased, we see from both SSTs and faunal tropical indicators that MD01-2444 site is warm. In addition, interstadials are equally warm through each so-called Bond cycle. This contrasts with the Greenland Ice Core Project (GRIP) record where interstadial peaks are successively cooler through each Bond cycle. This record confirms a link between tropical climate linked to ITCZ position and the climate of southern Europe at millennial timescales, in spite of showing a very good correlation with polar latitudes (GRIP) through d18O on Globigerina bulloides. In addition, because the warmest SSTs and the d18O on G. bulloides are so remarkably different, our work points to changes in seasonality as a strong control over the climatic pattern of the North Atlantic area and the marked influence of winter conditions.

Helium and oxygen isotope ratios of ODP Sites 193-1188 and 193-1189

Fluid mixing processes and thermal regimes within the Snowcap and Roman Ruins vent sites of the PACMANUS hydrothermal system, Papua New Guinea, were investigated using 3He/4He ratios from fluid inclusions within pyrite and anhydrite and the d18O signature of anhydrite. Depressed 3He/4He ratios of 0.2-6.91RA appear to be caused by significant atmospheric diffusive exchange, whilst He-Ne diffusive fractionation precludes correction using 20Ne. 40Ar/36Ar ratios of 295-310 are elevated above seawater, indicating the majority of argon is seawater derived but with a magmatic component. d18O anhydrite ratios are 6.5 per mil to 11 per mil for Snowcap and 6.4 per mil to 11.9 per mil for Roman Ruins. Using oxygen isotope fractionation factors for the anhydrite-water system, the temperatures calculated assuming isotopic equilibrium at depth are up to 100 °C cooler than fluid inclusion trapping temperatures. It is likely that anhydrite is precipitated rapidly, preventing d18O equilibration. By comparing new d18O values for anhydrite with corresponding published 87Sr/86Sr ratios, seawater is inferred to penetrate deep into the Snowcap system with little conductive heating. A simple fluid mixing model has been constructed whereby the differing venting styles can be explained by a plumbing system at depth which favors delivery of end-member hydrothermal fluid to the high temperature sites.

(Table 1) Age determination of sediment core PC17

We have investigated glacial-interglacial differences in sea surface temperature (SST) near Hawaii using two relatively high deposition rate, shallow-water piston cores collected near Oahu, Hawaii. Modern hydrographic data show that local surface water temperatures are broadly consistent with the regional pattern of SSTs in the southern subtropical North Pacific. Past SSTs were estimated on the basis of three independently measured parameters: (1) UK'37 values of alkenones, (2) d18O of Globigerinoides ruber, and (3) assemblages of planktonic foraminifera using the modern analog technique (MAT). The two cores yield similar SST records, and if differences in the ecology of foraminifera and coccolithophores are considered, the three different approaches to estimating SSTs yield consistent results. UK'37-based temperatures, which may represent winter values at this location, were ~2.5°C colder during the Last Glacial Maximum than today, which is consistent with the February MAT estimates. The d18O-based temperature estimates, likely biased toward summer temperatures, indicate that the glacial SSTs were at least 1°C cooler than today, which is comparable to the results of MAT August estimates.

Sea-surface temperature and salinity reconstruction for sediment core GeoB5844-2

We present high-resolution paleoceanographic records of surface and deep water conditions within the northern Red Sea covering the last glacial maximum and termination I using alkenone paleothermometry, stable oxygen isotopes, and sediment compositional data. Paleoceanographic records in the restricted desert-surrounded northern Red Sea are strongly affected by the stepwise sea level rise and appear to record and amplify well-known millennial-scale climate events from the North Atlantic realm. During the last glacial maximum (LGM), sea surface temperatures were about 4°C cooler than the late Holocene. Pronounced coolings associated with Heinrich event 1 (~2°C below the LGM level) and the Younger Dryas imply strong atmospheric teleconnections to the North Atlantic. Owing to the restricted exchange with the Indian Ocean, Red Sea salinity is particularly sensitive to changes in global sea level. Paleosalinities exceeded 50 psu during the LGM. A pronounced freshening of the surface waters is associated with the meltwater peaks MWP1a and MWP1b owing to an increased surface-near inflow of "normal" saline water from the Indian Ocean. Vertical delta18O gradients are also increased during these phases, indicating stronger surface water stratification. The combined effect of deglacial changes in sea surface temperature and salinity on water column stratification initiated the formation of two sapropel layers, which were deposited under almost anoxic condition in a stagnant water body.

Exploring the potential of clumped isotope thermometry on coccolith-rich sediments as a sea surface temperature proxy

Understanding past changes in sea surface temperatures (SSTs) is crucial; however, existing proxies for reconstructing past SSTs are hindered by unknown ancient seawater composition (foraminiferal Mg/Ca and d18O), or reflect subsurface temperatures (TEX86) or have a limited applicable temperature range (Uk'37). We examine clumped isotope (D47) thermometry to fossil coccolith-rich material as an SST proxy, as clumped isotopes are independent of original seawater composition and applicable to a wide temperature range and coccolithophores are widespread and dissolution resistant. The D47-derived temperatures from <63, <20, <10 and 2-5 µm size fractions of two equatorial Pacific late Miocene-early Pliocene sediment samples (c1; c2) range between ~18-29 {degree sign}C, with c1 temperatures consistently above c2. Removing the >63 µm fraction removes most non-mixed layer components; however, the D47-derived temperatures display an unexpected slight decreasing trend with decreasing size fraction. This unexpected trend could partly arise because larger coccoliths (5-12 µm) are removed during the size fraction separation process. The c1 and <63 µm c2 D47-derived temperatures are comparable to concurrent Uk'37 SSTs. The <20, <10 and 2-5 µm c2 D47-derived temperatures are consistently cooler than expected. The D47-Uk'37 temperature offset is probably caused by abiotic/diagenetic calcite present in the c2 2-5 µm fraction (~53% by area), which potentially precipitated at bottom water temperatures of ~6 {degree sign}C . Our results indicate that clumped isotopes on coccolith-rich sediment fractions have potential as an SST proxy, particularly in tropical regions, providing that careful investigation of the appropriate size fraction for the region and timescale is undertaken.

(Table 1) Stable isotope record of Middle Cretaceous benthic foraminifera

Preservation of planktic foraminiferal calcite has received widespread attention in recent years, but the taphonomy of benthic foraminiferal calcite and its influence on the deep-sea palaeotemperature record have gone comparatively unreported. Numerical modeling indicates that the carbonate recrystallization histories of deep-sea sections are dominated by events in their early burial history, meaning that the degree of exchange between sediments and pore fluids during the early postburial phase holds the key to determining the palaeotemperature significance of diagenetic alteration of benthic foraminifera. Postburial sedimentation rate and lithology are likely to be important determinants of the paleoceanographic significance of this sediment-pore fluid interaction. Here we report an investigation of the impact of extreme change in sedimentation rate (a prolonged and widespread Upper Cretaceous hiatus in the North Atlantic Ocean) on the preservation and d18O of benthic foraminifera of Middle Cretaceous age (nannofossil zone NC10, uppermost Albian/lowermost Cenomanian, ~99 Ma ago) from multiple drill sites. At sites where this hiatus immediately overlies NC10, benthic foraminifera appear to display at least moderate preservation of the whole test. However, on closer inspection, these tests are shown to be extremely poorly preserved internally and yield d18O values substantially higher than those from contemporaneous better preserved benthic foraminifera at sites without an immediately overlying hiatus. These high d18O values are interpreted to indicate alteration close to the seafloor in cooler waters during the Late Cretaceous hiatus. Intersite differences in lithology modulate the diagenetic impact of this extreme change in sedimentation rate. Our results highlight the importance of thorough examination of benthic foraminiferal wall structures and lend support to the view that sedimentation rate and lithology are key factors controlling the paleoceanographic significance of diagenetic alteration of biogenic carbonates.

Stable isotopes of benthic foraminifera from Site ODP 184-1146

We generated a high resolution (~8 ky) benthic record from a West Pacific marginal basin to investigate the detailed structure and spectral characteristics of deep water isotope fluctuations during the middle Miocene. The benthic record from ODP Site 1146 allows unprecedented resolution of the structure of the middle Miocene delta13C excursion, as well as tighter control on the chronology of climatic events. Spectral analysis of the variance in the delta18O and delta13C records from ODP Site 1146 reveals spectral power concentrated in the eccentricity band (400-, ~100-ky) over the time interval between 13 and 17 Ma. The amplitude evolution in the 400-ky band is strikingly similar to that of the long eccentricity in Laskar's solution. There is an abrupt switch to the obliquity band in the delta18O record at -14.9 Ma, suggesting a shift in the ocean/climate response to orbital forcing (from low latitude eccentricity to high latitude obliquity forcing). The obliquity signal is pervasive in the delta18O record until -13.9 Ma, when a sharp increase in delta18O values indicates a major climatic transition. Comparison of delta18O and delta13C profiles from DSDP Site 588 (SW Pacific Ocean), ODP Site 761 (E Indian Ocean) and ODP Site 1146 (South China Sea) reveals significantly cooler deep water in the NE Indian Ocean throughout the middle Miocene and a restricted deep water exchange between the Pacific Ocean and Indian Ocean.

Pollen record of sediment core GeoB1008-3 from the Congo fan

Palynological investigation of the marine core, GeoB1008-3, from near the mouth of the Congo river (6°35.6'S/10°19.1'E), provides information about the changes in vegetation and climate in West Equatorial Africa during the last 190 ka. The pollen diagram is divided into zones 1-6 which are considered to correspond in time with the marine isotope stages 1-6. Oscillations in temperature and moisture are indicated during the cold stage 6. During stage 5, two cooler periods (5d and 5b) can be shown with an expansion of Podocarpus forests to lower elevations on the expense of lowland rain forest. Extended mangrove swamps existed along the coast in times of high sea level (stages 5 and 1).

Deuterium isotope ratios of Victoria Lower Glacier Ice Core

The Little Ice Age (LIA) is one of the most prominent climate shifts in the past 5000 yrs. It has been suggested that the LIA might be the most recent of the Dansgaard-Oeschger events, which are better known as abrupt, large scale climate oscillations during the last glacial period. If the case, then according to Broecker (2000a, 2000b) Antarctica should have warmed during the LIA, when the Northern Hemisphere was cold. Here we present new data from the Ross Sea, Antarctica, that indicates surface temperatures were ~2 °C colder during the LIA, with colder sea surface temperatures in the Southern Ocean and/or increased sea-ice extent, stronger katabatic winds, and decreased snow accumulation. Whilst we find there was large spatial and temporal variability, overall Antarctica was cooler and stormier during the LIA. Although temperatures have warmed since the termination of the LIA, atmospheric circulation strength has remained at the same, elevated level. We conclude, that the LIA was either caused by alternative forcings, or that the sea-saw mechanism operates differently during warm periods.

Contents of water, sulphur, total organic and inorganic carbon, XRF counts of Ti, S and Ca and radiocarbon ages of sediment core Co1008 from Skua Lake, Rauer Group, East Antarctica

Limited information on the East Antarctic Ice Sheet (EAIS) geometry during Marine Isotope Stage 3 (MIS 3; 60-25 ka) restricts our understanding of its behaviour during periods of climate and sea level change. Ice sheet models forced by global parameters suggest an expanded EAIS compared to the Holocene during MIS 3, but field evidence from East Antarctic coastal areas contradicts such modelling, and suggests that the ice sheet margins were no more advanced than at present. Here we present a new lake sediment record, and cosmogenic exposure results from bedrock, which confirm that Rauer Group (eastern Prydz Bay) was ice-free for much of MIS 3. We also refine the likely duration of the Last Glacial Maximum (LGM) glaciation in the region. Lacustrine and marine sediments from Rauer Group indicate the penultimate period of ice retreat predates 50 ka. The lacustrine record indicates a change from warmer/wetter conditions to cooler/drier conditions after ca. 35 ka. Substantive ice sheet re-advance, however, may not have occurred until much closer to 20 ka. Contemporary coastal areas were still connected to the sea during MIS 3, restricting the possible extent of grounded ice in Prydz Bay on the continental shelf. In contrast, relative sea levels (RSL) deduced from field evidence indicate an extra ice load averaging several hundred metres thicker ice across the Bay between 45 and 32 ka. Thus, ice must either have been thicker immediately inland (with a steeper ice profile), or there were additional ice domes on the shallow banks of the outer continental shelf. Further work is required to reconcile the differences between empirical evidence of past ice sheet histories, and the history predicted by ice sheet models from far-field temperature and sea level records.

Talos Dome Ice Core Deuterium Data

During the 1996 Programma Nazionale di Ricerche in Antartide-International Trans-Antarctic Scientific Expedition traverse, two firn cores were retrieved from the Talos Dome area (East Antarctica) at elevations of 2316 m (TD, 89 m long) and 2246 m (ST556, 19 m long). Cores were dated by using seasonal variations in non-sea-salt (nss) SO42- concentrations coupled with the recognition of tritium marker level (1965-1966) and nss SO42- spikes due to the most important volcanic events in the past (Pinatubo 1991, Agung 1963, Krakatoa 1883, Tambora 1815, Kuwae 1452, Unknown 1259). The number of annual layers recognized in the TD and ST556 cores was 779 and 97, respectively. The dD record obtained from the TD core has been compared with other East Antarctic isotope ice core records (Dome C EPICA, South Pole, Taylor Dome). These records suggest cooler climate conditions between the middle of 16th and the beginning of 19th centuries, which might be related to the Little Ice Age (LIA) cold period. Because of the high degree of geographical variability, the strongest LIA cooling was not temporally synchronous over East Antarctica, and the analyzed records do not provide a coherent picture for East Antarctica. The accumulation rate record presented for the TD core shows a decrease during part of the LIA followed by an increment of about 11% in accumulation during the 20th century. At the ST556 site, the accumulation rate observed during the 20th century was quite stable.

Mortality and climatic/environmental correlates of Widdringtonia cedargensis trees in the Cederberg, South Africa

Background: Conifer populations appear disproportionately threatened by global change. Most examples are, however, drawn from the northern hemisphere and long-term rates of population decline are not well documented as historical data are often lacking. We use a large and long-term (1931-2013) repeat photography dataset together with environmental data and fire records to account for the decline of the critically endangered Widdringtonia cedarbergensis. Eighty-seven historical and repeat photo-pairs were analysed to establish 20th century changes in W. cedarbergensis demography. A generalized linear mixed-effects model was fitted to determine the relative importance of environmental factors and fire-return interval on mortality for the species. Results: From an initial total of 1313 live trees in historical photographs, 74% had died and only 44 (3.4%) had recruited in the repeat photographs, leaving 387 live individuals. Juveniles (mature adults) had decreased (increased) from 27% (73%) to 8% (92%) over the intervening period. Our model demonstrates that mortality is related to greater fire frequency, higher temperatures, lower elevations, less rocky habitats and aspect (i.e. east-facing slopes had the least mortality). Conclusions: Our results show that W. cedarbergensis populations have declined significantly over the recorded period, with a pronounced decline in the last 30 years. Individuals that established in open habitats at lower, hotter elevations and experienced a greater fire frequency appear to be more vulnerable to mortality than individuals growing within protected, rocky environments at higher, cooler locations with less frequent fires. Climate models predict increasing temperatures for our study area (and likely increases in wildfires). If these predictions are realised, further declines in the species can be expected. Urgent management interventions, including seedling out-planting in fire-protected high elevation sites, reducing fire frequency in higher elevation populations, and assisted migration, should be considered.

(Table S1) Stable oxygen isotopic values and Mg/Ca ratios of Globigerinoides ruber w from sediment core AAS9_21

Variations in sea surface temperature (SST), d18O of sea water (?18Ow), and salinity were reconstructed for the past 68 ka using a sediment core (AAS9/21) from the eastern Arabian Sea (EAS) in order to understand the changes in evaporation and precipitation associated with the monsoon system. The Mg/Ca-derived SST record varies by ~4°C; it shows that marine isotope stage (MIS) 4 was warmer than MIS 3, that the Last Glacial Maximum was 4°C cooler than the present, and that there was a 2°C increase within the Holocene. MIS 4 records higher d18Ow and salinity values than MIS 2, suggesting variable flow of low-salinity Bay of Bengal flow into the EAS during glacial periods. The transition from MIS 4 to MIS 3 was marked with a conspicuous shift from higher to lower d18Ow values, which reflects a decrease in the evaporation-precipitation budget in the EAS, perhaps due to the strengthening of southwest monsoon. Monsoon reconstructions based on d18Ow reveal that monsoon-driven precipitation was higher during MIS 3 and MIS 1 and was lower during MIS 2 and MIS 4. This is consistent with earlier monsoon reconstructions based on upwelling indices from the western Arabian Sea. However, the amplitude of monsoon fluctuations derived through upwelling indices and d18Ow varies significantly, which may indicate spatial variability of monsoon rainfall.

Measurement results of d18O, Mg/Ca, and Ti/Ca of sediment cores GeoB10042-1 and GeoB10043-3

The advection of relatively fresh Java Sea water through the Sunda Strait is presently responsible for the low-salinity "tongue" in the eastern tropical Indian Ocean with salinities as low as 32 per mil. The evolution of the hydrologic conditions in the eastern tropical Indian Ocean since the last glacial period, when the Sunda shelf was exposed and any advection via the Sunda Strait was cutoff, and the degree to which these conditions were affected by the Sunda Strait opening are not known. Here we have analyzed two sediment cores (GeoB 10042-1 and GeoB 10043-3) collected from the eastern tropical Indian Ocean off the Sunda Strait that cover the past ~40,000?years. We investigate the magnitude of terrigenous supply, sea surface temperature (SST), and seawater d18O (d18Osw) changes related to the sea level-driven opening of the Sunda Strait. Our new spliced records off the Sunda Strait show that during the last glacial, average SST was cooler and d18Osw was higher than elsewhere in the eastern tropical Indian Ocean. Seawater d18O decreased ~0.5 per mil after the opening of the Sunda Strait at ~10 kyr B.P. accompanied by an SST increase of 1.7°C. We suggest that fresher sea surface conditions have persisted ever since due to a continuous transport of low-salinity Java Sea water into the eastern tropical Indian Ocean via the Sunda Strait that additionally increased marine productivity through the concomitant increase in terrigenous supply.