Bulk Calcium and Titanium contents and Ti/Ca ratio of sediment core GeoB11804-4

Bulk Ca and Ti contents and Ti/Ca ratio of sediment core GeoB11804-4, measured by ICP-OES after HF/HNO3/H2O2 microwave pressure digestion.

Stable oxygen isotope and Mg/Ca data of Globigerinoides ruber white, water stable oxygen isotope data, SST and MAT records of sediment core GeoB6211-2

During Termination 1, millennial-scale weakening events of the Atlantic meridional overturning circulation (AMOC) supposedly produced major changes in sea surface temperatures (SSTs) of the western South Atlantic, and in mean air temperatures (MATs) over southeastern South America. It has been suggested, for instance, that the Brazil Current (BC) would strengthen (weaken) and the North Brazil Current (NBC) would weaken (strengthen) during slowdown (speed-up) events of the AMOC. This anti-phase pattern was claimed to be a necessary response to the decreased North Atlantic heat piracy during periods of weak AMOC. However, the thermal evolution of the western South Atlantic and the adjacent continent is so far largely unknown. Here we address this issue, presenting high-temporal-resolution SST and MAT records from the BC and southeastern South America, respectively. We identify a warming in the western South Atlantic during Heinrich Stadial 1 (HS1), which is followed first by a drop and then by increasing temperatures during the Bølling-Allerød, in phase with an existing SST record from the NBC. Additionally, a similar SST evolution is shown by a southernmost eastern South Atlantic record, suggesting a South Atlantic-wide pattern in SST evolution during most of Termination 1. Over southeastern South America, our MAT record shows a two-step increase during Termination 1, synchronous with atmospheric CO2 rise (i.e., during the second half of HS1 and during the Younger Dryas), and lagging abrupt SST changes by several thousand years. This delay corroborates the notion that the long duration of HS1 was fundamental in driving the Earth out of the last glacial.

(Table 1) Crystal sizes of measured samples from the Bush Hill region in the Gulf of Mexico and from ODP Leg 204 at the Hydrate Ridge offshore Oregon

The grain sizes of gas hydrate crystallites are largely unknown in natural samples. Single grains are hardly detectable with electron or optical microscopy. For the first time, we have used high-energy synchrotron diffraction to determine grain sizes of six natural gas hydrates retrieved from the Bush Hill region in the Gulf of Mexico and from ODP Leg 204 at the Hydrate Ridge offshore Oregon from varying depth between 1 and 101 metres below seafloor. High-energy synchrotron radiation provides high photon fluxes as well as high penetration depth and thus allows for investigation of bulk sediment samples. Gas hydrate grain sizes were measured at the Beam Line BW 5 at the HASYLAB/Hamburg. A 'moving area detector method', originally developed for material science applications, was used to obtain both spatial and orientation information about gas hydrate grains within the sample. The gas hydrate crystal sizes appeared to be (log-)normally distributed in the natural samples. All mean grain sizes lay in the range from 300 to 600 µm with a tendency for bigger grains to occur in greater depth. Laboratory-produced methane hydrate, aged for 3 weeks, showed half a log-normal curve with a mean grain size value of c. 40 µm. The grains appeared to be globular shaped.

Stable isotope and Mg/Ca ratio of sediment core GeoB12610-2

To reconstruct the still poorly understood thermocline fluctuations in the western tropical Indian Ocean, a sediment core located off Tanzania (GeoB12610-2; 04°49.00'S, 39°25.42'E, 399?m water depth) covering the last 35 ka was analysed. Mg/Ca-derived temperatures from the planktonic foraminifera Globigerinoides ruber (white) and Neogloboquadrina dutertrei indicate that the last glacial was ~2.5 °C colder in the surface waters and ~3.5 °C colder in the thermocline compared with the present day. The depth of the thermocline and thus the stratification of the water column were shallower during glacial periods and deepened during the deglaciation and Holocene. The increased inflow of Southern Ocean Intermediate Waters via 'ocean tunnels' appears to cool the thermocline from below, leading to a similarity between the thermocline record of GeoB12610-2 with the Antarctic EDML temperature curve during the glacial. With rising sea level and the corresponding greater inflow of Red Sea Waters and Indonesian Intermediate Waters, the proportion of Southern Ocean Intermediate Water within the South Equatorial Current is reduced and, by Holocene time, the correlation to Antarctica is barely traceable. Comparison with the eastern Indian Ocean reveals that the thermocline depth reverses from the last glacial to present.

(Table S1) Stable carbon and oxygen isotopes and Mg/Ca ratios of planktonic foraminifera from ODP Hole 198-1209B

The Paleocene-Eocene Thermal Maximum (PETM) has been attributed to a rapid rise in greenhouse gas levels. If so, warming should have occurred at all latitudes, although amplified toward the poles. Existing records reveal an increase in high-latitude sea surface temperatures (SSTs) (8° to 10°C) and in bottom water temperatures (4° to 5°C). To date, however, the character of the tropical SST response during this event remains unconstrained. Here we address this deficiency by using paired oxygen isotope and minor element (magnesium/calcium) ratios of planktonic foraminifera from a tropical Pacific core to estimate changes in SST. Using mixed-layer foraminifera, we found that the combined proxies imply a 4° to 5°C rise in Pacific SST during the PETM. These results would necessitate a rise in atmospheric pCO2 to levels three to four times as high as those estimated for the late Paleocene.

The martyrdom and miracles of Saint George of Cappadocia.

Mode of access: Internet.

The Feast of Herod and the Beheading of Saint John the Baptist

Benozzo Gozzoli; 9 3/8 in.x 1 ft. 1 37/64 in.; tempera on poplar panel