Stable isotopic record of planktonic foraminifera of the Pacific Ocean

We determined the d18O and d13C of individual Globigerinoides ruber and Pulleniatina obliquiloculata from sediment traps located from 5°N to 12°S along 140°W in the Pacific Ocean to evaluate the effects of varying [CO3=] on shell d18O and d13C. Variations in the offset between shell d13C and d13CDIC (Dd13Cs-DIC) are attributed to differences in [CO3]2-, temperature, and shell size between sample sites. When Dd13Cs-DIC of G. ruber was corrected for variations in [CO3]2- using the experimental slope of Bijma et al. (1998), the residual Dd13Cs-DIC was correlated with mixed layer temperature (+0.10±0.04 per mil °C**-1). The slope of this temperature effect is consistent with experimental results. In P. obliquiloculata, Dd13Cs-DIC and temperature were strongly anticorrelated (?0.14±0.03 per mil C**-1). We are unable to separate the influences of [CO3]2- and temperature in this species without independent experimental data. Correcting for [CO3]2- variability on d18Os of G. ruber improves the accuracy of estimated sea surface temperatures.

Ice and snow characteristics in Prydz Bay in 2006

Under the Chinese National Antarctic Research Expedition program in 2006, the annual thermal mass balance of landfast ice in the vicinity of Zhongshan Station, Prydz Bay, east Antarctica, was investigated. Sea ice formed from mid-February onward, and maximum ice thickness occurred in late November. Snow cover remained thin, and blowing snow caused frequent redistribution of the snow. The vertical ice salinity showed a 'question-mark-shaped' profile for most of the ice growth season, which only turned into an 'I-shaped' profile after the onset of ice melt. The oceanic heat flux as estimated from a flux balance at ice-ocean interface using internal ice temperatures decreased from 11.8 (±3.5) W/m**2 in April to an annual minimum of 1.9 (±2.4) W/m**2 in September. It remained low through late November, in mid-December it increased sharply to about 20.0 W/m**2. Simulations applying the modified versions of Stefan's law, taking account the oceanic heat flux and ice-atmosphere coupling, compare well with observed ice growth. There was no obvious seasonal cycle for the thermal conductivity of snow cover, which was also derived from internal ice temperatures. Its annual mean was 0.20 (±0.04) W/m/°C.

(Table 1) Soil density and concentration of 10Beryllium and 26Aluminium in samples from two ash deposits in the McMurdo Dry Valleys

The McMurdo Dry Valleys, Antarctica (MDV) are among the oldest landscapes on Earth, and some landforms there present an intriguing apparent contradiction such that millions of years old surface deposits maintain their meter-scale morphology despite the fact that measured erosion rates are 0.1-4 m/Ma. We analyzed the concentration of cosmic ray-produced 10Be and 26Al in quartz sands from regolith directly above and below two well-documented ash deposits in the MDV, the Arena Valley ash (40Ar/39Ar age of 4.33 Ma) and the Hart ash (K-Ar age of 3.9 Ma). Measured concentrations of 10Be and 26Al are significantly less than expected given the age of the in situ air fall ashes and are best interpreted as reflecting the degradation rate of the overlying sediments. The erosion rate of the material above the Arena Valley ash that best explains the observed isotope profiles is 3.5 ± 0.41 x 10**-5 g/cm**2/yr (~0.19 m/Ma) for the past ~4 Ma. For the Hart ash, the erosion rate is 4.8 ± 0.21 x 10**-4 g/cm**2/yr (~2.6 m/Ma) for the past ~1 Ma. The concentration profiles do not show signs of mixing, creep, or deflation caused by sublimation of ground ice. These results indicate that the slow, steady lowering of the surface without vertical mixing may allow landforms to maintain their meter-scale morphology even though they are actively eroding.