No abstract

The shells of marine mollusks are widely used archives of past climate and ocean chemistry. Whilst the measurement of mollusk δ¹⁸O to develop records of past climate change is a commonly used approach, it has proven challenging to develop reliable independent paleothermometers that can be used to deconvolve the contributions of temperature and fluid composition on molluscan oxygen isotope compositions. Here we investigate the temperature dependence of ¹³C-¹⁸O bond abundance, denoted by the measured parameter Δ₄₇, in shell carbonates of bivalve mollusks and assess its potential to be a useful paleothermometer. We report measurements on cultured specimens spanning a range in water temperatures of 5 to 25 °C, and field-collected specimens spanning a range of −1 to 29 °C. In addition we investigate the potential influence of carbonate saturation state on bivalve stable isotope compositions by making measurements on both calcitic and aragonitic specimens that have been cultured in seawater that is either supersaturated or undersaturated with respect to aragonite. We find a robust relationship between Δ₄₇ and growth temperature. We also find that the slope of a linear regression through the Δ₄₇ data for bivalves plotted against seawater temperature is significantly shallower than previously published inorganic and biogenic carbonate calibration studies produced in our laboratory and go on to discuss the possible sources of this difference. We find that changing seawater saturation state does not have significant effect on the Δ₄₇ of bivalve shell carbonate in two taxa that we examined, and we do not observe significant differences between Δ₄₇-temperature relationships between calcitic and aragonitic taxa

Results from eight cloud-resolving models are compared for the first time for the case of an oceanic tropical squall line observed during the Tropical Ocean/Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. There is broad agreement between all the models in describing the overall structure and propagation of the squall line and some quantitative agreement in the evolution of rainfall. There is also a more qualitative agreement between the models in describing the vertical structure of the apparent heat and moisture sources.The three-dimensional (3D) experiments with an active ice phase and open lateral boundary conditions along the direction of the system propagation show good agreement for all parameters. The comparison of 3D simulated fields with those obtained from two different analyses of airborne Doppler radar data indicates that the 3D models are able to simulate the dynamical structure of the squall line, including the observed double-peaked updraughts. However, the second updraught peak at around 10 km in height is obtained only when the ice phase is represented. The 2D simulations with an ice-phase parametrization also exhibit this structure, although with a larger temporal variability.In the 3D simulations, the evolution of the mean wind profile is in the sense of decreasing the shear, but the 2D simulations are unable to reproduce this behaviour.

Abstract. The shells of marine mollusks are widely used archives of past climate and ocean chemistry. Whilst the measurement of mollusk δ18O to develop records of past climate change is a commonly used approach, it has proven challenging to develop reliable independent paleothermometers that can be used to deconvolve the contributions of temperature and fluid composition on molluscan oxygen isotope compositions. Here we investigate the temperature dependence of 13C–18O bond abundance, denoted by the measured parameter Δ47, in shell carbonates of bivalve mollusks and assess its potential to be a useful paleothermometer. We report measurements on cultured specimens spanning a range in water temperatures of 5 to 25 °C, and field collected specimens spanning a range of −1 to 29 °C. In addition we investigate the potential influence of carbonate saturation state on bivalve stable isotope compositions by making measurements on both calcitic and aragonitic specimens that have been cultured in seawater that is either supersaturated or undersaturated with respect to aragonite. We find a robust relationship between Δ47 and growth temperature. We also find that the slope of a linear regression through all the Δ47 data for bivalves plotted against seawater temperature is significantly shallower than previously published inorganic and biogenic carbonate calibration studies produced in our laboratory and go on to discuss the possible sources of this difference. We find that changing seawater saturation state does not have significant effect on the Δ47 of bivalve shell carbonate in two taxa that we examined, and we do not observe significant differences between Δ47-temperature relationships between calcitic and aragonitic taxa.

Recently, much attention has been paid to an inductively coupled RF plasma as an innovative plasma source for nuetral beam production[ 1] as well as material processing.Even in such an inductive plasma, the capacitive coupling from a RF antenna has been observed[2] and leads to the sputtering of the insulating wall materials contacting the antenna. In this study, the capacitive coupling from an antenna has been quantitatively estimated, measuring a de self-bias voltage induced on the surface of the insulator by electrostatic fields.[3] Figure 1 shows the spatial distribution of de self-bias voltage V DC along a 1 tum loop antenna of 1 0 ,.., 11 em in radius for two different thickness of antenna insulating cover, where e is the azimuthal position along the circular antenna as defined in Fig.1. A large negative bias of,.., 130 V was observed at the input RF power of 500 W in the case of the antenna covered with thin insulator of 1 mm in thickness. For thick insulator of 8.8 mm in thickness, the bias V DC considerably decreased but ion energy Ei bombarding the insulator surface was still as high as ,.., 40 e V since Ei = e(VP-V DC) and the plasma potential V P = ,..., 20 V. Concerning the azimuthal distribution of V DC the bias becomes more negative at the point on the RF feed side (9 ,.., 350° ) than on the ground side (9 ,.., 10° ) of the antenna loop.On the other hand, the power dependence of V oc was examined for the thick insulator antenna and the thin insulator antenna where 9 = 330 ,.., 350° . As shown in Fig.2, the bias becomes increasingly negative with increasing RF power while the plasma potential remains almost constant at,.., 20 V and KTe= 2.5,.., 4 eV.Finally, in order to suppress the electrostatic coupling effectively, an electrostatic shield was formed, and its effect on the self-bias voltage was examined for the thick insulator antenna. The value of V DC becomes positive and close to the floating potential given by a Langmuir probe. Thus, the shield effect was clearly recognized in comparison with the unshielded antenna.