Ice Sheet and Climate Processes Driving the Uncertainty in Projections of Future Sea Level Rise: Findings From a Structured Expert Judgement Approach.

The ice sheets covering Antarctica and Greenland present the greatest uncertainty in, and largest potential contribution to, future sea level rise. The uncertainty arises from a paucity of suitable observations covering the full range of ice sheet behaviors, incomplete understanding of the influences of diverse processes, and limitations in defining key boundary conditions for the numerical models. To investigate the impact of these uncertainties on ice sheet projections we undertook a structured expert judgement study. Here, we interrogate the findings of that study to identify the dominant drivers of uncertainty in projections and their relative importance as a function of ice sheet and time. We find that for the 21st century, Greenland surface melting, in particular the role of surface albedo effects, and West Antarctic ice dynamics, specifically the role of ice shelf buttressing, dominate the uncertainty. The importance of these effects holds under both a high-end 5°C global warming scenario and another that limits global warming to 2°C. During the 22nd century the dominant drivers of uncertainty shift. Under the 5°C scenario, East Antarctic ice dynamics dominate the uncertainty in projections, driven by the possible role of ice flow instabilities. These dynamic effects only become dominant, however, for a temperature scenario above the Paris Agreement 2°C target and beyond 2100. Our findings identify key processes and factors that need to be addressed in future modeling and observational studies in order to reduce uncertainties in ice sheet projections.

Magnetic properties of uncultivated magnetotactic bacteria and their contribution to a stratified estuary iron cycle.

Of the two nanocrystal (magnetosome) compositions biosynthesized by magnetotactic bacteria (MTB), the magnetic properties of magnetite magnetosomes have been extensively studied using widely available cultures, while those of greigite magnetosomes remain poorly known. Here we have collected uncultivated magnetite- and greigite-producing MTB to determine their magnetic coercivity distribution and ferromagnetic resonance (FMR) spectra and to assess the MTB-associated iron flux. We find that compared with magnetite-producing MTB cultures, FMR spectra of uncultivated MTB are characterized by a wider empirical parameter range, thus complicating the use of FMR for fossilized magnetosome (magnetofossil) detection. Furthermore, in stark contrast to putative Neogene greigite magnetofossil records, the coercivity distributions for greigite-producing MTB are fundamentally left-skewed with a lower median. Lastly, a comparison between the MTB-associated iron flux in the investigated estuary and the pyritic-Fe flux in the Black Sea suggests MTB play an important, but heretofore overlooked role in euxinic marine system iron cycle.

Screening of cervical cytological samples using coherent optical processing. Part 1.

Coherent optical signal processing methods for screening Pap smears were evaluated and are presented in a three-part sequence. In Part 1, 2-D Fourier spectra of normal and abnormal cells generated from many high resolution cell photographs are presented. Each cell spectrum was measured with a coherent optical data processing system containing a special geometry detector and automated data collection capability. Several parameters, determined from weighted measures of the cell transform intensity variations, were tested as feature discriminators to separate normal from abnormal cells. An analysis of the experimental data demonstrates that several transform features are good discriminators of normal/abnormal cells (using standard Baysian decision algorithms with quadratic decision rules). In Part 2, mathematical model studies to guide and validate the experimental work show certain transform parameters to be functionally related to cell and nucleus diameter and optical density. Other parameters appear to be related to cell characteristics such as clumping of nuclear deoxyribonucleic acid (DNA). The model studies also show that the photographic variables play a key role in cell image preprocessing prior to Fourier analysis. Part 3 discusses an optical transducer that was used as a film replacement to modulate a laser beam spatially with a cell image. Several of the feature discriminators used in Part 1 with photographic film images served also to separate normal and malignant cell types when the cell Fourier spectrum was obtained from a transducer image. Based on an understanding of the procedure from the model studies and the demonstrated ability to separate normal and malignant cells using certain transform features, a coherent optical processing system to screen Pap smears from cell or slide photographs is feasible and appears practical in terms of the number of cells to be processed. A high-speed optical transducer would be required for processing large numbers of cells without photography in a reasonable time interval.

Screening of cervical cytological samples using coherent optical processing. Part 3.

This paper is the third of a three-part sequence. A modified Fourier spectrum analyzer system that uses an optical transducer to contain cell images is described. The photoconductor - liquid crystal transducer modulates a transmitted laser beam producing a high contrast cell image. The transducer is operated in a light scattering mode to achieve a contrast ratio in excess of 1000:1 and a gamma of about 10. Cell discriminant features are obtained from the transform spectrum of the transducer modulated image. The ability to classify cells from feature measurements is comparable with previous cell-by-cell classification performance based on cell photography.

Screening of cervical cytological samples using coherent optical processing. Part 2.

This paper is Part 2 of a three-part sequence dealing with coherent optical signal processing methods for screening Pap smears. Part 2 is devoted to model analysis and evaluation. A mathematical cell model is established to develop the radial spatial frequency profiles of representative cells F(rho). The quantity rho(2)|F(rho)|(2) is shown to be most effective in bringing out normal/malignant cell transform differences. Photographic contrast and gamma play a major role in amplifying cell discriminant features and reducing the effects of the aperture contribution.

Coherent optical processing of cervical cytologic samples.

Earlier research using a very limited data base gave encouraging results for the automated screening of exfoliated cytologic samples using coherent optical processing techniques to examine individual isolated cells. A more thorough investigation involving a larger data base has confirmed our initial results. This investigation was performed using a specially designed Fourier spectrum analyzer and a solid state optical detector array. An analysis was made to determine the performance of a screening system using such a cell-by-cell discriminating device. This analysis indicated that less than 20,000 cells would have to be examined to obtain a system performance level of 1% false negative and 10% false positive error rates with a 1% probability of occurrence of malignant cells in a malignant sample. This performance figure was inferred from measured statistical performance characteristics of a laboratory cell-by-cell screening device using optically generated Fourier transfrom techniques for cell discrimination. The performance of the system was shown to be much more sensitive to cell-by-cell false error rates than false negative error rates. It was also found that the majority of false positive errors were due to misclassifying parabasal cells as malignant. By eliminating parabasal cells, which comprised more than 25% of our normal cell data base, the number of cells needed to be screened dropped by an order of magnitude. It was also shown that there is an inverse quadratic relationship between the percentage of malignant cells in a malignant sample and the number of cells that must be screened to achieve any desired system performance.