Reconciling unevenly sampled paleoclimate proxies: a Gaussian kernel correlation multiproxy reconstruction

Reconstructing past hydroclimatic variability using climate-sensitive paleoclimate proxies provides context to our relatively short instrumental climate records and a baseline from which to assess the impacts of human-induced climate change. However, many approaches to reconstructing climate are limited in their ability to address sampling variability inherent in different climate proxies. We iteratively optimise an ensemble of possible reconstruction data series to maximise the Gaussian kernel correlation of Rehfeld et al. (2011) which reconciles differences in the temporal resolution of both the target variable and proxies or covariates. The reconstruction method is evaluated using synthetic data with different degrees of sampling variability and noise. Two examples using paleoclimate proxy records and a third using instrumental rainfall data with missing values are used to demonstrate the utility of the method. While the Gaussian kernel correlation method is relatively computationally expensive, it is shown to be robust under a range of data characteristics and will therefore be valuable in analyses seeking to employ multiple input proxies or covariates

Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination.

Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000-11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved 'horizontal ice core' from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600-12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise

Формування та розвиток загальної теорії стійкості (середина XVIII ст. — 30-і рр. ХХ ст.)

У статті розглянуто історію вивчення стійкості (середина XVIII — початок XX ст., світовий контекст). Досліджено внесок А. Пуанкаре та О.М. Ляпунова в розвиток загальної теорії стійкості. Показано розвиток їх ідей у працях російських та українських учених.В статье рассмотрена история изучения устойчивости (середина XVIII — начало XX в., мировой контекст). Исследован вклад французского ученого А. Пуанкаре и русского ученого А.М. Ляпунова в развитие общей теории устойчивости. Показано дальнейшее развитие их идей в трудах русских и украинских ученых.The history of basic research in stability is given. Contributions from H.Poincaré, a French mathematician, mechanic and physicist, and O. Lapunov, a soviet mathematician and mechanic (working in the Kharkiv university) to development of the general theory of stability are shown. In 1892—1902, O. Lyapunov constructed an original robust mathematical apparatus to study stability of motion. Development of ideas and methods of H.Poincar of H.Poincar³e and O. Lapunov in works of later Ukrainian and Russian scientists is shown

Mining the human phenome using allelic scores that index biological intermediates

J. Kaprio ja M-L. Lokki työryhmien jäseniä.It is common practice in genome-wide association studies (GWAS) to focus on the relationship between disease risk and genetic variants one marker at a time. When relevant genes are identified it is often possible to implicate biological intermediates and pathways likely to be involved in disease aetiology. However, single genetic variants typically explain small amounts of disease risk. Our idea is to construct allelic scores that explain greater proportions of the variance in biological intermediates, and subsequently use these scores to data mine GWAS. To investigate the approach's properties, we indexed three biological intermediates where the results of large GWAS meta-analyses were available: body mass index, C-reactive protein and low density lipoprotein levels. We generated allelic scores in the Avon Longitudinal Study of Parents and Children, and in publicly available data from the first Wellcome Trust Case Control Consortium. We compared the explanatory ability of allelic scores in terms of their capacity to proxy for the intermediate of interest, and the extent to which they associated with disease. We found that allelic scores derived from known variants and allelic scores derived from hundreds of thousands of genetic markers explained significant portions of the variance in biological intermediates of interest, and many of these scores showed expected correlations with disease. Genome-wide allelic scores however tended to lack specificity suggesting that they should be used with caution and perhaps only to proxy biological intermediates for which there are no known individual variants. Power calculations confirm the feasibility of extending our strategy to the analysis of tens of thousands of molecular phenotypes in large genome-wide meta-analyses. We conclude that our method represents a simple way in which potentially tens of thousands of molecular phenotypes could be screened for causal relationships with disease without having to expensively measure these variables in individual disease collections.Peer reviewe

Late Pleistocene and early Holocene change in the Weddell Sea: a new climate record from the Patriot Hills, Ellsworth Mountains, West Antarctica

The transition from the late Pleistocene to the Holocene (30 000-5000 years ago) was a period of considerable climate variability, which has been associated with changes in deep water formation and the intensity of the Meridional Overturning Circulation. Although numerous records exist across the North Atlantic region, few Antarctic ice core records have been obtained from the south. Here we exploit the potential of upwelling ancient ice - so-called blue ice areas (BIAs) - from the Patriot Hills in the Ellsworth Mountains to derive the first deuterium isotope record (D) from continental Antarctica south of the Weddell Sea. Gas analysis and glaciological considerations provide a first relative chronology. Inferred temperature trends from the Patriot Hills BIA and snow pit suggest changing climate influences during the transition between the last glacial period and Holocene. Under modern conditions, the interplay between the Antarctic high-pressure system and the Southern Annular Mode appears to play a significant role in controlling katabatic wind flow over the site while the BIA record suggests that greater sea ice extent during the last glacial period was a major control. Our results demonstrate the considerable potential of the Patriot Hills site for reconstructing past climate change in the south Atlantic region

A quasi-monthly record of 10Be concentration at Law Dome, Antarctica, from 2000 to 2015

This paper presents an overview of work undertaken over a number of Australian Antarctic Science projects, beginning in season 2001/02 with a shallow snow pit. In season 2005/06 this was augmented with a 260 m thermally drilled ice core and a 4.5 m snow pit. A core taken in 2008/09 overlapped the 2005/06 core and pit samples. From 2009/10, short cores spanning a few year’s deposition, along with snow pit samples spanning about half a year, have been taken each season. This has continued through to the current 2015/16 season. The cores permit an overlap with earlier years to match the chronology and to yield samples for 10Be analysis at the Australian Nuclear Science and Technology Organisation (ANSTO) by the technique of accelerator mass spectrometry (AMS). Together, the data provide a unique, continuous, quasi-monthly record over 2000 to 2015 as we have moved from Solar Cycle 23 to 24. The snow pits yield larger samples for 7Be analysis, earlier by gamma spectroscopy but lately by AMS. Along with comparison with neutron monitor data and GCM modelling, this unique, high-precision record has enabled us to learn much about the production, transport and deposition of 10Be to Law Dome and to improve our use of 10Be as a proxy for past solar variability