A Bell-Evans-Polanyi principle for molecular dynamics trajectories and its implications for global optimization

The Bell-Evans-Polanyi principle that is valid for a chemical reaction that proceeds along the reaction coordinate over the transition state is extended to molecular dynamics trajectories that in general do not cross the dividing surface between the initial and the final local minima at the exact transition state. Our molecular dynamics Bell-Evans-Polanyi principle states that low energy molecular dynamics trajectories are more likely to lead into the basin of attraction of a low energy local minimum than high energy trajectories. In the context of global optimization schemes based on molecular dynamics our molecular dynamics Bell-Evans-Polanyi principle implies that using low energy trajectories one needs to visit a smaller number of distinguishable local minima before finding the global minimum than when using high energy trajectories

Investigating the Arctic phytoplankton variability and diversity based on modeling and satellite retrievals

In our study we focus on improving our understanding of possible interactions between the open water and sea ice and the surface ocean biogeochemistry under the recently observed sea ice decline in the Arctic. In particular, the analysis of changes in phytoplankton functional types (PFTs) over 2002 to 2012 based on long-term time series of satellite retrievals and supported by a modeling study is presented. The phytoplankton dynamics as well as phytoplankton diversity in response to Arctic Amplification is simulated with the DARWIN biogeochemical model (Follows et al., 2007, Dutkiewicz et al., 2015) coupled to the Massachusetts Institute of Technology general circulation model (MITgcm) with a configuration based on a cubed‐sphere grid (Menemenlis et al. 2008). The model results are complemented with information on phytoplankton compositions retrieved with PhytoDOAS (Bracher et al. 2009, Sadeghi et al. 2012) from available hyper-spectral optical satellite measurements (SCIAMACHY and OMI), which are synergistically combined via an optimal interpolation technique with multi-spectral optical satellite data (OC-CCI)

Investigation on heat transfer in the Laptev Sea with respect to regional climate changes

The Laptev Sea around the Lena River delta in northern Siberia is a very remote area that in-situ measurements are only sparsely available. Polar night and long lasting ice coverage until the end of June makes it difficult to investigate the area all year round. Here satellite investigations of radiances measured e.g. with Envisat MERIS satellite and derived inherent optical properties (IOP) may help to generate a time series of changing water constituents, e.g. chlorophyll and coloured organic matter which can be split further into coloured dissolved organic matter (CDOM) and suspended particles (SPM). However, large solar zenith angles as well as thin cloud coverage in summer after ice break-off makes it difficult to investigate this region by remote sensing applications. Therefore modelling approaches seems to be a useful first approximation to identify the feedback to the radiation budget in these remote areas. With the current studies we investigate the influence of CDOM and SPM on the radiative heat transfer into the shelf regions of the Laptev Sea. As a first step we use the coupled atmosphere-ocean radiative transfer model SCIATRAN to assess energy input into coastal waters of this region dependent on different concentrations of CDOM varying significantly for different times of the year. Low solar elevations and high absorption by water constituents in this area extremely reduces the light penetration depth in the water body. An increased absorption in the surface water leads to higher sea surface temperatures and a high energy release into the atmosphere often occurring in late autumn and consequently influences the ice development process. In the context of climate change and thawing permafrost in Siberia the riverine input of those highly absorbing particles by Lena river may increase in the future. Therefore, a better understanding of these processes is necessary to predict possible future changes for that remote area

Assessing bio-physical feedbacks in the shelf areas of Laptev Sea

In the context of climate change and of thawing permafrost in Siberia, the freshwater and organic material supplied by rivers to the Arctic Ocean, may increase heavily in the future. Here, we investigate the effect of the variability of optically active water constituents on the heat budget of the Laptev Sea surface waters. As a first step, we simulate the radiative heating with coupled atmosphere-ocean radiative transfer modelling (RTM). By using satellite remote sensing retrievals of Coloured Dissolved Organic Matter (CDOM), Total Suspended Matter (TSM), Chlorophyll-a (Chla) and sea surface temperature data as input to the RTM simulations, we present the spatial distribution of potential radiative heating of Laptev Sea shelf areas. Additionally, an ocean biogeochemical model coupled to a general circulation model is used to simulate the dynamics of various constituents in response to Arctic Amplification and the feedback on surface heating and sea ice melting. Results suggest that high concentration of CDOM, TSM and Chla in Arctic waters increase the heating rate at the surface of the ocean and reduce the heat losses to the atmosphere during summer. The induced surface heating can result to higher ice melting rates with potential implications to upper ocean stratification and primary production

Assessing the Influence of Water Constituents on the Radiative Heating of Laptev Sea Shelf Waters.

The presence of optically active water constituents is known to attenuate the light penetration in the ocean and impact the ocean heat content. Here, we investigate the influence of colored dissolved organic matter (CDOM) and total suspended matter (TSM) on the radiative heating of the Laptev Sea shelf waters. The Laptev Sea region is heavily influenced by the Lena River, one of the largest river systems in the Arctic region. We simulate the radiative heating by using a coupled atmosphere-ocean radiative transfer model (RTM) and in situ measurements from the TRANSDRIFT XVII expedition carried out in September 2010. The results indicate that CDOM and TSM have significant influence on the energy budget of the Laptev Sea shelf waters, absorbing most of the solar energy in the first 2 m of the water column. In the station with the highest CDOM absorption (aCDOM(443) = 1.77 m−1) ~43% more energy is absorbed in the surface layer compared to the station with the lowest aCDOM(443) (~0.2 m−1), which translates to an increased radiative heating of ~0.6°C/day. The increased absorbed energy by the water constituents also implies increased sea ice melt rate and changes in the surface heat fluxes to the atmosphere. By using satellite remote sensing and RTM we quantify the spatial distribution of the radiative heating in the Laptev Sea for a typical summer day. The combined use of satellite remote sensing, RT modeling and in situ observations can be used to improve parameterization schemes in atmosphere-ocean circulation models to assess the role of the ocean in the effect of Arctic amplification

The complete genome sequence of a Neandertal from the Altai Mountains

We present a high-quality genome sequence of a Neandertal woman from Siberia. We show that her parents were related at the level of half siblings and that mating among close relatives was common among her recent ancestors. We also sequenced the genome of a Neandertal from the Caucasus to low coverage. An analysis of the relationships and population history of available archaic genomes and 25 present-day human genomes shows that several gene flow events occurred among Neandertals, Denisovans and early modern humans, possibly including gene flow into Denisovans from an unknown archaic group. Thus, interbreeding, albeit of low magnitude, occurred among many hominin groups in the Late Pleistocene. In addition, the high quality Neandertal genome allows us to establish a definitive list of substitutions that became fixed in modern humans after their separation from the ancestors of Neandertals and Denisovans

Protein-altering germline mutations implicate novel genes related to lung cancer development

Few germline mutations are known to affect lung cancer risk. We performed analyses of rare variants from 39,146 individuals of European ancestry and investigated gene expression levels in 7,773 samples. We find a large-effect association with an ATM L2307F (rs56009889) mutation in adenocarcinoma for discovery (adjusted Odds Ratio = 8.82, P = 1.18 × 10−15) and replication (adjusted OR = 2.93, P = 2.22 × 10−3) that is more pronounced in females (adjusted OR = 6.81 and 3.19 and for discovery and replication). We observe an excess loss of heterozygosity in lung tumors among ATM L2307F allele carriers. L2307F is more frequent (4%) among Ashkenazi Jewish populations. We also observe an association in discovery (adjusted OR = 2.61, P = 7.98 × 10−22) and replication datasets (adjusted OR = 1.55, P = 0.06) with a loss-of-function mutation, Q4X (rs150665432) of an uncharacterized gene, KIAA0930. Our findings implicate germline genetic variants in ATM with lung cancer susceptibility and suggest KIAA0930 as a novel candidate gene for lung cancer risk