(Table 3) Age-related trends of desert pavement properties in the Transantarctic Mountains

Compared to mid-latitude deserts, the properties, formation and evolution of desert pavements and the underlying vesicular layer in Antarctica are poorly understood. This study examines the desert pavements and the vesicular layer from seven soil chronosequences in the Transantarctic Mountains that have developed on two contrasting parent materials: sandstone-dolerite and granite-gneiss. The pavement density commonly ranges from 63 to 92% with a median value of 80% and does not vary significantly with time of exposure or parent material composition. The dominant size range of clasts decreases with time of exposure, ranging from 16-64 mm on Holocene and late Quaternary surfaces to 8-16 mm on surfaces of middle Quaternary and older age. The proportion of clasts with ventifaction increases progressively through time from 20% on drifts of Holocene and late Quaternary age to 35% on Miocene-aged drifts. Desert varnish forms rapidly, especially on dolerite clasts, with nearly 100% cover on surfaces of early Quaternary and older age. Macropitting occurs only on clasts that have been exposed since the Miocene. A pavement development index, based on predominant clast-size class, pavement density, and the proportion of clasts with ventifaction, varnish, and pits, readily differentiated pavements according to relative age. From these findings we judge that desert pavements initially form from a surficial concentration of boulders during till deposition followed by a short period of deflation and a longer period of progressive chemical and physical weathering of surface clasts. The vesicular layer that underlies the desert pavement averages 4 cm in thickness and is enriched in silt, which is contributed primarily by weathering rather than eolian deposition. A comparison is made between desert pavement properties in mid-latitude deserts and Antarctic deserts.

Heat index at 2 m above ground: A globally gridded dataset based on reanalysis data from 1979-2013, links to GeoTIFFs

The increase in global mean temperatures resulting from climate change has wide reaching consequences for the earth's ecosystems and other natural systems. Many studies have been devoted to evaluating the distribution and effects of these changes. We go a step further and evaluate global changes to the heat index, a measure of temperature as perceived by humans. Heat index, which is computed from temperature and relative humidity, is more important than temperature for the health of humans and other animals. Even in cases where the heat index does not reach dangerous levels from a health perspective, it has been shown to be an important factor in worker productivity and thus in economic productivity. We compute heat index from dewpoint temperature and absolute temperature 2 m above ground from the ERA-Interim reanalysis dataset for the years 1979-2013. The data is provided aggregated to daily minima, means and maxima. Furthermore, the data is temporally aggregated to monthly and yearly values and spatially aggregated to the level of countries after being weighted by population density in order to demonstrate its usefulness for the analysis of its impact on human health and productivity. The resulting data deliver insights into the spatiotemporal development of near-ground heat index during the course of the past 3 decades. It is shown that the impact of changing heat index is unevenly distributed through space and time, affecting some areas differently than others. The likelihood of dangerous heat index events has increased globally. Also, heat index climate groups that would formerly be expected closer to the tropics have spread latitudinally to include areas closer to the poles. The data can serve in future studies as a basis for evaluating and understanding the evolution of heat index in the course of climate change, as well as its impact on human health and productivity.

Development of bacterial and archaeal communities in erupted subsurface muds at the Håkon Mosby mud volcano

The microbial oxidation of methane controls the emission of the greenhouse gas methane from the ocean floor. However, some seabed structures such as mud volcanoes have leaky microbial methane filters and can be important sources of methane. We investigated the disturbance and recovery of a methanotrophic mud volcano microbiome (Håkon Mosby mud volcano, 1250 m water depth), to assess time scales of community succession and function in the natural deep-sea environment. We analyzed 10 surface and 5 subsurface sediment samples across HMMV mud flows from most recently discharged subsurface muds towards old consolidated muds as well as one reference site (REF) located approximately 0.5 km outside of the HMMV. Surface samples were obtained in 2003, 2009 and 2010. The surface of the new mud flows at the geographical center was sampled in 2009 and 2010. Around 100 m south of the center, we sampled more consolidated aged muds in 2003 and 2010. Old mud flows were sampled around 300 m southeast and 100 m north of the geographical center in 2003, 2009 and 2010. Surface sediment samples (0-20 cm) were recovered either by TV-guided Multicorer or by push cores using the remotely operated vehicle Quest (Marum, University Bremen). Subsurface sediments of all zones (>2 m below sea floor) were obtained in 2003 by gravity corer. After recovery, sediments were immediately subsampled in a refrigerated container (0°C) and further processed for biogeochemical analyses or preserved at -20°C for later DNA analyses. Our study show that freshly erupted muds hosted heterotrophic deep subsurface communities, which were replaced by surface communities within a few years of exposure. Aerobic methanotrophy was established at the top surface layer within less than a year, followed by anaerobic methanotrophy, sulfate reduction and finally thiotrophy. Our data indicate that it takes decades in cold environments before efficient methanotrophic communities establish to control methane emission. The observed succession provides insights to the response time of complex deep-sea communities to seafloor disturbances.

Mixed effects of elevated pCO2 on fertilisation, larval and juvenile development and adult responses in the mobile subtidal scallop Mimachlamys asperrima (Lamarck, 1819)

Ocean acidification is predicted to have severe consequences for calcifying marine organisms especially molluscs. Recent studies, however, have found that molluscs in marine environments with naturally elevated or fluctuating CO2 or with an active, high metabolic rate lifestyle may have a capacity to acclimate and be resilient to exposures of elevated environmental pCO2. The aim of this study was to determine the effects of near future concentrations of elevated pCO2 on the larval and adult stages of the mobile doughboy scallop, Mimachlamys asperrima from a subtidal and stable physio-chemical environment. It was found that fertilisation and the shell length of early larval stages of M. asperrima decreased as pCO2 increased, however, there were less pronounced effects of elevated pCO2 on the shell length of later larval stages, with high pCO2 enhancing growth in some instances. Byssal attachment and condition index of adult M. asperrima decreased with elevated pCO2, while in contrast there was no effect on standard metabolic rate or pHe. The responses of larval and adult M. asperrima to elevated pCO2 measured in this study were more moderate than responses previously reported for intertidal oysters and mussels. Even this more moderate set of responses are still likely to reduce the abundance of M. asperrima and potentially other scallop species in the world's oceans at predicted future pCO2 levels.