Paleomagnetic measurements of 10 sediment profiles from the Antarctic continental slope

Die im Rahmen des zweijährigen Forschungsprojekts über paläomagnetisch-sedimentologische Analysen sedimentärer Zyklen in der Weddell See und ihre stratigraphische Interpretation durchgeführten Arbeiten lieferten Ergebnisse zur Geschichte glaziomariner Sedimentationsprozesse am antarktischen Kontinentalrand. So konnte für ein Kernprofil mit einer außergewöhnlichen Terassenstruktur eine fazielle Gliederung und stratigraphische Einordnung erreicht werden, die auch auf größere Areale in der Weddell See anwendbar sind. Aufgrund der stratigraphischen Randbedingungen konnten die gewonnenen paläo- und gesteinsmagnetischen Messungen in eine Altersstruktur integriert und zusammen mit den sedimentologischen Parametern im Hinblick auf lokale und regionale Umweltveränderungen interpretiert werden. Insbesondere die gesteinsmagnetischen Analysen haben gezeigt, daß die magnetische Kornfraktion als accessorischer Bestandteil im Gesamtsediment dennoch an die Sortierungsprozesse des terrigenen Sedimenteintrags gekoppelt ist. Die ungewöhnlich deutlichen Variationen korngrößenabhängiger Parameter zeigten weiterhin, daß in Verbindung mit einer hochauflösenden Stratigraphie die magnetische Detailanalyse und ein besseres Verständnis der Sedimentationsprozesse in der Nähe der Schelfeiskante und speziell bei Meeresspiegeltiefständen die Möglichkeit eröffnen, unmittelbar Aussagen über die Bewegungen der Schelfeise und die Qualität der Meereisbedeckungen zu machen. Die gezielte Fortsetzung dieser Arbeiten in anderen Arealen am antarktischen Kontinentalrand ist daher wünschenswert. Die verwendeten Verfahren lassen sich mit den derzeit verfügbaren Instrumenten noch erweitern und versprechen durch die sehr sensitive Methodik detaillierte Aussagen zu glaziomarinen Sedimentationsprozessen.

Snow height on sea ice and sea ice drift from autonomous measurements from buoy 2014S24, deployed during Antarctic Fast Ice Network 2014 (AFIN 2014)

Snow height was measured by the Snow Depth Buoy 2014S24, an autonomous platform, installed close to Neumayer III Base, Antarctic during Antarctic Fast Ice Network 2014 (AFIN 2014). The resulting time series describes the evolution of snow depth as a function of place and time between 2014-03-07 and 2014-05-16 in sample intervals of 1 hour. The Snow Depth Buoy consists of four independent sonar measurements representing the area (approx. 10 m**2) around the buoy. The buoy was installed on the ice shelf. In addition to snow depth, geographic position (GPS), barometric pressure, air temperature, and ice surface temperature were measured. Negative values of snow depth occur if surface ablation continues into the sea ice. Thus, these measurements describe the position of the sea ice surface relative to the original snow-ice interface. Differences between single sensors indicate small-scale variability of the snow pack around the buoy. The data set has been processed, including the removal of obvious inconsistencies (missing values). Records without any snow depth may still be used for sea ice drift analyses. Note: This data set contains only relative changes in snow depth, because no initial readings of absolute snow depth are available.

Decelerated mass loss of Hurd and Johnsons Glaciers, Livingston Island, Antarctic Peninsula

A new 10 year surface mass balance (SMB) record of Hurd and Johnsons Glaciers, Livingston Island, Antarctica, is presented and compared with earlier estimates on the basis of local and regional meteorological conditions and trends.Since Johnsons is a tidewater glacier, we also include a calving flux calculation to estimate its total mass balance. The average annual SMB over the 10 year observation period 2002–11 is –0.15�0.10 m w.e. for Hurd Glacier and 0.05�0.10 m w.e. for Johnsons Glacier. Adding the calving losses to the latter results in a total mass balance of –0.09�0.10 m w.e. There has been a deceleration of the mass losses of these glaciers from 1957–2000 to 2002–11, which have nearly halved for both glaciers. We attribute this decrease in the mass losses to a combination of increased accumulation in the region and decreased melt. The increased accumulation is attributed to larger precipitation associated with the recent deepening of the circumpolar pressure trough, while the melt decrease is associated with lower summer surface temperatures during the past decade.

Antarctic climate change and the environment: an update

We present an update of the "key points" from the Antarctic Climate Change and the Environment (ACCE) report that was published by the Scientific Committee on Antarctic Research (SCAR) in 2009. We summarise subsequent advances in knowledge concerning how the climates of the Antarctic and Southern Ocean have changed in the past, how they might change in the future, and examine the associated impacts on the marine and terrestrial biota. We also incorporate relevant material presented by SCAR to the Antarctic Treaty Consultative Meetings, and make use of emerging results that will form part of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report.

Mitochondrial DNA reveals hidden diversity for tardigrades from across the Antarctic realm

Antarctica contains some of the most challenging environmental conditions on the planet due to freezing temperatures, prolonged winters and lack of liquid water. Whereas 99.7% of Antarctica is permanently covered by ice and snow, some coastal areas and mountain ridges have remained ice-free and are able to sustain populations of microinvertebrates. Tardigrades are one of the more dominant groups of microfauna in soil and limno-terrestrial habitats, but little is known of their diversity and distribution across Antarctica. Here, we examine tardigrades sampled from across an extensive region of continental Antarctica, and analyse and compare their partial mitochondrial cytochrome c oxidase subunit 1 (COI) gene sequences with those from the Antarctic Peninsula, maritime and sub-Antarctica, Tierra del Fuego and other worldwide locations in order to recognise operational taxonomic units (OTUs). From 439 new tardigrade COI sequences, we identified 98 unique haplotypes (85 from Antarctica) belonging to Acutuncus, Diphascon, Echiniscus, Macrobiotus, Milnesium and unidentified Parachela. Operational taxonomic units were delimited by Poisson tree processes and general mixed Yule coalescent methods, resulting in 58 and 55 putative species, respectively. Most tardigrades appear to be locally endemic (i.e. restricted to a single geographic region), but some (e.g. Acutuncus antarcticus (Richters, 1904)) are widespread across continental Antarctica. Our molecular results reveal: (i) greater diversity than has previously been appreciated with distinct OTUs that potentially represent undescribed species, and (ii) a lack of connectivity between most OTUs from continental Antarctica and those from other Antarctic geographical zones.