Middle to late Quaternary grain size variations and sea-ice rafting on the Lomonosov Ridge

Sea ice and icebergs are the dominant transport agents for sand-sized material to the central Arctic Ocean. However, few studies have investigated concurrent changes in the silt-sized fraction of Arctic sediments. Here we present an analysis of the coarse fraction content and silt grain size composition from middle and late Quaternary sediments recovered from the Lomonosov Ridge, in the central Arctic Ocean. A significant shift in the grain size record occurs at the marine isotope stage (MIS) 6/7 boundary, where larger amplitude variability in the sand fraction is seen in glacial and stadial periods. Below the MIS6/7 boundary, variations in the coarse fraction content are less pronounced, but prominent changes in the silt size fraction appear to define glacial and interglacial periods. Throughout the record, the percent weight of sortable silt in the fine fraction (SS % wtfines), sortable silt mean size, and coarse silt content all increase as the >63 µm % wt content increases. This is consistent with observations of grain size spectra obtained from modern sea-ice samples, and indicates a strong overprint from sea ice on the silt distribution. The mechanism by which this sea-ice signal is preserved in the sediments across glacial and interglacial periods remains unclear. We suggest that the coarsening of silt-sized material during glacial periods could be attributed to either the entrainment of larger size fractions during suspension/anchor ice formation when sea levels are lowered, or diminished input and advection of fine fraction material during glacial periods.

Keywords: Pleistocene; Lomonosov Ridge; grain size; sea ice.

(Published: 26 June 2014)

Citation: Polar Research 2014, 33, 23672, http://dx.doi.org/10.3402/polar.v33.23672

Continue ReadingMiddle to late Quaternary grain size variations and sea-ice rafting on the Lomonosov Ridge

Assessing the importance of human activities for the establishment of the invasive Poa annua in Antarctica

Because of its harsh environmental conditions and remoteness, Antarctica is often considered to be at low risk of plant invasion. However, an increasing number of reports have shown the presence and spread of non-native plants in Antarctica; it is therefore important to study which factors control the invasion process in this ecosystem. Here, we assessed the role of different human activities on the presence and abundance of the invasive Poa annua. In addition, we performed a reciprocal transplant experiment in the field, and a manipulative experiment of germination with P. annua and the natives Colobanthus quitensis and Deschampsia antarctica, in order to unravel the effects of physical soil disturbance on the establishment and survival of P. annua. We found a positive correlation between abundance of P. annua and level of soil disturbance, and that survival of P. annua was 33% higher in sites with disturbed soil than non-disturbed. Finally, we found that disturbance conditions increased germination for P. annua, whereas for native species germination in experimentally disturbed soil was either unchanged or reduced compared to undisturbed soil. Our results indicate that human activities that modify abiotic soil characteristics could play an important role in the abundance of this invasive species. If the current patterns of human activities are maintained in Antarctica, the establishment success and spread of P. annua could increase, negatively affecting native flora.

Keywords: Alien species; Colobanthus quitensis; Deschampsia antarctica; human disturbance; Poa annua; tourists.

(Published: 23 June 2014)

Citation: Polar Research 2014, 33, 21425, http://dx.doi.org/10.3402/polar.v33.21425

Continue ReadingAssessing the importance of human activities for the establishment of the invasive Poa annua in Antarctica

Late Holocene climate change recorded in proxy records from a Bransfield Basin sediment core, Antarctic Peninsula

The glacimarine environment of the Antarctic Peninsula region is one of the fastest warming places on Earth today, but details of changes in the recent past remain unknown. Large distances and widespread variability separate late Holocene palaeoclimate reconstructions in this region. This study focuses on a marine sediment core collected from ca. 2000 m below sea level in the Central Bransfield Strait that serves as a key for understanding changes in this region. The core yielded a high sedimentation rate and therefore provides an exceptional high-resolution sedimentary record composed of hemipelagic sediment, with some turbidites. An age model has been created using radiocarbon dates that span the Late Holocene: 3560 cal yr BP to present. This chronostratigraphic framework was used to establish five units, which are grouped into two super-units: a lower super-unit (3560–1600 cal yr BP) and an upper super-unit (1600 cal yr BP–present), based on facies descriptions, laser particle size analysis, x-ray analysis, multi-sensor core logger data, weight percentages and isotopic values of total organic carbon and nitrogen. We interpret the signal contained within the upper super-unit as an increase in surface water irradiance and/or shortening of the sea-ice season and the five units are broadly synchronous with climatic intervals across the Antarctic Peninsula region. While the general trends of regional climatic periods are represented in the Bransfield Basin core we have examined, each additional record that is obtained adds variability to the known history of the Antarctic Peninsula, rather than clarifying specific trends.

Keywords: Antarctic Peninsula; palaeoclimate; Holocene; marine; isotopes.

(Published: 11 June 2014)

Citation: Polar Research 2014, 33, 17236, http://dx.doi.org/10.3402/polar.v33.17236

Continue ReadingLate Holocene climate change recorded in proxy records from a Bransfield Basin sediment core, Antarctic Peninsula

Professor Tim Naish awarded the 2014 Martha T Muse Prize for Science and Policy in Antarctica

1Professor Tim Naish has been awarded the 2014 Muse Prize, for his outstanding research in understanding Antarctica’s response to past and present climate change and the role of Antarctica’s ice sheets in global sea-level change through time. He led the first season of the ambitious and highly successful Antarctic Drilling Program (ANDRILL) where his international team pioneered innovative drilling technology to obtain sedimentary records of the past 13 million years, paving the way for further successful drilling in previously inaccessible ice-covered areas. As Chair of the ANDRILL Steering Committee, he continued to be actively involved in overseeing the programme, including securing funding for the next phase. More recently, he has played an influential role in the process of translating science into policy as a lead author on the Paleoclimate chapter of the 5th Assessment Report of the Intergovernmental Panel on Climate Change. He is currently Director of the Antarctic Research Centre, Victoria University of Wellington, which continues to develop and has more than trebled its capacity under his direction.

The Prize Ceremony will be held at the SCAR Open Science Conference in Auckland in August.

Background information: The Martha T. Muse Prize for Science and Policy in Antarctica is a US$ 100,000 unrestricted award presented to an individual in the fields of Antarctic science or policy that has demonstrated potential for sustained and significant contributions that will enhance the understanding and/or preservation of Antarctica. The Tinker Foundation’s goal is to recognize excellence in Antarctic research by honouring someone in the early to mid-stages of his or her career. The Prize is inspired by Martha T. Muse’s passion for Antarctica and is a legacy of the International Polar Year. For further details please follow link http://www.museprize.org

Continue ReadingProfessor Tim Naish awarded the 2014 Martha T Muse Prize for Science and Policy in Antarctica

The July Sea Ice Outlook report is now available


The July Sea Ice Outlook (SIO) report is now available at:

The SIO is an activity of the Sea Ice Prediction Network project (SIPN) as a contribution to the Study of Environmental Arctic Change (SEARCH).

The organizers thank the groups and individuals that contributed to the 2014 July report, which includes 28 pan-Arctic contributions and three regional outlooks.


Continue ReadingThe July Sea Ice Outlook report is now available

Scientific Cooperation Task Force held its third meeting in Reykjavik

The Arctic Council’s Task Force for Enhancing Scientific Cooperation in the Arctic (SCTF) held its third meeting in Reykjavik on May 27-28, 2014.  The meeting focused on a draft document related to advancing scientific cooperation in the Arctic. The delegations decided that the task force would continue work on this document at its next meeting in September in Tromsø, Norway.

Continue ReadingScientific Cooperation Task Force held its third meeting in Reykjavik

New MODIS Mosaic of Antarctica 2008-2009 Image Map (NSIDC USO)

1The National Snow and Ice Data Center (NSIDC) is pleased to announce the release of the MODIS Mosaic of Antarctica 2008-2009 Image Map (MOA2009). This data set consists of two cloud-free digital image maps that show surface morphology and a quantitative measure of mean optical surface snow grain size on the Antarctic continent and surrounding islands.

MOA2009 represents the second in a series of MOA image mappings. The image map products have been generated and presented in a near-identical manner as the first mapping, the MODIS Mosaic of Antarctica 2003-2004 image Map (MOA2004). MOA2004 has also been updated with several new grain size image files providing both springtime and summer estimates of mean snow grain size.

A third MOA image mapping, based on data from the 2013-2014 austral summer (MOA2014), is planned for future publication later this year.

The data for MOA2009 were generated from 259 orbit swaths from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrumentation on board the NASA EOS Aqua and Terra satellites. The algorithm and tools for assembling the mosaic were developed by the NASA Cryospheric Sciences Program. Final processing and some adjustments to the snow grain size were completed under the NASA MEaSUREs Antarctic Ice Velocity grant. The Antarctic Glaciological Data Center (AGDC) at NSIDC offers data access, tools and information at the following page: http://nsidc.org/data/nsidc-0593

MODIS Mosaic of Antarctica 2008-2009 Image Map (MOA2009)

Continue ReadingNew MODIS Mosaic of Antarctica 2008-2009 Image Map (NSIDC USO)