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SEDIMENTS

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  • A sediment core was collected from the western side of Pidgeon Island, (66.3216 S, 110.445 E) at a water depth of 82.0 m. This sediment core (PG 1411-2) was recovered using a release-controlled piston corer, with a length of 3 m, using the coring technique described in Melles et al., (1994). The total core length was 240 cm. This core was stored in the dark, at 0 degrees C until required. Samples were taken for diatom analyses and radiocarbon (14C) dating. Prior to sub-sampling the core was split in half, along its length. One half was used for sampling, the other kept intact and stored at IASOS (University of Tasmania). To reduce potential contamination, resulting from the disturbance of sediments during the core-splitting procedure, a thin layer of sediment was removed from the exposed surface immediately prior to sampling. In order to obtain samples for diatom analysis, a toothpick was inserted into the core segment, and used to gouge a small amount of sediment from the middle of the core. Samples for diatom analyses were initially collected every 5 mm, however, sampling frequency progressively decreased down the core. Samples for radiocarbon data consisted of at least 1 cm 3 of sediment, collected from the middle of the core. These samples were collected from between 0-1 cm, 12-13 cm, 59-60 cm, 77-78 cm, 117-118 cm, and 229-230 cm depth. Diatom data are presented as raw counts, benthic abundances, the ratio of benthic to plankton species, and as the benthic index. Calculated ages (in years) are also given for all samples. The sedimentological core log is given as a powerpoint presentation. This work was completed as part of ASAC project 1130 (ASAC_1130) and project 2201 (ASAC_2201). Public summary from project 1130: Algal mats grow on sea floor in most shallow marine environments. They are thought to contribute more than half of the total primary production in many of these areas, making them a critical food source for invertebrates and some fish. We will establish how important they are in Antarctic marine environments and determine the effects of local sewerage and tip site pollution. We will also investigate the impact on the algal mats of the additional UV radiation which results from the ozone hole. Public summary from project 2201: As a signatory to the Protocol on Environmental Protection to the Antarctic Treaty Australia is committed to comprehensive protection of the Antarctic environment. This protocol requires that activities in the Antarctic shall be planned and conducted on the basis of information sufficient to make prior assessments of, and informed judgements about, their possible impacts on the Antarctic environment. Most of our activities in the Antarctic occur along the narrow fringe of ice-free rock adjacent to the sea and many of our activities have the potential to cause environmental harm to marine life. The Antarctic seas support the most complex and biologically diverse plant and animal communities of the region. However, very little is known about them and there is certainly not sufficient known to make informed judgements about possible environmental impacts. The animals and plants of the sea-bed are widely accepted as being the most appropriate part of the marine ecosystem for indicating disturbance caused by local sources. Attached sea-bed organisms have a fixed spatial relationship with a given place so they must either endure conditions or die. Once lost from a site recolonisation takes some time, as a consequence the structure of sea-bed communities reflect not only present conditions but they can also integrate conditions in the past. In contrast, fish and planktonic organisms can move freely so their site of capture does not indicate a long residence time at that location. Because sea-bed communities are particularly diverse they contain species with widely differing life strategies, as a result different species can have very different levels of tolerance to stress; this leads to a range of subtle changes in community structure as a response to gradually increasing disturbance, rather than an all or nothing response. This project will examine sea-bed communities near our stations to determine how seriously they are affected by human activities. This information will be used to set priorities for improving operational procedures to reduce the risk of further environmental damage. The fields in this dataset are: Species Site Benthic % Planktonic % Depth (cm) Age (years) Radiocarbon Age Corrected Age Benthic Index

  • Ellis Fjord is a small, fjord-like marine embayment in the vestfold Hills, eastern Antarctica. Modern sediment input is dominated by a biogenic diatom rain, although aeolian, fluvial, ice-rafted, slumped and tidal sediments also make a minor contribution. In areas where bioturbation is significant relict glaciogenic sediments are reworked into the fine-grained diatomaceous sediments to produce poorly sorted fine sands and silts. Where the bottom waters are anoxic, sediments remain unbioturbated and have a high biogenic silica component. Three depositional and non-depositional facies can be recognised in the fjord: an area of non-deposition around the shoreline; a relict morainal facies in areas of low sedimentation and high bioturbation; and a basinal facies in the deeper areas of the fjord.

  • AM02 borehole drilled December 2000. Several Niskin water bottle samples collected in ocean cavity. 1.44 m sediment core collected from seafloor at 780 m below sea level. Ongoing Automatic Weather Station data available on: http://aws.acecrc.org.au/ Consult Readme file.

  • AM01 borehole drilled mid-January 2002. Profiling measurements conducted over a period of one week. Long term monitoring instruments installed 2002-01-16. AM01b borehole drilled mid-December 2003. Video recording of borehole walls and sea floor benthos. Sediment sample collected from sea floor.

  • AM02 borehole drilled December 2000. Profiling measurements conducted over a period of one week. Long term monitoring instruments installed 2001-01-06. Consult Readme file for detail of data files and formats.

  • AM01b borehole drilled mid-December 2003. Profiling measurements conducted over a period of a few days. Video recording of borehole walls and sea floor benthos. Sediment sample collected from sea floor. No long term monitoring instruments installed. AM01b borehole was drilled within a few hundred metres of where the ice shelf had carried the original AM01 borehole to, in the intervening 2 years. As the AM01 borehole had a mooring suite of instruments, none were emplaced in the AM01b borehole. There are several video files attached to this metadata record, and further details about them are provided in the accompanying readme document. The data file contains downcam video, sidecam video and miscellaneous video.

  • AM01b borehole drilled mid-December 2003. Profiling measurements conducted over a period of a few days. Video recording of borehole walls and sea floor benthos. Sediment sample collected from sea floor. No long term monitoring instruments installed. AM01b borehole was drilled within a few hundred metres of where the ice shelf had carried the original AM01 borehole to, in the intervening 2 years. As the AM01 borehole had a mooring suite of instruments, none were emplaced in the AM01b borehole.

  • ---- Public Summary from Project ---- Most of the snow falling on inland Antarctica drains via large ice streams and floating ice shelves to the sea where it lost by iceberg calving or as melt beneath the shelves. Ocean interaction beneath the shelves is complicated, and regions of basal refreezing as well as melt occur. These processes are important not only because they are a major component of the Antarctic mass budget, but because they also modify the characteristics of the ocean, influencing the formation of Antarctic Bottom Water which plays a major role in the global ocean circulation. The processes are sensitive to climate change, and shifts in ocean temperature or circulation near Antarctica could lead to the disappearance of all Antarctic ice shelves. The Amery Ice Shelf is the major embayed shelf in East Antarctica, and the subject of considerable previous ANARE investigation. Ocean interaction processes occurring beneath the shelf are only poorly understood, and this project will directly measure water characteristics and circulation in the cavity underneath the ice shelf, and the rates of melt and freezing on the bottom of the shelf. These measurements will be made through a number of access holes melted through the shelf. The project is closely linked with other projects investigating the circulation and interactions in the open ocean to the north of the shelf, and studies of the ice shelf flow and mass budget. There will be child records for each of the following data sets: AM01 and AM01 b boreholes * CTD profiles through water column * CTD annual records at selected depths * Ocean current profiles through water column * Temperature measurements through ice shelf and across ice-water interface * Small ice core samples * 0.5 m sea floor sediment core * Video footage of borehole walls (including marine ice) and sea floor benthos * GPS records of surface tidal motion * Video AM02 borehole * CTD profiles through water column * CTD annual records at selected depths * Borehole diameter caliper profiles * Temperature measurements through ice shelf and across ice-water interface * 1.5 m sea floor sediment core * GPS records (surface elevation, ice motion) AM03 borehole * Aquadopp current meter data * Brancker thermistor data * Caliper data * FSI-CTD profile data * Drilling parameters data * Seabird MicroCAT CTD moorings at three depths in ocean cavity beneath the shelf * Video AM04 borehole * Aquadopp current meter data * Brancker thermistor data * Caliper data * FSI-CTD profile data * Drilling parameters data * Seabird MicroCAT CTD moorings at three depths in ocean cavity beneath the shelf * Video AM05 borehole * Aquadopp current meter data * Caliper data * FSI-CTD profile data * Drilling parameters data * Seabird MicroCAT CTD moorings in ocean cavity beneath the shelf AM06 borehole * Aquadopp current meter data * Caliper data * FSI-CTD profile data * Drilling parameters data * Seabird MicroCAT CTD moorings in ocean cavity beneath the shelf Taken from the 2008-2009 Progress Report: Progress Against Objectives: The work undertaken in the past 12 months has continued to relate chiefly to the first of our objectives - "quantify the characteristics and circulation of ocean water in the cavity beneath the Amery Ice Shelf". Data from the AMISOR project have provided the first record of a seasonal cycle of ice shelf-ocean interaction. After recovering the 2008 data we now have near-continuous oceanographic data from beneath the Amery at 3 different depths for 6, 6, 3, and 3 years from 4 different sites. Note that the instruments at AM01 and AM02 (6 annual cycles of data each) are no longer recording due to expiration of the onboard batteries (3-5 years expected life cycle). This allows us to investigate the "real" 3-D, seasonally varying, circulation and melt/freezing cycle beneath an ice shelf - rather than the steady state, simplified "2-D ice pump circulation" that has mostly been assumed previously. As much as 80% of the continental ice that flows into the Amery Ice Shelf from the Lambert Glacier basin is lost as basal melt melt beneath the southern part of the shelf, but a considerable amount of ice is also frozen onto the base in the north-western part of the shelf. These processes of melt and refreezing are due to a pattern of water circulation beneath the ice shelf which is driven by sea ice formation outside the front of the shelf. Our multi-year data from 4 sites beneath the Amery ice shelf show that there is a very strong seasonal cycle in the characteristics of the ocean water beneath the shelf, and strong interseasonal variability in this. The seasonal cycle is driven mostly by the seasonal cycle of sea ice formation and decay in Prydz Bay, and interseasonal variations are due to differences in the general ocean circulation, and in particular the upwelling of Circumpolar Deep Water onto the continental shelf in Prydz Bay. The melt and freeze processes beneath the ice shelf, also themselves modify the water characteristics. Taken from the 2009-2010 Progress Report: The AMISOR project drilled two new 600 m deep boreholes on the Amery Ice Shelf in 2009-10: the first on the marine ice flowline to enhance understanding of the re-freezing process beneath the shelf; and the second in a region of known interest with respect to circulation patterns in the ocean cavity below the shelf. Instrument deployments at both sites should provide valuable annual cycle data over the next 4-5 years.